Home

A Pre-processor for Numerical Analysis of Cross

1. Figure 2 13 Sihga Idefix innovative connection system Sihga 37 A pre processor for numerical analysis of cross laminated timber structures 2 7 1 Connections behaviour About the kinematic behaviour of the connections it can be assumed that 1 the shear connections angle brackets shear screws do not work in tension 2 the tension connections hold down do not work in shear These two hypotheses are nowadays widely used in the calculation of X Lam buildings and they are assumed to be valid in this thesis However if on one hand they allow to greatly simplify the calculations on the other hand they do not take into account the actual failure behaviour of the panels The behaviour of an X Lam panel subjected to horizontal forces is a combination of horizontal sliding and rigid rotation rocking consequently all connections at the base are subjected to a combination of horizontal forces or shear forces and lifting For further information about the behaviour of an X Lam panel subjected to horizontal forces see the thesis Una procedura numerica per il progetto di edifici in X Lam by Massimiliano Zecchetto Relatively to the first assumption different theoretical models have been proposed in order to take into account the actual presence of angle brackets in the rocking effect Gavric and Popovski 2014 In this case the interaction between shear and tension to which the angle brackets are subjected m
2. Figure 7 12 Forces causing the first floor rigid rotation Since the stabilising effect of the self weight is greater than the overturning one caused by the seism Figure 7 12 there is not rigid overturning of parts of the building Concerning the rocking effect for each wall the resulting forces due to the rocking effect and the stresses can be calculated depending on these which type of hold down disposing on that wall can be decided All these quantities are summarized in Table 7 3 with reference to Figure 7 13 154 Chapter 7 Modelling of a complex structure Table 7 3 a Summary of forces stresses and hold down disposed on walls in x direction is 18 42 18 18 18 18 18 18 37 5 375 750 37 5 375 oo oo 00 00 37 5 375 750 37 5 375 00 oo 00 00 1124 1124 2249 1124 1124 oo oo oo 00 156 156 589 156 156 oo oo 00 00 54 7 54 7 241 547 547 oo oo oo 00 1340 1 620 Table 7 3 b Summary of forces stresses and hold down disposed on walls in y direction 91 4 56 2 78 18 18 36 P2741 632 s43 1687 843 00 156 00 103 273 390 312 390 0 0 155 A pre processor for numerical analysis of cross laminated timber structures 1 5 W_F wau WALL 2 ee 2 5 W_F wauL3 WALL 6 WALL 7 ee re 2 5 W_F_ wau4 WALL 5 WALL 8 WALL 9 gt GROUND FLOOR 13 W
3. Figure 7 7 Afferent heights of the slabs Once the seismic weights are known an equivalent static analysis can be used to evaluate the storeys seismic forces It could not be used because the building is not regular in plan and elevation nonetheless it is used anyway with the sole purpose of testing the capabilities and reliability of the software 7 2 3 Equivalent static analysis Being the response history and response spectrum analyses still not available in Kratos solver and non linear analyses not available in the software because of the use of linear elastic spring elements an equivalent static analysis is performed 146 Chapter 7 Modelling of a complex structure According to EN 1998 1 2004 8 3 depending on their ductile behaviour and energy dissipation capacity under seismic actions timber buildings shall be assigned to one of the three ductility classes L M or H as given in the Table 7 1 Table 7 1 Design concept structural types and upper limit values of the behaviour factors for the three ductility classes EN 1998 1 2004 Design concept and Examples of structures ductility class Low capacity to dissipate 1 5 Cantilevers Beams Arches with two or three energy DCL inned joints Trusses joined with connectors Medium capacity to Glued wall panels with glued diaphragms issipate energy DCM connected with nails and bolts Trusses with doweled and bolted joints Mixed structures consis
4. Sz2 SHELL FORCE GLOBA 4 S200 347330105 24614005 144950206 43762 51429 1 6bb20 06 2598 10 05 3610105 step 1 f 6219005 Smooth Conos Fil Mean of DISPLACEMENT DISPLACEMENT Deformeston 1184 010 DISPLACEMENT of Kratos step 1 Figure 7 28 Shell Force Szz contour N m for the configuration A taking into account only the storeys seismic forces Syy SHELL FORCE GLOBA 1 7599e 05 1 3576e 05 95522 55287 15053 25182 65416 1 0565e 05 1 4588e 05 Y 1 8612e 05 step 1 Smooth Contour Fill Mean of SHELL FORCE GLOBAL quad4 element gp Syy SHELL FORCE GLOBAL Figure 7 29 Shell Force Syy contour N m for the configuration B 171 A pre processor for numerical analysis of cross laminated timber structures Sxx SHELL FORCE GLOBA 1 1721e 05 94795 72375 49955 27536 5115 9 17304 39724 62143 84563 Ls step 1 Smooth Contour Fill Mean of SHELL FORCE GLOBAL quad4 element gp Sxx SHELL FORCE GLOBAL Figure 7 30 Shell Force Sxx contour N m for the configuration B S22 SMELL FORCE GLOSA 42020 05 34141006 226056 1 638405 75043 13752 102550 05 191340 05 280140 05 gt er 3 89 0 05 Smooth Contour FA Moan of DISPLACEMENT DISPLACEMENT Detormaten 209 DISPLACEMENT ol Kratos stop 1 Figure 7 31 Shell Force Szz contour N m for the configuration B taking into account only the storeys seismic forces Figures 7 26 7 27 7 29 and 7 30 show t
5. Draw line section Of the CO dei a jones 116 Draw line groups and geometry cooooniconiciciniconacinnncnonccanr naar rrnn rara eee 117 More Matenals Hs tit lc 125 Materials py first section list of elements properties 127 Materials py added section dataOrtho file reading 128 Materials py added section Matrix CreAliOM oooionninnnnnnnnncnnncoinnecnnss 129 Materials py added section composite cross section creation 129 Stiffness calculation for Custom Parameters mode ono 132 xiv List of figures Figure 6 9 Figure 6 10 Figure 6 11 Figure 6 12 Figure 6 13 Figure 6 14 Figure 6 15 Figure 7 1 a Figure 7 1 b Figure 7 2 a Figure 7 2 b Figure 7 3 Figure 7 4 Figure 7 5 Figure 7 6 Figure 7 7 Figure 7 8 Figure 7 9 Figure 7 10 Figure 7 11 Figure 7 12 Values set in the code for the hold down WHT340 D4 40 with total E A A NA 134 Values set in the code for the bracket WBR100 B4 60 with total nailing c ncreteimber onene AA A A 134 Values set in the code for the distributed nailing with nail diameter of 4 mm and nail length of 30 a A A 134 Stiffness calculation for Standard MOde ccccccccccseesseessetetetntetenes 134 Design load carrying capacities calculation for Custom Stiffness mode Design load carrying capacities calculation for Standard mode 138 Building front views A
6. Finally the ETA allows manufacturers to place CE marking Conformit Europ enne on their products In the USA the American National Standards Institute ANSI recently approved ANSI APA PRG 320 2012 Standard for Performance Rated Cross Laminated Timber ANSI APA PRG 320 2012 2012 This Standard covers manufacturing qualification and quality assurance requirements for X Lam products Key stakeholders included X Lam manufacturers distributors designers users building code regulators and government agencies 20 Chapter 2 Generalities about timber and X Lam technology In general the production of cross laminated timber panels follows the following procedure e Selection of species The base species of timber used for X Lam panels depend on the region where it is manufactured For X Lam manufactured in Austria and Germany spruce is the main species used pine and larch can also be used on request X Lam plants in Canada are likely to use S P F spruce pine fir species Whilst production is yet to occur in Australia and New Zealand the timber species likely to be used is radiata pine e Timber laminates grouping Individual seasoned dimensional timbers are used generally softwood and usually finger jointed along their length to obtain the desired lengths and quality Individual timbers can be edged bonded together to form a timber plate before further assembly into the final panel e Adhesive application Gene
7. UNIVERSITA DEGLI STUDI DI PADOVA DIPARTIMENTO DI INGEGNERIA CIVILE EDILE E AMBIENTALE ICEA Corso di Laurea in Ingegneria Civile Tesi di Laurea Magistrale A Pre processor for Numerical Analysis of Cross Laminated Timber Structures LAUREANDO Alessandra Ferrandino RELATORE Prof Ing Roberto Scotta CO RELATORE Dr Antonia Larese De Tetto ANNO ACCADEMICO 2014 2015 Abstract ABSTRACT Cross laminated timber also known as X Lam or CLT is well established in Europe as a construction material Recently implementation of X Lam products and systems has begun in countries such as Canada United States Australia and New Zealand So far no relevant design codes for X Lam construction were published in Europe therefore an extensive research on the field of cross laminated timber is being performed by research groups in Europe and overseas Experimental test results are required for development of design methods and for verification of design models accuracy This thesis is part of a large research project on the development of a software for the modelling of CLT structures including analysis calculation design and verification of connections and panels It was born as collaboration between Padua University and Barcelona s CIMNE International Centre for Numerical Methods in Engineering The research project started with the thesis Una procedura numerica per il progetto di edifici in Xlam by Massimiliano Ze
8. different layers see Section 6 4 8 Each of the element properties parameters explained presents on the interface an abbreviated name that may be not perfectly clear for a matter of space at the interface 101 A pre processor for numerical analysis of cross laminated timber structures Anyway placing the mouse over the box corresponding to each of the parameters pop ups that explain their meaning will appear At the end of this step the elements Properties menu results as in Figure 5 37 E Properties O E Beam_prop Property type Beam Constitutive law Elastic Isotropic Material C14_beam Section type Rectangular Height 0 001 Width 0 001 EE Solid_prop Property type Solid Constitutive law Elastic Orthotropic Material C14_solid B P Shell_prop Property type Shell Constitutive law Elastic Orthotropic Material C14_shell Thickness 1 0 Angle 0 Number of layers 5 Thickness layer 1 0 2 Thickness layer 2 0 2 Thickness layer 3 0 2 Thickness layer 4 0 2 Thickness layer 5 0 2 Thickness layer 6 0 0 Thickness layer 7 0 0 Thickness layer 8 0 0 Thickness layer 9 0 0 Solid property Solid_prop Figure 5 37 Elements Properties end menu In this explanatory example only one property per element has been created in a real example it may be necessary to define more than one property per element to assign for instance a different beam section or different layer thicknesses t
9. Due to the light weight of the panels it is also common to use the building itself as a place to temporarily store panels It is also possible to assemble elements or modules of the building off site and deliver completed segments of the building to the site This speeds up the construction process even further Panels are lifted into place using pre inserted hooks e Flexibility in architectural implementation Versatility of X Lam technology comes from the fact that panels can be used for many different assemblies wall floor roof stairs etc just by varying the thickness X Lam construction system can be combined also with other timber structural systems such as light timber frames post and beam heavy timber system and glue laminated timber In addition X Lam elements are compatible with other building materials such as steel concrete and glass Compared to traditional light wood frame construction methods which rely on plywood sheathing over wood studs walls or rafters and beams roof the use of X Lam panels offers an alternative in the form of a single component that is load bearing and provides an aesthetically pleasing finished surface Depending on its intended use X Lam panels can be used for either visible or hidden construction applications Its ability to be used as either a panelised or a modular system makes it ideally suited for additions to existing buildings or their upgrade Good span to depth ratio allows shallow floors a
10. Figure 4 3 Difference in behaviour between a real and a modelled pane 67 Figure 5 1 Problem IV DES ECO A A ish eat Eds 71 Figure 5 2 GIO problem types TO de A ba 72 Figure 5 3 Xlam kratos command MEU accu sha auwabuecatacsaiueiiad cane Shitesns 72 Fig re 34 Gravi Wanin A A 73 Figure 5 5 Create E AAA A a 73 PUSIERA AA A aR 74 Figure 5 7 A A E 74 Figure 5 8 Copy menu for copying surfaces lt A AA NA 75 Figure 5 9 First and second surfaces A sty deahenatae scones vataaseatinins 76 Figure 5 10 First second and third SITES bs 76 Figur sAd End geomet y eiaa i oles O IN 77 xii List of figures Figure 5 12 Figure 5 13 Figure 5 14 Figure 5 15 Figure 5 16 Figure 5 17 Figure 5 18 Figure 5 19 Figure 5 20 Figure 5 21 Figure 5 22 Figure 5 23 Figure 5 24 Figure 5 25 Figure 5 26 Figure 5 27 Figure 5 28 Figure 5 29 Figure 5 30 Figure 5 31 Figure 5 32 Figure 5 33 Figure 5 34 Figure 5 35 CEOMENVADOS TA SA 78 Model properties METE a AS 79 C stom MODEM A da 80 AMES UVA od 81 Connection parameters MEU niece ronnie ceo 83 St ndard MORENA ae des dende 86 Gonnection MEU A E A 86 Hold down A cede Atvonta ted cated Aina heaters as oties 87 Brackets and distributed nailings database cccccccccccecsceesseesteteteteteeeees 88 Proper PUEDES A A RE 8 amp 9 Prop rty2 POROS A AA 90 Custom AMERICAS A Ai 91 Custom menu with all properties and their MOde c c cccccce
11. M The characteristic load carrying capacities of the single hold down and single bracket or single nail are already set in the code as shown in Figures 6 9 6 10 and 6 11 Figure 6 15 shows the section of the code which calculates the design load carrying capacities of the connections to write them in the More Connections file nchdl SRk1 kmod nchd2 SRk2 skmod expr nc Rk 5kmod gam Figure 6 15 Design load carrying capacities calculation for Standard mode 138 Chapter 7 Modelling of a complex structure CHAPTER 7 MODELLING OF A COMPLEX STRUCURE This Chapter will be a presentation of the modelling of an X Lam structure case study starting from the preliminary design phase up to the actual modelling in GiD The goal is indeed to show how the new problem type and the calculation work for a complex structure Thus the first sections focus on the preliminary design necessary for the choice of panels and connections Thereafter the modelling in GiD will be presented by means of the new problem type similarly to Chapter 5 but in a briefer manner and mostly focusing on the engineering point of view Finally the results of the analysis are displayed 7 1 Example introduction The structure that will be presented in this Chapter consists of a two storey building It will be submitted to seismic action and analysed with an equivalent static analysis even if it is not a regular
12. N m for the configuration A taking into account only the storeys seismic forces cccccccecsceeteteteteteteeeetnseenneteses 171 xvi List of figures Figure 7 29 Figure 7 30 Figure 7 31 Figure 7 32 Figure 7 33 Figure 7 34 Figure 7 35 Figure 7 36 Figure 7 37 Shell Force Syy contour N m for the configuration B ooo 171 Shell Force Sxx contour N m for the configuration B ooo 172 Shell Force Szz contour N m for the configuration B taking into account only the storeys seismic forces ooooooninnninnnnncononicanccanacioncncancnn no 172 Z Reaction vectors display for the configuration A oooionniinininnnininco 173 Z Reaction vectors display for the configuration A taking into account only the storeys seismic OPC ES nas ihiudead naavmen suerte upyieiiatetens 173 Z Reaction vectors display for the configuration B oooonnmonniinnnninnn 174 Z Reaction vectors display for the configuration B taking into account Only the storeys seismic JON CES ci oars Meine in 174 X Reaction vectors display for the configuration A oooionninninnnnninnn 175 Y Reaction vectors display for the configuration Boonic 175 xvii List of tables LIST OF TABLES Table 2 1 Load duration classes according to UNI EN 1995 1 2009 ooo 11 Table 2 2 Values of kmoa according to UNI EN 1995 12 2009 ooooionccicinccinnionccnno 13 Table 2 3 Recommended partial factors yu for material properties and res
13. TE MIX A N Lines SemiStructured Assign number of cells Cartesian b 5 Volumes Boundary layer Center structured Set cent Quadratic type aa Element type Mesh criteria Reset mesh data Draw gt Generate mesh Ctri g Erase mesh Edit mesh Show errors View mesh boundary Create boundary mesh Mesh quality Mesh options from model Figure 5 50 Structured mesh selection To use a structured mesh it can be selected from the top command line Mesh Structured Surfaces Figure 5 50 and then size or number of cells can be set Selecting for example Assign size the same or a different mesh size can be assigned to each surface then the mesh can be generated and the window of Figure 5 49 will appear In this case 1t is important to select Get meshing parameters from the model 112 Chapter 5 Pre processor and interface tutorial with reference to Figure 5 49 because the mesh is not a default unstructured one but a structured mesh with the assigned size For the example a mesh size of 0 5 m will be used which is not a refined mesh as the goal is not the calculation of the x lam panels but only to show how the pre processor works This will be more easily understood if fewer elements are present In general the mesh size depends on how much detailed the analysis will be The resulting geometry mesh showing also the GiD ID labels of lines an
14. and Orthotropic Even if the X Lam panels are made by an orthotropic material someone might prefer to model them with an isotropic material this is the reason why the material menu is predefined with isotropic material too In this case only two values are set the Young modulus and the Poisson ratio The former is set equal to Eo for any material type the latter is set to zero because of the particular mode of the panels manufacture as a matter of fact the tables are not perfectly disposed side by side and glued the ones with each other longitudinally on the short side 109 A pre processor for numerical analysis of cross laminated timber structures The Orthotropic section is divided into different sections the first one requires the three Young modulus and the three Poisson ratios the second one requires some strength values and the last section requires the characteristic and mean values of the density For any default material all the values of its properties are already set by means of the criteria mentioned in Sections 2 3 and 4 2 Gy c14 General Description Timber C14 Density 3433 5 EH Structural EH Elasticity E __ Isotropic Young modulus 7e 9 Poisson ratio 0 Ef Orthotropic Young modulus E11 7e 9 Young modulus E22 0 23e 9 Young modulus E33 0 23e 9 _ Poisson ratio v12 0 27 Poi
15. distributed nailing is disposed the number of nails multiplied by the number of brackets if more than one bracket are disposed Similarly the stiffness of the hold down can be calculated by multiplying Kser by the total number of nails of the connection meaning the product between the number of nails of each hold down and the number of hold down However in this case the stiffness inserted in the model does not coincide with the stiffness value suggested by the code This comes from the difference in behaviour under the action of horizontal forces of a single modelled panel compared with the same in a real situation see Section 4 3 2 7 3 Connections resistance The design resistance of a connection Ra load carrying capacity can be calculated as 39 A pre processor for numerical analysis of cross laminated timber structures Ry Ra Kmoa Yu where Rx is the characteristic value of load carrying capacity ym is the partial factor for a material property according to Table 2 3 kmoa is the correction factor taking into account the effect of the load duration and moisture content of the timber according to Table 2 2 Assuming that the characteristic load carrying capacity of a connection is governed by the number of fasteners then Rk Neff Fv rk being Fy rx the characteristic load carrying capacity of a single fastener and neft the effective number of fasteners of the connection itself This assumpt
16. 0 0 3 2 0 3 6 kN m 1 2 a BIB j un kN gl X Lam panel 20 cm g2 ceiling insulating roof j q overload snow height lt 1000 m 1 5 kN TOT 4 A F O 3 a gl X Lam panel 10 cm Figure 7 3 Loads analysis The seismic loads lead from the combination required by D M 14 01 2008 New Technical Standards for Construction in Section 2 5 3 according to which they are calculated as E G1 G P WV210x1 V220x2 where Qx represents the overhead for the slabs of residential use and Q 2 the overload on the roof the component P is in all cases equal to zero the seismic action E is calculated in Section 7 2 3 Without deepening too much about the coefficients w2 142 Chapter 7 Modelling of a complex structure provided by the code for the snow overload w2j 0 while for the overload of a residential building y 0 3 For the walls the loads acting on a unit width are considered shown in Figure 7 4 The total loads on the wall are indicated with a white arrow they result gr 9 0 9 0 4 5 4 5 27 KN dx 4 5 6 0 10 5 KN g 3m 3 kN mq 9kN q 3m 1 5 kN mq 4 5kN gr 3 m 1 5 kN mq 45kN g 3m 3kNimg 9kN q 3m 2kN mg 6kN gr 3 m 1 5 kN mqg 4 5 kN Figure 7 4 Loads representation on the geometry For the static preliminary design the load charts provided by manufacturers Rothoblaas are used these are only for preliminary design
17. 100 N m while the other ones are calculated in two steps First the slip modulus per shear plane per fastener for timber to steel connections is calculated as p4 q 8 Kser 2 ser 30 where Pm is the density of the panel and d is the nail diameter of the hold down or the bracket or distributed nailing Then the axial stiffness of the hold down and the shear stiffness in the plane of the panel are calculated as follows The axial stiffness of the two hold down Ka Kser total number of nails 2 The modelled stiffness is multiplied by two times the real one because of the different behaviour under the action of horizontal forces of a single modelled panel compared with the same in a real situation see Section 4 3 The shear stiffness in the plane of the panel the shear stiffness of the bracket or distributed nailing 131 A pre processor for numerical analysis of cross laminated timber structures Ka Kser total number of distributed nails Figure 6 8 shows the section of the code which calculates the stiffness to write them in the connection info file expr Dens1ty 9 81 Tah TensionDiameterl 100 expr Density 9 81 Ls TensionDiameter2 1006 expr Density 9 81 1 5 ShearDiameter 1006 expr kserTensionl TensionNumberNails1 expr kserTension2 TensionNumberNails2 expr kserShear ShearNumbernails Figure 6 8 Stiffness calculation for Custom Parameters m
18. 150 L5s 182 LSs 165 L55 asia 209 1762 Figure 7 5 Preliminary design table for single span floors Rothoblaas 144 Chapter 7 Modelling of a complex structure wm 2 External walls a la accordance with 791 59 DIN 082 COOS andr EN 1208 1 1 2008 Permanent impoced load load a m KN KN Re 1020 CEEE 20 00 67 C3z wc 30 00 20 00 40 00 sowo sscas 67 C3z 30 00 40 00 50 00 83 C3s 0 00 10 00 20 00 67 C3z 30 00 40 00 40 00 50 00 83 C3z coco Figure 7 6 Preliminary design table for external walls Rothoblaas 7 2 2 Seismic design of X Lam walls and slabs In order to calculate the seismic weights the Area and Perimeter of the ground and first floor are first determined resulting ground floor A 108 m2 Pwats 60 m first floor A 72 m Pwatis 42 m Then the seismic weights afferent to the floor and the roof depending on their afferent heights Figure 7 7 can be calculated as W Area seismic load Perimeter afferent height total walls load In the case of the floor it results W p 108 3 64 60 3 1 5 658 8 kN 145 A pre processor for numerical analysis of cross laminated timber structures w p W p Area 658 8 108 6 1 kN m In the case of the roof it results W r 72 3 0 42 1 5 1 5 310 5 kN w p We Area 310 5 72 4 3 kN m ROOF N 3 XN Ny N N A N Ae hs k Nx N x Xx N N N N W
19. 162 Chapter 7 Modelling of a complex structure nodes The same lines belonging to the slabs are modelled with all the stiffness equal to infinite Continuity connection property Thus to simulate that the slab is not really infinitely rigid An example of this modelling is represented by line 36 belonging to surfaces 6 and 31 shown in Figure 7 18 As belonging to surface 31 which represents the slab line 36 has the Continuity connection property conversely as belonging to surface 6 which represents the wall it has the property shown in Figure 7 17 In the case of surfaces which are actually a single panel but they are represented by two different surfaces the hold down is only disposed on one side and not the other corresponding to the side that flanks the other surface An example of this modelling is represented by lines 4 and 5 belonging to surfaces 4 and 5 respectively shown in Figure 7 18 The two surfaces are actually a unique wall yet they are drawn with two different surfaces to identify the centre of gravity of the first storey This means that actually there is a hold down on the left side of line 4 on the point with less coordinate respect to the x axis and one on the right of line 5 on the point with greater coordinate respect to the x axis Figure 7 19 shows the connection properties of the two lines line 4 has only hold down 1 with less coordinate while line 5 has only hold down 2 with greater
20. 2013 has been submitted to CEN members for validation and it will lead to the emergence of an EN code A subcommittee of experts within the commission CEN TC250 is working currently on the integration of the X Lam material in the UNI EN 16 Chapter 2 Generalities about timber and X Lam technology 1995 1 1 2009 In particular the main features that must be evaluated for the release of ETA are e load bearing capacity and stiffness relative to mechanical actions bending tension and compression shear determination of resistance to bearing stress e protection against noise e energy saving and heat retention e hygiene health and environment Therefore this certificate which also shows the class of the slats of which the panel is made provides all the mechanical features necessary for the structural calculation 2 4 Generalities about cross laminated timber Cross laminated timber X Lam or CLT is an engineered wood product fabricated by adhering and compressing wood layers called lamellae in perpendicular grain orientations to form a solid panel Wood layers are glued together on their wide faces and usually on the narrow faces as well X Lam technology was invented and developed in central Europe in the early 1990 s and since then it has been gaining increased popularity in residential and non residential applications The number of buildings constructed using X Lam panels as the main structural system
21. 3 Connections TESIS iii dass 39 2 8 X Lam structural application 45 vii A pre processor for numerical analysis of cross laminated timber structures 3 CHAPTER 3 GENERAL ABOUT GID KRATOS TCL AND PYTHON a oars te ae Sc ass a eae Mat A oink thea Ma Bega 49 Deli GID Processo O A A A eens Aa 49 3 1 1 Interaction of GiD with the calculating module oooonccnnconncnncnnnncconnccnss 49 3 1 2 GID PRE OCESS de 52 3 1 3 CD Post pr CES iii laos 52 A a a a Sata Sane es a ate Eei 53 3 2 1 TAMOS AL VAMOS ona Sede area dacs a a a a 55 3 3 GID Kratos o 55 3 4 A 56 Rs a a a a aa 58 4 CHAPTER 4 MODELLING STRATEGY OF X LAM BUILGINGS AND CONVENTIONS 00000ooccccccccccscsssceseteteteteteesenees 61 4 1 Modelling strate gy a 6l 4 2 Modelling of X Lam panels da 62 4 3 Connections modelling ii td 65 4 4 Units of measurement CON CMI a 68 4 5 Gravity CON yent ON es a ni E E A EAE RTS ac 68 5 CHAPTER 5 PRE PROCESSOR AND INTERFACE TUTORIAL E E A E E TE 69 A troduction nen aa e e Sean a i asa A aaa 69 5 2 Example A a a a E R here tule ge 70 5 3 Problem type lec a 71 54 Geometry Creation setinin init a a A 73 5 5 Model properties definition ts 79 5 5 1 Connection properties creation ooooooconoccnococonoconnnonononnnccono cono nonn nono nc co ncnnnno 79 5 5 2 Connection properties assignation ooooonnncoconnconcnooncconncconoconc nono ccnnncconocnnno 92 5 5 3 Elements properties Cro a 98 5 5 4 Elements properties assignatiON oooc
22. My rx is the characteristic fastener yield moment B is the ratio between the embedment strength of the members Fax rk is the characteristic axial withdrawal capacity of the fastener t by S a Ak 2009 Figure 2 14 b Failure modes for timber and panel connections with double shear UNI EN 1995 1 1 2009 42 Chapter 2 Generalities about timber and X Lam technology The characteristic load carrying capacity of a steel to timber connection depends on the thickness of steel plates Steel plates of thickness less than or equal to 0 5d are classified as thin plates and steel plates of thickness greater than or equal to d with the tolerance on hole diameters being less than 0 1d are classified as thick plates The characteristic load carrying capacity of connections with steel plate thickness between a thin and a thick plate should be calculated by linear interpolation between the limiting thin and thick plate values ma 3 Figure 2 14 c Failure modes for steel to timber connections UNI EN 1995 1 1 2009 The characteristic load carrying capacity for nails bolts dowels and screws per shear plane per fastener in case of steel to timber connections should be taken as the minimum value found from the following expressions with reference to the Figure 2 14c For a thin steel plate in single shear 0 4 fhi ti d a Fy Rk min A E A j i 15 2 My rx fax d ae b For a thick steel plate
23. and listed in the tree The file connection info provides a matrix necessary for the xlam driver application which shows the list of the new lines IDs the new surfaces IDs to which the lines belong and their stiffness connection properties For the example described in Chapter 5 the file connection info results as shown in Table 6 2 It is noticeable that the lines belonging to more than one surface appear in the table Table 6 2 more times For example line 6 former line 5 appears as belonging to surfaces 1 and 3 respectively former surfaces 2 and 4 This is foregone if you remember that the user assigns to each line belonging to each surface a connection property therefore if a line belongs to more than one surface he assigns more connection properties which in general will be different The third column reference is made to Table 6 2 shows the whole stiffness of the connection property meaning eight stiffness not only the ones set by the user or resulting from the parameters set by the user In addition to the five stiffness visible at the interface the last three values exhibit the rotational stiffness which are always set to a small value equal to 100 N m In case of Continuity connection property all the 120 Chapter 6 Pre processor programming detail stiffness are set to a very high value equal to 10 N m the only two lines that do not have this connection property exhibit differen
24. c Figure 2 8 Typical parallel wall to wall X Lam connections a Connection with an internal spline b d Connection with a surface spline c Connection with a half lapped joint d Tube connection system FPInnovations 2013 e Internal splines or strips For formation of this connection type single or double wooden splines strips made of structural composite lumber such as laminated veneer lumber LVL plywood or thin X Lam are used Connection between the spline or splines and the panel edges can be established using self tapping screws wood screws or nails The advantage of this detail is that it provides a double shear connection and resistance to out of plane loading However special attention is required due to necessity of accurate profiling for the fitting of different parts on a construction site e Surface splines or strips This fairly simple connection detail can be established quickly on site but it only provides single shear connection Since two sets of screws are used which results in doubling the number of shear planes resisting the load a better resistance can be achieved using this detail Panel edges are profiled from one side for a single surface spline or from both sides for a double surface spline Similarly as in the case of internal splines structural composite lumber elements are used for strips Traditional fasteners such as nails self tapping screws wood screws and lag screws can be used for
25. can be inserted in the interface is explained in detail in Section 5 5 3 64 Chapter 4 Modelling strategy of X Lam buildings and conventions 4 3 Connections modelling The kinematic behaviour of the connections and their stiffness and resistance calculation have already been described in Chapter 2 However the modelled hold down stiffness deserves special care because is not the same of the real one suggested by the code This comes from the difference in behaviour under the action of horizontal forces of a single modelled panel compared with the same in a real situation A real panel subjected to a horizontal force at the top because of a seismic action neglecting the effect of horizontal translation tends to rotate around its edge This happens because the panel is in contact with the soil and the hold down does not resist to compression The interaction between the panel and the soil can be considered a contact problem Alternatively the problem can be considered non linear for the material considering the hold down as a material resistant to compression and the soil as a material non reactive to traction The use of linear elastic constitutive law for the springs in the model leads to the impossibility of simulating the problem in its own non linearity Therefore a modelled panel subjected to the same horizontal force rotates around the mid point of the bottom side This difference in behaviour between real and mode
26. capacity due to the rope effect should be limited to following percentages of the Johansen part Round nails 15 Square and grooved nails 25 Other nails 50 Screws 100 Bolts 25 Dowels 0 2 8 X Lam structural applications This Section presents an introduction to the X Lam construction systems and their applications There are several ways to design and construct X Lam buildings They all differ in the way the load carrying elements panels are arranged the way the panels are connected together and by the type of wood and non wood based materials used The most common forms of X Lam construction systems are platform construction and so called balloon construction FPInnovations 2013 Platform construction in X Lam technology is a system where the floor panels rest directly on top of wall panels therefore forming a platform for subsequent floors This is the most commonly used type of structural system for X Lam assemblies for multi storey buildings This includes buildings constructed with X Lam panels only or combining the panels with other types of wood based products for example glulam There are several advantages to this system such as quicker erection of upper storeys possible application of simple connection systems and well defined load path Balloon construction is a type of structural system where the walls continue for a few storeys with intermediate floor assemblies attached to those wa
27. coordinate The brackets are calculated as usually depending on the length of the line the distributed axial stiffness and the orthogonal shear stiffness are set to a small value equal to 100 N m Mode Stiffness EF Stiffness Axial stiffness HD1 0 Axial stiffness HD2 0 Distributed axial stiffness 6 71e 7 Distributed parallel shear stiffness 1 0e 12 Distributed orthogonal shear stiffness 1 0e 12 Rk HD1 0 Rk HD2 0 Rk distributed 2 68e 4 Correction factor kmod 1 1 Material security coefficient 1 3 Figure 7 17 Connection property of line 36 belonging to surface 6 163 A pre processor for numerical analysis of cross laminated timber structures Figure 7 18 Example of line 36 belonging to wall surface 6 and slab surface 31 Example of lines 4 and 5 belonging to walls surfaces 4 and 5 which are actually a single wall E 44 E55 Mode Stiffness h Mode Stiffness Eb Stiffness Er Stiffness La Axial stiffness HD1 3 49e 8 E Axial stiffness HD1 0 i E Axial stiffness HD2 0 Axial stiffness HD2 3 49e 8 po Distributed axial stiffness 100 Distributed axial stiffness 100 Distributed parallel shear stiffness 6 04e 7 gt Distributed parallel shear stiffness 6 04e 7 Distributed orthogonal shear stiffness 100 i Distributed orthogonal shear stiffness 100 Rk HD1 2 01e 5 Rk HDA 0 e Rk HDZ 0 Rk HDZ 2 01e 5 Rk distributed 2 68e 4 gt Rk distributed 2 6
28. d4 60 WHT340 part nail d4 40 WHT340 part nail d4 60 WHT440 tot nail d4 40 WHT440 tot nail d4 60 WHT440 part nail d4 40 WHT440 part nail d4 60 WHT540 tot nail d4 40 WHT540 tot nail d4 60 WHT540 part nail d4 40 WHT540 part nail d4 60 WHT620 tot nail d4 40 WHT620 tot nail d4 60 WHT620 part nail d4 40 WHT620 part nail d4 60 Figure 5 19 Hold down database e Number of hold down HD1 this is the number of hold down for the first hold down e Hold down 2 this is the type of the second hold down which can be selected by an already default database equal to the one of the first hold down The hold down with greater coordinate on the x or y axis is considered as second hold 87 A pre processor for numerical analysis of cross laminated timber structures down in order to distinguish it from the first one As for the custom menu the two hold down are distinguished to leave the possibility of disposing two different types of hold down to one and the other side of the panel or to put only one of them in case of two surfaces which are actually a unique panel see Section 7 3 3 Number of hold down HD2 this is the number of hold down for the second hold down Bracket or distributed nailing this is the type of bracket or distributed nailing which can be selected by an already default database The database has been created following the Rothoblaas catalogue and distinguishing between total and partial nailing and concrete timber
29. evolution of a result of a point across all time steps of an analysis line graph boundary graph and point analysis in which a result can be plotted against another one for a point and optionally for all time steps 3 2 Kratos solver lt aaTos y MULTHHYSICS Kratos is a framework for the implementation of numerical methods for the solution of engineering problems It is written in C language and is designed to allow for collaborative development by large teams of researchers focusing on modularity as well as on performance The Kratos features a core and applications approach where standard tools databases linear algebra search structures etc come as a part of the core and are available as building blocks in the development of applications which focus on the solution of the problems of interest Its ultimate goal is to simplify the development of new numerical methods Kratos provides several tools for easy implementation of finite element applications and a common platform providing effortless interaction between them It has an innovative variable base interface designed to be used at different levels of abstraction and implemented to be very clear and extendible It also provides an efficient yet flexible data structure which can be used to store any type of data in a type 53 A pre processor for numerical analysis of cross laminated timber structures safe manner The Python scripting language is used t
30. fact that for lower qualities the knots determine the resistance while for higher qualities it is the wooden base quality to be decisive Thus for higher classes the dependence of the resistance on the load duration will be similar to that of the net wood while for lower classes the high defectiveness will be so decisive as to reduce the contribution to the decrease of resistance for the load duration due to the base material Indeed the presence of knots generates for short duration loads strong peaks of tension concentration elasticity of the material that will determine the level of resistance in the short term Conversely for long term loads the resistance relative to the timber itself would tend to decrease but the concentrations of tensions around knots viscosity of the material tend to be blunted by acting in a manner favourable to the resistance Therefore thanks to these two factors counteracting each other the gap between resistance for short and long term loads gets down Moreover the dependence on the moisture content should be considered Indeed it was found that for the worst qualities meaning low resistance values the influence of the moisture content in the timber appears more limited than in net wood The influence of moisture content on the reduction of resistance results less important the poorer the material Potentially the high defectiveness becomes so crucial to flatten the differences in resistance betw
31. has seen exponential growth in the last decade and market share for X Lam construction is expected to continue to escalate in the future The European experience showed that X Lam construction can be competitive particularly in mid rise and high rise buildings due to its easy handling during construction and a high level of prefabrication Recently X Lam was introduced also overseas in North America Australia and in New Zealand A number of production plants have been established or they are proposed to be built in aforementioned countries 17 A pre processor for numerical analysis of cross laminated timber structures E hex ieee GS WW ep e NA ITA Wy MAN ES SWE ee WAN WE gt Sa TE Figure 2 3 Cross laminated timber panel ETA 06 0138 2006 Cross laminated timber panels are manufactured to customized dimensions panel sizes vary by manufacturer Lamellae thicknesses are ranging between 10 and 40 mm and are produced of technically dried quality sorted and finger jointed planks Panel thickness is usually in the range of 50 mm to 300 mm but panels as thick as 500 mm can be produced Production sizes range from 1 2 m to 3 m in width and 5 m to 16 5 m in length limited by transportation restrictions or the length of a production line The mechanical properties of X Lam panels are provided by each producer due to the different cross section configurations and due to different properties of the single l
32. in single shear 43 A pre processor for numerical analysis of cross laminated timber structures fink tid c d la 4My Rk Fax Rk d Fy Rk min fakti y 2 hdt 7 d Fay Rk 2 3 2 Mynx fund e 4 For a steel plate of any thickness as the central member of a double shear connection fhrxtid 6 mae AA Fy Rk min fatal hadt zaa g 2 3 2 My rx fh1x d si h For thin steel plates as the outer members of a double shear connection 0 5fh2kt2d j Fy rk min ne Bey i i 15 2 My rx Shox d as k For thick steel plates as the outer members of a double shear connection froxtod Fy Rk min Se ee 2 3y My Rk fhok d SAE m where Fy rx is the characteristic load carrying capacity per shear plane per fastener fhx is the characteristic embedment strength in the timber member t is the smaller of the thickness of the timber side member or the penetration depth t2 is the thickness of the timber middle member d is the fastener diameter My rk is the characteristic fastener yield moment 44 Chapter 2 Generalities about timber and X Lam technology Faxrx is the characteristic withdrawal capacity of the fastener In all expressions of Fv rk above the first term on the right hand side is the load carrying capacity according to the Johansen yield theory while the second term Fax rk 4 is the contribution from the rope effect The contribution to the load carrying
33. menu 5 5 5 Loads and boundary conditions assignation The assignation of loads and boundary conditions is the same of any GiD problem type Hence this tutorial will not present it too extensively its description will be limited to showing Figure 5 43 and briefly explaining the menu H Loads W Self weight EHI Load W Over Points W Over Lines Over Surfaces 72 Moment Load 2 Over Points EHW Pressure Load Over Lines Over Surfaces E E Boundary conditions W Displacements WX Rotations Figure 5 43 Loads and Boundary conditions menu The Loads menu contains different types of loads that can be assigned the self weight a generic load a moment load and a pressure load The self weight can be assigned to points lines surfaces and volumes clicking twice on it there is the possibility to choose one of these geometrical entities and then assign 105 A pre processor for numerical analysis of cross laminated timber structures the load to the type of selected entity remember that it is set so that the gravity is on Z The generic load can be assigned to points lines and surfaces there are three sub menus which allow to assign a different value of force in x y and z direction to each type of entity The moment load can be only assigned to points there is a sub menu which allows to assign a different value of moment in x y and z direction to the points The pre
34. number next to which the surfaces end continuing up to their end 6 4 Files writing Many different files are written by the code some of them useful for x am driver application and others useful for the planned post process Because of the creation of these files in the code when the calculation is launched the processor automatically generates the files that can be used as data by the x am driver or by the post process In the following sections all these files will be analysed in order to understand what exactly the processor is doing with the information given by the user when he draws the geometry and assigns the elements and connection properties Additionally the files associated to the example of Chapter 5 will be shown to better understand what they provide graphically 118 Chapter 6 Pre processor programming detail 6 4 1 Geometry info The file geometry info provides a matrix necessary for xlam driver application which relates old and new ID of surfaces and lines After renumbering the surfaces and lines with the criteria described in Section 6 3 a file showing the list of the old and new ID of surfaces and lines is written For the example described in Chapter 5 the file geometry info results as shown in Table 6 1 Table 6 1 Geometry info file In order to understand the changes about the surfaces the first three rows of Table 6 1 can be analysed The first surface has been
35. of the problem This example introduces creation manipulation and meshing of the geometrical entities used in GiD To make the comprehension simpler it will be explained with the help of images adapted from the GiD interface which enables to avoid misunderstandings and allows repeating the same example with the only use of the manual without need of other basic knowledge The example presented in this tutorial consists of a simple geometry of 4 panels not a whole X Lam structure Since the goal is not the analysis but the explanation of the problem type and to allow a better understanding a trivial geometry will be used Thus the main aim is to understand the main features of the problem type without burdening the description and avoiding misunderstandings It is clear that the problem type xlam kratos works in the same way when applied to a more complicated problem like a real X Lam structure For this reason a very simple example not corresponding to a real structure is now displayed conversely a more complex example will be presented in Chapter 7 70 Chapter 5 Pre processor and interface tutorial 5 3 Problem type selection GiD is an evolving program meaning that many different versions are available from the official website it is always recommended to download the last one because any updating is an improvement of the previous one Once opened the desired version of GiD the first step is the selection of t
36. or timber timber for any type of bracket and identifying different lengths of nails for the distributed nailing it is shown in Figure 5 20 WEBR100 tot nail d4 60 conc tim WBR100 part nail d4 60 conc tir WBO100 tot nail d4 60 conc tirr WBO100 part nail d4 60 conc ti WBR100 tot nail d4 60 timb tim WEBR100 part nail d4 60 timb tir WBOL100 tot nail d4 60 timb tirr WBO100 part nail d4 60 timb tir diameter 4 length 30 diameter 4 length 35 diameter 4 length 40 diameter 4 length 45 diameter 4 length 50 diameter 4 length 60 diameter 4 length 70 diameter 4 length 80 Figure 5 20 Brackets and distributed nailings database Number of brackets or distributed nails this is the number of brackets or distributed nails of the shear connection Panel density this is the density of the panels that the connection should joint in N m This density will be also introduced in the definition of the material see Section 5 7 but it should be set here to enable the calculation of the connection stiffness by the processor 88 Chapter 5 Pre processor and interface tutorial e Correction factor Kmoa this is the correction factor taking into account the effects of load duration and moisture content on the timber strength which is prescribed by the code UNI EN 1995 1 1 2009 see Table 2 2 e Material security coefficient this is the partial factor for a material property ym which is prescribed by the code UNI EN 1995 1 1 2009 see Tabl
37. removed before the assignation of the connection properties to the lines see Section 5 5 2 so the list of old surfaces IDs which are the ones defined by default by GiD does not contain the ID number one To restore this jump in number for which the surfaces begin directly from the number two the surfaces IDs are renumbered starting from one up to three which is the total number of surfaces It is clear that if no surface had been deleted the new surfaces IDs would coincide with the old ones 119 A pre processor for numerical analysis of cross laminated timber structures Relatively to the changes about the lines lines 1 and 4 have been removed from the geometry see Section 5 5 2 so the list of old lines IDs which are the ones defined by default by GiD does not contain the IDs 1 and 4 Moreover the list of old lines IDs starts from the number two The lines IDs are renumbered starting from four because the surfaces are three and all the numbers are subsequent up to twelve that is equal to the sum of the number of surfaces and the number of lines Notably even if no line had been deleted the new lines IDs would still be different from the originals because they would start from the total number of surfaces 6 4 2 Connection info For any surface the lines belonging to them are known and listed in the tree of the Surfaces menu accordingly the connection properties of the lines assigned by the user are known
38. set as default Connection Mode Custom Custom Connections E Custom Property Continuity connection Stiffness Propertyl Mode Stiffness Stiffness Connection parameters El Property2 Mode Stiffness Stiffness Connection parameters Surfaces Figure 5 23 Custom menu with all properties The final custom menu with all the properties and their modes selected appears as in Figure 5 24 Connection Mode Custom Custom Connections E Custom Property Continuity connection Stiffness Propertyl Mode Stiffness _ EJ Stiffness Connection parameters Property2 Mode Parameters Stiffness Connection parameters Surfaces Figure 5 24 Custom menu with all properties and their mode 91 A pre processor for numerical analysis of cross laminated timber structures 5 5 2 Connection properties assignation The end section of the connection properties menu consists on the menu Surfaces on which we can focus to then understand how to assign the connection properties The menu Surfaces shows a list of all the surfaces of the geometry and for any surface the belonging lines the lines that belong to more than one surface are shown more times as belonging to the different surfaces they appertain In this example for the geometry created before the menu Surfaces is shown in Figure 5 25 Figure 5 26 shows the geometry with its ID labels i
39. the interior which provides additional aesthetic attributes The panels are used as prefabricated building components which can speed up construction practices or allow for off site construction While X Lam panels act as two way slabs the stronger direction follows the grain of the outer layers For example when used for walls X Lam is installed so the boards on the outer layer of the panel have their grain running vertically When panels are used in floor and roof applications they are installed so the boards on the outer layer run parallel to the span direction Panels may be connected to each other with half lapped single or double splines made from engineered wood products Dowel type mechanical fasteners such as nails screws dowels and bolts or bearing type e g split rings shear plates connectors are used to connect X Lam panels Typical X Lam connections will be presented more in detail in Section 2 7 of this Chapter 2 5 X Lam panels manufacturing Currently there are no standards in Europe that cover X Lam manufacturing or installation However various X Lam products have a European Technical Approval ETA that allows manufacturers to place CE marking The approval process includes preparation of a European Technical Approval Guideline ETAG that contains specific requirements of the product as well as test procedures for evaluating the product prior to submission to the European Organization for Technical Approvals EOTA
40. the only purpose of illustrating the assignation The two properties are named Property and Property2 and their parameters are shown in Figures 5 21 and 5 22 Stiffness Connection parameters Properties Nail diameter HD1 0 004 Y Total number of nails HD1 30 x Nail diameter HD2 0 004 X Total number of nails HD2 30 x Distributed nail diameter 0 004 Total number of distributed nails 6 Panel density 3433 5 x Fv Rk per nail HD1 2000 z Fv Rk per nail HD2 2000 Fv Rk per nail distributed 2000 Y Correction factor kmod 11 Material security coefficient 1 3 7 j Ok Cancel Figure 5 22 Property2 parameters Once defined the two properties that will be used in addition to the Continuity connection the custom menu appears as in Figure 5 23 For every new property defined below the name is the mode to which the connection property belongs it can be Stiffness or Parameters As default the mode is set on Stiffness so the first property does not need any modification of the mode but for the second property the mode should be changed clicking on Mode below its 90 Chapter 5 Pre processor and interface tutorial name and selecting Parameters The selection of the mode is very important because if it is not selected correctly the parameters used for the analysis would not be the desired ones but always the ones of the mode Stiffness since this is
41. the wood in the plane of the panel to an insignificant minimum and considerably increases the static load carrying capacity and dimensional stability e Durability Generally due to the quick erection time of X Lam based systems the short term exposure of X Lam panels to weather is not an issue Short term and occasional exposure to water will not have long term effect on X Lam panels During construction wall elements may be protected with vapour barriers or the building s scaffolding can be wrapped to form this protection Other strategies could be employed such as coating system for the construction period only Long term exposure of X Lam panels to weather is not recommended e Sustainable and environmental friendly building material As with all wood products the benefits of X Lam include the fact that wood grows naturally using solar energy and it is the only major building material that is renewable and sustainable It also has a low carbon footprint because the panels continue to store carbon absorbed during the tree s growing cycle and because of the greenhouse gas emissions avoided by not using products that require large amounts of fossil fuels to manufacture Harvesting from sustainably managed forests contribute to efficient use of the resource Many of the recent structures built from CLT benefit from these environmental considerations For example two mid rise residential projects in London used the fact that wood stores carb
42. them as C 4_ beam C14 solid and C14 shell These are the three materials selected in the definition of the elements properties importantly the materials should be created earlier otherwise they will not appear in the list of materials of the elements properties 5 8 Geometry meshing Once all the properties have been defined lines and surfaces should be meshed in order to launch the calculation In general the type of mesh can be selected from its menu but in this case a mesh with quadrilateral element type is set as default this is because the thick shell only works with linear quadrilateral mesh As default it is also set that the lines are meshed too while in general this would be selected from the mesh criteria menu With all these simplifications the only thing to decide is if using a structured or unstructured mesh As default GiD sets an unstructured mesh This implicates that selecting from the top command line Mesh Generate mesh or using the shortcut Ctrl g an unstructured mesh will be generated and a window for the selection of the mesh size Figure 5 49 will appear 111 A pre processor for numerical analysis of cross laminated timber structures Mesh generation Enter size of elements to be generated bas y Get meshing parameters from model OK Cancel Figure 5 49 Mesh generation window Mesh Calculate Kratos Help Unstructured gt
43. time surfaces lines and points could be useful for instance when removing surface 1 lines 1 and 4 and point 1 which do not belong to any other surface will be removed as well de Y A LS Ele b 4 aod G ho 2 r MIE Figure 5 27 Delete shortcut 93 A pre processor for numerical analysis of cross laminated timber structures Thus selecting surface lines and point previously mentioned they can be all removed at the same time Following removal of these entities the list of surfaces and lines previously shown changes surface 1 will not appear as well as lines 1 and 4 Obviously lines 2 and 3 have not been removed because they also belong respectively to surfaces 3 and 2 GiD has a hierarchy of entities for which lines cannot be removed if all surfaces containing them have not been removed first Likewise the same happens for lines and points and for surfaces and volumes The new list of surfaces and lines is shown in Figure 5 28 while the new geometry is shown in Figure 5 29 E Surfaces Surf 2 E Line 3 Connection Continuity_connection Er Line 7 Connection Continuity_connection E Line 5 Connection Continuity_connection Er Line 6 Connection Continuity_connection Surf 3 E Line 2 Connection Continuity_connection E Line 6 Connection Continuity_connection E Line 8 Connection Continuity_connection Er Line 9 Connection Continuity_connection Surf 4 E Line 10 Conn
44. 00049652 0 0062255 0 0074857 0 008746 0 010005 0011256 siop 1 Contour Fill of DISPLACEMENT DISPLACEMENT Deformation x120 871 DISPLACEMENT of Kratos step 1 Figure 7 22 Z displacement contour m for the configuration A 167 A pre processor for numerical analysis of cross laminated timber structures SERFS DISPLACEMENT 0 010974 0 009755 0 0085356 0 0073162 0 0060969 0 0048775 0 0036581 TTT 0 0024387 k gt 0 0012194 ao X step 1 3 Contour Fill of DISPLACEMENT DISPLACEMENT Deformation x207 DISPLACEMENT of Kratos step 1 Figure 7 23 Contour of the absolute value of the displacement m for the configuration A taking into account only the storeys seismic forces Y DISPLACEMENT 0 0085721 0 0076196 0 0066672 0 0057147 0 0047623 0 0038098 0 0028574 0 0019049 0 00095245 step 1 o Contour Fill of DISPLACEMENT DISPLACEMENT Deformation x112 DISPLACEMENT of Kratos step 1 Figure 7 24 Y displacement contour m for the configuration B 168 Chapter 7 Modelling of a complex structure DISPLACEMENT ke y up t Cortgur FA of OOS PLACEMENT DISPLACEMENT Deloematon 121 DISPLACEMENT of Kratos step 1 Figure 7 25 Contour of the absolute value of the displacement m for the configuration B taking into account only the storeys seismic forces Figures 7 21 7 22 and 7 24 show the displacement of the structure subjected to all the load conditions The buil
45. 20 30 40 50 60 0 10 20 30 40 50 60 Number of specimens ordered according to resistance Number of specimens ordered according to resistance a Net wood b Structural timber Figure 2 1 Effect of moisture content on flexural strength Giordano 1993 The code UNI EN 1995 1 1 2009 defines then a correction factor Kmoa that takes into account the effect on the strength parameters of both load duration and moisture content of the structure In case a combination load includes actions belonging to different classes of load duration the code requires the choice of a Kmoa value that corresponds to the shorter duration action The values for the correction factor Kmoa recommended by the code are given in Table 2 2 values are limited to solid timber glued laminated timber to which they refer X Lam panels and certain other products based on timber The design value of a generic property of the material can be defined as AE M a a mo Ym being ym the partial safety factor for a given material property Xx the characteristic value of the same property and Xq its design value The values for the partial factors ym recommended by the code UNI EN 1995 1 1 2009 are given in Table 2 3 12 Chapter 2 Generalities about timber and X Lam technology Table 2 2 Values of kmoa according to UNI EN 1995 1 2009 Load duration class Material Service class Permanent Long term Mediumterm Shortterm Instantaneous 0 60 0 70 0 80 0 90 1 10
46. 5 b Walls shell elements 553 facet aplasia te Goterlionda seta ntasnea tn oar ote 160 Figure 7 16 a Curbs beam elements A NOR 161 Figure 7 16 b Ordinary beam elements sd laos 161 Figure 7 17 Connection property of line 36 belonging to surface 6 oooionninnninn 163 Figure 7 18 Example of line 36 belonging to wall surface 6 and slab surface 31 Figure 7 19 Figure 7 20 Figure 7 21 Figure 7 22 Figure 7 23 Figure 7 24 Figure 7 25 Figure 7 26 Figure 7 27 Figure 7 28 Example of lines 4 and 5 belonging to walls surfaces 4 and 5 which are actually a single WOME ai naa occesorn aati sesit dicen aero aaa 164 Connection properties of lines 4 and 5 belonging respectively to surfaces A A NA AI E 164 Meshed view of the structure in GID ooonnnniiniiconnncnnnccinccnnccnariranrranno 166 X displacement contour m for the configuration A ono 167 Z displacement contour m for the configuration oooooninnniinnnnnnno 167 Contour of the absolute value of the displacement m for the configuration A taking into account only the storeys seismic forces 168 Y displacement contour m for the configuration B cccccccceeeeee 168 Contour of the absolute value of the displacement m for the configuration B taking into account only the storeys seismic forces 169 Shell Force Sxx contour N m for the configuration A ono 170 Shell Force Syy contour N m for the configuration A ooo 170 Shell Force Szz contour
47. 7 Figure 6 6 Materials py added section matrix creation Figure 6 7 Materials py added section composite cross section creation Moreover the shell cross section offers the possibility of declaring an offset from the reference surface of the shell useful to model slabs on beams when the real distance between beams and slab is not negligible The default value is 0 0 meaning that the cross section is aligned with the shell reference surface With the explanation of this application it is now clear why a solid property has been created but it has not been assigned to anything in GiD interface only one element 129 A pre processor for numerical analysis of cross laminated timber structures property can be assigned to any geometric entity Hence the shell element property is assigned to the surfaces while the solid property is defined to identify the material of the different layers of the shell Moreover two different materials for the solid and the shell need to be created even if they are actually the same material to assign the material properties of the shell to the whole panel and the material properties of the solid to the different layers 6 5 Connections Depending on the mode selected by the user to define the connection properties the stiffness and load carrying capacities are calculated or set in different ways to be used for calculation or verification 6 5 1 Connections stiffness
48. 8e 4 Correction factor kmod 1 1 Correction factor kmod 1 1 Material security coefficient 1 3 E Material security coefficient 1 3 Figure 7 19 Connection properties of lines 4 and 5 belonging respectively to surfaces 4 and 5 164 Chapter 7 Modelling of a complex structure 7 3 4 Boundary conditions and loads For the analysis of the structure all the displacements and rotations of the bottom lines are restrained Relatively to the loads considering that the seism can act in any direction two different analyses are performed one with the seismic forces applied in x direction and the 30 of the same forces applied in y direction another the other way around see Section 7 2 3 Acting the seism in x direction configuration A the forces that should be applied at the barycentre of the storeys are Wry 225 kN Wry 67 5 kN W rx 239 kN Wry 71 7 kN Acting the seism in y direction configuration B the forces that should be applied at the barycentre of the storeys are Wry 67 5 kN j Wry 225 kN W rx 71 7 kN A Wry 239 kN In addition to these forces in both analyses the seismic loads of the roof and floor and the walls loads are also applied see Section 7 2 1 All the forces and loads are applied as uniformly distributed to avoid concentrations of stresses 7 4 Results Meshing the geometry and launching the calculation the structure can be analysed The results are shown in the follow
49. A pre processor for numerical analysis of cross laminated timber structures oe Figure 7 15 a Slabs shell elements Figure 7 15 b Walls shell elements 160 Chapter 7 Modelling of a complex structure Moreover two different beam properties are defined to distinguish between the curbs which have a greater section of 0 15m 0 15m from the ordinary ones which have a small section of 0 001m 0 001m Figure 7 16 Figure 7 16 a Curbs beam elements Figure 7 16 b Ordinary beam elements 161 A pre processor for numerical analysis of cross laminated timber structures 7 3 3 Connection properties Many different connection properties are created to assign to each panel the previously calculated connections Obviously it is much more complicated to assign all the properties in the case of a real structure than in the Chapter 5 example because there are a lot of lines and surfaces and it might be easy to forget a few Moreover since a property consists of hold down and brackets it is not so common that different lines have exactly the same property therefore the connection properties are many The Custom Stiffness mode is exploited to have the possibility of changing the stiffness when desired mostly to model the top lines of the vertical panels From an engineering point of view the modelling is not so easy like just calculating the connections as in Section 7 2 4 In addition to the sides on which t
50. APTER 7 MODELLING OF A COMPLEX STRUCTURE 139 A pre processor for numerical analysis of cross laminated timber structures Tel Example Introduccion iio iaa 139 7 2 A A wacioveiaee avers 141 7 2 1 Static design of X Lam walls and slabS oooonoocnncninocinococonoconononnconncnnno 142 7 2 2 Seismic design of X Lam walls and slabs ooooooocnnncninccnoccnicacinancnnnonoss 145 7 2 3 Equivalent static analysis NE 146 7 2 4 Connections seismic design e ceeeaceundae ues ss 151 7 241 Shear COMMECHLONS cnica 151 T242 Tension CONNECHONS 45 as apciviasaieas E cecum E E REE 152 T243 Connections SUIPENESS esla sia 157 To Modellin e a a a asec cans A E a A teed Satori 157 7 3 1 A 157 7 3 2 Material and elements properties si tasa attain estes 159 7 3 3 Connection Properties aid OE R E E ee 162 7 3 4 Boundary conditions and loads cecceccceesseeeseceeeceeeeeeseeceaeeeeeneeeenseees 165 A O E EREE 165 7 4 1 Structire discretization derrito oia 166 7 4 2 Displacement feld irre ranie e a A R leans 166 7 4 3 Tension field seiringan anen e a a aai aa 169 7 4 4 PRG AC a o a 173 8 CHAPTER 8 CONCLUSION coodocconcocnccnncncncncncnononononononononcnonononcncncnononinos 177 8 1 Man contrib tionS ns rry Sey baad eara ioe natai aari ea AAE aAA RASER aA IAEA RTS 177 8 2 Recommendations for further researCh ocoonionicnnnnnnccnncnonncoconononancnncnancnnc conan conos 178 REFERENCES coda dai 181 List of figures LIST OF FIGURES
51. B interface only for 2D linear elastic analysis Follows the phase started in March 2015 consisting in extending the 2D software to a 3D one with the severity caused by modelling in three dimensions This phase is described in this thesis and in An algorithm for numerical modelling of Cross Laminated Timber structures by Gabriele D Aronco it consists in the pre process and analysis phases of the 3D software Further research is still needed to develop the post process and verification phases The development of this research project arises from the need to model and analyse an X Lam structure in the most efficient and reliable way taking into account its peculiarities Proper modelling strategy results in the development of a special software This comes from the non adaptability to X Lam technology of the established procedures for numerical modelling adopted for other types of buildings Nowadays the commercial FEM software available do not provide an automatic way to model a CLT structure All software regardless of the strategy chosen for modelling the connections only enable to model them manually For instance if they are modelled with punctual springs the user needs to duplicate the nodes and create the spring elements one by one at the pre process interface Follows that if the structure is big and complex as it can be a real one the use of these software could require time and cost expenditure and it may cause several errors b
52. CNC routers are generally used to cut the X Lam panel to the final length and width Sometimes manufacturers also pre cut openings for windows doors and service channels connections and ducts The addition of insulation and exterior cladding may also take place in the factory and the completed panels are shipped to the job site ready to be erected into place 1 Primary lumber selection 3 Lumber planing 7 Assembly pressing pjs m i 9 parki packaging and no Figure 2 5 Manufacturing process of X Lam panels FPInnovations 2013 22 Chapter 2 Generalities about timber and X Lam technology 2 6 Advantages of X Lam technology X Lam technology has several advantages in structural applications e Low weight The X Lam buildings can weigh up to four times less than its concrete counterpart which can reduce transportation costs allows the designers to reduce the foundation size and eliminate the need for a tower crane during construction Yates et al 2008 Mobile cranes can be employed saving substantial erection hire and labour costs e Prefabrication The prefabricated nature of X Lam technology permits high precision in terms of dimensional accuracy due to CNC controlled cutting and quality controlled production Wall floor and roof elements can be pre cut including openings for doors windows stairs service channels and ducts Insulation and finishes can also be applied prior to installation reducing dema
53. EN 1993 1 1 2005 Eurocode 3 Design of steel structures Part 1 1 General rules and rules for buildings CEN Brussels Belgium EN 1995 1 1 2009 Eurocode 5 Design of timber structures Part 1 1 General rules and rules for buildings CEN Brussels Belgium EN 1998 1 2004 Eurocode 8 Design of structures for earthquake resistance Part 1 General rules seismic actions and rules for buildings CEN Brussels Belgium 181 A pre processor for numerical analysis of cross laminated timber structures ETA 06 0138 2006 European technical approval KLH solid wood slabs European Organisation for Technical Approvals Brussels Belgium FPInnovations 2013 CLT Handbook Cross laminated timber US Edition Frangi A Bochicchio G Ceccotti A Lauriola M P 2008 Natural Full Scale Fire Test on a 3 Storey XLam Timber Building 10th World Conference on Timber Engineering Miyazaki Japan Gavric I 2012 Seismic behaviour of Cross Laminated Timber Buildings Trieste Italy Gavric I Fragiacomo M e Ceccotti A 2014 Cyclic behaviour of typical metal connectors for cross laminated CLT structures Gavric I e Popovski M 2014 Design models for CLT shearwalls and assemblies based on connection properties GiD http www gidhome com Giordano G 1993 Tecnica delle costruzioni in legno Hoepli Milano KLH http www klh at Kratos http kratos wiki cimne upc edu index php Kratos http www c
54. Figure 1 1 Figure 1 2 Figure 2 1 Figure 2 2 Figure 2 3 Figure 2 4 Figure 2 5 Figure 2 6 Figure 2 7 Figure 2 8 Figure 2 9 Figure 2 10 Figure 2 11 Figure 2 12 Example of an offset SUTfACE ccccccccccccceseceeeceeseecnseeeseceneeeeseecsseeueenseeensees 5 Exploded view of a pareados 5 Effect of moisture content on flexural strength Giordano 1993 12 Effects of timber classification according to resistance Piazza Tomasi and Mod n 2007 r riar T T R ES 14 Cross laminated timber panel ETA 06 0138 2006 cccccccccceetseeteeeees 18 Examples of different cross sections of X Lam panels ETA 06 0138 ZUG ae alice ce Metin Sola da ae leas oh uae eed Soak SN A Taso ae 19 Manufacturing process of X Lam panels FPInnovations 2013 22 Typical three storey X Lam building showing various connections between the X Lam panels lt A dls 28 Typical wall to foundation X Lam connections a Connection with an exposed metal plate b Connection with a concealed connector c Connection with a wooden profile FPInnovations 2013 29 Typical parallel wall to wall X Lam connections a Connection with an internal spline b Connection with a surface spline c Connection with a half lapped joint d Tube connection system FPInnovations 2013 Typical perpendicular wall to wall X Lam connections a Connection with self tapping screws b Connection with a wooden prof
55. Mises No Plastic strain No Plastic strain rate No Beam moments No Beam forces No Shell forces local No Shell forces global No Shell moments local No Shell moments global No Shell strain local No Shell strain global No Shell curvature local No Shell curvature global No EO Material direction X No Material direction Y No Material direction Z No ptions Result format Ascii Write deformed mesh No Write conditions No Write particles No Result file Single Figure 5 44 Results menu The Results menu contains options can be changed at will 5 6 Group properties d the output delta time the results that will be shown in the post process and a number of options for the results format each one of the efinition The first icon of the xlam kratos menu enables to define the group properties clicking on it the window of Figure 5 45 will appear 107 A pre processor for numerical analysis of cross laminated timber structures Layers and groups Double click here to integrate the window Layers Groups SPxK Gee Name C BeamElem0 E Shelthicl le Ol SoliElem1 Figure 5 45 Groups menu The groups that appear in this menu are the ones just created by the definition of the elements properties Other groups can be created directly from this menu it is another possibility to define the elements properties then they sh
56. Relatively to the stiffness calculation is done in a different way depending on the three modes of definition of the connection properties the stiffness calculated are used for the analysis of the problem 6 5 1 1 Custom Stiffness mode When the user defines the connection properties with the Custom Stiffness mode it is not necessary to calculate the stiffness because they are just set by the user More precisely the axial stiffness of the hold down the axial stiffness of the brackets or distributed nailing and the shear stiffness are set by the user while the rotational stiffness are set as default equal to 100 N m Relative to the example of Chapter 5 we can focus on line 7 then renamed as line 8 see Section 6 4 1 to which Property has been assigned Table 6 7 shows that 130 Chapter 6 Pre processor programming detail the stiffness displayed in the file connection info are actually the ones defined by the user excepting for the rotational stiffness which are set as default equal to 100 N m Table 6 7 Connection info file for line 7 1 0E 07 1 0E 07 100 00 1 0E 07 100 00 100 00 100 00 100 00 6 5 1 2 Custom Parameters mode When the user defines the connection properties with the Custom Parameters mode the axial stiffness of the brackets or distributed nailing the shear stiffness out of the plane of the panel and the three rotational stiffness are set as default equal to
57. Solid timber y 0 60 0 70 0 50 0 90 1 10 0 50 0 55 0 65 0 70 0 90 0 60 Glued Laminated timber y 0 60 0 50 0 60 0 60 0 50 Fibreboard MDF Table 2 3 Recommended partial factors yu for material properties and resistances according to UNI EN 1995 1 2009 Fundamental combinations Solid timber 1 3 Glued laminated timber 1 25 LVL plywood OSB 1 2 Particleboards 1 3 Fibreboards hard 1 3 Fibreboards medium 1 3 Fibreboards MDF 1 3 Fibreboards soft 1 3 Connections 1 3 Punched metal plate fasteners 1 25 Accidental combinations 1 0 2 3 Timber classification and strength classes To allow a secure and reliable design of the timber structural elements the characteristics of the material must be known with sufficient reliability The mechanical characteristics of the wood show a very large dispersion of values for example the ratio between the smallest and the largest value of the failure resistance of a sawn wood element can reach 1 10 This would prevent in absence of an effective classification 13 A pre processor for numerical analysis of cross laminated timber structures the use of timber as a structural element properly The procedure for the classification of the material is intended to achieve the following goals with reference to Figure 2 2 e determination of classes of resistance with differentiated properties and reliable characteristic values e smaller dispersion of t
58. _R wai WALL 2 ae 1 3 W_R_ watr3 Sp 1 3 W_R_ waww4 WALL 5 gt FIRST FLOOR Figure 7 13 a Scheme of walls and relative forces in x direction E F o LTIVAA t TIVA 9 TIVA 4d MS Z Z TYM J MOZ S TIVM 3 MG L GROUND FLOOR E A 3 S S py ps FIRST FLOOR Figure 7 13 b Scheme of walls and relative forces in y direction 156 Chapter 7 Modelling of a complex structure 7 2 4 3 Connections stiffness Modelling is very important to properly evaluate the connections stiffness because it affects in a significant way the global response of the building and the distribution of seismic forces Assuming to use a C22 timber pm 410 kg m the service stiffness per shear plane per fastener for timber to steel connections can be calculated as pr 7 q 8 41015 a 40 8 Resey 2 Ba se p A Multiplying the service stiffness by the number of nails of the tension and shear connections the stiffness of a single connection can be calculated It is important to stress the point that the modelled stiffness of the hold down is equal to two times the real one taking into account the difference in behaviour under the action of horizontal forces of a single modelled panel compared with the same in a real situation Section 4 3 7 3 Modelling This Section will concern on the modelling of the structure in GiD especially focusing on the engineering perspective since the features o
59. a programming code This is the real work in the creation of a new problem type because without this phase it is not possible to have a graphical feedback Moreover this part is the more difficult yet interesting one in the project of the pre process the interface is only the result of the code whilst the code is the real work The interface has been described previously in Chapter 5 in order to better understand which were the purposes when programming the TCL code Having seen the interface it is now easier to understand what we are talking about describing the tools of the code The following sections will focus on the main features of the code and how the interface menu and the desired data have been obtained 6 1 Surface creation and removal from the menu tree The Surfaces menu is a section of the tree that belongs to both the modes of connection properties the custom and the standard one it enables to assign the connection properties to each line as already described in Section 5 5 2 The menu is at first empty then as the user draws the geometry it goes growing Any time the user draws a surface its identification number appears in the tree with all the lines belonging to it the lines are also shown with their ID In the same way when a surface is removed by the user the surface and its belonging lines are removed from the tree 115 A pre processor for numerical analysis of cross laminated timber str
60. and Bwi cecccecccccccccecceeteceeeceeseeeseecsesusesenseenseeenseees 139 Building front views C 1 2 and It dhe telex uu Raikes 140 Ground floor plan ccs chaste Gude gs od 140 First floor DOW occ ca a 141 LOTES UIGIVSIS SAS E A A a 142 Loads representation on the geometIY ooooonionincninncnnncinncncannnnnrronccnnnnns 143 Preliminary design table for single span floors Rothoblaas 144 Preliminary design table for external walls Rothoblaas 145 Afferent heights of the slabs A 146 Elastic response spectrum for Gerona Friuli Venezia Giulia Italy 148 Barycentre position at the two storeys of the building 150 Selected shear connection Rothoblaas ooooooninnnninnninnnicnnncncoonnnron anos 151 Selected tension connections Rothoblaas ooononnninnnnnnnnnnnnicccnnnnronnnoss 153 Forces causing the first floor rigid rotation ccccccceeceeesceeseeeneteeees 154 XV A pre processor for numerical analysis of cross laminated timber structures Figure 7 13 a Scheme of walls and relative forces in x direction oooooonninninnnnnnnnnn 156 Figure 7 13 b Scheme of walls and relative forces in y direction ooonnonnioninnnnnnnninco 156 Figure 7 14 Building geometry in CID aci 158 Figure 7 14 b Building geometry in GiD Di no 158 Figure 7 14 c Building geometry in GiD Dusni d s averse estnieoingeaicess 159 Figure 7 15 a Floors shell elements a ES dc 160 Figure 7 1
61. arked difference of the stiffness and resistance values according to the direction of the applied load or in a dual way depending on the grain direction Wood is more resistant and rigid to stresses oriented along the grain direction Conversely solid timber in structural dimensions is a non homogeneous material which contains defects related to the growth of the plant from which it comes in the form of nodes localized grain deviations and many others These defects significantly reduce the resistance when the wood is sawn and used for other uses Therefore it is evident that the mechanical characteristics of the structural timber cannot be derived from those of the net wood without taking into account the defects Besides the presence of defects within the wood mass the study of the timber subjected to external stresses is complicated by the strong influence of moisture variation and load duration on the resistance A pre processor for numerical analysis of cross laminated timber structures 2 2 Load duration and moisture influences on timber strength Firstly strength is affected by load duration For timber as for all construction materials the resistance to short term loads is higher than for long term loads Additionally studies conducted by Madsen have shown that load duration influence depends on the timber quality and it is significantly lower for low qualities than high ones In principle this can be explained by the
62. ary conditions The user does not need to create manually the connections as conversely needs for all commercial FEM software currently available he just set the connection properties to the different sides of the panels The creation of the connections is made automatically keeping into account different typologies of connections and assembling of Cross Lam panels The problem type is special for X Lam structures meaning that all features are intentionally studied for this kind of structures and the software architecture is planned for future developments of the post process phase It can be concluded that a strategy for numerical modelling of cross laminated timber structures has been developed Sound bases for the pre process and analysis phases of the software have been laid However future research is required to develop the post process and verification phases of the research project Acknowledgments ACKNOWLEDGMENTS First I would like to express my sincere gratitude to my supervisor Prof Roberto Scotta for giving me possibility to be part of this very interesting research project guiding me through it with great dedication and enthusiasm His insight advice and ideas have been extremely valuable to the outcomes of this research project I deeply appreciate the encouragement availability patience and help which he gives me Roberto thank you for guiding me starting from the degree In turn deep gratitude t
63. attention by designers In addition damages and failures in X Lam buildings during a seismic event are localized in connections thus structural repairs after an earthquake are relatively easy and cost effective When structural members are attached with fasteners or some other types of metal hardware such joints are referred to as mechanical connections Currently there is a wide variety of mechanical fasteners and many different types of joint details that can be used for panel to panel connections in X Lam assemblies or to connect X Lam panels to other wood based concrete or steel elements in hybrid construction A combination of metal hold downs angle brackets and self tapping screws are typically recommended by the X Lam manufacturers for connecting the cross lam panels Metal brackets hold downs plates and straps are used to transfer forces from walls to floors from one level to another level and to foundations Hold downs are mainly used in the corners of wall segments and close to door opening to resist overturning forces that result from an earthquake or wind On the other hand the main role of L shaped metal brackets is to resist shear forces in wall panels caused by wind or 27 A pre processor for numerical analysis of cross laminated timber structures a seismic event Nails with specific surface features such as grooves or helically threaded nails are mostly used with perforated metal plates and brackets a
64. ayers and boards Openings within panels can be pre cut in the factory to any dimension and shape including openings for doors windows stairs service channels and ducts In order to rule out any damage caused by pests fungi or insects technically dried wood with an average wood moisture of 12 2 is used to produce X Lam solid wood panels In plane deformation rate of X Lam panels is about 0 01 per percentage of change in wood moisture content while perpendicular to panel plane the deformation rate is about 0 20 per percentage of change in wood moisture content Typically the panels are consisted of three five seven or more layers of industrial dried boards symmetrical around the mid layer By using double layers the longitudinal or transverse rigidity of the panel can be further enhanced Softwood such as spruce pine and fir is currently used in X Lam production Boards with different grading classes might be used for longitudinal parallel and transversal perpendicular layers to optimise mechanical and fire performances of X Lam product The density of a 18 Chapter 2 Generalities about timber and X Lam technology CLT timber panel is generally around 400 to 500 kg m i e around the density of the base laminate species used The external loads are carried by the longitudinal parallel layers whereas the transversal perpendicular layers have lower strength and stiffness in the main panel direction since the s
65. be achieved with hidden metal plates However some CNC machining work is required to produce the grooves in the X Lam panel to conceal the metal plates Tight dowels or bolts can be used to attach the plates to the X Lam panel In addition some innovative types of fasteners that can be drilled through metal and wood or other types of screws that can penetrate through both materials can also be used for this purpose e Wooden Profiles Wooden profiles which are fabricated from high density and stable materials such as engineered wood products or high density hardwood are commonly used for connecting structural insulated panels SIP and other types of prefabricated wood framed walls The major advantage of this system is the ease of assembly The wooden profiles are typically attached to X Lam panels with wood screws or self tapping screws and are often used in combination with metal plates or brackets to improve the lateral load resistance Wooden profiles can also be used for wall to wall or floor to wall connections 2 Wall to wall connections 2a Parallel wall panel connection This connection type is used to connect panels along their longitudinal edges The parallel wall wall panel connection facilitates the transfer of in plane forces shear and 30 Chapter 2 Generalities about timber and X Lam technology out of plane forces bending through the wall assembly Several connections details are b possible a
66. building in neither plan nor elevation Figures 7 1 and 7 2 show the front views and plans of the two storey building that will be analysed AN Front view A Front view B Figure 7 1 a Building front views A and B 139 A pre processor for numerical analysis of cross laminated timber structures ES 300 Front view C Frontview 1 Front view 2 Front view 3 Figure 7 1 b Building front views C 1 2 and 3 1200 Ground floor Figure 7 2 a Ground floor plan 140 Chapter 7 Modelling of a complex structure A 6 or a 1 2 3 First floor Figure 7 2 b First floor plan 7 2 Preliminary design phase The preliminary design consists on the static design of walls and slabs considering the static loads and their seismic design by means of the calculation of the seismic weights which then can be used for the equivalent static analysis Moreover it concerns the seismic design of the connections and the calculation of their resistance and stiffness 141 A pre processor for numerical analysis of cross laminated timber structures 7 2 1 Static design of X Lam walls and slabs The first step is the analysis of all the loads acting on the floor on the roof and the load bearing walls they are summarised in Figure 7 3 22 ceiling floor dividers 2 q overload residential building 2 Wseismic 1 0 2
67. cchetto which develops a software using MATLAB interface only for 2D linear elastic analysis Follows the phase started in March 2015 consisting in extending the 2D software to a 3D one with the severity caused by modelling in three dimensions This phase is developed as a common project and described in this thesis and in An algorithm for numerical modelling of Cross Laminated Timber structures by Gabriele D Aronco The final aim of the software is to enable the modelling of an X Lam structure in the most efficient and reliable way taking into account its peculiarities Modelling of CLT buildings lies into properly model the connections between panels Through the connections modelling the final aim is to enable the check of preliminarily designed connections or to find them iteratively starting from hypothetical or random connections This common project develops the pre process and analysis phases of the 3D software that allows the automatic modelling of connections between X Lam panels To achieve the goal a new problem type for GiD interface and a new application for A pre processor for numerical analysis of cross laminated timber structures KRATOS framework have been performed The problem type enables the user to model a CLT structure starting from the creation of the geometry and the assignation of numeric entities beam shell ecc to geometric ones having defined the material and assigning loads and bound
68. cealed spaces within floor and wall assemblies which reduces the risk of a fire spreading Fire performance of X Lam panels can also be enhanced by lining with fire resisting gypsum boards and in case of floor panels additional layers and coverings A demonstration test conducted by IVALSA on a full scale three storey X Lam building confirmed that X Lam panels protected by one layer of gypsum board were able to withstand the burn out of the room contents without fire spread to adjacent rooms or floors Frangi et al 2008 e Thermal performance Cross lam panels have the same fundamental thermal insulation and thermal mass properties as the wood from which they are made thermal conductivity 0 13 W m K according to EN 12524 2000 Wood has a low thermal conductivity so reduces problems such as thermal bridging from the internal to the external environments and the other way around thus reducing heat transfer and energy wastage e Acoustic performance Solid wood panels offer acoustical advantages when used for floor and wall systems When used in conjunction with insulation and gypsum board it is possible for an X Lam building to exceed code requirements related to the acoustical performance of floors and walls 25 A pre processor for numerical analysis of cross laminated timber structures e Dimensional stability The crosswise arrangement of the longitudinal and transverse layers reduces the swelling and shrinkage of
69. ceeteete eee 91 TAA A NO ee ee 92 Geometry created DETER ia 93 DAS DOCU A A a 93 End Surfaces E aia 94 End oeometly nd 95 Selection of a connection property alias 96 Drawn OF INEA Ai 96 Surfaces menu with assigned connection PrOPertieS c cccccececcees 97 Elements Properties ME da 98 Beam property parameters tt RIA AAA AA AS 99 Solid property parameters oooococicononacinnnncannnnan aran cc on nn canon nan r nn raro nario 99 xiii A pre processor for numerical analysis of cross laminated timber structures Figure 5 36 Figure 5 37 Figure 5 38 Figure 5 39 Figure 5 40 Figure 5 41 Figure 5 42 Figure 5 43 Figure 5 44 Figure 5 45 Figure 5 46 Figure 5 47 Figure 5 48 Figure 5 49 Figure 5 50 Figure 5 51 Figure 6 1 Figure 6 2 Figure 6 3 Figure 6 4 Figure 6 5 Figure 6 6 Figure 6 7 Figure 6 8 Shell property DOTA A 100 Elements Properties end Menu anti cus iain ii Si dio Oy ove ales 102 Elements MOTA A oe a 103 Beam ALERTAS SIN A et vennnsgisigae 103 Shell thick element as ROO devdeesunabetay oosvigiacices 104 Solid EEES RO O tattoadinsvic eats 104 Elem nts end TE 105 Loads and Boundary Conditions MeMU oooonnnionnnnnnnininncnnnccianicnns 105 Results meniren nana a AAA RIN E 107 SI 108 MBIERIALS MEM AA 109 MITA sub menu AO AAA AA 110 Material creation removal and renaming WINdOW ooo 111 Mesh generation IMA a ea 112 Structured NESS Cl RAS 112 Meshed A OS 113
70. create other two surfaces from lines already created lines should be copied and surfaces extruded it means to choose Lines as Entities type and to select Surfaces in the line Do extrude reference is made to Figure 5 7 The copy menu modifies as shown in Figure 5 8 Copy Entities type Lines W Transformation Translation Y First point Num x 10 0 y 0 0 a z 00 Second point Num x 0 0 y 10 0 a z 00 X Collapse Do extrude Surfaces Y Create contacts X Maintain layers Multiple copies 1 Select Figure 5 8 Copy menu for copying surfaces 75 A pre processor for numerical analysis of cross laminated timber structures Thus another surface can be created writing 1 0 as z coordinate of the second point and selecting the top line of the previous surface created it returns the geometry shown in Figure 5 9 First and second surfaces Figure 5 9 Figure 5 10 First second and third surfaces 76 Chapter 5 Pre processor and interface tutorial In a similar way writing 1 0 as z coordinate of the second point and selecting the right line of the first surface created another surface can be created the geometry results as in Figure 5 10 In order to create another surface copying the first surface in z direction Surfaces should be selected as Entities type and No on the line Do extrude in the copy menu Figure 5 7 Hence selecti
71. ctor 1 2173e 05 Deformation x96 DISPLACEMENT of Kratos step 1 Figure 7 34 Z Reaction vectors display for the configuration B Display Vectors of REACTION Z REACTION factor 3 4303e 5 Deformation x199 142 DISPLACEMENT of Kratos step 1 Figure 7 35 Z Reaction vectors display for the configuration B taking into account only the storeys seismic forces 174 Chapter 7 Modelling of a complex structure a wept Display Vectors of REACTION X REACTION tactor 0 00011832 Deformation 197 DISPLACEMENT of Kratos step 1 Figure 7 36 X Reaction vectors display for the configuration A z M x step 1 Display Vectors of REACTION Y REACTION factor 0 00011995 Deformation x96 DISPLACEMENT of Kratos step 1 Figure 7 37 Y Reaction vectors display for the configuration B The reactions vector field is a reply of the correct functioning of the software Figures 7 32 7 35 testify that the hold down axial stiffness and the distributed axial stiffness are assigned to the correct springs because only the ones set as hold down present a vertical reaction Figures 7 36 and 7 37 testify that the distributed parallel and orthogonal shear stiffness are correctly assigned because only the springs allocated on the sides in direction parallel to the seismic action presents an horizontal reaction 175 Chapter 8 Conclusion CHAPTER 8 CONCLUSION 8 1 Main contributions Within the scope of the research projec
72. d down with greater coordinate on the x or y axis in order to distinguish it from the first one The two hold down are distinguished to leave the possibility of disposing two different types of hold down to one and the other side of the panel or to put only one of them in case of two surfaces which are actually a unique panel see Section 7 3 3 Distributed axial stiffness this is the axial stiffness of the brackets or distributed nailing in N m This stiffness is in general considered zero because the shear connections do not work in tension see Section 2 7 1 anyway it is set to enable the user to use a different one if he wants to assign an axial stiffness to the shear connections or to simulate a distributed axial stiffness see Section 7 3 3 Distributed parallel shear stiffness this is the shear stiffness in the plane of the panel in N m meaning the brackets or distributed nailing s shear stiffness Distributed orthogonal shear stiffness this is the shear stiffness out of the plane of the panel in N m Rx HD1 this is the characteristic load carrying capacity of the first hold down in N which can be calculated as explained in Section 2 7 3 Rx HD2 this is the characteristic load carrying capacity of the second hold down in N which can be calculated as explained in Section 2 7 3 Rk distributed this is the characteristic load carrying capacity of the brackets or distributed nailing in N which can be calculated as explained
73. d elements is shown in Figure 5 51 te be Figure 5 51 Meshed geometry 5 9 File saving The calculation cannot be launched if the file is not saved so if it has not been done before at this point it will be necessary to save it As for any ordinary program using the command File Save as the file can be saved in the desired folder 113 A pre processor for numerical analysis of cross laminated timber structures When a file is saved the processor generates a folder containing the different files described in Section 3 1 1 which all have the same name This means that if you want to change the name of the folder when it has been saved it cannot be done simply renaming the folder but all the within files must be renamed 5 10 Calculation Once the file has been saved the calculation can be launched using the command Calculate of the top command line or the shortcut FS 114 Chapter 6 Pre processor programming detail CHAPTER 6 PRE PROCESSOR PROGRAMMING DETAIL The problem type xlam kratos has been described in Chapter 5 only at interface level providing a user tutorial It is clear that when it has been created the tools were not just available and a TCL code has been written in order to obtain the necessary features As a matter of fact to create a new problem type it is necessary to explain to the processor what we need and this should be done by means of
74. ded to enable clear programs on both a small and large scale Python supports multiple programming paradigms including object oriented imperative and functional programming or procedural styles It features a dynamic type system and automatic memory management and has a large and comprehensive standard library Python was conceived in the late 1980s and its implementation was starts in December 1989 by Guido van Rossum at CWI Centrum Wiscunde amp Informatica in the Netherlands as a successor to the ABC language capable of exception handling and interfacing with the Amoeba operating system Python 2 0 was released on 10 October 2000 and included many major new features including a full garbage collector and support for Unicode With this release the development process was changed and became more transparent and community backed Python 3 0 also called Python 3000 or py3k a major backwards incompatible release was released on 3 December 2008 after a long period of testing Many of its major features have been backported to the backwards compatible Python 2 6 and 2 7 Python is a multi paradigm programming language object oriented programming and structured programming are fully supported and there are a number of language features which support functional programming and aspect oriented programming Many other paradigms are supported using extensions including design by contract and logic programming 58 Chapter 3 Gen
75. ding results quite rigid since the maximum displacements are in the order of magnitude of 1 cm In Figures 7 23 and 7 25 the structure is only subjected to the seismic forces condition The spring elements are clearly visible the hold down springs behave correctly since each wall tends to rigidly rotate around its mid point of the lower side 7 4 3 Tension field The tension field for the two load configurations and taking only into account the storeys seismic forces are shown in Figures 7 26 7 31 The shell forces are actually displayed rather than the tensions meaning that they are already integrated through the shell thickness 169 A pre processor for numerical analysis of cross laminated timber structures Sxx SHELL FORCE 2 0018e 05 1 5867e 05 1 1716e 05 75652 34143 7364 9 48873 90382 1 3189e 05 i step 1 1 734e 05 Smooth Contour Fill Mean of SHELL FORCE quad4 element gp Sxx SHELL FORCE Deformation x120 871 DISPLACEMENT of Kratos step 1 Figure 7 26 Shell Force Sxx contour N m for the configuration A Syy SHELL FORCE GLOBA 1 191e 05 95942 72781 49621 26461 3300 4 19860 a 43020 t 66181 89341 y step 1 Smooth Contour Fill Mean of SHELL FORCE GLOBAL quad4 element gp Syy SHELL FORCE GLOBAL Deformation x120 871 DISPLACEMENT of Kratos step 1 Figure 7 27 Shell Force Syy contour N m for the configuration A 170 Chapter 7 Modelling of a complex structure
76. ding to the 1 axis of the shell local x axis otherwise it should be set equal to ninety degrees see Section 4 2 e Number of layers this is the number of layers of the panel which can be equal to 3 5 7 or 9 It is not possible to set values different from these ones because the modelling of the composite shell is only predisposed for these values see Section 6 4 8 e Thickness layer i this is the thickness of the i layer in m The first layer is the outer one being the number of layers always odd the two sides of the panel can be interchangeably used as reference for the outer layer e Solid property this is the name of the solid related to the shell To any shell defined with a special material a solid is related thus enabling the creation of the composite shell and the assignation of the material properties to it see Section 6 4 8 It is noticeable that the three element properties have been created with three different materials Actually the material is always the same it is timber C14 nonetheless any element property needs a different material even if their parameters are equal This is because the beam uses an Elastic Isotropic constitutive law while the other two elements use an Elastic Orthotropic constitutive law Moreover the solid and the shell despite using the same constitutive law need to be characterised by different materials to enable the assignation of the material properties to the whole panel and its
77. e 2 3 Each of the parameters explained presents on the interface an abbreviated name that may be not perfectly clear for a matter of space at the interface Anyway placing the mouse over the box corresponding to each of the parameters pop ups that explain their meaning will appear Explained all kinds of menus for the definition of a connection property it can be now decided which mode will be used if the Custom or the Standard one For the example it will be selected the Custom menu in order to explain another peculiarity of this menu considering that it contains two different types of connection property Stiffness Connection parameters Properties Property Id Property v Axial stiffness HD1 1 0e 7 hag Axial stiffness HD2 1 0e 7 z Distributed axial stiffness 100 z Distributed parallel shear stiffness 1 0e 7 z Distributed orthogonal shear stiffness 100 v Rk HD1 1 0e 5 z Rk HD2 1 0e 5 z Rk distributed 7 0e 4 v Correction factor kmod 11 z Material security coefficient 1 3 z Ok Cancel Figure 5 21 Property parameters 89 A pre processor for numerical analysis of cross laminated timber structures We define two different properties one belonging to the menu Stiffness and the other one belonging to the menu Connection parameters Both of them will be defined with random parameters because the goal of this simple example is not the analysis the values have
78. e University of British Columbia campus Vancouver Canada was the first North American commercial application in X Lam technology The building was built using a combination of massive timber systems including X Lam composite laminated strand lumber with concrete floors and glulam heavy timber braced frames Wood Works A prototype of a wind turbine was currently built from X Lam panels in Hannover Germany the structure reaches 100 m in height Timber Tower 47 Chapter 3 General about GiD Kratos Tcl and Python CHAPTER 3 GENERAL ABOUT GID KRATOS TCL AND PYTHON This Chapter provides an overview of general information about the processor the solver and the programming languages used for this thesis GiD Kratos Tcl and Python Thus only a brief description rather than a detailed explanation of each one of them will be presented in order to provide the reader an idea of what they are and how they work 3 1 GiD processor GiD is a universal and adaptive pre and post processor for numerical simulations in science and engineering It has been designed to cover all the common needs in the numerical simulations field from pre to post processing geometrical modelling effective definition of analysis data meshing data transfer to analysis software as well as visualization of numerical results 3 1 1 Interaction of GiD with the calculating module GiD pre process makes a discretization of the object und
79. e value is arbitrary negligible compared to the ordinary connections stiffness The standard menu is shown in Figure 5 17 Inside the Standard Connections there is a sub menu of Standard Property which as for the custom menu in turn contains a property already defined called Continuity connection 85 A pre processor for numerical analysis of cross laminated timber structures Connection Mode Standard Standard Connections EF Standard Property E Continuity connection E Connection old down 1 No umber of hold down HD1 0 old down 2 No umber of hold down HD2 0 Bracket or distributed nailing No umber of brackets or distributed nails 0 Surfaces Figure 5 17 Standard mode menu The connection property Continuity connection has all the parameters set to zero it can be used for example when the user wants to guarantee the continuity between two panels meaning that actually two surfaces are only one panel so there is no connection between them In case of selection of this connection property the stiffness are not calculated as for the other standard connections but they are all set to infinite to guarantee continuity as for the similar already defined custom property The parameters of the connection property Continuity connection cannot be changed by the user he should define another connection property in order to assign other parameters Connecti
80. ecause of its complexity hundreds or thousands if not more may be the nodes elements and properties that should be assigned The aim of this research project is exactly to provide a software that allows the automatic modelling of connections between X Lam panels trying to avoid the human error and the cost in doing it manually Chapter 1 Introduction The most convenient strategy for modelling X Lam structures has to be defined Such strategy must be suitable for automatic generation of numerical models and must have the ability of keeping into account all the possible typologies of connections and assembling of Cross Lam panels In view of future evolution of the research the possibility of non linear behaviour of joints and optimal automatic design via iterative solutions has to be accomplished too 1 2 Objectives and scope The focus of this thesis is on the continuation of the research project on the development of a software for the modelling of CLT structures including analysis calculation design and verification of connections and panels The research work will include the pre process phase and the analysis one the first of which is discussed in this thesis the second one in An algorithm for numerical modelling of Cross Laminated Timber structures by Gabriele D Aronco The procedure is developed using GiD as interface support and processor and KRATOS Multiphysics as FEM framework Relatively to the pre proces
81. ection Continuity_connection E Line 8 Connection Continuity_connection E Line 5 Connection Continuity_connection E Line 11 Connection Continuity_connection Figure 5 28 End Surfaces menu 94 Chapter 5 Pre processor and interface tutorial Figure 5 29 End geometry As expected surface 1 has been removed from the tree as well as the lines belonging to it lines 1 and 4 do not appear in the tree because they only belonged to surface 1 while lines 2 and 3 persist in the list as belonging respectively to surfaces 3 and 2 All the IDs mentioned so far are the GiD IDs dependent on the order of drawing of the geometry as already explained currently we refer to them every time we mention the IDs The Surfaces menu just described enables to assign the previously created connection properties to the lines they are assigned to the lines because it is simpler for the user to select a line and to assign it the properties of the connection he wants on this side of the panel For the pre process the connection remains a property of the line because we only care about geometrical entities then in the x am driver application the stiffness will be assigned to the springs see Section 4 1 Thereafter these springs will assume the physical meaning of connections between panels The hold down axial stiffness is also assigned at the interface to the lines and then in the xlam driver app
82. eel beams or to concrete foundations with concrete footing which are most common for the te ground storeys in X Lam buildings b a Figure 2 7 Typical wall to foundation X Lam connections a Connection with an exposed metal plate b Connection with a concealed connector c Connection with a wooden profile FPInnovations 2013 e Visible or exposed metal plates Exterior metal plates and brackets are commonly used in such applications as there is a variety of such metal connectors readily available on the market and due to its simple installation Lag screws or powder actuated fasteners can be used to connect the metal plate to the concrete footing or slab while nails lag screws or self tapping screws are 29 A pre processor for numerical analysis of cross laminated timber structures used to connect the plate to the X Lam panel Exposed metal plates and fasteners need to be protected against corrosive exterior environments Galvanized or stainless steel should be used in such cases Direct contact between the concrete foundation and X Lam panel should be avoided in all cases Connection details should be designed to prevent potential moisture penetration between the metal plates and the X Lam wall as water may get trapped and cause potential decay of the wood e Concealed connectors For better fire resistance and improved aesthetics designers sometimes prefer concealed connection systems This can
83. een the dry base material and the same wet base material The European regulations UNI EN 1995 1 2009 take into account these influences defining for loads the so called load duration classes and for hygrometric conditions the so called humidity classes or service classes 10 Chapter 2 Generalities about timber and X Lam technology The loads are distinguished in permanent loads always of long duration of course and accidental loads which may be of long medium short term or instantaneous they are shown in Table 2 1 Table 2 1 Load duration classes according to UNI EN 1995 1 2009 Load duration class Order of accumulated duration of characteristic load Permanent more than 10 years Long term 6 months 10 years Medium term 1 week 6 months Short term less than one week Instantaneous Generally permanent loads are represented by the weight of the structure medium term loads are loads imposed to the slabs for example overload for residential use whereas snow and wind contribute to short term earthquakes to instantaneous loads To take into account changes in moisture in the timber the code prescribes that the constructions are assigned depending on the thermo hygrometric environment to one of the following service classes Service class 1 this class is characterised by a content of moisture in the materials corresponding to a tempe
84. er study and generates a mesh of elements to each one of whom is assigned a material and some conditions This pre processing information in GiD mesh materials and conditions enables the 49 A pre processor for numerical analysis of cross laminated timber structures calculating module to generate results Finally the results generated by the calculating module will be read and visualized in GiD post process GiD must adapt these data to deal with them Materials boundary and or load conditions and general problem data must be defined by the user GiD configuration is accomplished through text formatted files The following files are required prb configuration of the general parameter not associated to entities mat configuration of materials and their properties cnd configuration of the conditions imposed on the calculation bas template file the file for configuring the format of the interchange file that mediates between GiD data and the calculating module The file for interchanging the data exported by GiD has the extension dat This file stores the geometric and physical data of the problem bat the file that can be executed called from GiD This file initiates the calculating module The calculating module solves the equations in the problem and saves the results in the results file this module may be programmed GiD post process reads the following files generated by the calculating m
85. eral about GiD Kratos Tcl and Python Python uses dynamic typing and a combination of reference counting and a cycle detecting garbage collector for memory management An important feature of Python is the dynamic name resolution late binding which binds methods and variable names during program execution Rather than requiring all desired functionality to be built into the language s core Python was designed to be highly extensible a small core language with a large standard library is supported by an easily extensible interpreter Python can also be embedded in existing applications that need a programmable interface 59 Chapter 4 Modelling strategy of X Lam buildings and conventions CHAPTER 4 MODELLING STRATEGY OF X LAM BUILDINGS AND CONVENTIONS This Chapter provides a description of the philosophy adopted for modelling Cross Lam buildings it is an innovative strategy used in the software This explanation is the main point to understand the development of the interface and the programming code implemented for the pre process which will be presented in the following chapters Modelling of panels and connections is detailed along the Chapter finally conventions about units of measurement and gravity are presented 4 1 Modelling strategy The most convenient strategy for modelling X Lam structures has to be defined Such strategy must be suitable for automatic generation of numerical models and must
86. es shown in the thesis An algorithm for numerical modelling of Cross Laminated Timber structures by Gabriele D Aronco testify that the algorithm implemented for the automatic modelling of the connections works as expected and the connections stiffness are actually correctly assigned to the springs Therefore the behaviour of the structure can 177 A pre processor for numerical analysis of cross laminated timber structures be considered reliable within the limits imposed by linear elastic analysis The analysis works as expected for each kind of CLT structure The goals of these phases of the research project have been achieved partly developing a strategy that allows the automatic modelling of connections between X Lam panels However the developed phases of the software are still not perfectly ready being available improvements aimed at a better end result The large probability of error of the other commercial software due to the need of manually duplicate the nodes and create the spring elements one by one in the interface is drastically reduced by this new software which does it automatically The modelling of an X Lam structure is now easier faster and safer thanks to the reduced possibility of human errors 8 2 Recommendations for further research While this thesis together with An algorithm for numerical modelling of Cross Laminated Timber structures tries to lay sound bases for the pre process and anal
87. es the stiffness to write them in the connection info file expr Density 9 81 1 5 TensionDiameter1 1006 expr 51 9 81 1 5 nDiameter2 1 expr y 81 S rDiameter 1006 expr kserTensionl s 2 expr kserTension2 2 Figure 6 12 Stiffness calculation for Standard mode 134 Chapter 6 Pre processor programming detail 6 5 2 Connections resistance Relatively to the design load carrying capacities calculation is done in a different way depending on the three modes of definition of the connection properties the capacities calculated will be used for verification of the connections 6 5 2 1 Custom Stiffness mode When the user defines the connection properties with the Custom Stiffness mode he sets the characteristic load carrying capacities of the hold down and brackets or distributed nailing With these parameters the design load carrying capacities are easily calculated in the following way see Section 2 7 3 Rolas d mod y set foreach sbaseNode set propnode if propid list set propnode append else if propid list set expr propnode append 2 return retstr Figure 6 13 Design load carrying capacities calculation for Custom Stiffness mode Figure 6 13 shows the section of the code which calculates the design load carrying capacities of the connections to write them in the More Connections file Relative to the example of Chapter 5 we can focus on line 7 then
88. esistance to the walls To simulate properly the contact problem the springs should present a non linear constitutive law in axial direction Alternatively the problem can be considered non linear for the material considering the hold down as a material resistant to compression and the soil as a material non reactive to traction Within this project the springs present a linear elastic constitutive law leading to the need of modifying the hold down stiffness compared to the real one This is to take into account the difference in behaviour under the action of horizontal forces of a single modelled panel compared with the same in a real situation Therefore being the spring elements currently added in Kratos only implemented with linear elastic constitutive law the analysis is always considered linear elastic In reference to the behaviour of a single X Lam panel this is an orthotropic rather than an isotropic material This is due to the different total thickness of the layers in longitudinal and transversal direction and to the difference in value of the elastic modulus of the timber which is one order of magnitude greater in the direction parallel to the grain than in the transversal direction These two topics lead to adopt an elastic orthotropic constitutive law for the shell elements The research work developed in this common project concerns the creation of a new problem type especial for X Lam structures It enables the user to m
89. ess external forces are referred to the stiffness distribution of the previous iteration therefore the connections can be updated in the model up to their convergence with the dichotomous method see Una procedura numerica per il progetto di edifici in X Lam by Massimiliano Zecchetto 179 References REFERENCES Augustin M 2008 Timber structures Handbook 1 of Educational materials for designing and testing of timber structures TEMTIS Leonardo da Vinci Pilot Project No CZ 06 B F PP 168007 Ostrava Czech Republic VSB Technical University of Ostrava Bathon L A Bletz O 2006 Long term performance of continuous wood concrete composite systems 9th World Conference on Timber Engineering Portland Oregon USA Briani A Simeone P Ceccotti A 2012 MAI IVALSA modular house Proceedings of the 12th World Conference on Timber Engineering Auckland New Zealand D Aronco G 2015 An algorithm for numerical modelling of Cross Laminated Timber structures Padova Italy D M 14 01 2008 New Technical Standards for Construction CSLP Roma Italy EN 338 2004 Strength classes for solid wood CEN Brussels Belgium EN 1194 1999 Timber structures Glued laminated timber Strength classes and determination of characteristic values CEN Brussels Belgium EN 12524 2000 Building materials and products Hygrothermal properties Tabulated design values CEN Brussels Belgium
90. f the problem type have been described in detail in Chapter 5 7 3 1 Geometry The geometry can be drawn in GiD using the plans and front views of Section 7 1 it is shown in Figure 7 14 from different points of view 157 A pre processor for numerical analysis of cross laminated timber structures Figure 7 14 a Building geometry in GiD a Figure 7 14 b Building geometry in GiD b 158 Chapter 7 Modelling of a complex structure Le Figure 7 14 shows that the slabs are drawn with different surfaces this is to guarantee Figure 7 14 c Building geometry in GiD c that the barycentre points of the first storey and the roof belong to the surfaces hence the seismic forces can be applied on them To identify these points starting in drawing from the bottom also some walls are drawn with different surfaces 7 3 2 Material and elements properties Relatively to the material timber C22 is used this is already defined in GiD material database with all its properties already set Relatively to the elements properties two different shell properties for the slabs and walls Figure 7 15 are defined since they have a different thickness meaning also two solid properties Additionally the slabs are assumed to have the grain orientation of the outer layer in x direction angle 09 while for the walls the grain orientation of the outer layer is assumed in z direction angle 90 159
91. ferring in plane diaphragm forces in principle and maintain the integrity of the diaphragms Connection details used in floor to floor panel connection are equal to parallel wall to wall panel connection types described earlier in this Chapter 5 Wall to roof connections For sloped or flat roof systems connections similar to those used for attaching floors to walls is used Screws and metal brackets are the most commonly used fastening systems in this application 36 Chapter 2 Generalities about timber and X Lam technology 1141 Figure 2 12 Typical wall to roof X Lam connections FPInnovations 2013 Innovative types of connection systems can also be used including mechanical and carpentry connection systems Some interesting innovative connection systems are finding their way to the X Lam construction market mostly facilitated and enabled by CNC technology For example glued in rods can be used for connections under high longitudinal and transverse loads HBV Shear Connectors a proprietary product from Germany can also be used to create composite floors with structural concrete over X Lam panels Bathon amp Bletz 2006 Further KNAPP system Knapp and Idefix connectors Sigha are relatively new innovative connection systems on the market Due to the relatively recent introduction of X Lam technology into the construction market 1t is expected that even more new connection types will be developed over time
92. fferent analyses are considered one with the seismic forces applied in x direction and the 30 of the same forces applied in y direction another the other way around 150 Chapter 7 Modelling of a complex structure 7 2 4 Connections seismic design The distribution of the seismic forces on the walls does not depend on the X Lam panel characteristics thickness inertia length but it only depends on the connections at the base and at the interstory 7 2 4 1 Shear connections The calculation of the resistance of the shear connections can be made preliminarily by means of the manufacturers catalogues Brackets type WBR100 with total nailing and 12 nails Anker 4X60 referring to the technical data sheet Rothoblaas Figure 7 10 will be used GIUNZIONE LEGNO CEMENTO Fissaggio Cemento Trave o Cemento Pilastro CONNETTORI LATO LEGNO CHODIANKER gS 4 0 X60 jos GH VITI SPECIALI tJ 05 0 X60 Fissu Forza di taglio agente sull ancorante Fabs Forza assiale sull ancorante ll collegamento dell ancoraggio al cemento da verificare a parte sulla base delle forze sollecitanti lancorante stesso e Chiodatura parziale Chiodatura totale as as 7 esas ia te a Figure 7 10 Selected shear connection Rothoblaas According to EN 1995 1 1 2009 2 4 3 the design value of the load carrying capacity can be obtained as 151 A pre processor for numerical analysi
93. ffness 1 0e 12 E Surfaces Figure 5 14 Custom mode menu The connection property Continuity connection has all the stiffness set to infinite or better to a very high value equal to 10 N m The choice of the value is arbitrary appropriately larger than the ordinary connections stiffness In future development of the software the stiffness values of the continuity constraints will be defined automatically properly higher than the stiffer panel of the structure This type of property can be used for example when the user wants to guarantee the continuity between two panels meaning that actually two surfaces are only one panel so there is no connection between them Thus because it is not obvious that the user draws a surface for each panel he can draw the surfaces how he prefers the calculation works well in every case as shown in the thesis An algorithm for numerical modelling of Cross Laminated Timber structures by Gabriele D Aronco The parameters of the 80 Chapter 5 Pre processor and interface tutorial connection property Continuity connection cannot be changed by the user he should define another connection property in order to assign other stiffness Clicking twice on Custom Property a new connection property with custom mode can be created the menu of Figure 5 15 will appear Stiffness Connection parameters Properties Property Id Propertyl v Axial stiffness HD1 0 z Axia
94. file Can lla di tile Cartella di file Dimensione Choosing the problem type another set of menu will appear in the GiD interface this is the main menu of the selected problem type In this case of xlam kratos problem type the new command line will be the one shown in Figure 5 3 the first two columns belong to the GiD menu while the third column is the x am kratos menu BD GiD x64 Files View Geometry Utilities Data Mesh Calculate Kratos Help O8 S a at we GS MEH BS ise Figure 5 3 Xlam kratos command menu _ Project UNNAMED xlam kratos ii B eh The choice of the x am kratos problem type leads the appearance of a window which remembers to the user to use the z axis for gravity Figure 5 4 72 Chapter 5 Pre processor and interface tutorial Figure 5 4 Gravity warning The reasons for recommending the use of the z axis as vertical one are explained in Section 4 5 the warning window is just to remember it to the user before he starts drawing 5 4 Geometry creation As mentioned in the introduction the geometry that will be created consists of only 4 panels two in the plane x y one in the plane x z and another in the plane y z In this Section all the steps for its creation will be explained in detail DABBA Oas 2900 Ey Figure 5 5 Create object shortcut The first surface can be created using the command Create line and defining the fou
95. g as a library into application programs language design and general scripting The language is commonly used for rapid prototyping scripted applications GUIs and testing The first major GUI extension that works with Tcl is Tk a toolkit that aims to rapid GUI development that is why Tcl is now more commonly called Tcl Tk The language features far reaching introspection and the syntax while simple is very different from the Fortran Algol C Java world Although Tcl is a string based language there are quite a few object oriented extensions for it like Snit incr Tcl and XOTcl to name a few The main Tcl features are e All operations are commands including language structures They are written in prefix notation e Everything can be dynamically redefined and overridden e All data types can be manipulated as strings including source code e All commands defined by Tcl itself generate error messages on incorrect usage e Extensibility via C C Java and Tcl e Full Unicode support first released in 1999 57 A pre processor for numerical analysis of cross laminated timber structures 3 5 Python language e python Python is a widely used general purpose high level programming language Its design philosophy emphasises code readability and its syntax allows programmers to express concepts in fewer lines of code than would be possible in languages such as C or Java The language provides constructs inten
96. hat if the grain of the outer layer is arranged according to 1 axis local x axis the angle of orientation is equal to zero otherwise it is ninety degrees Being the other layers arranged transversely relative to the previous one and identified the orientation of the outer layer the orientations of the other ones are directly known Moreover since the number of layers is always odd the two sides of the panel can be interchangeably used as reference for the outer layer Considering the Kratos convention on the local axes orientation and the convention about the angle if the angle of grain orientation of the outer layer of the X Lam panel is zero modulus E11 corresponds to the elastic modulus Eo while moduli E22 and E33 correspond to Evo On the contrary if the angle of grain orientation of the outer layer of the X Lam panel is ninety degrees modulus E22 corresponds to the elastic modulus Eo while moduli E11 and E33 correspond to Eso As it will be shown in Chapter 5 Section 5 7 the different classes of timber defined by the standard EN 338 2004 are predefined in the GiD interface they are all set so that the angle of grain orientation of the outer layer is equal to zero If it is not zero the material should not be changed but it should be set the angle equal to ninety degrees instead of zero the elastic moduli are directly changed in the calculation of the orthotropic shell How the angle of grain orientation of the outer layer
97. hat the program can prepare data to be analysed Thus a new problem type has been created with the current goal of analysing an X Lam structure and with the prospective one of calculating the optimal connections between panels In order to analyse the features of the new problem type any part of the menu will be explained in the following sections by means of a simple example which makes the understanding very easy 69 A pre processor for numerical analysis of cross laminated timber structures 5 2 Example introduction To understand how the new problem type works a simple example will be used all the steps will be explained in detail to enable the user to reproduce the same example without any uncertainty The following sections will be a tutorial for learning the basics and advanced features of the new problem type covering full flow of GiD pre processing The philosophy of this tutorial is to get familiarised with x am kratos problem type how to select the problem type draw the geometry deal with the IDs assign the connection properties to the lines and assign the material and other basic features Some of these features are both in the pre processing and the post processing parts of GiD although the example that will be shown is from the pre processing one The example will develop a finite element problem in one of its principal phases the pre process and will include the consequent data and parameter description
98. have the ability of keeping into account all the possible typologies of connections and assembling of Cross Lam panels The finite element modelling technique adopted in the developed software concerns the modelling of panels connections and curbs The panels are modelled by shell elements with orthotropic linear elastic constitutive law The connections are modelled by punctual spring elements with isotropic linear elastic constitutive law The curbs are modelled by beam elements with isotropic linear elastic constitutive law The modelling philosophy consists in the automatic creation of the connections between X Lam panels To achieve this goal an abstract offset is applied between each border shell in which a surface is discretized and the beam elements in which a line is discretized The offset implies the duplication of the nodes that belong to both beams and shells It has zero distance to allow an easy management of the nodes since the 61 A pre processor for numerical analysis of cross laminated timber structures duplicated nodes will have the same coordinates of the original ones An example of the offset is shown in the introductive Chapter in Figure 1 1 The information about the connection properties is set at interface level to the lines which are then discretized in beams numeric entities Therefore spring elements with the stiffness values inserted by the user at the interface are used to join nodes wi
99. he hold down and brackets are calculated with the preliminary design it is important to think about the modelling of the other sides Some simplifications are used in order not to overly complicate the problem since it is just an example not aimed at a real project therefore e The vertical lines in z direction of the panels that represent the walls are modelled with infinite stiffness instead of calculating a distributed nailing it is used the Continuity connection property In general a connection property with a distributed axial stiffness would be created and it could be assigned to the vertical line of one panel a Continuity connection property could be assigned to the same line of the other panel This implicates to assign all the actual stiffness to one line and guarantee continuity to the other one considering that the stiffness are then added belonging to the same line This is suitable because being the springs in series the force is distributed equally on the springs and the stiffness sum as Kio 1 1 1 k2 e The top lines of the vertical panels are modelled with a distributed axial stiffness the hold down axial stiffness is set to zero while the parallel and orthogonal shear stiffness are infinite a great value equal to 10 N m Setting to zero the hold down axial stiffness but assigning a distributed axial stiffness the latter distributes along the entire top line of the panel including extreme
100. he problem type by the top command line as in Figure 5 1 Gal Gio x64 Project AA Files View Y Utilities Data Data Mesh Calculate Help 06912232 qi ass lr B B TE E Caltep o F s ing Examples ViaLefials ES Fluent Fi x De P 2 gt EJ kratos a F g es blem data ig OpenFoam ata units pa SAP2000 a i y E ocal axes PM AA E Transform A a D Internet retrieve Es Load CS Unload AS XL Debugger Fa lt Ey Figure 5 1 Problem type selection The problem type will appear in the top command line only if it is saved in the folder of the corresponding version of the GiD problem types The problem type specifically created for the analysis of X Lam structures is xlam kratos it uses the solver Kratos it is saved in the special folder so that it appears in the list of the problem types as shown in Figure 5 2 71 A pre processor for numerical analysis of cross laminated timber structures Gori b Computer OS C Programmi GiD gt GiD1216d problemtypes Organza v includi nella raccolta Nome de ansys55 de Caltep gid L Examples L Fluent gid de kratos gid d OpenFoam gid 2 SAP2000 gid dam Condividi con Moasteriza Uitur Nuova cartella ma modifica 29 05 2015 15 04 Figure 5 2 GiD problem types folder Tipo Cartella di file Cartella di file artella di file Cartella di file artella di file Cartella di
101. he 3 axis local z axis is identified by the normal of the panel 62 Chapter 4 Modelling strategy of X Lam buildings and conventions e the l axis local x axis is identified by the vector product between global Z axis and 3 axis e the 2 axis local y axis is identified by the vector product between 3 axis and 1 axis Ifthe panel lies on the global X Y plane floor panel e the 3 axis local z axis corresponds to the global Z axis e the 1 axis local x axis corresponds to the global X axis e the 2 axis local y axis corresponds to the global Y axis Figure 4 1 Orientation of local axes in wall X Lam panels le Figure 4 2 Orientation of local axes in a floor X Lam panel 63 A pre processor for numerical analysis of cross laminated timber structures To fully define the material of an orthotropic shell three elastic modulus E11 E22 and E33 and three Poisson ratios vi2 vi3 and v23 should be provided Three shear moduli G12 Gi3 and G23 are automatically calculated by means of the previous six parameters As already seen in Tables 2 4 and 2 5 X Lam panels are identified by the elastic moduli Eo and Eso where subscripts 0 and 90 indicate the direction parallel to the grain and the orthogonal one respectively To relate the elastic moduli of the orthotropic shell with the X Lam panel ones the grain orientation of the outer layer of the panel should be taken into account It is assumed t
102. he generality flexibility and reusability required for the current and future challenges in numerical methods Kratos is free because is devoted mainly to developers researchers and students and therefore is the most fruitful way to share knowledge and built a robust numerical methods laboratory adapted to their users needs Free means you have the freedom to modify and distribute the software 3 3 GiD Kratos interaction GiD pre and post processor needs the creation of a problem type to be able to create suitable input data files and to be able to read the Kratos results file The GiD problem type is the only connection between the pre processor and the Kratos such as between the Kratos and the post processor Any GiD Graphical User Interface GUI should communicate with Kratos in two ways 55 A pre processor for numerical analysis of cross laminated timber structures 1 it must be able to generate the files which are necessary for Kratos to run These files are usually mdpa input files that contain geometrical data and other py input files that contain parameters options important for the run 2 It must be able to start the run by calling Python plus a main script When the user starts a calculation GiD runs a bat file located in the problem type folder What these files do essentially is to set some environment variables to certain values and when all these variables have been set call Python to start
103. he shell forces of the structure subjected to all the load conditions The peaks of tension are discoverable at the windows corners In Figures 7 28 and 7 31 the structure is only subjected to the seismic forces condition The peaks of tension are correctly localized at the hold down springs the compression and tension zones follow correctly the deformation of the structure 172 Chapter 7 Modelling of a complex structure 7 4 4 Reactions The reactions vector field is shown in Figures 7 32 7 37 it could be a check of the correct behaviour of the structure The Z reactions vector field is shown for the two load configurations and taking only into account the storeys seismic forces to visualise the hold down reactions The X reactions vector field and the Y reactions vector field are also shown respectively for the configurations A and B A A x step 1 Display Vectors of REACTION Z REACTION factor 9 7329e 06 Deformation x97 DISPLACEMENT of Kratos step 1 Figure 7 32 Z Reaction vectors display for the configuration A step 1 Display Vectors of REACTION Z REACTION factor 2 3128e 5 1 Deformation x164 019 DISPLACEMENT of Kratos step 1 Figure 7 33 Z Reaction vectors display for the configuration A taking into account only the storeys seismic forces 173 A pre processor for numerical analysis of cross laminated timber structures z ak step 1 Display Vectors of REACTION Z REACTION fa
104. he user during the definition of the shell element property the angle of grain orientation of the outer layer the number of layers and the thickness of each layer This file is necessary for the calculation especially for the modelling of the orthotropic shell as a composite cross section with a defined number of layers which will be explained in Section 6 4 8 126 Chapter 6 Pre processor programming detail 6 4 8 Materials py The file materials py is generated by Kratos when the calculation is launched and it has the python format In general it shows for any element property its identification number the material assigned the constitutive law used and for the beam also the height and width of the rectangular section For the example described in Chapter 5 the first section of the file materials py results as shown in Figure 6 4 Figure 6 4 Materials py first section list of elements properties In addition to this section another one has been implemented which is printed inside the same file To achieve this a modification has been done to the TCL file which prints this one adding it another section written as a comment in python format therefore this additional section can be read by Kratos because it is written in python language The additional section enables the modelling of shells with composite cross section each layer of the composite cross section is modelled as an orthotro
105. he values of the mechanical properties inside of each class of resistance compared to the totality of the material this effect is defined homogenisation of the material h4 Figure 2 2 Effects of timber classification according to resistance Piazza Tomasi and Modena 2007 Numerous and complexes are the factors that can affect the resistance of timber elements leading the regulators to adopt an approach consisting in the following points e selection of elements suitable for structural use and having minimum physical mechanical guaranteed characteristics classification according to resistance e assignment to classified elements of characteristic values of the main mechanical properties strength classes and characteristic performance profiles e design of the elements by means of calculation rules specifically designed to use these characteristic values The method used to define the properties of the timber elements for structural purposes in the European legislation is the semi probabilistic limit state In order to fall under this methodology it is necessary to abandon the mechanical characterisation of the 14 Chapter 2 Generalities about timber and X Lam technology net wood and enlist to a mechanical description of the structural element for a given applied stress The characteristic values of strength and modulus of elasticity are therefore defined as values to the 5 percentile of the population
106. ibuted nailing calculated by means of the three characteristic load carrying capacities set by the user In case of Continuity connection property nothing is set because this property means that there is no connection on the line it is ensured the continuity The only two lines that do not have this connection property exhibit the three values of the capacities calculated by the processor as explained in Section 2 7 3 Table 6 5 More Connections file 84615 38 84615 38 59230 77 50769 23 50769 23 10153 85 6 4 6 More materials The file More Materials provides some information about the material necessary for the post process it shows for any material assigned to an element property the strength and density values belonging to the orthotropic material For the 124 Chapter 6 Pre processor programming detail example described in Chapter 5 relatively to the shell material the file More Materials results as shown in Figure 6 3 Begin Mat C14 shell ending 14 ensionpar 8e 6 ensionort Compressionpar 16e 6 ompressionort 2 0e 6 Shear 1 7e 6 Characteristic 2844 9 Mean 3433 5 nd Mat Figure 6 3 More Materials file The first six lines Figure 6 3 show the strengths bending resistance tension parallel to the grain tension orthogonal to the grain compression parallel to the grain compression orthogonal to the grain shear resistance The last two li
107. ication number To avoid problems in case of removal of a surface but to leave the user the possibility of deleting it without having to redraw the whole geometry the surfaces IDs are renumbered Renumbering consists in removing 117 A pre processor for numerical analysis of cross laminated timber structures the possible jumps of numbers and assigning to the surfaces a number from one up to the total number of surfaces of the final geometry Relatively to the lines it is necessary that all the identification numbers are subsequent between them and that they are subsequent to the surfaces ones too As for the surfaces when a line is deleted it is removed from the tree As mentioned it is noticeable that GiD has a hierarchy of entities which imposes that lines cannot be removed if firstly all the surfaces containing them have not been removed This means that if a line is removed also all the surfaces to which it belongs should have been previously removed from the drawing and so from the tree To avoid problems in case of removal of a line but to leave the user the possibility of deleting it without having to redraw the whole geometry the lines IDs are renumbered Renumbering consists in removing the possible jumps of numbers and assigning to the lines a number that differently from the surfaces does not start from one Due to computational reasons the second criteria of renumbering the lines IDs is that they start from the
108. ile c Connection with a metal bracket d Connection with a concealed metal plate FPInnovations 2013 eos ii aaa 33 Typical wall to floor X Lam connections a Connection with self tapping screws b Connection with a metal bracket c Connection with concealed metal plates FPInnovations 2013 ccccccccceseeesteeiees 34 Typical wall to floor X Lam connections in balloon construction FPInnovations 2013 5 sisiehsieteiohe nds 35 Typical wall to roof X Lam connections FPInnovations 2013 37 xi A pre processor for numerical analysis of cross laminated timber structures Figure 2 13 Sihga Idefix innovative connection system SiNQ cccccccccceeeseeseeees 37 Figure 2 14 a Failure modes for timber and panel connections with single shear UNI PEN TOO Sol FLOOD och a R 42 Figure 2 14 b Failure modes for timber and panel connections with double shear UNI ENTIIS ATL DONA AAN 42 Figure 2 14 c Failure modes for steel to timber connections UNI EN 1995 1 1 2009 Figure 2 15 Residential and non residential X Lam projects a 10 storey Fort in Melbourne b 9 storey Stadthaus in London c Open Academy in GFT CLAD AA A O nscale 47 Figure 3 1 Diagram of GiD workflow GiD User Manual onu 51 Figure 3 2 Diagram depicting the files system GiD User Manual ooo 51 Figure 4 1 Orientation of local axes in wall X Lam panels ono 63 Figure 4 2 Orientation of local axes in a floor X Lam panel ooo 63
109. ily recognise the line For example selecting the drawing of line 2 the geometry will appear as in Figure 5 31 For the example analysed Property will be assigned to line 7 and Property2 to line 11 the other connection properties are left with the default Continuity connection All the connection properties are randomly assigned because the real analysis is not the goal of this simple example In the example of Chapter 7 they will be assigned sensibly depending on the connection of the floor slabs and walls assigning sensible parameters to the different connection properties as well The Surfaces menu completed by the assignation of the connection properties to the lines is shown in Figure 5 32 Surfaces E Surf 2 Line 3 Connection Continuity_connection E Line 7 Connection Propertyl E Line 5 Connection Continuity_connection E Line 6 Connection Continuity_connection Surf 3 E Line 2 Connection Continuity_connection E Line 6 Connection Continuity_connection E Line 8 Connection Continuity_connection E Line 9 Connection Continuity_connection E Surf 4 E Line 10 Connection Continuity_connection F Line 8 Connection Continuity_connection E Line 5 Connection Continuity_connection E Line 11 Connection Property2 Figure 5 32 Surfaces menu with assigned connection properties 97 A pre processor for numerical analysis of cross
110. imne com kratos Martinson http www martinsongroup com Piazza M Tomasi R e Modena R 2007 Strutture in legno Hoepli Milano Popovski M Schneider J Schweinsteiger M 2010 Lateral load resistance of cross laminated wood panels Proceedings of the 11th World conference on timber engineering Riva del Garda Italy Python https en wikipedia org wiki Python programming language Rothoblaas http www rothoblaas com 182 References Sihga http www sihga com en products idefix idefix ifs html Stora Enso http www storaenso com Tel http en wikipedia org wiki Tcl Tel http zetcode com lang tcl tcl Tel https en wikibooks org wiki Tcl Programming Introduction Timber Tower http www timbertower de Traetta G 2007 Connection Tecniques for CLT elements Temtis Seminar Cross Laminated Timber Graz Austria Wood Works http www wood works ca Yates M Linegar M Dujic B 2008 Design of an 8 storey Residential Tower from KLH Cross Laminated Solid Timber Panels Proceedings of the 10th World Conference on Timber Engineering Miyazaki Japan Zecchetto M 2015 Una procedura numerica per il progetto di edifici in X Lam Padova Italy 183
111. in Section 2 7 3 Correction factor kmoa this is the correction factor taking into account the effects of load duration and moisture content on the timber strength which is prescribed by the code UNI EN 1995 1 1 2009 see Table 2 2 Material security coefficient this is the partial factor for a material property ym which is prescribed by the code UNI EN 1995 1 1 2009 see Table 2 3 82 Chapter 5 Pre processor and interface tutorial Each of the parameters explained presents on the interface an abbreviated name that may be not perfectly clear for a matter of space at the interface Anyway placing the mouse over the box corresponding to each of the parameters pop ups that explain their meaning will appear The stiffness introduced in the processor for the analysis are not only this one there are actually other three rotational stiffness hidden to the user which are set as default to a small value equal to 100 N m this small value is to mean zero Similarly to the Continuity connection values the choice of the value is arbitrary negligible compared to the ordinary connections stiffness These three stiffness are not defined by the user because they are in general a small value that the user does not calculate every time they are only necessary to define all the stiffness of the springs that simulate the connections in the xlam driver application see the thesis An algorithm for numerical modelling of Cross La
112. ing sections starting from the discretization up to the displacement tension and reactions fields in the two load configurations analysed 165 A pre processor for numerical analysis of cross laminated timber structures 7 4 1 Structure discretization A structured mesh is used for the discretization of the structure The dimension of each meshed element is equal to 400 mm for a total amount of 2976 quadrilateral elements 910 linear elements and 3059 nodes Figure 7 20 ah A ale Figure 7 20 Meshed view of the structure in GiD After the application Xlam driver comes into play the discretization used leads to a different number of elements and nodes The system increases the number of nodes to 5103 and the number of elements to 6215 2329 of which are spring elements 7 4 2 Displacement field The displacement field for the two load configurations and the total displacement of the structure taking only into account the storeys seismic forces are shown in Figures 7 21 7 25 166 Chapter 7 Modelling of a complex structure X DISPLACEMENT 0 0097713 0 0086586 0 007546 0 0064333 0 0053207 0 004208 0 0030954 0 0019827 0 00087008 4 step 1 0 00024257 Contour Fill of DISPLACEMENT X DISPLACEMENT Deformation x109 DISPLACEMENT of Kratos step 1 Figure 7 21 X displacement contour m for the configuration A Z DISPLACEMEN 7 51770 05 00011945 00024447 0 003705
113. ion a b c Figure 2 10 Typical wall to floor X Lam connections a Connection with self tapping screws b Connection with a metal bracket c Connection with concealed metal plates FPInnovations 2013 34 Chapter 2 Generalities about timber and X Lam technology e Self tapping screws The simplest method for connecting a floor or a roof to walls below is to use long self tapping screws driven from the X Lam floor directly into the narrow side of the wall edge Self tapping screws can also be driven at an angle to maximize the fastening capacity in the panel edge The same principle could be applied for connecting walls above to floors below where self tapping screws are driven at an angle in the wall near the junction with the floor However this type of connection has relatively low seismic capacity in terms of strength and stiffness Popovski 2010 e Metal brackets Metal L shaped brackets are commonly used to connect floors to walls above and below to transfer lateral loads from diaphragm to shear walls Nails or wood screws can be used to attach the metal brackets to the X Lam panels They are also used for connecting roofs to walls e Concealed metal plates As discussed before while concealed metal plates have considerable advantages over exposed plates and brackets especially fire resistance the system requires precise profiling at the plant using CNC machining technology 3b Balloon constructio
114. ion leads to impose a hierarchy of resistance within the single connection the relationship considered is only valid in case of failure of the connection on the fasteners and not on the steel plate The resistance of the connection would actually be equal to Rotate N prk Ry min Rfast Neff Fv rk being Nirx the characteristic value of the tensile strength for steel plates with holes as defined in the UNI EN 1993 1 1 2005 This assumption in fact implies further verifications after the post process to check that the actual failure mode of each connection is the one assumed This verification will imply the following main problems whose checks will be not deepened in this thesis e statistical distribution of all the resistances e different safety factors for the resistances Fv rk and Nirk e different resistance values for a single fastener The characteristic load carrying capacity Fv prk of a single fastener can be calculated according to UNI EN 1995 1 1 2009 as the minimum of all the resistances associated to the possible modes of failure of a single fastener The code differentiates the timber to timber and panel to timber connections from the steel to timber ones 40 Chapter 2 Generalities about timber and X Lam technology Figure 2 14 For each of these families both possible failure modes and relative resistance values referred to single fastener are shown The characteristic load carrying ca
115. ismo con gran dedicaci n y entusiasmo Su perspicacia ideas y consejos han sido extremadamente valiosos para los resultados del mismo Aprecio profundamente toda ayuda fomento disponibilidad y paciencia que por su parte he recibido Roberto gracias por guiarme a partir del grado A su vez profunda gratitud a mi co supervisor Dr Antonia Larese De Tetto quien me gui durante mi periodo de investigaci n en la Universitat Polit cnica de Catalunya compartiendo conmigo sus ideas y ricas experiencias y d ndome sugerencias muy valiosas para mi trabajo de investigaci n Antonia gracias por toda tu colaboraci n Muchas gracias al personal de CIMNE por su ayuda con los c digos de programaci n Sobre todo al Ing Massimo Petracca por su especial y destacado inter s proporcion ndome sabios consejos para este proyecto investigativo Gracias a Javier G rate Vidiella por su inestimable ayuda en la programaci n Tambi n me gustar a expresar mi m s sincero agradecimiento a todos aquellos profesores que me han ense ado y aportado mucho no s lo desde el punto de vista profesional sino tambi n desde el punto de vista humano Gran agradecimiento al Prof Ing ngel Carlos Aparicio Bengoechea por creer en m desde el primer momento y por transmitirme tanta fuerza y energ a incluso en ocasiones hasta con unas simples palabras Tambi n agradezco a Gabriele quien comparti conmigo este proyecto de investigaci n A ti g
116. istances according to UNI EN 1995 1 2007 ideas 13 Table 2 4 Strength classes according to EN 338 2004 for solid wood of conifers anad POD UAE esse Correa a E Rlerdcgun cava EEE olsen aes 16 Table 2 5 Strength classes according to EN 338 2004 for hardwood poplar A O A ease 16 Table 2 6 Values of Kser for fasteners and connectors in N mm in timber to timber and wood based panel to timber connections according to UNI EN 1995 1 1 2009 the density pm is expressed in kg m and the diameter is expressedin MM AA Nee cis Hao Res 39 Table 6 1 E TO filer archaea Gee TA 119 Table 6 2 Co nnection info HO A a 121 Table 6 3 ESTA CEC MENTON a Oe 122 Table 6 4 Line element info ME A 123 Table 6 5 More Connections TE AAA aan 124 Table 6 6 SO 126 Table 6 7 Connection info file for line TN RA 131 Table 6 8 Connection info file for line TL tia 133 Table 6 9 More Connections file for line 7 cccccccccccceecceesseceteceteteeeeeeseeenseeneenaes 136 Table 6 10 More Connections file for line Il ccccecccccccccsccceteteteeeeeeeseetneteteeeaes 137 Table 7 1 Design concept structural types and upper limit values of the behaviour factors for the three ductility classes EN 1998 1 2004 ooo 147 Table 7 2 DION SEISMIC A E a E noir sata E E TA 150 xix A pre processor for numerical analysis of cross laminated timber structures Table 7 3 a Summary of forces stresses and hold down disposed on wa
117. l be explicated in Section 5 7 In case of shell property type the Constitutive law can be Elastic Isotropic or Elastic Orthotropic however according to the assumption that will be explained in Section 4 2 an orthotropic shell will be used For this example a shell property named Shell_prop is created with the parameters of Figure 5 36 New property Properti Property Id Shell_prop Y Property type Shell ed Constitutive law Elastic Orthotropic Material C14 shell y Thickness 1 0 Angle 0 Number of layers 5 Thickness layer 1 0 2 Thickness layer 2 0 2 Thickness layer 3 0 2 Thickness layer 4 0 2 Thickness layer 5 0 2 Thickness layer 6 0 0 Thickness layer 7 0 0 Thickness layer 8 0 0 Thickness layer 9 0 0 Solid property Solid_prop Ok Cancel Figure 5 36 Shell property parameters 100 Chapter 5 Pre processor and interface tutorial Relatively to the material similarly to the other elements properties it can be selected from the already default materials database currently it can be considered just a name then it will be explicated in Section 5 7 The other parameters that should be set in case of shell property type are e Thickness this is the total thickness of the panel in m e Angle this is the angle of grain orientation of the outer layer of the panel in degrees It is assumed to be equal to zero if the grain of the outer layer is arranged accor
118. l nuts Usually no edge profiling along the panel is needed as it relies principally on the pull out resistance of the screwed or glued in rods Traetta 2007 2b Perpendicular wall panel connection This Section presents connection details for connecting wall panels to wall panels positioned at right angles transverse direction Such connection details include interior partition walls to exterior walls or just exterior corner walls Several systems have been adopted to establish connection between perpendicular walls 32 Chapter 2 Generalities about timber and X Lam technology L a b c d Figure 2 9 Typical perpendicular wall to wall X Lam connections a Connection with self tapping screws b Connection with a wooden profile c Connection with a metal bracket d Connection with a concealed metal plate FPInnovations 2013 e Self tapping screws This is the simplest form of connecting X Lam wall panels together There are some concerns related to this form of connection due to the fact that the screws are driven in the narrow side of panels in particular if screws are installed in the end grain of the cross layers Self tapping screws can be driven straight into the X Lam panel or at an angle to avoid direct installation of screws in the narrow side of the panel e Wooden profiles Concealed wooden profiles or keys can also be used in a similar way with self tapping screws or traditional wood sc
119. l stiffness HD2 0 v Distributed axial stiffness 0 z Distributed parallel shear stiffness 0 z Distributed orthogonal shear stiffness 0 z Rk HD1 0 ia Rk HD2 0 v Rk distributed 0 z Correction factor kmod 0 z Material security coefficient 0 z Ok Cancel Figure 5 15 Stiffness menu The custom property contains in turn two ways to define a connection property the first one is Stiffness Figure 5 15 and the second one is Connection parameters Figure 5 16 The menu Stiffness requires a new property name and some parameters which are five stiffness three load carrying capacities and two coefficients which should be introduced by the user While the stiffness are used for the analysis the load carrying capacities and the coefficients come into play only in the verification phase but they 81 A pre processor for numerical analysis of cross laminated timber structures should be already set at this interface level meaning in the pre process for being available for the post process The values that should be set in the menu Stiffness are Axial stiffness HD1 this is the axial stiffness of the first hold down in N m The hold down with less coordinate on the x or y axis is considered as first hold down in order to distinguish it from the other one of the panel Axial stiffness HD2 this is the axial stiffness of the second hold down in N m As second hold down it is considered the hol
120. laminated timber structures At this point the connection properties are completely defined and assigned to the lines therefore other model properties can be created and assigned 5 5 3 Elements properties creation The elements properties can be actually created after the assignation of the material Section 5 7 but they will be explained before as belonging to the model properties They can be created clicking twice on the menu Properties see Figure 5 13 so that the window of Figure 5 33 will appear New property Properties Property Id Propertyl y Property type Beam My Constitutive law Elastic Isotropic lod Material c14 v Section type Rectangular k Ok Cancel Figure 5 33 Elements Properties menu With reference to Figure 5 33 the Property Id is the name of the new property that will be created to whom any name can be assigned The Property type can be Beam Solid or Shell The subsequent parameters change depending on the property type so the different property types will be explained separately In case of beam property type the Constitutive law can only be Elastic Isotropic the Material can be selected from the already default materials database the Section type is rectangular and the Height and Width of the section should be set For the example a beam property named Beam prop is created with the parameters of Fig
121. lements if not set as curbs at the interface Their geometric and structural properties are so that their presence is negligible in the analysis of the structure Figure 1 2 shows the springs connecting the shells and beams e e a e SHELL SHELL SHELL SHELL SHELL SHELL S gt i e Ka e 2 SPRING a MA E AA EL CEA TA BEAM BEAM BEAM BEAM BEAM BEAM Figure 1 2 Exploded view of a panel edge The pre process phase concerning the creation of a new problem type in GiD is described in this thesis It enables at interface level the creation of geometry and the A pre processor for numerical analysis of cross laminated timber structures assignation of elements properties material loads boundary conditions and above all connection properties Moreover it allows the creation of suitable input data files for the analysis and the modelling of the panels as orthotropic shells with composite cross section The analysis phase concerning the numerical changes in Kratos framework is described in the thesis An algorithm for numerical modelling of Cross Laminated Timber structures by Gabriele D Aronco It consists in the implementation of spring elements and the numerical procedure for automatic modelling of the connections meaning duplication of panels border nodes and joint of nodes by means of spring elements 1 3 Thesis structure A brief summary of each chapter of the thesis is given in this Section In each chapte
122. lication the extreme points of the lines are identified and the hold down stiffness is assigned to the springs of these points 95 A pre processor for numerical analysis of cross laminated timber structures In the Surfaces menu any line has an assigned connection set as default to the property Continuity connection It can be changed assigning previously created properties these properties allow to choose a particular type of connection for a line that is a connection between two consecutive panels which have that line in common Clicking twice on Connection of the desired line another connection property of the ones already created can be selected for that line with reference to Figure 5 30 E Surf 3 E Line 2 L Continuity E Lii ntinuity_connection _ Propertyl yu Property2 y Continuity_connection Line 9 Connection Continuity_connection Figure 5 30 Selection of a connection property lo a DrawGroupOff E DrawGroupOn Figure 5 31 Drawing of line 2 With a more difficult geometry it may be difficult to recognise the line to which you are assigning a property To overcome this problem you can click with the right 96 Chapter 5 Pre processor and interface tutorial mouse button on the desired line and select Draw thus the selected line will be visualised in blue colour and the other ones in red for 5 seconds therefore allowing to eas
123. lled panel leads to the need of modelling the hold down stiffness with a different value compared to the real one For further information about the behaviour of an X Lam panel subjected to horizontal forces see the thesis Una procedura numerica per il progetto di edifici in X Lam by Massimiliano Zecchetto With reference to Figure 4 3 the stiffness value Kyp moa of a modelled hold down can be obtained by imposing the effects of rotation at the base of the panel in terms of displacement dx to be the same of a real panel subjected to equal overturning moment With reference to Figure 4 3b for a modelled panel subjected to a given moment M follows B dy mod mod 2 Umoa 2 dy mod A B 65 A pre processor for numerical analysis of cross laminated timber structures d Fup ymod K HD mod dx mod moa H dymod 23 dymod dza B For a real panel subjected to the action of the same moment M Figure 4 3a follows 1 dy real Oreal B T Oreal dy real i B d _ Fi y real Kup real H Creel Urea deca dy real B To finally get equal components of horizontal displacement in the two cases modelled and real panel the value of Kyp mod can be obtained by means of simple algebraic steps dy real dymod ee Kup real Kup moa Kup mod 2 Kup real Ultimately the hold down stiffness used in the model is equal to two times the real one to properly take into account the diffe
124. lls Due to the 45 A pre processor for numerical analysis of cross laminated timber structures limitations in the length of the X Lam panels this system is often used in low rise commercial or industrial buildings connections are usually more complex in this form of construction Balloon construction is generally less common compared to platform construction X Lam solid wood panels are used both as load bearing reinforcing elements and non load bearing elements Areas of application e houses and apartment buildings e multi storey residential buildings e public buildings e hotels and restaurants e schools and kindergartens e offices and administrative buildings e event halls e industrial and commercial buildings e reconstructions extensions and upgrades e building retrofits e bridges Numerous buildings using X Lam panels have already been erected around the world starting in Europe and recently some projects were realized in North America and in Australia In Europe the tallest X Lam structure to date is the 9 storey Stadthaus residential building in London which includes eight storeys of X Lam over one storey of concrete At the time of the erection in 2009 this building was the tallest wooden residential building in the world Short erection time environmental benefits and cost efficiency of the building illustrated how X Lam can be a competitive system in the marketplace Yates et al 2008 In 2011 ano
125. lls in x a EEE ees E AE alana ten E E AE ENE A 155 Table 7 3 b Summary of forces stresses and hold down disposed on walls in y diretti on arana A A EE E E 155 XX Chapter 1 Introduction CHAPTER 1 INTRODUCTION 1 1 Research background and motivation Wood as a building material possesses some inherent characteristics that make timber structures particularly suited for the use in regions with a high seismic risk both due to material properties such as lightness and load bearing capacity good weight to strength ratio and to system properties like ductility and energy dissipation Recently there have been new developments with prefabricated timber elements which aim to address modern building requirements for cost constructability and structural performance Massive cross laminated timber panels X Lam which can be used as wall panels floor panels or roof panels in timber buildings are becoming a stronger and economically valid alternative to traditional masonry or concrete buildings in Europe and recently also overseas Especially in seismic prone countries X lam buildings are gaining more and more popularity However due to relatively short time since this wood engineered product has been launched to the market the knowledge about cross lam as a structural material is still limited In recent years several research projects around Europe and in North America have been launched with an aim to better understa
126. making the connection on site In case of double surface spline connection the strength and stiffness of the connection can be increased If SCL structural composite lumber is 31 A pre processor for numerical analysis of cross laminated timber structures used as the spline the joint can be designed to resist moment for out of plane loading Augustin 2008 Structural adhesives could be used to enhance the strength and stiffness e Half lapped joint In this connection type long self tapping screws are usually used to connect the panel edges The joint can carry normal and transverse loads but it is not considered to be a moment resisting connection Augustin 2008 This connection detail is considered as very simple so it facilitates quick assembly of X Lam elements However there is a risk of splitting of the cross section due to concentration of tension perpendicular to grain stresses in the notched area This is particularly emphasized for cases where uneven loading on the floor elements occur Augustin 2008 e Tube connection system Tube connection system incorporates a profiled steel tube with holes in the X Lam panel Panel elements are delivered on site with glued in or screwed rods driven in the plane of the two panels which are supposed to be connected The tube connector is inserted at certain locations along the edges of the panels where the metal tubes are to be placed The system is tightened on site using meta
127. miento por la constante lucha y fuerte perseverancia para conseguir cada gota de este oc ano He tenido momentos m s dif ciles y duros aun as no cambiar a nada de lo que he vivido en mi vida todo me ha llevado a ser la persona que hoy en d a soy Gracias a m misma porqu nunca me di por vencida Alessandra Ferrandino Padua 16 de septiembre de 2015 vi Table of contents TABLE OF CONTENTS A II O eh chats atl chats i ACKNOWLEDGMENTS cocos iii AGRADECIMIENTO 00 srta v TABLE OF CONTENTS una eke ane AG ta ni vii LIST OF FIGURES corra a xi LISTOR TABLES squer T xix 1 CHAPTER 1 INTRODUCTION coccion 1 1 1 Research background and Motivation 1 1 2 Objectives and scope naaa 3 13 Thesis SAUCES AA A Sd 6 2 CHAPTER 2 GENERALITIES ABOUT TIMBER AND X LAM TECHNOLOGY nner Pa 9 2 1 Generalities about wood and timber 0 0 00 eeeeeeeeeeesecesecneeeseeeeeeeeeeseceaecaeeeaeeneees 9 2 2 Load duration and moisture influences on timber strength 0 0 0 0 eee 10 2 3 Timber classification and strength classes ccccccssceseceseceeeeeeeeceeceteeeeeeenseees 13 2 4 Generalities about cross laminated timber ooooncccinocinococonoconoconcnononcnnnoconocannconnnoos 17 2 5 X Lam panels manufacturing ec 8 aliases iG iss rca udecee sbadaeauseucae ones otuseous soade aston 20 2 6 Advantages of X Lam technology viii iii iii 23 Zid X Lam connection A A a a 27 2 7 1 CONNECTIONS Denda li 38 2 1 2 Connections A o 38 2 7
128. minated Timber structures by Gabriele D Aronco Stiffness Connection parameters Properties Nail diameter HD1 b y Total number of nails HD1 0 Nail diameter HD2 0 x Total number of nails HD2 0 z Distributed nail diameter 0 Y Total number of distributed nails 0 z Panel density 0 z Fv Rk per nail HD1 0 bi Fv Rk per nail HD2 0 z Fv Rk per nail distributed 0 z Correction factor kmod 0 x Material security coefficient 0 x Ok Cancel Figure 5 16 Connection parameters menu 83 A pre processor for numerical analysis of cross laminated timber structures The menu Connection parameters Figure 5 16 requires a new property name and some parameters through which the stiffness and the design load carrying capacities are calculated by the processor as explained in Sections 2 7 2 and 2 7 3 Also in this case the initial parameters are used for the analysis while the load carrying capacities and the coefficients come into play only in the verification phase but the relative parameters should be already set at this interface level meaning in the pre process for being available for the post process The values that should be set in the menu Connection parameters are Nail diameter HD1 this is the nail diameter of the first hold down in m the hold down with less coordinate on the x or y axis Total number of nails HD1 this is the total number of nails of the first hold down meani
129. mm plana Pp Similarly to the surf elem info this file enables to know the identification number of the lines to which the elements of the mesh belongs in order not to lose the information about them It is obtained in the code defining an occult group that in fact refers the mesh elements to the original lines of the geometry 6 4 5 More connections The file More Connections provides a matrix necessary for the post process which shows the list of the new lines IDs the new surfaces IDs to which the lines belongs and their resistance connection properties For the example described in Chapter 5 the file More Connections results as shown in Table 6 5 It is noticeable that the lines belonging to more than one surface appear in the table Table 6 5 more times For example line 6 former line 5 appears as belonging to 123 A pre processor for numerical analysis of cross laminated timber structures surfaces 1 and 3 respectively former surfaces 2 and 4 This is foregone if you remember that the user assigns to each line belonging to each surface a connection property therefore if a line belongs to more than one surface he assigns more connection properties which in general will be different The third column reference is made to Table 6 5 shows the whole resistance of the connection property meaning three design load carrying capacities one for any hold down and one for the brackets or distr
130. n Figure 2 11 Typical wall to floor X Lam connections in balloon construction FPInnovations 2013 35 A pre processor for numerical analysis of cross laminated timber structures In Europe the most common type of structural form in X Lam construction is the platform type of system due to its simplicity in design and erection However in non residential construction including industrial buildings it is common to use tall walls with an intermediate floor between the main floors of a building So called mezzanine floor is often located between the ground floor and the first floor However it is not unusual to have a mezzanine in the upper floors of a building Several attachment options to connect X Lam floor to a continuous X Lam tall wall exist for such applications The simplest attachment detail includes the use of a wooden ledger made of structural composite lumber to provide a continuous bearing support to the X Lam floor panels Another type of attachment is established with the use of metal brackets Attachment of wooden ledger or metal brackets to the X Lam wall and floor panels is established through the use of screws lag screws or nails However out of plane bending due to wind suction could be an issue with this type of detail and designers need to take that into account 4 Floor to floor connections When the connection is used in floor assemblies acting as diaphragms the connection must be capable of trans
131. n order to quickly identify the surfaces and lines shown in the Surfaces menu Surfaces E Surf1 E Line 1 Connection Continuity_connection Line 2 Connection Continuity_connection E Line 3 Connection Continuity_connection Line 4 Connection Continuity_connection o o E Surf 2 E Line 3 Connection Continuity_connection Line 7 Connection Continuity_connection E Line 5 Connection Continuity_connection Line 6 Connection Continuity_connection o o D w urf 3 Line 2 Connection Continuity_connection Line 6 Connection Continuity_connection E Line8 Connection Continuity_connection Line9 Connection Continuity_connection o 0 q D w urf 4 Line 10 Connection Continuity_connection Line 8 Connection Continuity_connection Line 5 Connection Continuity_connection Line 11 Connection Continuity_connection i i n o Figure 5 25 Surfaces menu 92 Chapter 5 Pre processor and interface tutorial Figure 5 26 Geometry created before Checking the geometry and the Surfaces menu it is clear that the four surfaces and all the lines belonging to them are shown in the tree Pretending that one of the surfaces was drawn by mistake and it needs to be removed it can be removed selecting the command Delete Figure 5 27 at the bottom section of the GiD menu In particular the command that allows removing at the same
132. n value of the load carrying capacity can be obtained as Poe Rk Kmod Ym Rawur340 met mes 33 kN Rawura4o Melt mec es 49 kN Rawurs40 Tar Tal 69 kN Rawnrezo ETS mod _ 1004 11 85 kN Ym 7 1 3 WHT CHIODATURA PARZIALE Resistenza caratteristica a trazione Fissaggio ori 5 TYP WHT conmettori By acta Chiodi Anker Viti Spedali 040x40 050x40 340 040x40 050x40 40x60 5 0x50 4 0x40 5 0x40 440 40x60 5 0x50 24 0x40 050x40 2 050x50 40x40 5 0x 40 620 40x60 5 0 x50 se Utilizzando 2 angolari TYP WHT per singola giunzione le resistenze di progetto raddoppiano WHT CHIODATURA TOTALE Resistenza caratteristica a trazione Fissaggio Fori 5 connettori TYP WHT Sonn Viti Speciali pz 350x40 20 85 0x 50 05 0 x 40 05 0 x 50 50x40 5 0x50 5 0x40 5 0x50 Rondella ULSS05610 Rondella ULS707720 Figure 7 11 Selected tension connections Rothoblaas The stresses on the hold down can be calculated with equilibrium relationships the rigid rotation of the first floor and the rocking effect on one single wall should be considered 153 A pre processor for numerical analysis of cross laminated timber structures Concerning the rigid rotation of the first floor the overturning and stabilising moment result Movert W g h 225 3 675 kNm B 6 Mstav Wroog y 310 5 5 931 5 kNm
133. nd for skilled workers on site Construction process is characterized by increased safety on the construction site faster project completion and availability for occupancy in a shorter time For example it took four carpenters just nine weeks to erect nine storeys and the entire construction process was reduced from 72 weeks to 49 weeks Yates et al 2008 compared to a traditional reinforced concrete building In addition there is less disruption to the surrounding community and less waste is produced As most of the work occurs off site at the factory there is a lower demand for skilled workers on site e Easy handling and erection Handling the X Lam panels requires smaller cranes which also influences on the lower cost of a building construction One of the biggest benefits of using X Lam panels is that the structure can be built quickly and efficiently Because panels are designed for specific end use applications they are often delivered and erected using a just in time construction method making X Lam ideal for projects with limited on site storage capacity Panels are usually loaded into the truck at the manufacturing plant in the sequence that they will be required for installation on site Where it is not possible to 23 A pre processor for numerical analysis of cross laminated timber structures install X Lam panels immediately they can be off loaded and stored off the ground under a waterproof covering until required
134. nd installed on the surface of the panel Long self tapping screws are typically recommended by X Lam manufacturers due to their ease of installation along with high lateral and withdrawal capacity which make these fasteners popular because they can take combined axial and lateral loads Bolts and dowels are very common in heavy timber construction They can also be used in the assembly of X Lam panels especially for lateral loading If installed in the narrow face care must be taken during the design especially in X Lam panels with unglued edges between the individual planks in a layer This could eventually compromise the lateral resistance since there is a potential that such fasteners are driven in the gaps Figure 2 6 Typical three storey X Lam building showing various connections between the X Lam panels 28 Chapter 2 Generalities about timber and X Lam technology However there are other types of traditional and innovative fasteners and fastening systems that can be used efficiently in X Lam assemblies The choice of the type of connection to use depends largely on the type of assemblies to be connected panel configurations and the type of structural system used in the building With these mechanical connections several possibilities for assembling X Lam panels are possible as shown in Figure 2 6 1 Wall to foundation connections Several fastening systems are available for connecting X Lam wall panels to st
135. nd slender construction elements can increase the net building are e Static properties High in plane and out of plane strength and stiffness properties of X Lam panels enable in plane stability of the panels and lack of susceptibility to soft storey failures The cross lamination provides relatively high strength and stiffness properties in both directions giving it a two way action capability similar to a reinforced concrete slab e Seismic performance In terms of seismic performance timber buildings in general perform well because wood is relatively light as a construction material thus inertial forces caused by 24 Chapter 2 Generalities about timber and X Lam technology earthquakes are lower than in case of buildings made of other materials High ductility and energy dissipation capacities of X Lam buildings together with sufficient strength capacity make this construction system very effective at resisting lateral forces caused by earthquake ground motions e Fire resistance X Lam assemblies have inherently excellent fire resistance due to the thickness of panels which when exposed to fire slow down the heat propagation within the cross section and char at a slow and predictable rate 0 67 mm min according to ETA 06 0138 2006 Once formed this char protects the wood from further degradation helping to maintain structural integrity of the building In addition X Lam structures also tend not to have as many con
136. nd the potential of cross lam technology as a seismic resistant construction system Still limited is also the knowledge about the modelling of X Lam structures reason why a large research project started to investigate the development of a software for the analysis calculation design and verification of X Lam structures This project was born as collaboration between Padua University and Barcelona s CIMNE International Centre for Numerical Methods in Engineering Modelling of CLT buildings lies into properly model the connections between panels they play an essential role in maintaining the integrity of the timber structure and providing strength stiffness stability and ductility to the structure The connections may be modelled with A pre processor for numerical analysis of cross laminated timber structures punctual or distributed spring elements or with shell elements Anyway the goal is to provide the needed flexibility to the connecting points to avoid a fully unreal behaviour of the building being the panels very rigid in comparison to the anchoring connections Through the connections modelling the final aim is to enable the check of preliminarily designed connections or to find them iteratively starting from hypothetical or random connections The research project started with the thesis Una procedura numerica per il progetto di edifici in Xlam by Massimiliano Zecchetto which develops a software using MATLA
137. nes Figure 6 3 show the density values characteristic density mean density These are the values set by default because the material selected is the C14 so it is one of the already defined materials if the user defines another material with different strength and density values the values shown in the file More Materials will be the ones inserted 125 A pre processor for numerical analysis of cross laminated timber structures 6 4 7 Data orthotropic The file data Ortho provides a matrix necessary for the calculation which shows some information about the shell elements properties it shows for any shell element assigned at least to one surface almost all the values relative to the shell For the example described in Chapter 5 having been defined only one shell thick element the matrix is converted into a vector and the file data Ortho results as shown in Table 6 6 Table 6 6 Data Orthotropic file Table 6 6 shows the data Ortho file as a vector of one column but it is actually printed as its transposed a vector of one row The first row is the shell ID which is a way to identify each element with a number instead of the name given by the user GiD assigns as default a number to any element property defined The second row is the solid ID which as the shell ID is assigned by default by GiD instead of the name given by the user The subsequent rows are values assigned by t
138. ng the first surface created the final geometry results as in Figure 5 11 Figure 5 11 End geometry Even if the goal is not the calculation of the structure the surfaces have been created considering the gravity on z axis as if it was a real example meaning that the first and last surfaces created will be slabs and the two others walls the slabs are in the plane x y and the walls are in the planes x z and y z In order to understand the following steps the GiD ID identification number labels of each node line and surface can be visualised clicking the right mouse button and selecting Label All The IDs of the geometry are shown in Figure 5 12 77 A pre processor for numerical analysis of cross laminated timber structures Figure 5 12 Geometry IDs The identification numbers of the nodes are shown in black of the lines in blue and of the surfaces in pink These are the original GiD IDs which are assigned by default by the processor when a geometry is drawn It is noticeable that the IDs are defined according with the order of the drawing meaning that if the surfaces are created in a different order for example the right line is copied in z direction before the top one the identification numbers will be different As a matter of fact the end geometry could have also been created copying the lines at the same time without selecting them one at a time but in this way the order of creation of the surface
139. ng the number of nails if only one hold down is disposed the number of nails multiplied by the number of hold down if more than one hold down are disposed Nail diameter HD2 this is the nail diameter of the second hold down in m the hold down with greater coordinate on the x or y axis As for the Stiffness menu the two hold down are distinguished to leave the possibility of disposing two different types of hold down to one and the other side of the panel or to put only one of them in case of two surfaces which are actually a unique panel see Section 7 3 3 Total number of nails HD2 this is the total number of nails of the second hold down meaning the number of nails if only one hold down is disposed the number of nails multiplied by the number of hold down if more than one hold down are disposed Distributed nail diameter this is the nail diameter of the brackets or distributed nailing in m Total number of distributed nails this is the total number of nails of the brackets or distributed nailing meaning the number of nails if only one bracket or a distributed nailing is disposed the number of nails multiplied by the number of brackets if more than one bracket are disposed 84 Chapter 5 Pre processor and interface tutorial e Panel density this is the density of the panels that the connection should joint in N m This density will be also introduced in the definition of the material see Section 5 7 but i
140. non linear constitutive law for the spring elements that model the connections to enable the simulation of the contact problem Thus the use of non linear static pushover and non linear time history dynamic analyses will also be available Relatively to the post process and verification phases recommendations for further research are outlined to develop the missing phases of the research project Development of a procedure for the automatic verification of connections and panels according to the European codes This phase is already pre set by the pre process because the design load carrying capacities of the connections are already calculated and printed in the file More Connections as well as the strength values of the material of the panels are printed in the file More Materials Development of a procedure for the iterative calculation of the optimal connections once set first attempt solution The iterative nature of the design is not only a peculiarity of the X Lam structures but it is a particular feature of the design in general This peculiarity is immediately realised recalling that the intensity of the seismic action depends through the design spectrum on the periods of the fundamental modes of vibration of the structure which in turn depend significantly on the stiffness of the connections At each iteration the optimal connections necessary to resist to the active external forces can be calculated Nonethel
141. o define the main procedure of Kratos which significantly improves the flexibility of the framework in time of use The kernel and application approach is used to reduce the possible conflicts arising between developers of different fields Also layers are designed to reflect the working space of different people considering their programming knowledge Kratos is parallelized for Shared Memory Machines SMMs and Distributed Memory Machines DMMs In the same way it provides tools for its applications to adapt easily their algorithms to these architectures its scalability has been verified up to thousands of cores The Kratos structure due to its multi disciplinary nature has to support the wide variety of algorithms involved in different areas That s the principal reason which explains the variety of people mostly engineers composing the Kratos Community Some potential users of Kratos are e Finite Element Developers These developers are considered to be more expert in FEM from the physical and mathematical points of view than C programming For this reason Kratos provides their requirements without involving them in advanced programming concepts e Application Developers These users are less interested in finite element programming and their programming knowledge may vary from very expert to higher than basic They may use not only Kratos itself but also any other application provided by finite element developers or othe
142. o my co supervisor Dr Antonia Larese De Tetto who guided me during my research period at Universitat Polit cnica de Catalunya sharing with me her ideas and rich experiences and providing me valuable suggestions for my research work Antonia thanks for all your help Thanks are also expressed to the staff of CIMNE for their help with the programming codes Especially to Ing Massimo Petracca for his special and outstanding interest giving me sapient advice for this research project Thanks to Javier Garate Vidiella for his invaluable help on the programming I would also like to express my sincere thanks to all those professors who have taught me so much not only from a professional point of view but also from the human point of view I would like to thank so much Prof Ing Angel Carlos Aparicio Bengoechea for believing in me from the first moment and for giving me so much strength and energy many times with a few simple words I am also grateful to Gabriele who shared with me this research project To you thanks for your technical support and for the constant encouragement when strength and motivation to keep going were lacking Warm and special thanks to Barcelona my Barcelona for teaching me so much and turning me into what I really am today My very deepest gratitude to my nearest my parents and my brother who supported me all the time during my studies economically and morally Many thanks to my friends the true one
143. o the shells 102 Chapter 5 Pre processor and interface tutorial 5 5 4 Elements properties assignation Once the elements properties have been created they should be assigned to the elements the Elements menu is shown in Figure 5 38 E H Elements HH Solid Element HH Beam Element FH Shell thick Figure 5 38 Elements menu Firstly the property can be assigned to the beams clicking twice on Beam Element a new group for the beams can be created with the property Beam_prop this will be assigned to all the lines reference is made to Figure 5 39 Similarly the property can be assigned to the shells clicking twice on Shell thick so that a new group for the shells is created with the property Shell prop this will be assigned to all the surfaces reference is made to Figure 5 40 Finally clicking twice on Solid Element a new group of solid can be created with the property Solid_prop reference is made to Figure 5 41 Importantly this will not be assigned to any geometric entity because they are not solid elements it is only created to give the properties of the material to the different layers of the shell Section 6 4 8 Beam Element Properties Element type Linear X Property Beam_prop Y Wi Group BeamElem0 MA Ok Cancel Figure 5 39 Beam element assignation 103 A pre processor for numerical analysis of cross laminated timber struct
144. obtained from tests with loading time of about 300 seconds on specimens under normal conditions The performance of a structural element in timber as already briefly noted are strongly affected by the presence and position in the same element of some natural features that in structural field are called defects For this reason the structural design needs a classification according to resistance of the structural element in the dimensions of use rather than on the net material for both elements in laminated wood and hardwood Tables 2 4 and 2 5 adapted from the code EN 338 2004 show the strength classes and the related characteristic values of the main properties for coniferous wood poplar wood and hardwood in general With reference to the glue laminated timber and X Lam panels these tables give the values of some mechanical properties relative to the slats they contain It is clear that the performance characteristics of the finished product for example the bending resistance in glulam beams are related to the resistance characteristics of the individual boards as well as of course to other aspects related to the proper execution of butt joints and the bonding between overlapping slats As concern the glue laminated timber elements excluding the X Lam panels the approach of the new European legislation is to suggest the manufacturer the mechanical features of the starting sawn to use to get a glued laminated timber elemen
145. ococccnoccnoncconncconoconnnonnnoonncconocananonnnoos 103 viii Table of contents 5 55 Loads and boundary conditions assignation ocooococcncccnnoccconncconacannn nnnonn 105 5 5 6 RSSA E PA EE A ae oda cose E E E ee 106 5 6 Group properties detinit viii dida ta clsadaivsadedeessavavhes 107 5 7 Material properties definition on socunsuncstsiatase teint amass anaes 108 5 8 Geometry Me SAINT sensro i a E E ais na E E a ees 111 HIG SETS VAIN E u a O E r a A aat 113 5 10 Calcula id aa 114 6 CHAPTER 6 PRE PROCESSOR PROGRAMMING DETAIL 115 6 1 Surface creation and removal from the menu tree ooooonnccnincononociccnononcnnnaconocnnoo 115 a IN ee ea sticresas aie e reteans A eats E Ea a e ai 116 6 3 New IDs ION isa 117 A PINES WIS eni e aE E EE E R RE A a 118 6 4 1 Geometry IEG annonsere alee iioi tt oda 119 6 4 2 Conn cO A O 120 6 4 3 Surfac element info A teea i 122 6 4 4 Line element mios riean e A T 122 6 4 5 More connections a di aee i a 123 6 4 6 Mote materials deca ad 124 6 4 7 Data OTTO aa a ia 126 6 4 8 Materials Pyerin tac desir un A E E ae R N 127 63 PC OMMECTIONS id taa 130 6 5 1 COMES a a e 130 6 5 1 1 Custom Stiffness mode si dd ds 130 6 5 1 2 Custom Parameters MI aio ada ue Sel 131 6 5 1 3 SAN ar AAA e 133 6 5 2 Connections resistance iii cat enzsuitescevenentess 135 0 5 2 1 Cu stom Stitiness A ew E duns E E 135 6 5 2 2 Custom Parameters Mo dial 136 6 5 2 3 Standard A a 137 7 CH
146. ode Relative to the example of Chapter 5 we can focus on line 11 then renamed as line 12 see Section 6 4 1 to which Property2 has been assigned It can be verified that the stiffness are actually correctly calculated The slip modulus per shear plane per fastener for both the tension and shear connections results pis 408 3433 5 9 81 15 0 004 1000 Kser 2 a 1000 30 1323301 49 N m The axial stiffness of the two hold down results Ka Kser 30 2 79398089 22 N m The shear stiffness of the brackets or distributed nailing results Ky kser 6 7939808 92 N m Table 6 8 shows that the axial stiffness of the brackets or distributed nailing the shear stiffness out of the plane of the panel and the three rotational stiffness are set as default equal to 100 N m while the other ones are actually calculated correctly 132 Chapter 6 Pre processor programming detail Table 6 8 Connection info file for line 11 79398089 22 79398089 22 100 00 7939808 92 100 00 100 00 100 00 100 00 6 5 1 3 Standard mode When the user defines the connection properties with the Standard mode the axial stiffness of the bracket or distributed nailing the shear stiffness out of the plane of the panel and the three rotational stiffness are set as default equal to 100 N m while the other ones are calculated in two steps First the slip modulus per shear plane per fastener for timbe
147. ode but it can be changed simply clicking on Connection mode and selecting the other one The difference between the two modes lays in the way of defining the connections The standard menu allows to select a type of connection already default by a database conversely the custom menu allows to assign some parameters through which the stiffness are 79 A pre processor for numerical analysis of cross laminated timber structures calculated or to directly set the stiffness In general the standard mode is recommended if all connections have already been calculated in detail and the analysis is used only for verification Differently the custom one is recommended in case of first attempt connections or to assign possibly even random stiffness when the analysis is used to determine the optimal connections At this stage it would be complex to decide which mode to use thus before selecting one for the example both the modes will be explained The custom menu is shown in Figure 5 14 Inside the Custom Connections there is a sub menu of Custom Property which in turn contains a property already defined called Continuity connection Connection Mode Custom E Custom Connections E Custom Property E Continuity connection E Stiffness Axial stiffness HD1 1 0e 12 Axial stiffness HD2 1 0e 12 Distributed axial stiffness 1 0e 12 Distributed parallel shear stiffness 1 0e 12 Distributed orthogonal shear sti
148. odel a CLT structure starting from the creation of the geometry and the assignation of numeric entities beam shell ecc to geometric ones having defined the material and assigning loads and boundary conditions The user does not need to create manually the connections he just set the connection properties to the different sides of the panels Also the punctual connections hold down are assigned at the interface to the lines conversely in the analysis they are assigned only to the extreme points of the panel side Chapter 1 Introduction The creation of the connections is made automatically an abstract offset is applied between each surface and line or better between each border shell in which the surface is discretized and beam elements The information about the connection property is stored at interface level to the line geometric entity which is discretized depending on the mesh in one or more beams numeric entities The offset Figure 1 1 implies the duplication of the nodes that belong to both beams and shells It has zero distance to allow an easy management of the nodes since the duplicated nodes will have the same coordinates of the original ones Figure 1 1 Example of an offset surface Therefore spring elements with the stiffness values inserted by the user at the interface are used to join nodes with equal coordinates The beam elements necessary for the duplication of the nodes are considered fake e
149. odule project_name post res results file Each element of the mesh corresponds to a value project_name post msh file containing the post process mesh If this file does not exist GiD uses the pre process mesh also for post process 50 Chapter 3 General about GiD Kratos Tcl and Python GiD ry SOLVER INPUT OUTPUT FILE FILE Figure 3 1 Diagram of GiD workflow GiD User Manual mat Proprocess GID E a D TTA prejoct_namo datf Results file Postprocess mesh file ta OE pioject_name post res Pisa ama post muy Pasiprocess GID Figure 3 2 Diagram depicting the files system GiD User Manual 51 A pre processor for numerical analysis of cross laminated timber structures 3 1 2 GiD Pre process GiD is a CAD system that features the widely used nurbs surfaces for the geometry definition Typical geometrical operations can be used as transformations translations rotations etc boolean operations in surfaces and volumes a complete set of tools are provided for quick geometry definition GiD allows for the generation of large meshes for linear and quadratic elements in a fast and efficient manner using several in house meshers both for surfaces and volumes following different structured type criteria e structured mesher including triangular quadrilateral hexahedral prism and tetrahedral meshes e unstructured meshes are automatically generated based on quality and
150. on Properties Property Id Propertyl y Hold down 1 No Z Number of hold down HD1 0 y Hold down 2 No Z Number of hold down HD2 0 v Bracket or distributed nailing No z Number of brackets or distributed nails 0 v Panel density 0 z Correction factor kmod 0 z Material security coefficient 0 v Ok Cancel Figure 5 18 Connection menu 86 Chapter 5 Pre processor and interface tutorial Clicking twice on Standard Property a new connection property with standard mode can be created the menu of Figure 5 18 will appear The standard property contains only one way to define a connection property Connection which requires a new property name and some parameters which should be introduced by the user In this case some parameters are only used for the analysis while other ones are both used for the analysis and the verification The values that should be set in the menu Connection are e Hold down 1 this is the type of the first hold down which can be selected by an already default database The database has been created following the Rothoblaas catalogue and distinguishing between total and partial nailing for any type of hold down it is shown in Figure 5 19 and it is the same for the first and second hold down The hold down with less coordinate on the x or y axis is considered as first hold down in order to distinguish it from the other one of the panel WHT340 tot nail d4 40 WHT340 tot nail
151. on and that substantial greenhouse gas emission were avoided by substituting cross lam in place of concrete or steel to get preferential approval from local planning authorities Yates et al 2008 e Recycling and reuse X Lam panels can also be recycled and reused for the same or for a different purpose Structural flexibility of the panels is very wide as well as their durability thus enabling 26 Chapter 2 Generalities about timber and X Lam technology panels to be reused For example after a series of shake table tests on a 7 storey SOFIE building in Japan the building was disassembled and the panels were shipped back to Italy The panels were stored for a couple of years before they were used as main load carrying elements in the prototype of a sustainable modular house unit made of X Lam panels Briani et al 2012 2 7 X Lam connection systems X Lam wall panels are very rigid in comparison to the anchoring connections so most of the flexibility is concentrated in the connections Thus connections play an essential role in maintaining the integrity of the timber structure and providing strength stiffness stability and ductility to the structure The structural efficiency of the floor system acting as a diaphragm and that of walls in resisting lateral loads depends on the efficiency of the fastening systems and connection details used to connect individual panels and assemblies Consequently they require detailed
152. ould be assigned to the elements Similarly in case of creation of loads or boundary conditions groups they will appear in this window Figure 5 45 Again other loads or boundary conditions groups can be created directly from this menu then they should be assigned to the elements 5 7 Material properties definition The third icon of the x am kratos menu enables to define the material properties clicking on it the window of Figure 5 46 will appear As Figure 5 46 shows the Materials menu contains a database of already default materials these are the different types of timber classified by the code EN 338 2004 see Section 2 3 Any material presents a sub menu Figure 5 47 in which the values of its main properties are defined this will be not explained in detail because it is almost the same of the code table Section 2 3 108 Chapter 5 Pre processor and interface tutorial Model Materials Materials E E i Timber was wae was yg 020 tw 022 Ty c24 27 a 30 wos T c40 T cas T c50 T D30 a D35 T D40 T D50 060 y D70 XS Figure 5 46 Materials menu With reference to Figure 5 47 in the first section there is just a description of the material with its density then it is sub classified in Isotropic
153. pacity for nails staples bolts dowels and screws per shear plane per fastener in case of timber and panel connections can be calculated in different ways for fasteners in single and double shear For fasteners in single shear it should be taken as the minimum value found from the following expressions with reference to Figure 2 14a fraktid a fox tad b fnaktid ta 2 7 a t A B 282 ae 33 i146 ya A FI EA c t Fax Rk 3 14 2 5 ti 4 Se ee t f B 2 BIA d 1051014 log 1 2802 B MyRk _ y H FY pk min 2 8 V faaxdti st d Fax Rk 4 froxtid 4B 2 B MyRk 1 05 28 1 8 s E 2 8 y BT fa xdt3 a x ai e ax Rk 1 28 F 1 15 2M ni fn kd Via y RkFh 1 k 4 For fasteners in double shear it should be taken as the minimum value found from the following expressions with reference to the Figure 2 14b faiktid g 0 5 fh tad h tid 48 2 8 M Toan 2u 8 Ee als Fo Rk min ATE fraxdty G Fax Rk 4 128 ro oaa FR 1 15 2M k 5y i BW y Rkfh 1 kd 4 k 41 A pre processor for numerical analysis of cross laminated timber structures where Fy rx is the characteristic load carrying capacity per shear plane per fastener ti is the timber or board thickness or penetration depth with 1 either 1 or 2 fhix is the characteristic embedment strength in timber member i d is the fastener diameter
154. pic material to fit the characteristics of X Lam panels It will be explained below because it also 127 A pre processor for numerical analysis of cross laminated timber structures helps to understand the need of defining different materials for the shell element and the solid one First it reads the file dataOrtho described in the previous paragraph and defines any column of this file as an empty vector then it fills the vectors with the values printed in the file dataOrtho Figure 6 5 Figure 6 5 Materials py added section dataOrtho file reading Thereafter the vectors defined Figure 6 5 are used to fill a matrix called data as shown in Figure 6 6 After defining the matrix the application for the modelling of the composite shell works in the following fashion Depending on the number of layers first the shell cross section is created then depending on the angle of grain orientation of the outer layer each layer is added to the cross section with its own thickness orientation angle number of through the thickness integration points a Simpson s 128 Chapter 6 Pre processor programming detail integration rule is used and the material property of the solid Finally the composite section is added to the property assigned to the shell in GiD For the example described in Chapter 5 the panel is composed by five layers hence the modelling is done as shown in Figure 6
155. ps delete DrawGroupOff G1D_Redraw Figure 6 1 Draw line section of the code The two groups are hidden to the user but currently they will be made visible to show how they work Considering the example of Chapter 5 especially Section 5 5 2 line 2 can be drawn Two groups will be created DrawgroupOn and 116 Chapter 6 Pre processor programming detail DrawgroupOff the former contains only line 2 which is the selected one the latter contains all the other lines x Layers and groups Double click here to integrate the window Layers Groups SeKGECE Name Cc YO Tr DrawGroupOff amp 4 38 DrawGroupOn El vs BB Close z t m DrawGroupOff x ma DrawGroupOn Figure 6 2 Draw line groups and geometry Figure 6 2 shows the Groups menu in which the two drawing groups appear and the geometry coloured according to the colours of the groups 6 3 New IDs definition A fundamental issue is the description of the procedure implemented in the code about the definition of the new surfaces and lines IDs they are changed because of computational reasons of the x am driver application Relatively to the surfaces it is necessary that all the identification numbers are subsequent This is in general true if the user does not delete any surface but if he does as seen in Section 5 5 2 this surface is removed from the tree and the other ones maintain the same identif
156. purposes and cannot substitute a structural analysis 143 A pre processor for numerical analysis of cross laminated timber structures For the floor known the permanent load gx 2 0 kN m and the overload qx 2 0 kN m and known the span length L 6m it results that 5 timber layers can be disposed with a total thickness of the X Lam floor equal to 196 mm Figure 7 5 For the roof known the permanent load gx 2 0 kN m and the overload qx 1 5 kN m and known the span length L 6m it results that 5 timber layers can be disposed with a total thickness of the X Lam roof equal to 182 mm Figure 7 5 For the walls considering a permanent load of 30 kN m an overload of 10 kN m and an height of 2 9 m it results from the load charts provided by manufacturers Rothoblaas that 3 timber layers can be disposed with a total thickness of the X Lam wall equal to 97 mm Figure 7 6 Single span floors 5 in accordance wih approval Z 9 1 560 DIN 022 2008 andor EN 1995 1 1 2008 Permanent Imposed load load 9 m KNim KNim 223 L7s 2 3 00m 103 L3s 112 L3s 182 LSs 211 Los 165 L5s 209 Lez 113 182 L KE 243 L7s 2 150 L5s 165 LS6 112 L3s 126 L3s 150 LSs 182 L 119 Lis 150 L56 211 L55 223 L76 2 20 uz 211 L5s 209 L75 2 oe EE 136 L gt Ez 209 LEZ 182 LSs 211 L56 Ea LSs 223 L7s 2 182 L55 209 L75 2 2491762 165 LS Iae 1 Se DIA 7 9 asin 223 L7s 2 211 L 211 L55
157. r the first section overviews general information about the chapter topic in subsequent sections theoretical and numerical investigations are described Chapter 2 provides an overview of general information about wood timber and cross laminated timber technology First influences on timber strength and timber classification are introduced Then description of cross lam panels and typical X Lam connection systems are presented A state of the art of cross lam timber application is highlighted at the end of this Chapter Chapter 3 provides an overview of general information about the processor the solver and the programming languages used for the thesis GiD Kratos Tcl and Python First description of GiD pre process and post process and Kratos tools and advantages is introduced up to their interaction then a brief description of Tcl and Python features is presented Chapter 4 provides a description of the strategy adopted for modelling Cross Lam buildings explaining in detail panels and connections modelling At the end of the Chapter significant conventions assumed in the modelling are particularised Chapter 1 Introduction Chapter 5 provides an extensive explanation of the pre processor at interface level It is a user tutorial starting from the problem type selection and geometry creation up to the model properties and material definition and the calculation of the desired structure Chapter 6 provides an ex
158. r application developers Developers of optimization programs or design tools are the typical users of this kind e Package Users Engineers designers are other users of Kratos They use the complete package of Kratos and its applications to model and solve their problem without getting involved in internal programming of this package For these users Kratos has to provide a flexible external interface to enable them use different features of Kratos without changing its implementation 54 Chapter 3 General about GiD Kratos Tcl and Python 3 2 1 Kratos advantages Kratos is multi physic One of the main topics in engineering nowadays is the combination of different analysis thermal fluid dynamic structural with optimising methods in one global software package with just one user interface and even more the possibility to extend the implemented solution to new problems Kratos is finite element method FEM based Many problems in engineering and applied science are governed by Partial Differential Equations PDE easily handled by computer thanks to numerical methods The FEM is one of the most powerful flexible and versatile existing methods Kratos is object oriented An integration of disciplines in the physical as well as in the mathematical sense suggests the use of the modern object oriented philosophy from the computational point of view The modular design hierarchy and abstraction of these approaches fits to t
159. r corner points after that it would be necessary to use the command Create NURBS surface to assign a surface to the four lines created In this case the surface is created in an easier way using the command Create object on the left command line 73 A pre processor for numerical analysis of cross laminated timber structures of GiD Figure 5 5 and defining the two corner points with coordinates 0 0 and 1 1 Being the units of measurement in meters reference is made to Section 4 4 this means to create a surface of 1 m Figure 5 6 shows the first surface created in the plane x y Figure 5 6 First surface Entities type Points v Transformation Translation First point Num x 10 0 y 10 0 2 z 00 Second point x 0 0 y 0 0 z 0 0 Do extrude Multiple copies 1 Select Figure 5 7 Copy menu 74 Chapter 5 Pre processor and interface tutorial The other surfaces can be created using the commands Create line and Create NURBS surface as explained before or following the same procedure used before by means of the command Create object In this case the other surfaces are created copying the first one in different directions it is an easier and fastest way and it also allows the use of other GiD commands Using the top command line and selecting Utilities Copy the menu of Figure 5 7 will appear In order to
160. r to steel connection is calculated as 5 q 8 30 1 Keep 2 a where pm is the density of the panel and d is the nail diameter of the hold down or the bracket or distributed nailing Then the axial stiffness of the hold down and the shear stiffness in the plane of the panel are calculated as follows The axial stiffness of the two hold down Ka Kser number of nails number of hold down 2 The modelled stiffness is multiplied by two times the real one because of the different behaviour under the action of horizontal forces of a single modelled panel compared with the same in a real situation see Section 4 3 The shear stiffness in the plane of the panel if they are disposed brackets is calculated as Ka Kser number of nails number of brackets 133 A pre processor for numerical analysis of cross laminated timber structures The shear stiffness in the plane of the panel if it is disposed a distributed nailing is calculated as Ka Kser number of nails of the distributed nailing The nail diameter and the number of nails of the hold down and brackets are already set in the code as shown in Figures 6 9 and 6 10 The nail diameter of the distributed nailing is already set in the code as Figure 6 11 shows Figure 6 11 Values set in the code for the distributed nailing with nail diameter of 4 mm and nail length of 30 mm Figure 6 12 shows the section of the code which calculat
161. racias por tu apoyo t cnico y por el aliento constante cuando carec a de la fuerza y la motivaci n para seguir adelante Agradecimiento cordial y especial a Barcelona m Barcelona Por ense arme tanto y convertirme en lo que realmente soy hoy Un agradecimiento profundo a mis m s queridos mis padres y mi hermano quienes han sido el apoyo constante A pre processor for numerical analysis of cross laminated timber structures econ mico y moral durante todos mis estudios Muchas gracias a mis amigos los verdaderos aquellos que estan siempre en cada momento Agradecer tambi n a esa persona que m s de una vez me dijo Fuerza mujer t puedes Personalmente no creo en el para siempre en cambio creo en lo que se ha podido construir ayer y antes de ayer y en todo aquello que vivimos hoy en d a planeando y organizando el d a de ma ana y de pasado ma ana Me gustar a agradecer a mi querido amigo Eddy por haberme apoyado y continuar haci ndolo cada d a en mi incre ble crecimiento interior Amigo Gracias por tu autenticidad y por todos aquellos momentos que llevo guardados en mi coraz n Me faltar an palabras nunca ser an suficientes simplemente gracias por tu preciosa presencia en mi vida Y por ltimo no menos importante me siento muy orgullosa y agradecida conmigo misma por todo lo que he logrado siempre con muchas ganas voluntad y todo mi esfuerzo Me siento orgullosa de todo mi trabajo y creci
162. rally the choice of adhesives is dependent on manufacturers but the new polyurethane PUR adhesives are normally used as they are formaldehyde and solvent free Occasionally and manufacturer dependent melamine urea formaldehyde and phenol resorcinol formaldehyde adhesives could be used Both face and edge gluing can be applied e Panel assembly and arrangement The main difference that occurs between X Lam manufacturers is the treatment of individual layers Some manufacturers edge bond the individual dimensional timber together to form a layer before pressing each layer into the final X Lam panel Other manufacturers just face bond individual dimensional timber in layers and press all of them together into the final X Lam panel in the one operation Panel sizes vary by manufacturer and application as mentioned in the beginning in this Chapter 21 A pre processor for numerical analysis of cross laminated timber structures e Pressing Gluing at high pressure reduces the timbers expansion and shrinkage potential to a negligible level thus the right pressure is essential Hydraulic presses are normally employed however use of vacuum and compressed air presses is also possible depending on panel thickness and the adhesive used Vertical and horizontal pressings can be applied e Planing and sanding The assembled X Lam panels are planed or sanded for a smooth surface finish e Panel final shaping Computer numerical controlled
163. rature of 20 2 C and at a relative humidity of the surrounding air which exceeds 65 only for a few weeks per year In the service class the timber average humidity in the majority of conifers is not greater than 12 Service class 2 this class is characterised by a content of moisture in the materials corresponding to a temperature of 20 2 C and at a relative humidity of the surrounding air which exceeds 80 only for a few weeks per year In the service class 2 the timber average humidity in the majority of conifers is not greater than 20 Service class 3 this class includes all climatic conditions which give rise to higher moisture content in the timber 11 A pre processor for numerical analysis of cross laminated timber structures To service class 2 belong buildings heated in a non continuous way and ventilated such as houses for leisure garages without heating warehouses and cellars To service class 3 belong buildings exposed to rainfall or in any case to water including the shuttering for the concrete and scaffolding outdoors as well as support structures of the roofs not adequately insulated Kan ra ge dry N pt ae p Y tt ait wr of g 8 ES cl H 4 E i A a E t bh 3 A ss t sl op g pane da i nte cd S 1 ete v T BERR Saa E t A at i z y 50 x 250 mm section Small net specimens j x 25 5 a e i T 0 i o 0 t 0 10
164. re processor for numerical analysis of cross laminated timber structures 6 4 3 Surface element info The file surf elem info provides a matrix necessary for the xlam driver application which shows the list of the identification numbers of the mesh elements associated to the ID the new one of the surface to which they belong For the example described in Chapter 5 the file surf elem info results as shown in Table 6 3 Table 6 3 Surface element info file o es a EM SC E a ETRE AO E AO TE E op _ a a po ww 3 AA F ho i This file enables to know the identification number of the surfaces to which the elements of the mesh belongs in order not to lose the information about them It is obtained in the code defining an occult group that in fact refers the mesh elements to the original elements of the geometry 6 4 4 Line element info The file line elem info provides a matrix necessary for the xlam driver application which shows the list of the identification numbers of the mesh elements associated to the ID the new one of the line to which they belong For the example described in Chapter 5 the file line elem info results as shown in Table 6 4 122 Chapter 6 Pre processor programming detail Table 6 4 Line element info file Blele le le le ouija ina w NIN INININ Pl _WwlNle o pa pa 5 e a ae ee ee ee A O NES N i o o m
165. renamed as line 8 to which Property has been assigned It can be verified that the design load carrying capacities are actually correctly calculated 10 Ra hold down 1 1 i 13 84615 38 N 135 A pre processor for numerical analysis of cross laminated timber structures 7 10 Ra brackets distributed nailing 7 1 1 42 59230 77 N Table 6 9 shows that the design load carrying capacities of the two hold down and the brackets are actually calculated correctly Table 6 9 More Connections file for line 7 Pst 8465 38 84615 38 59230 77 6 5 2 2 Custom Parameters mode When the user defines the connection properties with the Custom Parameters mode he sets the characteristic load carrying capacity per single fastener of the hold down and brackets or distributed nailing With these parameters the characteristic load carrying capacities are calculated in the following way Ry Fy gg total number of nails So the design load carrying capacities are easily calculated as see Section 2 7 3 Rx Ra kmoa Yu Figure 6 14 shows the section of the code which calculates the design load carrying capacities of the connections to write them in the More Connections file expr FvRkHD1 TensionNumberNails1 expr FvRkHD2 TensionNumberNails2 expr ISS TEE expr rk1 5kmod gam expr rk2 5kmod gam expr rk skmod gam now w Figure 6 14 Design load ca
166. rence in behaviour between a real and modelled panel 66 Chapter 4 Modelling strategy of X Lam buildings and conventions dy Teal A I Kup real SSS B a Real behaviour lec b Modelled behaviour Figure 4 3 Difference in behaviour between a real and a modelled panel 67 A pre processor for numerical analysis of cross laminated timber structures 4 4 Units of measurement convention Relatively to the units of measurement it is assumed that all parameters are expressed in Newton meters This is because Kratos works with these units and not with those of the international system All the values inserted by the user should be set with these units of measurement as well as all the parameters already set refer to this assumption 4 5 Gravity convention The gravity convention lies into adopt the Z axis as vertical one This is mainly due to two computational reasons the way of identification of the horizontal and vertical beams in the x am driver application by Gabriele D Aronco see the thesis An algorithm for numerical modelling of Cross Laminated Timber structures Gabriele D Aronco the convention about the local axes orientation of the orthotropic shells used for modelling panels Section 4 2 The gravity convention is important for the correct functioning of the software as it is till now Because of the convention the user must use Z as vertical axis during
167. rews The advantage of this system over the direct use of self tapping screws is the possibility of enhancing the connection resistance by driving more wood screws to connect the profiled panel to the central wood profile which is in turn screwed to the transverse wall e Metal brackets Another simple form of connecting walls in the transverse direction is the use of metal brackets with screws or nails This connection system is one of the simplest and most efficient types of connection in terms of strength resulting from fastening in the 33 A pre processor for numerical analysis of cross laminated timber structures direction perpendicular to the plane of the panels or recessed However adding protective membrane i e gypsum board for improved fire resistance is required e Concealed metal plates As previously discussed while it has considerable advantages over exposed plates and brackets especially when it comes to fire resistance this system requires precise profiling at the plant using CNC machining technology Self drilling dowels that can penetrate through wood and steel can also be used Metal plate thickness ranges from 6 mm up to 12 mm 3 Wall to floor connections Several possibilities exist when it comes to connecting walls to the floors above depending on the form of structural systems i e platform or balloon on the availability of fasteners and the degree of prefabrication 3a Platform construct
168. rizontal force acting on storey 1 Fp is the seismic base shear Si sj are the displacements of the storey masses mi mj in the fundamental mode shape When the fundamental mode shape is approximated by horizontal displacements increasing linearly along the height the horizontal forces F can be taken as being given by Zi Wi Eako l b ZW where zi zj are the heights of the masses mj and mj above the level of application of the seismic action foundation or top of a rigid basement 149 A pre processor for numerical analysis of cross laminated timber structures Table 7 2 Storeys seismic forces 310 5 6 18630 180 191 969 3 38394 3m For the preliminary design of the connections the storeys seismic forces Table 7 2 are multiplied by an approximate factor that takes into account the non regularity of the structure Wp 180 1 25 225 kN W p 191 1 25 239 kN The forces should be applied at the barycentre of the storeys this means to apply the force of the roof at the point with coordinates 3 6 6 and the force of the floor at the point 5 5 3 with reference to Figure 7 9 7m 6m eG2 G1 5m y 6m y x X p p 5m 7m 3m 3m H 1 H 1 Ground floor First floor Figure 7 9 Barycentre position at the two storeys of the building The seism can act in any direction in particular not necessarily in x or y direction to take into account this effect two di
169. rrying capacities calculation for Custom Parameters mode 136 Chapter 6 Pre processor programming detail Relative to the example of Chapter 5 we can focus on line 11 then renamed as line 12 to which Property2 has been assigned It can be verified that the design load carrying capacities are actually correctly calculated The characteristic load carrying capacities of the hold down and brackets or distributed nailing result Rk hold down 2000 30 60000 N Rk brackets distributed nailing 7 2000 6 12000 N The design load carrying capacities result 60000 Ranota down 1 1 3 50769 23 N 12000 Ra brackets distributed nailing 7 a 13 10153 85 N Table 6 10 shows that the design load carrying capacities of the tension and shear connections are actually calculated correctly Table 6 10 More Connections file for line 11 al 3 50769 23 50769 23 10153 85 6 5 2 3 Standard mode When the user defines the connection properties with the Standard mode the design load carrying capacities of the hold down and brackets or distributed nailing are easily calculated as k mod Ranold down Rk single hold down wae number of hold down M 137 A pre processor for numerical analysis of cross laminated timber structures k mod Ra brackets Rx single bracket y number of brackets M k mod b il Ra distributed nailing Rx single nail y number of nails
170. s those that there are always Thanks to the person who more than once said me Fuerza mujer t puedes A pre processor for numerical analysis of cross laminated timber structures I do not believe in forever but I believe in what has been built yesterday and the day before yesterday and in what we live today planning tomorrow and the day after tomorrow I would like to thank my dear friend Eddy for having supported and support me every day in my incredible inner growth Dear friend thank you for your authenticity and for all those moments I saved in my heart I do not mean many words will never be enough just thanks for your precious presence in my life And last but not least I feel very proud and grateful to myself for everything I ve accomplished always with desire will and all my effort I m proud of all my work and growth for the constant struggle and strong perseverance to get every drop of this ocean Even if I ve had hard times I would not change anything I ve experienced in my life everything has led me to become the person I am today Thanks to myself because I never gave up Alessandra Ferrandino Padua 16 September 2015 Agradecimiento AGRADECIMIENTO En primer lugar me gustaria expresar mi mas sincero agradecimiento a mi supervisor Prof Ing Roberto Scotta por haberme dado la posibilidad de formar parte de este interesante proyecto de investigaci n conduci ndome a trav s del m
171. s of cross laminated timber structures Rx mod 8 9 7 1 1 Rg 7 56 kN a Ym 1 3 The number of brackets needed at the two floors is at the ground floor W We Wr 225 239 n x 62 brackets Raang Raang 7 56 at the interstory W r 225 30 brackets Raang 7 56 n The distribution of the brackets is made depending on the length of the seismic resistant walls Lseismic resistant walls_ ground floor x 18 6 m gt 62 18 6 3 3 angle brackets m Lseismic resistant walls ground floor y 22 8 m gt 62 22 8 2 7 angle brackets m Lseismic resistant walls_first floor x 11 4 m gt 30 11 4 2 6 angle brackets m Lseismic resistant walls first floor_y 16 8 m gt 30 16 8 i 1 8 angle brackets m 7 2 4 2 Tension connections The calculation of the resistance of the tension connections can be made preliminarily by means of the manufacturers catalogues The following types of hold down referring to the technical data sheet Rothoblaas Figure 7 11 will be used hold down WHT 340 with total nailing and 20 nails Anker D4X60 hold down WHT 440 with total nailing and 30 nails Anker 4X60 hold down WHT 540 with total nailing and 42 nails Anker 4X60 152 Chapter 7 Modelling of a complex structure hold down WHT 620 with total nailing and 52 nails Anker 04X60 Similarly to the shear connections and according to EN 1995 1 1 2009 Art 2 4 3 the desig
172. s phase the work involved in programming and numerical implementation of the interface and the data needed for the analysis by creating a problem type Relatively to the analysis phase the work consisted in the development of the whole procedure of connections modelling by creating a new application in Kratos Considering the numerical and computational aspects of X Lam structures several are the limits and issues that make it difficult to create models fully representative of their real behaviour Cross Lam wall panels are very rigid in comparison to the anchoring connections so most of the flexibility is concentrated precisely in the latter To correctly model the building avoiding to make it too rigid the connections are modelled with punctual spring elements They enable to simulate the behaviour of the different kind of connections available in X Lam technology A pre processor for numerical analysis of cross laminated timber structures Additionally a limit lies in the behaviour of the spring elements to use in the modelling The behaviour of a CLT structure in static conditions can be assimilated to a contact problem because the walls are supported all along their lower side by the soil In this condition the walls only work to compression they do not offer any resistance to tension The possible lifting of the walls which may occur in seismic conditions is resisted by the hold down connections that offer the tension r
173. s would have been random meaning that not necessarily the IDs would be the same For this reason it is recommended to follow the same procedure and order used in this example in order to better understand the following steps since the IDs play an important role 78 Chapter 5 Pre processor and interface tutorial 5 5 Model properties definition The second icon of the x am kratos menu enables the definition of the model properties clicking on it the window shown in Figure 5 13 will appear Double click here to tear off the windowlgal Model Materials Define the model properties pi E General application data El Domain Spatial dimension 3D 11 40 Structural simulation E Analysis type El A Solution strategy Properties HEH Elements Ef Loads El E Boundary conditions E 25 Results Connection types E Surfaces a limo Mio E a Figure 5 13 Model properties menu This menu allows to define different properties each one of them will be discussed in detail in the following sections They will not be explained in the order in which they appear but in the order that in general the user will follow for the solution of a problem 5 5 1 Connection properties creation The connection properties can be defined in the lower section of the model properties menu The first step is the definition of the Connection mode which can be Custom or Standard as default it is set a custom m
174. spacing criteria defined by the user or using a background mesh for defining a certain size distribution Several element types can be generated triangular quadrilateral circles spheres and tetrahedral GiD also can generate 2D and 3D anisotropic meshes useful for boundary layer Several mesh editing tools like edge collapsing elements splitting smoothing etc allow the user to have the total control of any kind of mesh Simple assignment of any kind of data to the geometry and or the mesh boundary conditions material properties etc is available This information can be sent to the solver with other analysis data which is easily included because of GiD customization 3 1 3 GiD Post process All the widely used types of visualization for the numerical results coming from simulations that are present in GiD such as contour fill and contour lines vector plots isosurfaces beam diagrams stream lines and ribbons surface extrusions deformations 52 Chapter 3 General about GiD Kratos Tcl and Python etc Each visualization type has several options such as showing the contour fill of a result over an isosurface of another result GiD also offers the possibility of visualizing the results on several meshes for adaptive solutions combining different visualization styles and results and creation of animated sequences All the typical graph types can be done in GiD like point evolution which shows the
175. sson ratio v13 0 27 Poisson ratio v23 0 14 Strength Bending 14e 6 Tension parallel to grain 8e 6 Tension orthogonal to grain 0 4e 6 Compression parallel to grain 16e 6 Compression orthogonal to grain 2 0e 6 Shear 1 7e 6 E Density Characteristic 2844 9 Mean 3433 5 Figure 5 47 Material sub menu Selecting an existing material and clicking the right mouse button the window of Figure 5 48 will appear This window enables to create a new material delete rename and copy it Selecting New Material a new material can be created and all the values of its properties should be set Because of this if you want to create a new material with the same properties of the one selected it is more convenient to use the command Copy material which indeed creates a new material with the same properties values 110 Chapter 5 Pre processor and interface tutorial of the previous one This command is particularly useful when you want to use the same material for all the element types but you have to define a different one for each one of them see Section 5 5 3 Therefore any material can also be renamed or deleted using the relative command ae New Material Delete Material Rename material Copy material Figure 5 48 Material creation removal and renaming window For the example analysed three different materials have been created copying the C14 and renaming
176. ssure load can be assigned to lines and surfaces there are two sub menus that allow to assign the direction and the value of the pressure load to the type of selected entity The Boundary conditions menu contains different types of conditions that can be assigned displacements and rotations The displacements can be assigned to points lines surfaces and volumes clicking twice on it there is the possibility to choose one of these geometrical entities and then assign the desired value to the type of selected entity The rotations can be assigned to points lines and surfaces clicking twice on it there is the possibility to choose one of these geometrical entities and then assign the desired value to the type of selected entity For the example described nor loads nor boundary conditions will be assigned since they are not features of the new problem type they are not interesting in this case of trivial example not aimed to analysis 5 5 6 Results menu The Results menu is the same of any GiD problem type therefore it will not be outlined too extensively in this tutorial The menu will be only shown Figure 5 44 and briefly explained 106 Chapter 5 Pre processor and interface tutorial Ola Results 0 amp O E O utput delta time 0 1 n nodes Displacements Yes Rotations Yes Reactions Yes Loads Yes n gauss points Green Lagrange Strain tensor No Cauchy stress tensor No Von
177. t the pre process and analysis phases of a software for the analysis calculation design and verification of X Lam structures have been performed The pre process is discussed in this thesis while the analysis phase is detailed in An algorithm for numerical modelling of Cross Laminated Timber structures by Gabriele D Aronco The key objective of this research work was to allow the automatic modelling of connections between X Lam panels lying in the connections the modelling of CLT buildings To achieve the goal a new problem type for GiD interface and a new application for KRATOS framework have been performed The primary conclusions about the developed phases focus on the achieved goals within the scope of the whole research project The main contribution is the development of a strategy for numerical modelling of cross laminated timber structures Found the strategy sound bases for the pre process and analysis phases of the software have been laid The pre processor allows to assign the connection properties the material and the elements properties as well as the classical conditions of all other problem types The panels are modelled as orthotropic with a cross section composed by layers which can have different thickness and obviously different grain orientation The post process phase is already pre set relatively to the iterative calculation of optimal connections and the verification of connections and panels The exampl
178. t belonging to a particular class of resistance The standard EN 1194 1999 in particular provides a set of relations here omitted for brevity for calculation of mechanical properties of timber laminated elements according to resistance properties of the individual slats 15 A pre processor for numerical analysis of cross laminated timber structures Table 2 4 Strength classes according to EN 338 2004 for solid wood of conifers and poplar Characteristic values Classes C22 C24 C27 C30 C35 Resistances MPa Bending Compression parallel to grain Compression orthogonal to grain Shear Elastic modulus GPa Mean parallel to grain Characteristic parallel to grain Mean orthogonal to grain Characteristic values Classes D40 Resistances MPa Characteristic parallel to grain Mean orthogonal to grain Despite X Lam panels are produced and marketed since 1995 they have so far never been integrated in any product standards Their use as a material for load bearing structures is therefore to date regulated through national approvals or by European Technical Approval ETA The approvals contain and describe the requirements which must be imposed to the product and its production from the materials used as well as the indications for use dimensioning and necessary verifications In case of European approvals there are also indications concerning the marking CE The standard EN 16351
179. t should be set here to enable the calculation of the connection stiffness by the processor e Fypk per nail HD1 this is the characteristic load carrying capacity per nail of the first hold down in N which can be calculated as explained in Section 2 7 3 e Fypk per nail HD2 this is the characteristic load carrying capacity per nail of the second hold down in N which can be calculated as explained in Section Dad e Fy rk per nail distributed this is the characteristic load carrying capacity per nail of the brackets or distributed nailing in N which can be calculated as explained in Section 2 7 3 e Correction factor kmoa this is the correction factor taking into account the effects of load duration and moisture content on the timber strength which is prescribed by the code UNI EN 1995 1 1 2009 see Table 2 2 e Material security coefficient this is the partial factor for a material property ym which is prescribed by the code UNI EN 1995 1 1 2009 see Table 2 3 Each of the parameters explained presents on the interface an abbreviated name that may be not perfectly clear for reasons of space at the interface Anyway placing the mouse over the box corresponding to each of the parameters pop ups that explain their meaning will appear Also in this case there are other three rotational stiffness hidden to the user which are set as default to a small value equal to 100 N m this small value is to mean zero The choice of th
180. t stiffness Line 8 former line 7 is the one to which Property has been assigned see Section 5 5 2 The property was defined by means of the Stiffness mode so it shows the stiffness as they have been set by the user Line 12 former line 11 is the one to which Property2 has been assigned The property was defined by means of the Connection parameters mode so the hold down axial stiffness and the shear stiffness in the plane of the panel are calculated by the processor as explained in Section 2 7 2 while the others stiffness are set to 100 N m Table 6 2 Connection info file a aaa 1 0E 12 1 0E 12 1 0E 12 1 0E 12 4 2 1 0E 12 1 0E 12 1 0E 12 1 0E 12 aa 1 0E 12 1 0E 12 1 0E 12 1 0E 12 1 0E 12 1 0E 12 1 0E 12 1 0E 12 a 1 0E 12 1 0E 12 1 0E 12 1 0E 12 1 1 0E 12 1 0E 12 1 0E 12 1 0E 12 MO 1 0E 12 1 0E 12 1 0E 12 1 0E 12 3 1 0E 12 1 0E 12 1 0E 12 1 0E 12 ie is 1 0E 12 1 0E 12 1 0E 12 1 0E 12 7 1 1 0E 12 1 0E 12 1 0E 12 1 0E 12 Ce De 1 0E 12 1 0E 12 1 0E 12 1 0E 12 7 2 1 0E 12 1 0E 12 1 0E 12 1 0E 12 MEA 1 0E 07 1 0E 07 100 00 1 0E 07 100 00 100 00 100 00 100 00 ie a 1 0E 12 1 0E 12 1 0E 12 1 0E 12 1 0E 12 1 0E 12 1 0E 12 1 0E 12 1 0E 12 1 0E 12 1 0E 12 1 0E 12 1 0E 12 1 0E 12 1 0E 12 1 0E 12 1 0E 12 1 0E 12 1 0E 12 1 0E 12 1 0E 12 1 0E 12 1 0E 12 1 0E 12 1 0E 12 1 0E 12 1 0E 12 1 0E 12 1 0E 12 1 0E 12 1 0E 12 1 0E 12 79398089 22 79398089 22 100 00 793980892 100 00 100 00 100 00 100 00 121 A p
181. tensive explanation of the pre processor at programming level It presents the code implemented to obtain all the tools of the pre process with a detailed description of the files generated by the processor the composition of the shell cross section and the calculation of the connections stiffness and resistance Chapter 7 provides a presentation of the modelling of an X Lam structure case study starting from the preliminary design phase up to the actual modelling in GiD especially from an engineering point of view Finally the results of the analysis are displayed Chapter 2 Generalities about timber and X Lam technology CHAPTER 2 GENERALITIES ABOUT TIMBER AND X LAM TECHNOLOGY This Chapter presents the main characteristics of wood and timber providing a classification according to resistance Later general information about cross laminated timber technology is displayed Typical X Lam connection systems are detailed focusing specifically on their stiffness and capacity calculation Finally state of the art of cross lam timber application is highlighted 2 1 Generalities about wood and timber The wood mechanical properties are intimately related to the natural origin of the material Cell morphology guarantees high resistance values with low self weight The cellular organization of the wood is however also at the origin of a marked anisotropy of the mechanical properties of the material and this results in a m
182. th equal coordinates The beams are fake elements because they are not necessary for the modelling and analysis of the structure apart from those set as curbs at the interface The fake beams must have geometric and structural properties so that their presence is negligible in the analysis Experimental tests have testified that a proper section could be equal or less than 104 10 m7 Hence fake beams are only used for the automatic process of nodes duplication and springs creation 4 2 Modelling of X Lam panels X Lam panels are considered as an orthotropic linear elastic material this particular property is mainly due to two concurrent factors e X Lam panels generally have in a generic cross section different values of the total thicknesses t and t2 in the two directions of the medium plane which defines the panel itself Figures 4 1 and 4 2 the total thicknesses t and t2 are defined as the sum of the thicknesses of the layers with the grain oriented in the direction defined by the subscript e The values of the elastic modulus of the timber in the direction orthogonal to the grain as highlighted in Tables 2 4 and 2 5 are one order of magnitude lower than the same module evaluated in parallel to the grain Considering the gravity in Z direction Section 4 5 the local axes of the orthotropic shell implemented in Kratos are identified in the following way Ifthe panel lies on the global X Z or Y Z planes wall panel e t
183. the calculation 3 4 Tel language Tel was originally developed by John Osterhout in 1988 as a reusable command language for experimental computer aided design CAD tools The source code is compiled into bytecode which is later interpreted by the Tcl interpreter The interpreter is implemented as a C library that could be linked into any application It is very easy to add new functions to the Tcl interpreter so it is an ideal reusable macro language that can be integrated into many applications However Tcl is a programming language in its own right which can be roughly described as a cross breed between e LISP Scheme mainly for its tail recursion capabilities e C control structure keywords expr syntax e Unix shells but with more powerful structuring 56 Chapter 3 General about GiD Kratos Tcl and Python The name Tcl is derived from Tool Command Language and is pronounced tickle it is a string based scripting language which does not belong to the most popular programming languages in use today Tcl is a radically simple open source interpreted programming language that provides common facilities such as variables procedures and control structures as well as many useful features that are not found in any other major language While Tcl is flexible enough to be used in almost any application imaginable it does excel in a few key areas including automated interaction with external programs embeddin
184. the geometry creation Section 5 4 The removal of this restraint is one of the aspects that could be improved in future development of the software 68 Chapter 5 Pre processor and interface tutorial CHAPTER 5 PRE PROCESSOR AND INTERFACE TUTORIAL This Chapter focuses on the pre processor at interface level providing a user tutorial It is clear that the actual creation of a new problem type is not at the interface level since this is just the result of a programming code The interface is the only part visible to the user and understandable by all types of users but everyone should know that the graphical feedback of the interface is only possible by means of a programming code The pre processor at interface level precedes the relative programming code Chapter 6 because it is simpler to understand firstly the features of the new problem type with a graphical feedback and then how these features have been implemented Moreover the programming code implemented is probably not suitable to all types of users whilst the interface is 5 1 Introduction GiD pre and post processor needs the creation of a problem type to be able to create suitable input data files and to be able to read the Kratos results file The GiD problem type is the only connection between the pre processor and the Kratos such as between the Kratos and the post processor A problem type is a set of files configured by a solver developer so t
185. ther multi storey residential building was constructed in London named Bridport House It is consisted of two joined blocks one eight storeys high and the other five storeys high both entirely built with X Lam technology including the ground floor which is traditionally made of concrete Stora Enso Total erection time of the building was only 12 weeks X Lam construction system is also gaining popularity for educational buildings such as the Norwich Open 46 Chapter 2 Generalities about timber and X Lam technology Academy also in the UK KLH In Austria numerous numbers of hotels single family and multi family X Lam buildings were realized in the last decade KLH A project of four residential X Lam buildings each 9 storeys tall started in 2012 in Milano Italy Stora Enso In V xjo Sweden four 8 storey residential X Lam building were built in 2008 For each floor four construction days were needed Martinson Recent initiatives of introducing the X Lam technology overseas namely in North America and Australia resulted in realisation of several interesting projects In Melbourne Australia a 10 storey X Lam building has been erected making it the tallest residential wooden building in the world KLH et b e Figure 2 15 Residential and non residential X Lam projects a 10 storey Fort in Melbourne b 9 storey Stadthaus in London c Open Academy in Norwich KLH A four storey building on th
186. ting of timber framing resisting the horizontal forces and non load bearing infill Hyperstatic portal frames with doweled and bolted joints see 8 1 3 3 P High capacity to dissipate Nailed wall panels with glued diaphragms energy DCH connected with nails and bolts Trusses with nailed joints 4 Hyperstatic portal frames with doweled and bolted joints see 8 1 3 3 P Nailed wall panels with nailed diaphragms connected with nails and bolts Being the building non regular in elevation the q values listed in Table 7 1 should be reduced by 20 but need not be taken less than q 1 5 For the analysed building it results q 1 6 The two storey building is located in Gerona Friuli Venezia Giulia Italy where the ground type is B and the elastic response spectrum for the ultimate limit state ULS and damage limit state DLS is the one shown in Figure 7 8 According to EN 1998 1 2004 4 3 3 2 2 being a building with height less than 40 m the value of the fundamental period of vibration T may be approximated by the following expression Ti Ci H3 4 0 050 62 4 0 192 s where 147 A pre processor for numerical analysis of cross laminated timber structures C is 0 085 for moment resistant space steel frames 0 075 for moment resistant space concrete frames and eccentrically braced steel frames and 0 050 for all other structures the last is the case of X Lam buildings H is the height of the b
187. tresses are perpendicular to the grains Provided that the longitudinal layers are connected via flexible transverse layers bending caused by transverse forces can no longer be disregarded The so called rolling shear shear in the radial tangential plane in the transversal layers leads to relatively low load bearing capacities Cross lamination in X Lam panels have reinforcing effect for prevention from brittle failure modes such as splitting and increases strength capacity of connections The cross laminating process provides improved dimensional stability to the product which allows for prefabrication of long and wide panels Additionally cross laminating provides relatively high in plane and out of plane strength and stiffness properties giving it two way action capabilities similar to a reinforced concrete slab 3 Layered panel SENA EN wayne Sy SS Stee lt 4 PEI ES SS IES OZ lizz VIN S EELS ESN 5 Layered panel SAS __ _ _ z gt E5EI R AA EE Figure 2 4 Examples of different cross sections of X Lam panels ETA 06 0138 2006 By varying the number of layers as well as the lumber species grade and thickness X Lam panels can be used in various assembly types such as walls floors 19 A pre processor for numerical analysis of cross laminated timber structures roofs elevator shafts stairways etc The wall and floor panels may be left exposed in
188. uctures 6 2 Line drawing In order to easily recognise a line to which you are assigning a connection property the line can be drawn with a different colour respect to all the others see Section 5 5 2 This feature has been obtained creating two hidden groups with different colours a group contains only the selected line that the user want to recognise the other one contains all the other lines The two groups only persist for 5 seconds in the Groups menu then they are automatically removed to allow identification of other lines Figure 6 1 shows the section of the code which enables the drawing of the selected line proc xlam DrawLine nombre set id lindex nombre end catch GiD_Groups delete DrawGroupOn catch GiD_Groups delete DrawGroupOff GiD_Groups create DrawGroupOn G1D_Groups create DrawGroupOff GiD_Groups edit state DrawGroupOn hidden GiD_Groups edit state DrawGroupOff hidden Ffff GiD_Groups edit color DrawGroupOn GiD_Groups edit color DrawGroupOff GiD_EntitiesGroups assign DrawGroupOn lines 1d set assignedlines list _EntitiesGroups assign DrawGroupOff lines G1D_Geometry list line 1 end G1D GiD_EntitiesGroups unassign DrawGroupOff Lines id GiD_Groups draw DrawGroupOn DrawGroupOff G1D_Redraw after 5006 catch GiD_Groups end_draw catch GiD_Groups delete DrawGroupOn tl catch G1D_ Grou
189. uilding in m from the foundation or from the top of a rigid basement Elastic response spectrum se g 0 600 0 500 0 400 0 300 0 200 0 100 0 000 0 00 0 50 1 00 1 50 2 00 2 50 3 00 3 50 4 00 Period T s Figure 7 8 Elastic response spectrum for Gerona Friuli Venezia Giulia Italy The seismic base shear force F for each horizontal direction in which the building is analysed shall be determined using the following expression W TOT 0 85 Fp Sa T m A 0 45g where Sa T1 is the ordinate of the design spectrum T is the fundamental period of vibration of the building for lateral motion in the direction considered 148 Chapter 7 Modelling of a complex structure m is the total mass of the building above the foundation or above the top of a rigid basement 2 is the correction factor whose value is equal to 0 85 if T lt 2 Tc and the building has more than two storeys otherwise 1 0 The total seismic load can be determined as the sum of the roof seismic load and the floor one just calculated before Wror Wrtoor Wroof 658 8 310 5 969 3 kN In this way the seismic base shear force Fp results Wror F Sa T m A 0 45g 0 85 0 45 969 3 0 85 371 kN The seismic action effects can be determined by applying horizontal forces Fj to all storeys where F is the ho
190. ure 5 34 98 Chapter 5 Pre processor and interface tutorial New property Properties Property Id Beam_prop Property type Beam he Constitutive law Elastic Isotropic Material Ci4_beam y Section type Rectangular z Height 0 001 z Width 0 001 Z Ok Cancel Figure 5 34 Beam property parameters Again in this case height and width of the section are set with random values because the goal is not the analysis Relatively to the material currently it can be considered just a name which can be selected from the already default materials database it will be explicated in Section 5 7 In case of solid property type the Constitutive law can be Elastic Isotropic or Elastic Orthotropic if later you want to use an orthotropic shell you should select the Elastic Orthotropic constitutive law for the solid as well For this example a solid property named Solid_prop is created with the parameters of Figure 5 35 New property Properties Property Id Solid_prop 7 Property type Solid ng Constitutive law Elastic Orthotropic 7 Material C14 solid Y Ok Cancel Figure 5 35 Solid property parameters 99 A pre processor for numerical analysis of cross laminated timber structures Relatively to the material similarly to the beam property it can be selected from the already default materials database currently it can be considered just a name it wil
191. ures Shell thick Properties Element type Quadrilateral in Property Shell_prop y gt M Group Shelthict IT Ok Cancel Figure 5 40 Shell thick element assignation Solid Element Properties Element type Tetrahedra y Property Solid_prop 7 mi Group SoliElem1 1 Ok Cancel Figure 5 41 Solid element assignation The order of assignation of the properties to the elements does not matter the shells can be assigned before the beams and this would not constitute a problem As already mentioned one property per element has been created so any different element property is assigned to all the geometric entities to which it refers Differently in a real example any property can be assigned to the desired entities not necessarily to all the same geometric entities The only restriction is to assign only one property to any geometric entity because it is not permitted for instance that a beam has two different materials or two different section heights At the end of this step the Elements menu appears as shown in Figure 5 42 104 Chapter 5 Pre processor and interface tutorial CH Elements GHH Solid Element E 3 SoliEleml Element type Tetrahedra Property Solid_prop JEH Beam Element E a BeamElem0 Element type Linear Property Beam_prop JEH Shell thick E 3 Shelthicl Element type Quadrilateral Property Shell_prop Figure 5 42 Elements end
192. ust also be considered Finally it results necessary to define a domain of resistance in the plane N V Regarding the second assumption the hypothesis is fully confirmed by experimental research on X Lam walls Popovski 2010 and on individual connecting elements Gavric Fragiacomo and Ceccotti 2014 2 7 2 Connections stiffness Regardless of the behaviour of the connections shear or tension the code UNI EN 1995 1 1 2009 provides the relations for the calculation of the slip modulus Kser per shear plane per fastener which are shown in Table 2 6 38 Chapter 2 Generalities about timber and X Lam technology Table 2 6 Values of Kser for fasteners and connectors in N mm in timber to timber and wood based panel to timber connections according to UNI EN 1995 1 1 2009 the density pm is expressed in kg m and the diameter is expressed in mm Fastener type Dowels Bolts with or without clearance Screws Nails with Nails without pre drilling Staples The slip modulus kser for fasteners in timber to steel connections is equal to two times the slip modulus in timber to timber connections Once identified the stiffness per shear plane per fastener the stiffness of the brackets or distributed nailing and hold down can be calculated The stiffness of the brackets is obtained by simply multiplying kser by the total number of nails of the connection meaning the number of nails if only one bracket or a
193. ysis phases of the software a significant amount of further research is required for the development of the post process and verification phases in addition to some improving about the already developed phases Particularly some specific aspects that could be improved about the pre process and analysis phases are e Setting or calculation depending on the mode of the stiffness of the distributed springs in N m instead of N m meaning setting the distance between the brackets or the nails instead of their number This improvement needs the splitting of the hold down connection property from the brackets or distributed nailing one because currently the combination of the two connections is assigned to each line e Leaving the possibility to choose a different material for each layer of the panel This improvement will be possible with the new version of Kratos which will present a refined structure of the interface e Adaptation of the orthotropic shell to inclined surfaces meaning surfaces not lying on X Y X Z or Y Z axes 178 Chapter 8 Conclusion Removal in the x lam driver application of the restraint about the z axis as vertical one thus the hold down springs will also be created on the vertical beams Implementation of other types of linear analysis response history analysis response spectrum analysis in the Kratos framework to allow the calculation of non regular and more complex structures Implementation of

A Pre-processor for Numerical Analysis of Cross

Contents

Download Pdf Manuals

Related Search

Related Contents