Home

lift401 - Stewart Technology Associates

1. Hence when the response amplitude is zero the percentage critical damping will be set to 2 When the response amplitude increases to one leg radius the percentage critical damping will be set to 7 if the user clicks on the Auto coefficients button The user may always over write the value for this term or introduce another functional relationship if desired Contact STA if you wish to enter another relationship MomSwitch O off If this cell is set to 1 the reduction in hull lateral deflection coming from moment at the pads is correctly accounted for If the cell is set to zero the hull lateral deflection will be over estimated and the P delta effect will be exaggerated Cu surface This is the undrained shear strength of the surface soil on the sea bed Typically for a soft sediment as in many places in the Gulf of Mexico the surface shear strength is around 40 pounds per square foot psf For over consolidated clays as in many places in the North Sea the cu value may be 1000 psf If a firm sandy sea bed is to be modelled a cu value of 100 may also be appropriate Cu rate This is the rate of increase of undrained shear strength with depth A value of 10 psf ft is typical in many muddy sea beds If a value of 10 psf ft is used for the cu rate and a value of 40 psf is used for cu at the surface of the sea bed then at a depth of 20 feet below the surface the undrained shear strength will be 240 psf This is calculated as follows
2. 12 46 feet theta wave wind direction 90 00 degrees Air gap 15 00 feet Wind force COMPUTED BELOW Wind speed 40 00 knots Leg equiv av diameter 4 00 feet Av leg mass coef 1 75 coef 5 10 crit Av leg drag coef 0 70 coef 1500 kips Beta top fixity 0 00 ratio ks soil rotational stiffness 1 55E 05 kipft rad Mu bottom fixity 0 68 ratio su soil undnd shear strnth 189 54 psf kj Jack Hull stiffness 8 00E 05 kipft rad coef on su to get Gsoil 100 00 coef Equivalent pad radius 10 56 feet LCG 31 20 feet TCG 0 00 feet Ke0 Offset coef 0 LegLength VCG excluding legs 19 00 feet Fwd aft leg dist 85 50 feet Fwd leg spacing 67 00 feet LegLength extended 154 46 feet Total leg length 170 00 feet Graphical Results Boat Name Print this screen Legs are dry internally Dennis Doyle 5 Width Added Pad1 before envmt loads 341 kips Pad2 before envmt loads 413 kips Pad3 before envmt loads 341 kips Weight buoyancy 1096 kips Av leg buoyancy 135 kips Total buoyancy 404 kips Lateral Stiffness used 28 5 kips ft lateral x stiffness 39 8 kips ft Wind force 20 kips lateral y stiffness 28 5 kips ft Max wave current force 36 25 kips Mean wave current force 17 kips Wind O T moment 3232 ft kips Max total
3. 20 x 10 40 240 Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 40 7 2 Jacking Tower Data VCG lower guide ft This is the height above the keel or hull baseline to the center of the lower guide For transit conditions the program makes the assumption that the top of the pad will be 6 below this guide center when the legs are fully elevated b jack vcg ft This is the height of the center of the pinions above the keel or hull baseline h jack support spacing ft used only if two racks This term is ignored unless there are two racks on each leg in which case it will be used to limit the maximum value of Beta the top fixity coefficient Beta is zero with a single rack For modeling Beta correctly with two racks please consult with STA geometry select switch There are three settings for this switch They indicate rack arrangements corresponding to those shown in the diagram in Figure 22 below Valid inputs are 1 2 or 3 Values outside this range may cause unpredictable results Use only integer values ALTERNATIVE RACK ARRANGEMENTS In each case the rack may be single or double and internal stiffening may or may not be present All racks point inboard or outboard Geometry Selection Switch 1 All racks point forward or backward 0008 Geometry Selection Switch 2 1 Fwd racks point fwd or bkwd aft
4. C4 1 n for sway modes C4 1 n rg r for torsion mode Co 0 5 0 25Mu n number of legs r distance from center of legs to hull s cg ro radius of gyration of the mass Mu with respect to vertical axis through center of gravity 9 11 Dynamic Amplification Factor DAF The method for calculating the DAFs is conventional being based upon an equivalent single degree of freedom system The equation involves the vessel s natural period and the period of the waves together with the damping value selected The dynamic amplification factor is found from DAF 1 Tg T 2 2 Eta Ty T 2 2 Where To is the vessel natural period and T is the period of the wave The above equation is appropriate to response evaluation in long crested regular waves and may be unreasonably conservative in real sea conditions To account for this DnV introduced the concept of a stochastic dynamic amplification factor SDAF The accepted result of this approach is to compute DAFs with twice the equivalent linear damping term Eta This method is also adopted in STA LIFTBOAT where input Eta values are doubled in order to find reasonable DAFs If the user wishes to evaluate response in long crested regular waves a value of only one half of the desired damping coefficient should be input Damping alone limits vessel response values at resonance where the wave period and the vessel first natural period are coincident Away from resonance as is the norm
5. Password breng Cancel Step 5 If you want to analyze the selected vessel begin editing data on the Liftinpt xls screen shown in Figure 2 below If you want to input data for a new vessel not already stored in the library Edit the boat name in the upper right hand corner of Figure 1 and click the button File Management Now go to Step 6 Licenced User US Coast Guard l i ight 1990 and onwards Stewart Technology Associates THIS IS THE MAIN DATA INPUT SCREEN CLICK BUTTON TO GO TO RESPONSE Go on to Structural Response Print Input Screen and Wind Loads Go to Master Input File Management Only data in shaded cells can be edited Last data used is displayed Build New Boat Master Input File _ Wave attack angle deg Input wave height ft Leg diams 1 2 3 ft Input wave period sec T S 75 Cm1 Cm2 Cm3 Input water depth ft 70 CD1 CD2 CD3 Lattice area sqft lattice av ht ft wind v2 kn d tide vel kn 500 Total weight kips distance from aft to fwd legs ft LCG ft to foward legs distance bet fwd leg centers ft TCG ve towards L1 pad penetration ft leg buoy 1 dry 2 flooq init phase ang deg windforce kips wind elev ft Wind force switch 1 input 2 computed tot leg length ft 22 54 ft leg length above hull bottom min leg length to be above hull botto FIGURE 2 Liftinpt xls Workbook Main Screen start of your ana
6. 15 21 Ems Your screen should now appear as above All areas of the screen are protected meaning that you cannot type data into them or change their formatting with the Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 6 exception of the cells that will appear highlighted in yellow with bold blue or black data input numbers within them Type the hard disk drive letter and directory name where you have installed the program into the appropriate cells before proceeding 08 12 98 Date of DS run Licenced User US Coast Guard pyright 1990 and onwards Stewart Technology Associates THIS IS THE MAIN DATA INPUT SCREEN CLICK BUTTON TO GO TO RESPONSE Go on to Structural Response Print Input Screen and Wind Loads Go to Master Input File Management Only data in shaded cells can be edited Last data used is displayed Build New Boat Master Input File AvShield Wave attack angle deg Input wave height ft Leg diams 1 2 3 ft Input wave period sec 5 Cm1 Cm2 Cm3 Input water depth ft CD1 CD2 CD3 Lattice area sqft lattice av ht ft wind v2 kn tide vel kn Total weight kips distance from aft to fwd legs ft LCG ft to foward legs distance bet fwd leg centers ft TCG ve towards L1 pad penetration ft leg buoy 1 dry 2 flooq init phase ang deg windforce kips i wind elev ft Wind force switch 1 input 2 computed to
7. February 1992 Available from DnV Veritasvein 1 1322 Hovik Norway American Institute of Steel Construction Manual of Steel Construction Allowable Stress Design Ninth Edition 1989 Available from AISC 1 East Wacker Drive Suite 3100 Chicago Illinois 60601 American Bureau of Shipping Rules for Building and Classing Mobile Offshore Drilling Units 1988 Available from ABS P O Box 910 Paramus New Jersey 07653 0910 American Petroleum Institute Recommended Practice For Planning Designing and Constructing Fixed Offshore Platforms 19th Edition August 1991 Available from API 1220 L Street NW Washington DC 20005 Det norske Veritas Classification Note No 30 1 Buckling Strength Analysis of Mobile Offshore Units 1992 Available from DnV Veritasvein 1 1322 Hovik Norway Stewart W P et al Observed Storm Stability of Jackup Boats Liftboats Proceedings of 23rd Annual Offshore Technology Conference May 1991 Houston TX Stewart W P et al Structural Design of a Harsh Environment 4 Legged Jack Up Boat Fifth International Conference on The Jack Up Drilling Platform Design Construction Operation September 1995 London England SNAME T amp R Bulletin 5 5A Site Specific Assessment of Mobile Jack up Units May 1994 and subsequent amendments Rules for Classification of Mobile Offshore Units Det norske Veritas Part 3 Chapter 1 Section 5 1985 Stewart W P Liftboat Leg Structur
8. if present The leg final weight is found as final leg wt input for all cross sections x 1 appendage factor OD in This is the outside diameter for the leg assumed constant throughout the leg length although the wall thickness may change from section to section Bottom Length ft This input prompt will only appear if you have specified more than one leg section Input the value for the bottom leg length from the pad bottom tip to the elevation of the first section change If you change from having more than one to having only one section length the value that was in the input cell next to bottom length will be ignored and the program will assume the first section properties are used throughout the leg length Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 43 next length ft This input prompt will only occur if you have specified three or more leg sections Specify the length of each one in turn Up to three next section prompts may occur depending upon how many leg sections five maximum you specify Note that you may get error messages if you input impossible leg section lengths and this may occur inadvertently while you are editing data You should see messages appear Error Correct leg sections amp click Manual coefs button if you give the program impossible data Simply follow the instructions and click the Manual coefficients button after you h
9. there may be significant differences 9 13 Corrected Stabilizing Moment The minimum static stabilizing moment found from boat weight multiplied by distance to the centerline of the nearest pair of legs must be reduced by a factor which accounts for secondary leg bending effects This factor is a function of the maximum deflection of the hull center of gravity the average axial leg loads and the Euler buckling loads of the legs lengths extended beneath the hull The reduced stabilizing moment is tabulated in the Results Summary and is determined from the formula below Ms Mso nP eo e 1 z P Pe Where Mso Stabilizing moment as calculated if the legs are perfectly straight and vertical n number of legs eo maximum static horizontal offset of platform in absence of environmental loads e maximum horizontal deflection of platform caused by static and dynamic effects of wind wave and current P average axial leg load Pe Eulerload of one leg Note that eg is calculated by the program using KeO the leg out of straightness coefficient The term Ke0 is multiplied by the leg length extended to give a static offset of the hull accounting for leg out of straightness hull leg clearances and a slight heel of the platform DnV recommend a minimum value of 0 005 for the coefficient The value of e is made up from the mean hull deflection plus the hull deflection amplitude which is where the DAF is used The mean hull deflection
10. 01 Page 47 PadMax Id corrected This is the maximum computed vertical reaction beneath a pad during the wave cycle accounting for the flexural or sway response of the structure The response is considered dynamically and the initial static offset is included Pad mean angle This is the mean rotation angle of the pads during the wave cycle A value of zero implies that the pads are fully fixed and do not rotate Under this condition there would be a larger moment calculated at the pads The maximum pad rotation that would occur during a wave cycle for the same applied environmental forces and same structural model would be with the model pinned at the pads Max OTT w o P delta This is the maximum overturning moment computed during a wave cycle without the effect of structural response In other words the structure is treated as being infinitely rigid and does not move This result is generally greater than the max apparent O T moment as the amplitude of the wave current force must be multiplied by the DAF Max hull ax F1 F3 This is the maximum axial load calculated at the level of the hull for either of the two forward legs F1 port F3 stbd accounting for all vessel responses Max hull ax F2 This is the maximum axial load calculated at the level of the hull for the aft leg accounting for all responses max fb legs 1 3 This is the maximum bending stress induced in either leg 1 port or leg 3 stbd at the level of the lower gui
11. 2kn 14 10s 120 15 4 Tabular Results Input Summary Back to Input File UC Stresses Auto Calc Penetration Go to Master Graphical Results Print this screen Print graphs Print all tables Print all results Set 5 Penetrn Input 4 02 DE equiv leg diam ft 0 78 CDEaverage 0 86 CDEmax max drag coef deflection multiplier 1 2 normal Young s Modulus leg steel ksf MomSwitch 0 off 1 40 K equivalent nat period multiplier norm 1 no dyn 01 1037 Average maximum allowable pad moment yield stress for leg steel cu surface 871 pad moment amplitude accept calc wt ft 1 no 2 yes add mass coef 1 normal accept hull gyrad 1 no 2 yes 12 46 ft pad pen VCG excluding legs ft for transit su needed to support pad psf 12 46 ft pad pen input 10 56 pad equiv radius ft su soil und shear str below pad 0 577 calculated leg kips ft coef on su to get soil G modulus 39 45 calculated hull gyrad 1 55E 05 ks calc rot stiff soil kip ft rad Maximum pad USER SPEC leg kips foot 800000 Kj rot stiff jack hull kip ft rad moment USER SPEC gyrad ft ke horiz offset coef 1585 kp ft 0 00 Beta calculated cylinder drag coef w marine growth 0 68 Mu calculated marine growth thickness inches 2 461778867 total damping crit VCG lower guide ft geometry select switch b jack vcg ft guide space multiplier 1 or 0 d g
12. 5 hull deflection amplitude leg radius Hence when the response amplitude is zero the percentage critical damping will be set to 2 When the response amplitude increases to one leg radius the percentage critical damping will be set to 796 if the user clicks on the Auto coefficients button 9 10 Calculation of Boat Natural Periods After leg mass and stiffness properties including hydrodynamic added mass have been found the program computes vessel natural periods in sway and torsion Full account is taken of the hull inertia and relative position of the center of gravity position Values for Mu and Beta both influence natural period results The longer the natural period the larger will be the vessel s response in normal conditions where the natural period is less than the wave period The boat s natural periods are given by To 2 n melke 2 Where Ke effective stiffness of one leg me effective mass related to one leg For the elevated condition the effective stiffness is taken as ke k 1 P Pe The effective mass for one leg is taken as Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 66 Me C My Co ML Where My total mass of the hull with all equipment and the portions of the legs located above the lower guides Mu mass of the portion of one leg located between the lower guides and the top of the pads including hydrodynamic added mass
13. 70 kt wind ksi Hydrodynamic Calculation Method Note user input beam ft As of 04 18 91 the calculation of roll water plane area sqft period is approximate as the program 1 00 CW coefficient roll center assumed at still water level assumes a rectangular water plane area 107 33 di fwd distance to fwd leg cg from roll center ft and approx hull dimensions based on 101 97 di aft distance to aft leg cg from roll center ft leg spacing The method is fast and 105609 25 IL mass moment of inertia of legs ft 2 kip g 38 40 MH mass of hull kip g 20132 70 IH mass moment of inertia hull ft 2 kip g 1 17 consistent and will be improved shortly KB approx based on leg lengths extnd ft 176122 11 IA hydrodynamic add mass mom ft 2kip g 192 25 GM ft approximate calculation 80 50 Application Notes rO radius of gyration of boat ft 6 43 TO roll period sec approx calc Only data values in shaded cells need be edited For example the user should specify roll amplidude and period as well as vessel draft if not correctly calculated by program and leg length extended which should be zero for fully raised legs The user may investigate leg stresses and forces as well as roll period changes when the legs are lowered simply by specifying a leg length extended greater than zero in the input data block If leg stresses are un
14. Change Wind Loads from calculated to user input e Change LCG and TCG Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 12 3 Change vessel site parameters such as e Air gap e Pad penetration e Water depth 4 Change a combination of all of the above 5 Build a New Boat Master Input File If you select to build a new MASTERINPUT xIs file by clicking on the orange button on the Liftinpt xls screen Figure 2 the data presently displayed in Liftinpt xls will be pasted onto all 50 worksheets in the MASTERINPUT xls workbook You will be warned that all existing data will be overwritten STA LIFTBOAT Warning If you continue the existing 50 Load Cases The warning message box is IN for this vessel will be overwritten with the data on this screen shown to the right Do you want to continue Yes If you continue by clicking Yes the 50 load cases in MASTERINPUT xls New MASTERINPUT XLS workbook built old file overwritten will be created from the data on the screen and a message box will appear as shown to the right The advantage of this procedure is that a new boat can be built with appropriate characteristics However you will have to re enter any environmental load cases you want to analyze Step 8 Instead of simply editing the data on the Liftinpt xls screen you can edit any one of 50 load cases in the MASTERINPUT xls workbook You can switch to this w
15. For a given combination of applied vertical and horizontal loads the moment at the spudcan cannot exceed the value defined above Reference 9 If the maximum permissible spudcan moment is exceeded during a wave cycle there will be plastic deformation of the soil The path in unloading will be different from the path when the maximum loads were reached Stable conditions are unlikely to develop after a single wave cycle but will tend towards a condition where a permanent rotation is locked in This is especially true where the leeward leg of a vessel is loaded close to or even above its preload level This commonly occurs with liftboats and further pad penetration during storms is simply compensated for by jacking the hull up When the pad penetrates further into the soil under a large vertical load simultaneously experiencing a rotation caused by the environmental overturning moments the pad ends up at an angle The upper bounds for the final pad angle may be the pad angles that would occur during the wave cycle if the leg was pinned However because of some plastic resistance of the soil to the pad rotation the maximum equivalent pinned angle is unlikely to be reached The liftboat analysis procedure used in STA LIFTBOAT now uses the pad mean angle calculated as if the soil rotational stiffness was correctly assessed Then the amplitude of pad rotation about this mean is used to determine the maximum pad moments during a wave cycle This proced
16. Mu SEI 1 a d 1 Mu l PGAq The simplified wave forces not shown leg force and moment diagram is shown in the figure below Liftboat Leg Free body Shear force Bending moment and Guides diagram diagram diagram E Qu Mo u H Ru 1 f Mo d A 2 BMo TI erie Ri Ru P Mo PJ 1 p Qo P Qu Ru iia X i Qo uMo LEG FORCE AND MOMENT DIAGRAM Wave forces not shown 9 8 Euler Leg Load Pg STA LIFTBOAT finds the Euler load Pg of a leg from Pe n El K 2 Where K is an effective length factor given by Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 65 K 2 c 9 9 Equivalent Linear Damping Eta The user may change the default value for Eta the equivalent linear damping term STA LIFTBOAT will show results with the user selected value for Eta as well as results with twice this value and half this value Note also that STA LIFTBOAT accounts for the effect of irregular seas when computing response and uses a stochastic DAF as described in Reference 2 Since hydrodynamic damping increases with vessel response it is often difficult to predict what damping may be appropriate in advance of determining response STA has automated the selection of s in STA LIFTBOAT v2 01 Automatic selection of this term occurs when the user clicks on the Auto coefficients button see page 12 The equation used to find s is shown below e 2
17. Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 37 The equation used for the soil shear strength needed to give the minimum necessary bearing capacity is given below su max pad load pad length x pad width x Nc The bearing capacity coefficient Nc is defined by Nc 5 1 0 2 pad width pad length x 1 0 2 penetration pad width coef on su to get soil G modulus In order to account for rotational soil restraint to the pads STA LIFTBOAT uses a rotational linear spring at the pads The stiffness k of this spring is a function of the soil G modulus and the user specified coefficient Gracto according to the following equations G Gractor Su ks 8 G r9 3 1 v Where r pad radius v Poisson s ratio for the soil taken by the program as 0 5 The stiffness equation is based upon the equation for a disk in an elastic half space Reliable estimation Of Graco is not presently possible as the soil is generally highly non linear For small rotations and deep penetrations in cohesive soil a value of 100 has been suggested Reference 1 STA cautions against using values of Gfactor in excess of 1000 Generally the coefficient should be in the range 40 to 300 See section on General Theory Ke0 LEG OUT OF STRAIGHT coef This term is used to multiply the extended leg length to give the hull an initial lateral offset in the same direction as the applied loading This resul
18. Theta1 area sqin Theta1 angle deg Theta1 radius in Theta2 area sqin Theta2 angle deg Theta2 area radius in Theta3 area sqin Theta3 angle deg Theta3 area radius in FIGURE 16 Leg Structural Data Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 26 Boat Name Dennis Doyle 5 Width Added Run Ref 40kn 2kn 14 10s 120 15 4 Tube in 4 26101 36 Rack in 4 9579 52 Stiff area inside rack in 4 2777 64 Stiff area opposite rack in 4 2777 64 Theta y lever arm in 0 00 Theta2 y lever arm in 0 00 Theta3 y lever arm in 0 00 Theta1 contribution in 4 0 00 0 00 Theta2 contribution in 4 Theta3 contribution in 4 0 00 Total Y area moments in 4 Tube in 4 41236 17 26101 36 X axis stiffeners in 4 0 00 0 00 0 00 Theta1 x lever arm in Theta2 x lever arm in Theta3 x lever arm in 0 00 Theta1 contribution i 0 00 n 4 n 0 00 Theta2 contribution in 4 Theta3 contribution in 4 0 00 Total X area moments in 4 26101 36 154 4618 tot leg length extended inc pad 101 38 total weight 1 leg w o pad kips 152 4618 total leg length extended p
19. axial comp str gt gt Fb ksi ABS allowable comp str due to bending gt gt fa Fa 1 using K 2 using K equiv gt gt gt fb Fb 1 using K 2 using K equiv gt gt gt fa Fa 2 using K 2 using K equiv gt gt gt fb Fb 2 using K 2 using K equiv gt gt gt fa Fa 3 using K 2 using K equiv gt gt gt fb Fb 3 using K 2 using K equiv gt gt gt Is fa Fa 0 15 Yes hence ABS require 2nd unity check but not appropriate for liftboats 0 85 Cm coefficient K equiv legs 1 fwd leg gt gt i 0 05 lt lt leg 2 stern gt gt 0 12 lt lt legs 3 fwd leg gt gt i 0 17 lt lt ksi F e ABS Euler str 4 3 2nd ABS unity check is inappropriate for liftboats 0 52 combined leg 1 fwd leg 0 04 static leg 1 0 55 combined leg 2 stern 0 06 static leg 2 0 56 combined leg 3 fwd leg 0 07 static leg 3 Print this screen Input Leg Sections 1 61 sigma x tot axial stress comp leg 1 59 91 sigma cr critical stress leg 1 2 02 sigma x tot axial stress comp leg 2 59 92 sigma cr critical stress leg 2 2 48 sigma x tot axial stress comp leg 3 59 93 sigma cr critical stress leg 3 24 80 sigma e von Mises equiv leg 1 0 74 Rational DnV unity check Leg 1 26 47 sigma e von Mises equiv leg 2 0 80 Rational DnV unity check Leg 2 27 05 sigma e von Mi
20. be invoked by clicking on Help on the Excel main menu Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 31 6 0 MAIN INPUT DATA 1st Data Screen The previous chapter has described how to run the program This chapter describes the technical and control data that the user may input to the program The first part of this section describes data that is entered in the cells of the main input data screen first worksheet Liftinpt xls see Figure 2 In the upper right hand corner of the main input data screen the user can specify the boat name and the run reference These terms will appear on the all the tabular output from the program as well as on the input data screen which can also be printed and on all the graphs Each of the headings below represent the labels adjacent to the input data cells that can be edited in the main input data screen or on any of the Load Case sheets in the MASTERINPUT xls workbook and then pated into Liftinpt xls with the Paste Data button Input wave height ft This is the height from trough to crest of a regular wave which is used for the wave loading This wave is stepped through the structure at twenty phase angles At each phase angle the drag and inertia forces are calculated using ABS shallow water wave theory The current velocity is added in an equivalent vectorial manner to the wave particle velocity before the drag loads are calculated
21. force 56 kips Amp wav cur O Tm 1740 ft kips Mean wav cur O Tm 1434 ft kips Tnxx sway period 5 89 seconds Max apparent O Tm 6406 10 ft kips Tnyy sway period 6 96 seconds Max torsion moment 66 71 ft kips Natural torsional period 5 39 seconds DAF stochastic 1 87 ratio Mean hull deflection 1 41 feet Hull deflection amplitude 1 24 feet Max hull deflection 2 65 feet Offset deflection 2 65 feet Uncorrected stabilizing mom 23383 ft kips Euler leg load 1627 kips Corrected stabilizing mom 18661 ft kips Max base shear 74 kips Max Up guide reac 171 kips Max low gde reac 179 kips Max equiv top load 62 kips Max horiz pad reaction 21 kips Pad max calc bend mom 1591 ft kips BM hull max w oPD 1724 ft kips PDelta leg BM max 1150 ft kips BM hull max w PD 4190 ft kips PadMax Id uncorrd 437 kips PadMin Id uncorrd 246 kips Pad mean angle 0 3209 degrees Pad max angle 0 5901 degrees Max OT w o PDelta 7871 26 ft kips Max OT mom w PD 10987 ft kips Max axial load at lower guide Leg1 371 52 kips Pad Ultimate Moment Capacity 1037 kip ft Max axial load at lower guide Leg2 467 22 kips Hull max shr str 0 78 ksi Max axial load at lower guide Leg3 560 15 kips K Equivalent 1 40 coef Max axial stress at lower guide L
22. has been saved to a new set of files p Dennis Doyle A LJ Dennis Doyle Di Width Added twice Dennis Doyle1 and Dennis Doyle11 E Dennis Doyle E Width Added directories have been created 1 amp 3 Dennis doylet C3 Dennis doyle11 In each of the Projects directories three workbook files exist These files are shown in the figure below Bl Lift001 xls 657 408 8 3 38 12 18 18 PM 2 Liftinpt xls 264 704 8 9 98 12 18 22 PM E Masterlnput sls 358 400 8 9 98 12 18 22 PM In the main Liftboat directory or folder there should be the liftboatopen xls workbook the STA LIFTBOAT icon file and the Projects directory See section on deleting unwanted files before trying to delete any saved liftboat files Step 7 If you are at the liftboatopen xls workbook because you have clicked the File Management button but you have an open set of liftboat files click the Begin Editing Data button and you will be jumped to the Liftinpt xls workbook The screen you will see is illustrated in Figure 2 If you have simply selected a vessel to analyze and have already been jumped to the screen in Figure 2 you may begin editing data There are several routes you can now take 1 Simply change one ore more environmental parameters and go on to Structural Response 2 Change the basic vessel configuration for example e Change leg spacing e Change wind areas e Change total weight e Change leg diameters Change legs from dry to flooded e
23. is determined statically In the Results Summary the maximum hull deflection is e and the term Offset plus deflection is e eg If the user does not wish to consider the static offset associated with leg out of straightness simply set KeO to zero Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 68 9 14 Corrected Pad Reactions As indicated in the section describing pad loads pad reactions must be corrected for the effect of the lateral movement of the center of gravity of the boat as a result of response to environmental forces This effect is especially important in deep water where hull deflections of several feet may occur Maximum and minimum corrected pad loads are tabulated in the RESULTS SUMMARY Additionally PAD1 PAD2 and PADS pad loads with legs assumed vertical and hull level before environmental loading is applied are tabulated Note that the summation of these loads is equal to the result of weight buoyancy with average leg buoyancy and total buoyancy shown also Buoyancy is calculated for each leg from the equivalent diameter and water depth plus pad penetration 9 15 Moment Amplification The industry recognizes two moment amplification effects The first is accounted for simply as a result of the dynamic amplification of sway response As described above the pad reactions are calculated by the program for the maximum deflected position including static
24. linear SDOF approach The calculated and ultimate pad moments are reported to the user on the second data input screen and in the Results Summary A warning is printed on both screens if the calculated moment exceeds the ultimate moment The user may decrease the coef on su to get soil G modulus until the warning disappears Alternatively the coef on su to get soil G modulus may be increased up to a recommended maximum value of 300 to maximize the soil restraint provided the calculated pad moments do not exceed the ultimate capacities Increasing the size of the pads keeping them as nearly square as possible is the best way to improve pad moment capacity Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 56 8 4 Leg Hydrodynamic Coefficients At the beginning of each run the user must input the leg hydrodynamic coefficients However the program calculates the equivalent leg diameter the leg average and maximum drag coefficients and the variation of the drag coefficient with wave attack angle in the last worksheet Lift001 xIls The drag coefficient varies with direction as a consequence of the leg rack s The user must select the drag coefficient for the cylindrical part of the leg in the last worksheet The equivalent leg diameter average and maximum drag coefficients are reported near the top of the second data input screen Normally the user would input the calculated equiv
25. of four The total area of each of these maximum three sets is four times the individual stiffener area you input These Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 42 three sets of stiffeners are referred to by their angles off the x axis as theta1 theta2 and theta3 In addition to the stiffeners you must also input the wall thickness of the cylindrical part of each leg section and the rack properties which are assumed constant throughout the leg length The paragraphs below describe the data input in detail Only the yellow cells may be edited cells shown shaded with bold numbers in them in Figure 16 Number of sections This must be an integer number from 1 to 5 inclusive and represents the number of different sections within each leg for which you wish to define different properties In response to your input the program will prompt you with different requests to enter data For example if you specify 5 sections the program will respond with Define bottom 4 sections just below see Figure 16 Alternatively if you specify only 2 sections the program will respond with Define bottom length The program will give a column title for the stiffeners for however many sections you defined see Figure 16 Unless there is only one section there will always be a top section but only those existing intermediate sections all called next section columns will be titled If
26. of this run LC1 Licenced User US Coast Guard Rig Name Copyright 1990 and onwards Stewart Technology Associates Loadcase description This data set will be pasted into the LIFTINPT XLS file when the user presses the Paste Data button The user may then immediately examine the results b ing the Go on to Structural Response button Go on to Structural Response Print this screen Paste Data Go back to Input File Only data in shaded yellow cells can be edited Last data used is displayed Wave attack angle deg Input wave height ft Leg diams 1 2 3 ft Input wave period sec Cm1 Cm2 Cm3 Input water depth ft CD1 CD2 CD3 Lattice area saft lattice av ht ft wind v2 kn tide vel kn 300 Total weight kips distance from aft to fwd legs ft LCG ft to foward legs distance bet fwd leg centers ft TCG ve towards L1 pad penetration ft leg buoy 1 dry 2 flood init phase ang deg windforce kips air gap ft wind elev ft Wind force switch 1 input 2 computed tot leg length ft Select Load Case Each of the 50 sheets appears similar to the figure above In the upper right corner of the screen you will se the load case identifier in this example LC1 You may use the Select Load Case button to choose another load case or elect to use Excel s sheet tabs to move around the Masterlnput workbook When you have edited a load c
27. offset In the Results Summary the equivalent corrected maximum overturning moment including the additional overturning moment effect from hull sway is shown The corresponding corrected overturning safety factor is also tabulated This overturning safety factor is the ratio between the maximum overturning moment and the minimum corrected stabilizing moment Where the cg is above the lower guides the corrected O T moment M is found from Mc M W e ep Where M is the uncorrected moment and W is the boat weight Where the cg is below the lower guides the program compensates for a smaller lateral movement of the cg than of the hull The second approach adopted in the industry and recommended by DnV is to multiply the amplitude of the environmental forces moment by the DAF This method may differ significantly from the method described above For many location approvals it is pad loading which limits operability and the above discrepancy in calculation of overturning safety factor becomes somewhat irrelevant Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 69 10 0 REFERENCES 1 Brekke J N Murff J D Campbell R B and Lamb W C Calibration of Jack Up Leg Foundation Model Using Full Scale Structural Measurements OTC 6127 Houston TX May 1989 Det norske Veritas Classification Note No 31 5 Strength Analysis of Main Structures of Self Elevating Units
28. pads on to the sea bed multiplied by the distance to the center line of the nearest pair of pads Unlike the uncorrected stabilizing moment the vessel position is considered to be in the maximum deflected position including a static offset plus the maximum hull lateral deflection caused by environmental forces Hence the hull has deflected laterally moving the weight center closer to the nearest pair of pads Both the uncorrected and the corrected stabilizing moment account for total hull weight less buoyancy Max Upper guide reaction This is the maximum force provided to the leg by the upper guide in a horizontal direction See theoretical section Max equivalent lateral top load This is the equivalent horizontal load that would have to be applied to the hull to cause the same lateral deflection as calculated to be caused by the environmental forces Pad max calc bend mom This is the maximum bending moment at the pad If this value exceeds the ultimate moment capacity of the soil pad system a warning is printed at the top of the Results Summary PDelta leg BM max This is the maximum contribution to leg bending moment caused by the P delta effect PadMax Id uncorrected This is the maximum pad vertical reaction found during the wave cycle without the influence of the flexural response of the structure or consideration of the dynamics Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4
29. rack points to port or stbd Geometry Selection Switch 3 FIGURE 22 GEOMETRY SELECT SWITCH FOR RACK ORIENTATION Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 41 d guide spacing ft This is the height between the lower guide vcg defined above and the upper guide centers The leg is considered pinned to the hull at the guides and free to flex between them unless there are two racks and Beta is non zero 1 OR 2 RACK SWITCH Set this switch to 1 if each leg has one rack or to 2 if each leg has 2 racks 7 3 Pad Data pad 1 2 height ft This is the height of the pad from the bottom tip if it has one to the top surface at which the bottom of the leg begins Overall leg length is defined from the bottom of the pad the tip to the top of the leg The leg is fixed at the pad mid point pad length ft This is the longitudinal fore aft dimension of the liftboat forward rectangular pads and the lateral beam dimension of the aft pad If dimensions of pads are not identical use the average of these values pad width ft This is the lateral beam dimension of the liftboat forward rectangular pads and the longitudinal fore aft dimension of the aft pad If dimensions of pads are not identical use the average of these values 7 4 Leg Structural Data Figures 16 and 17 show the input and standard pages of output from the program for the det
30. reactions of liftboats in the elevated mode subject to environmental and gravity loads The program accounts for wind loading on exposed sections of legs in the air gap and above the hull as well as on the hull and superstructure including the crane Wave and current loads are calculated on the legs below the still water level and in the splash zone Shallow water wave theory is used as embodied in the ABS MODU Rules and the legs are modeled as equivalent cylinders with the correct equivalent diameter drag coefficient and inertias which represent the full leg with rack The drag coefficient varies with wave attack angle being strongly influenced by the rack or racks on each leg A graph of drag coefficient with wave attack angle is produced by the program once the user has input the rack geometry In order to calculate structural response the vessel is treated as having a relatively stiff hull Structural flexibility comes from the legs and the leg hull connection Rotational stiffness provided to the pad at the soil structure interface is also modeled The structural characteristics for each unit to be analyzed are based primarily on the leg structural properties as input by the user The user may alter the loading condition of the boat the water depth the air gap the amount of pad penetration into the sea bed and environmental conditions Additionally the user may control the stiffness of the pad restraint provided by the soi
31. rectified Also the user should click the Set 5 Penetrn button before clicking the Auto Coefficients button if the program indicates errors in formulae e Graphical Results Clicking on this button opens a dialogue box where the user may select which of ten graphs he or she may wish to view Once a graph is selected from the dialogue box the user should click OK in the dialogue box and the program will jump to the graph selected Buttons on the graphs provide the user an option to either return to the main menu at the top of the screen or to print the graph After the graphs have printed the user will be returned back to the main area at the top of the screen Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 18 Select Graph to View 21x Cancel Click on button to select graph Pad Reactions Stresses at Lower Guide Sway Response C DAF C O T Moments C Forces on Legs and Base Shear C Waves at Each Leg C Torsion Moments C Wave Forces on Leg 1 Moments on Leg 1 C Drag Coefficient FIGURE 8 Graph Selection Dialog Box Applied Wave Current Overturning Moments at Leg 1 2 x Cancel Dennis Doyle 5 Width Added MOMENTS AT LEGI 40kn 2kn 14 10s 120 A5 1200 1000 e amp x L E ul z S z TIME IN SECONDS o Drag mom Inertia mom z Total mom FIGURE 9 Example Graph e Print this screen Clicking on t
32. surface 39 cylinder drag coef w marine growth 37 DAF 38 39 67 DAF dynamic amplification factor 48 damping 38 39 Damping 65 Data Screen 31 deflection multiplier 38 Distance bet fwd leg centers 32 Distance from aft to fwd legs 32 Distribution Diskettes 4 DnV O T safety factor 50 double racks 63 drag coefficient 56 dynamic amplification factor 38 Dynamic Amplification Factor 67 Dynamic Response Analysis 68 effective length factor 65 effective mass 66 End Session 15 equivalent leg diameter 56 Euler buckling stress 58 Euler leg load 49 Euler Leg Load 65 expanded memory 5 F1 F3 47 F2 47 fa Fa 47 factors of safety 59 fatigue crack 59 fatigue damage 59 fb Fb 47 flooded leg 59 GENERAL THEORY 61 geometry select switch 40 Gfactor 37 Global Leg Strength 57 Go on to Structural Response 36 Go On To Structural Responses 15 Graphical Results 17 graphics resources 5 gyrad ft 38 Hull deflection amplitude 48 Hull max shr str 47 Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 71 hydrodynamic added mass 66 hydrodynamic coefficients 56 Init phase ang deg 34 INPUT DATA 31 Input Leg Sections 16 Input Summary 16 44 Input water depth ft 31 Input wave height ft 31 Input wave period sec 31 interaction equation 58 irregular seas 66 jack support spacing 40 Jacking
33. taken For simplification of the dynamic response analysis each pad is considered to have the same horizontal load and the same moment same rotation at every instant during the wave cycle Provided that the amplitude of this induced moment is less than the average allowable moment calculated using Equation 3 the vessel is considered to be responding reasonably In order to achieve this balance the shear stiffness of the soil G s is adjusted manually For liftboat pads in storm conditions experience has shown that shear stiffness values in the range of 15 to 50 are required when this methodology is applied In the mild Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 55 conditions generally associated with liftboat design much larger values of shear stiffness sometimes up to 1000 are possible However values larger than 300 are generally not recommended It is considered that in storm conditions where the leeward leg moment at the pad fails to stay within the yield surface after the pad has ceased to penetrate further the time Soil Moment Variation soil moment spring moment time history of the moment at the pad will be as shown idealized in the figure above The nonlinearity induced by the elasto plastic behavior of the pad moment induces hysterisis which is not accounted for in the
34. term as the calculated deflections are directly multiplied by this term When this term is set to zero deflections are set to zero before calculating secondary stresses Note that any initial static offset will remain after deflection responses have been set to zero add mass coef 1 normal This term is normally to be set to 1 00 The user may experiment with the effect of added hydrodynamic leg mass by varying this term which is a direct multiplier on leg added hydrodynamic mass For example setting this term to zero puts added leg mass to zero and will reduce the natural sway period This term does not effect the internal mass of water inside legs where the user has specified flooded legs VCG excluding legs ft for transit This is the height of the vertical center of gravity of the boat excluding the legs and pads above the hull bottom or keel line It is used to calculate natural roll periods for transit conditions weight of one pad kips This is the weight in air of a single pad without any internal ballast water All pads are assumed to be equal weight hence an average value should be used if they are not equal The pads are assumed to flood and provide negligible buoyancy when the vessel is elevated USER SPEC leg kips ft excl pads This is the average leg weight per foot in air excluding the pads If the second switch in this input data block see above is set to 1 the program will use this user specified leg weight per
35. the lower guide using the calculated stresses with all so called secondary effects and using the value of K Equivalent defined above The equation for this stress check is given by Stress check value fa Fa fb Fb ABS pre 88 unity str chk leg 2 This is the maximum calculated unity stress check in leg 2 at the location of the lower guide using the calculated stresses with all so called secondary effects and using the value of K Equivalent defined above The equation for this stress check is given by Stress check value fa Fa fb Fb Rational Unity str chk legs 1 3 This is the rational stress check used by DnV for jack up rigs with tubular legs applied to the heaviest loaded of either leg 1 port or leg 3 stbd The interaction equation for this stress check is given by the maximum of either Stress check value 1 25 JA fy foo fort Stress check value 1 25 It fp fbo fer x 1 1 P Pg Where fy is as defined above and includes secondary bending stress components f and f are defined as above but fy does not include secondary stress components local critical stress average axial leg load due to functional or self weight loads only see Note 1 below PE Euler load for leg using weakest axis cr Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 51 The safety factor of 1 25 is equivalent to making the unfactored interaction equation eq
36. 3 3 1 v The user may set k equal to zero pin jointed pads by either specifying soil undrained shear strength equals zero or Graco equals zero In cohesionless soils the user should use the same terms to select a soil shear modulus realizing that the undrained shear strength term is now simply a multiplier for specifying G The program will automatically find the soil undrained shear strength needed to support the legs based upon the user specified pad penetration into the sea bed and the maximum calculated pad vertical reaction during a single wave cycle Just click on the Auto coefficients button to use this feature 9 6 Jacking Mechanism Stiffness kj This rotational spring stiffness kj is zero for boats with a single rack on each leg For boats with two racks per leg some advantage can be taken of the jacking mechanism stiffness This stiffness can work to reduce leg bending moments at the lower guide Consult STA when you have legs with double racks Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 63 9 7 Bending Moment Coefficients Beta and Mu Two coefficients are used Beta and Mu Beta determines the fraction of the upper leg bending moment which is reacted by vertical forces in the chords It is found automatically by the program from the following equation Beta 1 1 G AQo dk Where G is the shear modulus of steel Ago is the average shear area of the leg port
37. 988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 3 2 0 PROGRAM INSTALLATION AND QUICK START The latest release version 4 0 April 1998 of the program runs in the environment of Windows 95 or NT with Microsoft Excel version 8 Office 97 The program is distributed as a series of Excel worksheet files with Visual Basic and macro controls on two 3 5 floppy disks This document provides instructions for loading the program setting up the Windows icon and gives preliminary guidance for running the program 2 1 Install Files and Create Directories STA LIFTBOAT should be set up in a directory called LIFTBOAT on your hard disk drive Before installing STA LIFTBOAT you must have Excel Version 8 already installed on your hard disk The manual installation procedure is as follows e Insert disk 1 of 2 click start button on the lower end of your windows screen Type a setup in the given box and click ok e Welcome message will appear Click install icon Type a user name must be at least 4 characters and a company name in user information dialog box e Target directory will appear Liftboat installation disk will automatically choose c liftboat as the target directory User can change the hard drive directory from c to others d for example The director name can also be changed say from Litboat to Liftboat1 when installing a new version of the program e Let the installation begin Change to disk 2 o
38. 9k 2k 14 16r 120715 74 sa Tum Licenced User US Coast Guard DH mm wv TIME IM SECONDS Guaq ala Slal Of fuel mmm Baan Sal Offer applird OFT Hassel das O T Hemel phase lag 8 deg FIGURE 13 Third Set of Graphs Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 23 PAD VERICALREACTIONINKIPS Deaniz Dogle 5 width Add amp TERTICAL REACTIONS INC RESPONSE Licenced User US Coast Guard 49 ks 2k 14 16r 120 71 MR wa TIME IN SECONDS amp Ed Flee amm Pad Flee om Pad Flee ge Padd rigid Pad rigid B Pad rigid phase lag 8 deg Dennis Doyle 5 Width A Beading Sierens is hei pgp COMBINED STRESSES IB LEGS l Leonel sf Lane Guide diconced User US Coast Guard 4 ke 2k 14 16x 126 715 25 08 aun 15 08 un sn Lu U D 4 D U 17 wv TIME IM SECOHDS et Lea d Flore Lrg 2 flessee iim beg J flesses Llradoomhinrd H Lea s mhinrd Lrg on mhinrd FIGURE 14 Fourth Set of Graphs Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 24 10 00 feet Tidal current Run date 8 12 98 Copyright Stewart Technology Associates 1990 and onwards Licenced User US Coast Guard 2 00 knots 10 00 seconds Wave crest elevation 5 14 feet 120 00 feet Pad penetration
39. Dennis Dogle 5 Width Added TORSIONAL HONENTS TORSIONAL HOHEHT IH PT KIPS FIGURE 12 Second Set of Graphs Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 22 Dennis Dogle 5 width Added COMI TALENT LINEAR WOTES AT FACE LEG 46k Zka 14 16r 120 15 74 e Licenced User US Coast Guard WAVE HEIGHT IH TEET D D DH H D D 1 7 TIME LEGI ep LEG LEGI Home Print these graphs D e e IES CTERTRESIEG HOHEBTS Le Se sl es amis amplifinaline Dennis Doyle 5 width L i be i d 49k ka 14 16x 120715 an Aceonced User US Coast Guard 1 1 1 1 1 1 1 i HII g e e i Ree eee eee eee ae eee ee eee eee 4 l CEET Ree eee ee ee eee D 1 1 1 1 1 amp D 1 sos Se ee mm zm ae eee ee eee eee d e mm mm z ee oe eee eee eee Se E 1 D D 1 D 1 1 1 e m l Deer de an Ape or de e e em em em e mm mm mm wm EE 1 1 1 t H LI S ws beeen eae nee mms mimm mam a si Dg T I EE P 5 7 1 T Z D 1 we ll em wm wm em e em e em em em em wm doo L e e e e e e e e e e e Lk we e e e e e e e em em em wl LI H a 1 1 1 F T J 2 TQ M gt D D c D Li Ld lp Se A d M 1 1 1 T 1 1 1 1 i U D 4 D U 17 7 TIHE IH SECOHDS U Lei beg lt lr PTHAHIC Swat RESPONSE OF HELL iik spplird sod des ap PY Denaiz Dogle 5 width Added 4
40. E sigma cr legt 1 915 lambda reduced slenderness 0 414 local buckling stress check DnV leg 1 leg 3 0 200 lambda 0 coef for buckling curve a 0 152 sigma a sigma cr leg2 0 178 0 200 alpha coef for non dim buckl curve a 0 248 alpha sigma_b 1 sigma_a sigma_E sigma_cr 0 254 13 839 sigma cr ksi from 2 3 2 CN30 1 0 500 local buckling stress check DnV leg2 0 540 Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 61 9 0 GENERAL THEORY AND ANALYSIS PROCEDURES 9 1 Overview STA LIFTBOAT computes wave wind and current forces on a liftboat The forces are calculated at twenty phase angles during the passage of a single regular wave Wind forces are considered to be steady Wave forces are combined with current forces The forces calculated as described above are applied to a structural model of the boat The forces cause deflections in the structural model which result in secondary bending moments and changes in the pad vertical reactions at the sea bed The structural model is described in more detail later The pads at the sea bed are treated as having a rotational stiffness which may be varied from zero to fully fixed by the user The flexural and shear stiffnesses of the legs which both generally vary along the length of each leg is set within the program for each leg hull model The overall sway stiffness of the boat will vary depen
41. Mechanism 63 Jacking Tower Data 40 Ke0 LEG OUT OF STRAIGHT coef 37 K Equivalent 50 ks 37 62 Lateral Stiffness 45 48 Lattice area sqft 31 Lattice av ht 32 LCG ft to aft legs 34 Leg buoy 1 dry 2 flood 32 Leg diams 1 2 3 ft 33 Leg Hydrodynamic Coefficients 56 LeverArm 33 liability 2 LICENSE AGREEMENT 2 local buckling 58 Local Buckling Stress Checks 60 Lotus Symphony 1 Manual coefficients 29 Manual Coefficients 17 marine growth 37 marine growth thickness inches 38 max fa legs 1 3 47 max fa top leg 2 47 max fb legs 1 3 47 max fb top leg 2 47 Max hull lateral deflection 46 Max wave current force 45 Max axial leg load lower guide 49 Max base shear 49 Max horizontal pad reaction 49 Max torsional moment 48 Max total force 48 Max apparent O T moment 48 Max equivalent lateral top load 46 Max lower guide reaction 49 Max OTT moment w o P delta 47 Max OT mom w PD 49 Max upper guide reaction 46 Mean hull lateral deflection 46 Mean wave current force 48 Mean wave current O T moment 48 Microsoft Excel 1 Microsoft Windows 1 Min leg length to be above hull bottom 35 Moment Amplification 69 moment diagram 64 MomSwitch O off 39 Mouse 4 Mu bottom fixity coefficient 44 natural period multiplier 36 Natural Periods 66 Natural sway period 45 46 Natural torsional period 46 next section 42 Number of sections 42 Offset defl
42. O T SF This is the safety factor against overturning computed from the environmental loading applied to the undeflected structure In other words the loading is treated as static the structure is treated as being rigid and without deflections and the uncorrected stabilizing moment is used The equation used is Uncorrected O T safety factor uncorrected stabilizing moment max O T moment Corrected O T SF This is a safety factor against overturning This term is found dividing the uncorrected stabilizing moment by the maximum overturning moment with P delta effect Note that if the wave loading direction is not perpendicular to the line joining the pair of legs nearest to the center of gravity the reported overturning safety factors are not strictly correct The error is always conservative A corrected overturning safety factor 1 implies that the environmental forces and structural response during the passage of a wave result in a maximum overturning moment which is just equal to the uncorrected stabilizing moment DnV O T Safety F This is the factor of safety against overturning computed by dividing the corrected stabilizing moment by the maximum overturning moment without the P delta effect Generally the value found is close to that described above for the corrected overturning safety factor ABS pre 88 unity str chk legs 1 3 This is the maximum calculated unity stress check in either of the liftboat legs 1 or 3 at the location of
43. Run Ref 40kn 2kn 14 10s 120 15 4 Tabular Results Input Summary Back to Input File UC Stresses Auto Calc Penetration Go to Master Graphical Results Print this screen Print graphs Print all tables Print all results Set 5 Penetrn Input FIGURE 7 Buttons on Upper Part of Lift001 XLS Screen e File Management This button takes the user back to the Liftboatopen xls workbook where another set of files for another boat may be opened or a new boat may be saved etc e Input Leg Data Clicking on this button will jump the user to the section of the worksheet directly below the upper left corner of the main input section where detailed information on leg cross section data internal stiffening etc is to be input e Tabular Results This jumps to the section of the results file where a table of results is given e Input Summary This jumps to the input summary contained within the results file e Back to Input File This takes the user immediately back to the input data file where environmental conditions for example could be changed e UC Clicking on this button jumps the user to the unity stress checks portion of the Results Summary e Stresses This takes the user to the top of the portion of the worksheet where the stress calculations are performed Use the scroll bars and the mouse to move down this section to investigate the stress calculations e Transit Clicking on this but
44. S SUBJECT Page 1 0 INTRODUCTION WE 1 2 0 PROGRAM INSTALLATION AND QUICK START sseessoeeeeeeeeneessererrrerrrnessernne 3 2 1 Install Files and Create Directories eesseeesesesssss 3 2 2 lnstall COM eL EE 3 2 3 Program Files On Distribution Diskettes ssssesessss 4 2 4 PUGET dieit ert ess een EE Ee 4 2 5 le A 3 0 PROGRAM OPERATION WE 5 3 1 Q ick Start E 5 4 0 GENERAL PROGRAM OPERATION Step By Step Process 9 5 0 BUTTON CONTRO S r hana ee aaa eed a RAI 15 5 1 SALINE T XLS BONS ee 15 5 2 LiftOO T AES re 16 6 0 MAIN INPUT DATA 1st Data Screen ssee 31 IGM CONV ie recien EN 33 7 0 SECONDARY DATA INPUT 2nd Data Gcreen 36 7 1 Control and Miscellaneous Data 36 7 2 Jacking Tower Data codo occ a ra o e i oro o e i on news 40 7 3 ele WR 41 7 4 e Ee RR EE 41 8 0 TABUEAPHRE H EE 44 8 1 Input SUMMary EE 44 8 2 Res lts Suritmidly oct oes aep ron ei RO ee nes 45 8 3 Pad Moment RESUS s eege 53 8 4 Leg Hydrodynamic Coefficients cccccceceeeeeeeeeeeeeeeeeeeeeeeeeenneeeeeeeees 56 8 5 Unity Stress Checks Global Leg Gtrength 57 8 6 Local Buckling Stress Checks t eer obe erect tens 60 9 0 GENERAL THEORY AND ANALYSIS PROCEDURES sees 61 9 1 REENEN ee 61 9 2 Soil Structure Intel aeWOE se sacs tee celeste Sia See 61 9 3 Structural Calculations Intoduction sssnneeeeeeeeeeeennnennneeeeeernnnnnrr
45. S g 7 Theta 0 Leg 2 D be ves eee ems x axis di e Er fe d 7 E 90 PLAN VIEW OF LIFTBOAT Theta FIGURE 21 SIGN CONVENTION FOR WAVE DIRECTION Leg diams 1 2 3 ft Three terms must be input to the program for this single data description These are the equivalent diameters for each of the three legs They are normally equal but in the event that the user wishes to study an unusual phenomenon perhaps of additional marine growth on one leg or additional secondary structures added to one leg this may be done Note that the equivalent leg diameter is multiplied by the inertia coefficient in order to find inertia forces and is multiplied by the drag coefficient in order to find drag forces Similarly this leg diameter is multiplied by the drag coefficient in order to find wind loading on the exposed parts of the legs Additionally it should be noted that the leg diameter is used in order to Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 34 calculate buoyancy forces on each leg These buoyancy forces have the effect of reducing the vertical leg reaction on the sea bed Cm1 Cm2 Cm3 These are the leg inertia coefficients used in Morison s equation They are normally all equal and a typical value is 1 75 to 2 0 However lower values down to 1 5 are often used CD1 CD2 CD3 These are the leg drag coefficients Although they are freq
46. S which is represented by formulae H1 1 H1 2 and H1 3 in Reference 9 Expressing the DnV formula as a unity check yields both 1 25 fa for 1 25 fy fpo 1 P Pe for gt 1 0 1 25 fa for 1 25 f fbo for gt 1 0 The program STA LIFTBOAT reports a value for f which equals fy f 9 The value of eg is controlled by the input term Ke0 LEG OUT OF STRAIGHT coef Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 58 The local critical stress for for legs which are proportioned and stiffened in such a way that local buckling is excluded is determined from the yield criterion as for fx fe fy Where fx actual value of axial stress component in the leg fe von Mises equivalent stress component fy yield stress of leg steel In practice the von Mises stress is almost identical to the axial stress component as shear stress is small and in any case the point of maximum shear stress is at 90 degrees around the leg circumference from the point of maximum bending stress Consequently the critical stress fcr is generally approximately equal to the leg yield stress Note The above stress checks are governing only if the legs are proportioned and stiffened in such a way that local buckling is excluded If the effective D t internal diameter divided by average equivalent thickness for the leg beneath the lower guide ratio exceeds the E 9fy Young s modul
47. STA LIFTBOAT STA LIFTBOAT is a computer program for analyzing liftboats in the elevated mode Version 4 01 August 1998 USER MANUAL and THEORY The program accounts for wind wave and current loading on the unit and computes static and dynamic structural response as well as pad reactions at the sea bed This version of the program runs in the environment of Microsoft Windows and Microsoft Excel A mouse is used to click on option buttons in order to move rapidly through the analysis No experience of Excel is required to use STA LIFTBOAT This program has been Technology Associates STA and documentation remains are cautioned to exercise engineering judgment when STA LIFTBOAT This is LIFTBOAT since response seconds on a 486 based PC use does not alter the care and associated with selecting the loading environmental and Care is also needed when response variables including properties and damping developed by Stewart All copyright for the software with STA Users of the program experienced and careful interpreting the results from especially important with STA results can be obtained in This rapid speed and ease of attention needed from the user appropriate input vessel other important conditions selecting certain structural leg preload levels soil No part of this document should be taken in isolation or out of context and interpreted in a manner inconsistent with the overall framework and intent of this
48. Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 20 WATE FORCES 8 CACHE LEC PASE SECAR Dennis Dogle 5 width Added 40k Zka 14 16x 120 215 4 licenced User US Coast Guard L zou H a a gt e zu E r gt mu lt 1 1 s 1 m TIHE IH SECOHDS Zo Leni Lef O Le EET Puer obrar Print these graphs E Home HeHEBTS AT LEGI Dennis Doyle 5 width Added 49 ks 2ks 14 16r 12071574 sn a m s m x coa E m 5 M os 2 Ioan TIME IH SECOHDS Deaniz Dogle 5 width Added WATE FORCES AT LEGIT Licenced User US Coast ord 49k 2k 14 16r 120 71574 FORCE IM KIPS DO Dean foror te lerrlis Farsar 9 Talal foror FIGURE 11 First Set of Graphs Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 21 PTHAHIC QHFLIFICATION FACTORS Deaniz Doyle 5 Width Added 49k 2k 14 10r 120 715 74 Licenced User LS Coast Guard 7 17 DYHAHIC AMPLIFICATION FACTOR en WAVE PERIOD IR SECONDS o Home E Print these graphs Wi EANIT BRAC COEFFICIENT VITE WATE ABCLE Deanniz Doyle 5 width ES oeren 40k ka 14 165 120 215 24 iconced Leer ast Guard 1 mmm EM Ke Meter Seite 9 EEN p ee EQUIVALENT DRAG COEFFICIENT DEGREES EGUIY DIAM IN FEET BELOW mn Dal Beles som Shell iR
49. These generally include different environmental conditions and loading conditions for the vessel selected in liftboatopen xls Note the directory structure is described later Note the file names are case sensitive The icon file is shown to the right 2 4 Printer As with any Excel application you may print to a Windows configured printer Most results include colored cells and objects A color printer is recommended 2 5 Mouse A mouse is required to run STA LIFTBOAT Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 5 3 0 PROGRAM OPERATION Once the program files are installed on your hard disk program operation is extremely simple 3 1 Quick Start For users of previous versions of STA LIFTBOAT or for those who do not wish to spend time reading the User Manual until you have seen the program running this Quick Start section is provided Note that unless you have a large amount of expanded memory you may not be able to run other applications in Windows when running STA LIFTBOAT This is because STA LIFTBOAT requires a large amount of graphics resources when it runs The first workbook that will be opened is Liftboatopen xls Three other workbooks Liftinpt xls Lift001 xls and MASTERINPUT xls will be opened You will be prompted to provide the password for LiftOO1 xls Licenced User US Coast Guard Copyright 1988 and onwards Stewart Technol
50. a column for section properties is not titled the data in it will be ignored This obviates the need to delete data that you have entered if you elect to reduce the number of sections within a leg You may move down the worksheet with the scroll bars to investigate the area moments for each leg section to ensure your data input is as you expected it to be Rack width in This is the width of the rack on the leg The rack is assumed to be of constant properties throughout the length of the leg rack ht to top teeth in this is the distance from the outside of the leg at the rack center to the top of the rack teeth rack ht to bot teeth in This is the distance from the outside of the leg at the rack center to the bottom of the rack teeth The rack within this dimension multiplied by the rack width dimension is treated as structural steel adding to the leg stiffness The teeth above this are considered only as adding weight and hydrodynamic drag and volume to the leg No racks 1 or 2 If this number is 1 the program accounts for the stiffness weight and drag of one rack Otherwise the input rack properties described above are used to model these characteristics for two racks appendage wt factor This term is used to model additional non structural weight attached to the leg A value of around 0 02 may be used to account for excess weld metal in heavily stiffened legs This term may also be used to account for anodes on the legs
51. acceptable at the upper guide the user may increase the leg area moments at this location by changing the stiffening in the bottom section of the leg see leg structural input data Normally the load cases caused by 6 degrees roll amplitude at the vessel natural period and 15 degrees roll amplitude at a 10 seconds period should be investigated to satisfy ABS criteria For restricted service liftooats use a 70 knot wind speed Home Stresses Tabular Results FIGURE 19 Transit Results Graphical Results Print this screen Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 29 120 00 ft water depth from input assumed to be flood water height in leg 87 88 kip weight of water in flooded leg internal leg area accounts for stiffeners 67 00 ft vcg of flood water in leg 38 48 ft vcg of vessel if upright with one leg flooded 1 67 ft rise in vcg caused by flood water in one leg 190 58 ft GM with flooded leg 2944 kip ft inclining moment caused by upright flooded leg 0 59 deg list caused by upright flooded leg 0 70 ft additional moment arm caused by inclination of flooded leg 3006 kip ft total inclining moment caused by inclined flooded leg Reset if Iteration Failec 0 60 deg list caused by inclined flooded leg found iteratively 0 83 deg vessel heel angle where bilge emerges above SWL Vessel bilge remains submerge
52. ad Bottom length ft 93 58 total weight 1 leg w pad kips top length ft 85 00 0 00 0 00 LxM ftin 4 3505074 49 0 00 0 00 deltaL ft 85 00 0 00 0 00 Print this screen of leg cross section data Av area mom below LG in 4 Bottom length ft average for whole leg in 4 85 00 0 00 0 00 LxM ftin 4 2218615 68 0 00 0 00 deltaL ft 85 00 0 00 0 00 Av area mom below LG in 4 Bottom length ft average for whole leg in 4 85 00 0 00 0 00 deltaL ft 85 00 0 00 0 00 Area in 2 107 02 0 00 0 00 Area deltaL ft in 2 9096 75 0 00 0 00 Av sect area below LG in 2 Equiv wall t for unstiff tube in Area moment non rack bending at lower guide in 4 49087 26 Cross section area of leg at lower guide in 2 230 78 Equivalent wall thickness for unstiffened tube in 1 583 Average cross section area for whole leg in 2 FIGURE 17 Calculated Leg Structural Data Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 27 Transit 08 12 98 Date of this run Boat Name Dennis Doyle 5 Width Added Geometry Switch Selected gt 2 Run Ref 40kn 2kn 14 10s 120 15 4 Licenced User US Coast Guard Tabular Results 2 stern 3 stbd Area in 2 230 78 3 0267 3 0267 fore aft bending directi
53. ad reaction during the analysis what the equivalent minimum cohesive soil shear strength must be in order to support the pad The user may input this value manually to the next cell below or may use the Auto coefs option su soil undrained shear strength beneath pad psf The user may either input this term based upon site specific soil data or alternatively may input the minimum su value needed to support the maximum pad reaction found during a wave cycle which should be equal to the preload reaction achieved during the preload process If the user clicks on the Manual coefs button the value of su is over written by the program as 160 psf If the user clicks on the Auto coefs button the program iterates while adjusting the soil su value until it is equal to the minimum value needed to support the maximum pad reaction during the wave cycle This iteration process involves the recalculation of the soil shear modulus G at each cycle This in turn creates a new value for the equivalent linear rotational spring beneath each leg at each iteration cycle The stiffer the rotational spring the smaller is the leg effective length the smaller is the lateral hull deflection and the lower is the pad vertical reaction Strictly the method is only correct for cohesive sea bed soils but practically may be used for cohesionless soils also The magnitude of the soil shear modulus also depends upon the coefficient in the next data input cell Stewart
54. ailed leg structural data Up to 5 different cross sections can be defined within a single leg All legs must be the same although they may be oriented differently see Figure 22 For each leg section a group of internal stiffeners may be defined or there may be no stiffeners in a section or in any section The diagram in Figure 16 shows how stiffeners may be arranged in a single section The general principles of stiffener specification are described below A single stiffener may be specified immediately behind the rack You must define its area and the radial distance of the center of its area from the cylindrical leg center A similar single stiffener may be defined on the opposite side of the leg away from the rack if a double rack is defined these stiffeners should be identical The rack direction is referred to as the local leg section y axis as shown in Figure 16 A pair of stiffeners may be defined on the local leg x axis You specify the area and radial distance of the center of area of one of these stiffeners from the cylindrical leg center The total area of the stiffeners on the x axis is twice the area you input Up to three additional sets of four stiffeners in each set may be specified Each of these sets is arranged symmetrically about the x axis as illustrated in Figure 16 You specify the area the radial distance of this area from the cylindrical leg center and the angle from the x axis of just one stiffener in each set
55. al case with storm waves the damping value is less critical However because of the uncertainty in the damping value the program also shows the stochastic DAFs that result for values of one half the selected Eta and for twice the selected Eta The stochastic DAFs are presented graphically for a wide range of wave periods The actual DAF used to calculate response amplification is that for the selected value of Eta at the selected wave period The user can judge from the DAF curves if the selection of a different Eta value would have a strong influence on the DAF If this is the case it is advisable to try a different value for Eta and repeat the analysis This takes only a few seconds Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 67 9 12 Dynamic Response Analysis Having found the environmental loading the program applies this loading to the structural model and finds deflections The loading is divided into a mean or steady part and an amplitude or dynamic part The response is found from the combination of static response to the steady loading and dynamic response to the dynamic loading The dynamic response is found from multiplying the equivalent static response to the amplitude of the dynamic forces multiplied by the DAF found above Where the DAF is small the total response is approximately the same as would have been found by static analysis alone Where the DAF is large
56. al Analysis Draft Final Report prepared for US Coast Guard Research and Development Center Groton CT July 1990 Report DTCGT 89 C 80825 Hambley E C Imm G R Stahl B Jack Up Performance and Foundation Fixity Under Developing Storm Conditions Proc 22 Offshore Technology Conference Houston OTC 6466 May 1990 SINTEF Foundation Fixity Study for Jack up Units Report Number STF22 F96660 August 1996 Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 70 INDEX 11 OR 2 RACK SWITCH 41 ABS pre 88 unity str chk 50 ABS Stress Checks 58 accept calc wt ft 36 accept hull gyrad 36 add mass coef 38 added mass 56 afloat stability 59 Air gap ft 32 Airy wave theory 1 Amplitude wave current O T moment 45 appendage wt factor 42 Auto coefficients 17 39 Auto Coefficients 17 Average leg buoyancy 45 AvShield 32 axial stress component 51 b jack vcg 40 Back to Input File 16 Bending Moment Coefficients 63 Bending Stiffness 62 Beta and Mu 63 Beta top fixity coefficient 44 BM hull max w oPD 49 BM hull max w PD 49 buttons 15 capsize 59 CD1 CD2 CD3 34 Cm 59 Cm1 Cm2 Cm3 34 coef on su to get soil G modulus 37 coefficient on cu 17 compact 60 CONTENTS 3 Corrected O T safety factor 50 Corrected Spud Can Reactions 69 Corrected stabilizing moment 46 Corrected Stabilizing Moment 68 Cu rate 39 Cu
57. alent diameter and average drag coefficient at the first data input screen The input diameter is then used for wave loading calculations and for leg buoyancy calculations However it should be noted that the equivalent leg diameter as computed in each leg hull file is used to calculate the added hydrodynamic mass of each leg This added mass contributes to the terms used to compute the natural sway period of the boat For most liftboat legs the rack effect is small and the actual leg cylinder OD is virtually the same as the computed leg equivalent diameter The leg drag coefficients calculated in each leg hull file should also be input by the user to the first input data screen as described for the leg equivalent diameter above The average drag coefficient found as the wave attack angle is varied may not be appropriate for all wave attack angles and the user should consult the graph of drag coefficient variation with wave attack angle produced by the program Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 57 8 5 Unity Stress Checks Global Leg Strength Rational Stress Check STA LIFTBOAT uses a rational formula for its unity stress checks of the liftboat legs Only the maximum stresses at the level of the lower guide are directly checked The input stresses are calculated correctly accounting for the second order stresses induced by large sway deflections An interaction equation relat
58. amping term e This method is also adopted in STA LIFTBOAT where input e values are doubled in order to find reasonable stochastic DAFs If the user wishes to evaluate response in long crested regular waves a value of only one half of the desired damping coefficient should be input Damping alone limits vessel response values at resonance where the wave period and the vessel first natural period are coincident Away from resonance as is the normal case with storm waves the damping value is less critical However because of the uncertainty in the damping value the program also produces a graph which shows the stochastic DAFs that result for values of one half the selected e and for twice the selected e The actual DAF used to calculate response amplification is that for the selected value of s at the selected wave period The user can judge from the DAF curves if the selection of a different e value would have a strong influence on the DAF If this is the case it is advisable to try a different value for e and repeat the analysis This takes only a few seconds The selection of an appropriate value for e is a trial and error process since e increases with increasing response amplitude STA has automated the selection of s in STA LIFTBOAT v2 01 Automatic selection of this term occurs when the user clicks on the Auto coefficients button see page 12 The equation used to find e is shown below 2 5 hull deflection amplitude leg radius
59. appropriate factors of safety for a and c are generally 1 25 as they represent combined live loadings The factor of safety for b is either 1 25 or 1 44 depending on the slenderness ratio the yield stress etc The overall buckling stress is defined in Reference 3 The local buckling stress must be found from another source API RP 2A is used Reference 5 to find elastic and inelastic local buckling stresses Note that stresses at the bottom of the legs may be high under some situations and fatigue damage may occur at the leg and pad connection Initially a through thickness fatigue crack would permit the leg to flood with water On re floating the vessel the water in the flooded leg may not drain as quickly as the leg is raised This may lead to a complete loss of afloat stability and capsize if the problem is not quickly recognized Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 60 8 6 Local Buckling Stress Checks If the leg diameter thickness ratio exceeds the ratio of Young s modulus divided by nine times the steel yield stress the leg column section is no longer regarded as compact In this case a local buckling check must be performed The method used in the program is that used by DnV and is fully described in Reference 6 STA LIFTBOAT always performs a local buckling stress check but only prompts the user to check the results if the leg properties require the c
60. arm for FTD ft xW vertical lever arm for FW kips Note that nomenclature in this section is as in DnV Class Note 31 5 May 84 FLS static axial force w ABS multiplier kips 168 90 average cross section area of leg sqin 1983 94 FLD inertia axial force kips does not act on aft leg which is on vessel centerline MTS static transverse BM ft kips Leg moments are resisted by the horizontal guide reactions 2587 88 MTD inertial tansverse BM ft kips 0 00 Beta moment coefficient for pinions jacks 316 07 MTW 1 wind transverse BM Vwind1 ft kips 139 48 RL lower guide reaction with Vwind1 kip 619 51 MTW 70 wind transverse BM 70 kt ft kips 199 51 RU upper guide reaction wi Vwind1 kips 4887 89 total leg BM in wind speed Vwind1 ft kip 148 00 RL lower guide reaction 70 kt wind kip 5191 32 total leg BM in 70 kt wind ft kip area moment of inertia bot section ft 4 211 89 RU upper guide reaction 70 kt wind kips area moment of inertia bot section ft 4 area moment of inertia bot section ft 4 area moment of inertia bot section ft 4 fb bend str fwd legs w Vwind1 ksi fb bend stress aft leg wi Vwind1 ksi fa axial stress in fwd leg ksi fa axial stress in aft legs ksi 10270 00 fb bend str fwd leg w 70 kt wind ksi user input waterline length of hull ft fb bend str aft leg w
61. ary The list can be manually edited but the directory structure may become corrupted The root directory is C LIFTBOAT The directory containing the individual boat directories is C ALIFTBOAT PROJECTS Each set of boat files is then found in the projects directory ina directory or folder with the boat s name This library is setup to hold up to 50 lifrboats Each boat has a master input file where up to 50 load cases can be stored To enter a new boat into the library select a new boat change its name click the File Management button and come back to this sheet Then press Save New Liftboat Files in New Directory Directory Name User MUST give drive letter and Directory name where Liftboat Files are located FIGURE 1 liftboatopen xls Main Screen If necessary change the drive letter and directory name where you installed the STA LIFTBOAT program Step 2 Open Stored Liftboat Files Click this button next Select a vessel from the list below A scroll list will appear in a dialog box as shown to the right Dennis Doyle Dennis Doyle 5 Width Added DENNIS DO YLE1 Step 3 DENNIS DOYLE11 Select a previously stored vessel and click OK Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 10 Step 4 Password HEI Enter password to required to open a o LiftO01 xls is protected selected vessel data files
62. ase data set you wish to use for analysis press the Paste Data button and your data will be transferred to the Liftinpt xls workbook From there it is automatically linked to the structural response workbook Lift001 xIs For more details on controls data input and results read the rest of this manual Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 9 4 0 GENERAL PROGRAM OPERATION STEP BY STEP PROCESS STA LIFTBOAT is designed so that almost all operations that the user may wish to perform can be undertaken by clicking with the mouse Actual data entry is from the keyboard but no keyboard commands are necessary Figure 1 below shows the initial screen of data that is presented to the user when the program starts Date of this run 08 13 98 Licenced User US Coast Guard Copyright 1988 and onwards Stewart Technology Associates Close Open Close and Save Close and Save Save All Open Files Not Active Liftboat Active Files in Files In New Saving Data Files New Directory Directory Open Existing Liftboat Files This worksheet keeps track of up to 50 Liftboat File Sets edited Number of boats in libraray 2 1 Boat number by the user selected Name of active boai Dennis Doyle 5 Width Added Dennis Doyle 5 Width Added 1 Begin Editing Data 2 Dennis Doyle5 Width Addedi 1 Po Use the control buttons to select existing or add new vessels to Liftboat Libr
63. ave got the data correct then click the Auto coefficients button again if you want automatic damping and soil iterative calculations top length ft This information will appear if you have specified two or more leg sections The program calculates this value based on the overall leg length plus the bottom and any intermediate next length leg section lengths you have specified Thickness in You must specify a wall thickness for each section of leg you have defined Stiff area inside rack sqin You may specify a stiffener area immediately behind the rack for each of the leg sections you have defined see Figure 16 Inside rack area radius in This is the radial distance of the center of area of the stiffener behind the rack in each leg section from the cylinder center Stiff area opposite rack sqin You may specify a stiffener area opposite to the stiffener immediately behind the rack for each of the leg sections you have defined see Figure 16 Inside rack area radius in This is the radial distance of the center of area of the stiffener opposite the rack in each leg section from the cylinder center Stiff area x axis sqin This is the area of one of an optional pair of stiffeners on the x axis of the leg see Figure 16 in each of the leg sections you have defined X axis area radius in This is the distance from the leg cylinder center of one of the centers of area of the x axis stiffeners Theta1 area sqin Thi
64. be understood by considering the horizontal force applied to the hull needed to displace the hull horizontally by a distance of one foot Mean wave current force This is the mean value of the horizontal force on the legs coming from wave and current loads during a single wave cycle Max total force This is the maximum horizontal force on the boat calculated from wave and current loading plus wind loading during a wave cycle Mean wave current O T moment This is the mean value of the applied overturning moment caused by wave and current forces on the legs Max apparent O T moment This is the maximum applied overturning moment coming from environmental forces It is described as the maximum apparent moment because the response of the structure is not included The sway response of the structure increases the effective overturning moment Max torsional moment This is the maximum torsional moment computed from environmental loads applied to the structure Like the term above it is the force available and does not include the effect of structural response This term is reported but is not used to calculate additional force or moment contributions to the legs DAF stochastic This is the stochastic dynamic amplification factor as described previously This term is used to multiply the amplitude of the applied loads form wave and current in order to compute the structural response of the vessel dynamically Hull deflection amplitude Th
65. cks on the button at the top of the input summary screen marked Print all tables see Figure 15 or when the user clicks on the button marked Print all results on this same data screen Alternatively the user may print the table in isolation by clicking on one of the buttons marked Print this screen when the user is viewing the table Most of the terms in the input summary are self explanatory and were entered by the user either at the main input data screen first screen or at the second input data screen A few terms require further explanation as described below Wind force The result for wind force appearing in the Input Summary will either read COMPUTED BELOW or a value for wind force in kips will be given The value in kips will only be given if the user has set the wind force switch to be equal to 1 in the main first data input screen Where the result is shown as COMPUTED BELOW the value for wind force will be shown in the Results Summary table Beta top fixity coefficient This term is a ratio representing the effective stiffness of the leg hull connection coming from the jacking system or from the rack chock system if appropriate A value of beta 1 0 implies that the rack chocks or pinions have taken the full moment at the top of the leg and that no moment is supplied by horizontal reactions at the guides Conversely a low value of beta implies that the horizontal guides are taking most of the leg bending moment into the hull In thi
66. ctural Calculations 62 structural model 61 su 36 su soil undrained shear strength 36 Tabular Results 16 TCG ve towards L1 34 Thickness 43 Tide vel kn 32 Tnxx 45 Tnyy 46 torsion 46 Total buoyancy 48 total damping crit 38 Total leg length ft 34 Total weight kips 34 Transit 16 transverse stiffness 64 UC 16 ultimate 49 ultimate moment capacity 61 Uncorrected O T safety factor 50 Uncorrected stabilizing moment 46 undrained shear strength 61 Unity Stress Checks 57 USER SPEC gyrad ft 38 USER SPEC leg kips ft excl cans 38 VCG excluding legs ft 38 VCG lower guide 40 von Mises 51 wall thickness 43 WARRANTY 2 Wave crest elevation 44 Wave direction deg 33 WB ft 31 Weight buoyancy 48 WH1 ft 31 WH2 ft 32 Wind elevation ft 34 Wind force 44 45 Wind force kips 32 Wind force switch 15 Wind loading results 15 16 Wind O T moment 45 Wind v2 kn 34 WL ft 32 Young s Modulus 36 Stewart Technology Associates 1988 and onwards
67. ctural characteristics of the system The methodology is adapted from that described in the DnV Classification Note 31 5 February 1992 Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 62 Details of the most important calculations and explanation of user input required are given below 9 4 Shear and Bending Stiffness Average shear areas Ao and moments of inertia are used and corrections to these terms within the guides are made depending upon the leg length extended in the run in question For uniform legs the method is quite accurate For non uniform legs there may be localized errors of the order 10 20 but this is generally acceptable in view of other uncertainties in response and load evaluation By running upper and lower bound stiffness cases STA has found that response results are normally within 5 of those found with a detailed FE model 9 5 Pad Restraint ks The pad support spring needs the user input of undrained shear strength sy for the soil and a term Gfactor Which will yield a soil shear modulus G based upon sy The program uses the input Gfactor as follows G Gtactor Su The program will calculate a value kg for a rotational spring representing the pad soil restraint at the bottom of the legs The stiffness ks is based upon the equation for a circular disk radius r in an elastic half space taking Poisson s ratio v as 0 5 ks 8 G r
68. d hull depth user must input 10 72 ft freeboard 3 88 deg vessel heel angle at which deck edge submerges Deck edge is not predicted to submerge by linear method FIGURE 20 Check On Effect Of Raising a Flooded Leg Immediately beneath the Transit Results section in the workbook the data seen in Figure 20 can be found This is simply a useful check to see if raising a flooded leg could lead to capsize The loaded condition of the rig is based upon the data provided by the user in the Liftinpt xls starting workbook Because of deliberate use of a circular reference in the calculation of the list angle the result may become corrupted you will see a result REF If this happens click the reset button see Figure 20 No other formulae are affected Print all This will print all tables and all graphs Set 5 Penetration This button sets a 5 pad penetration on the Liftinpt xls workbook The user can change this to any value desired However the program will calculate the actual penetration cased by the environmental loads on the heaviest loaded leg and warn the user if the pad penetration specified is too much or too little in cells D17 E17 Setting pad penetration calculations to automatic by clicking Auto Calc Penetration will override the user input fixed pad penetrations Manual coefficients Clicking on this button will set the Auto coefficient see above iterative calculation feature of
69. de and accounts for all structural responses including so called secondary bending P delta effects max fb top leg 2 This is the maximum bending stress induced in leg 2 aft leg at the level of the lower guide and accounts for all structural responses including so called secondary bending P delta effects max fa legs 1 3 This is the maximum axial stress induced in either leg 1 port or leg 3 stbd at the level of the lower guide and accounts for all structural responses max fa top leg 2 This is the maximum axial stress induced in leg 2 aft leg at the level of the lower guide and accounts for all structural responses Hull max shr str This is the maximum shear stress induced in the heaviest loaded leg at the level of the lower guide fa Fa ABS legs 1 3 note if leg 2 is the heaviest loaded leg this term will be fa Fa ABS leg 2 This is the maximum calculated axial leg stress from leg axial loads F1 F2 or F3 induced in either leg 1 port or leg 3 stbd at the lower guide divided by the maximum allowable axial stress Fa in this leg Fa is calculated according to ABS rules see section on stress checks If leg 2 is heavier loaded than either legs 1 or 3 the fa Fa value for leg 2 will be shown fb Fb ABS legs 1 3 note if leg 2 is the heaviest loaded leg this term will be fb Fb ABS leg 2 This is the maximum bending stress from bending moment at lower guide induced in either leg 1 port or leg 3 stbd divided by the
70. ding upon the leg length extended and the variable loads included within the total weight of the boat The stiffness of the leg to hull connection is set within the program for each leg hull model The response of the structure to loading is computed both statically and dynamically The dynamic model is a relatively simple single degree of freedom model with carefully balanced distributed mass and inertias of the main structural components The dynamic response reported is effectively a steady state response to the environmental forcing function which is treated as being sinusoidal 9 2 Soil Structure Interaction The soil is treated as providing a rotational spring stiffness to each pad This stiffness is nominally modeled by selection of two input terms One is a coefficient and the other is the soil undrained shear strength The combination of these terms as described below results in a rotational spring stiffness The response of the structural model is computed and the moment applied by the rotational spring to each pad is then found The large pads on liftboats give the legs significant bottom rotational restraint The ultimate moment capacity of the soil is reported and a warning is given if the maximum calculated moment at the pad exceeds this theoretical upper bound limit 9 3 Structural Calculations Introduction Having found the environmental loads and their distribution the next step in evaluating boat response is to model the stru
71. document LIFT401 8 10 98 Stewart Technology Associates 5619 Val Verde Houston TX 77057 Tel 713 789 8341 Fax 713 789 0314 e mail Stewart neosoft com Stewart Technology Associates 1988 and onwards STA LIFTBOAT USER MANUAL and THEORY Ver 4 01 Page ii EXTRACTS FROM LICENSE AGREEMENT LIMITATION OF USE This License is granted to the USER for an indefinite period The USER agrees that no individual outside consultant government organization or any person who is not on permanent staff with the USER or under direct in house control of USER shall have access to the PROGRAM or shall use the PROGRAM for any purpose at any time The use of the PROGRAM is not limited to a single machine and the USER may make copies of PROGRAM and run it on several machines simultaneously The USER agrees to make any reasonable effort to assure that the PROGRAM file or disk is not copied without authorization by OWNER and that all users in USER s organization are familiar with these Limitations of Use The USER agrees not to modify copy sell lease rent give free of charge or otherwise distribute or alter the PROGRAM or any part thereof to any individual government agency or organization outside of the USER organization COPYRIGHTS All copyrights to the PROGRAM are reserved by OWNER All versions of the PROGRAM are copyrighted by OWNER worldwide beginning with 1988 The following is a trademark of OWNER STA LIFTBOAT The USER shall cl
72. e Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 52 E 9fy Young s modulus divided by nine times yield stress ratio then a local buckling check must also be performed in order to ensure local buckling will not occur Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 53 8 3 Pad Moment Results The moments calculated at the pads are dependent upon the rotational spring stiffness simulated at the pads This stiffness is user specified by input of the undrained soil shear strength su and the term coef on su to get soil G modulus in the second input data screen In general the stiffer the soil spring the larger will be the moment generated in response to environmental loads If the spring has zero stiffness the pads will not find any moment and their rotation will be a maximum If the spring is very stiff the pads will hardly rotate at all and the moment generated will be high Moment Capacity of Pads It is becoming accepted that the maximum moment capacity of a fully embedded spudcan in clay can be described by the yield function given below Reference 9 Pial F F Nees dee E 1 VHM _ 2 VHM _ VHM HM RA M e re ell ns pech 2 2 F F 1 a E 0 when Fygy lt 3 Vio Equation 2 LO LO where Fygy vertical foundation capacity in combination with horizontal and moment load Fyn horizonta
73. e av ht ft wind v2 kn tide vel kn 500 Total weight kips distance from aft to fwd legs ft LCG ft to foward legs distance bet fwd leg centers ft TCG ve towards L1 pad penetration ft leg buoy 1 dry 2 flood init phase ang deg windforce kips air gap ft wind elev ft Wind force switch 1 input 2 computed tot leg length ft Select Load Case FIGURE 4 MASTERINPUT xls Workbook Example Screen Step 9 Go on to structural response by pressing the appropriate button Your screen will appear as shown in Figure 5 below 8 12 98 Date Stewart Technology Associates Boat Name Dennis Doyle 5 Width Added Input Leg Data Licenced User US Coast Guard Run Ref 40kn 2kn 14 10s 120 15 4 Tabular Results Input Summary Back to Input File Stresses Auto Calc Penetration UU Auto coefs o to Master Graphical Results J Print this screen Print graphs Print all tables Print all results J Set Sr Penetrn J Manual coefs Input 4 02 DE equiv leg diam ft 0 78 CDEaverage 0 86 CDEmax max drag coef EDIT USER DEFINED VARIABLES deflection multiplier 1 normal Young s Modulus leg steel ksf MomSwitch O off K equivalent nat period multiplier norm 1 no dyn 01 1037 Average maximum allowable pad moment yield stress for leg steel pad moment amplitude accept calc wt ft 1 no 2 yes add mass coef 1 normal accept hul
74. e bottom of the hull Lattice av ht This is the average height of the lattice area defined by the user previously This height is related to the bottom of the hull or keel line See section on wind loading Tide vel kn This is a current velocity uniform with depth throughout the water column It is typically attributed to a tidal velocity hence its name Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 33 LeverArm This is the horizontal distance from the geometric leg center to the center of the lateral area exposed to wind The program reports torsional forces on the boat If the geometric wind center is not at the geometric leg center this contributes to torsional forces However note that torsional forces although reported are not included in leg moments or forces Wave direction deg This is the direction of the wind and waves and current relative to the boat The sign convention for defining this direction is shown in Figure 4 below This term should normally be varied in order to find which direction provides most critical results Typically there will be a worst direction for maximum leg bending moments and a different worst direction for maximum pad reactions SIGN CONVENTION FOR WAVE DIRECTION wind and current use same convention Waves on the port side come from 90 Waves on the bow come from 02 Waves on the stern come from 1802 Z
75. early and distinctly indicate the copyright in all published and public references to the PROGRAM WARRANTY While the OWNER has carefully developed the software and the software has been tested for accuracy and proper functioning nevertheless the OWNER cannot guarantee its accuracy and correctness If the software fails to perform correctly as a result of errors or omissions by the OWNER or its staff the OWNER will at its discretion rectify those errors and omissions free of all charges to the USER This shall be the limit of the OWNER s liability in this respect OWNER warrants that it has the right to grant this license The PROGRAM and its documentation is sold as is and the USER assumes the entire risk as to quality and performance HOLD HARMLESS The OWNER shall not be liable to the USER or any other party for any design performance or other fault or inadequacy of the PROGRAM or its manual or for any direct or implied damages of any kind arising out of or in any way related to or connected with any use of the PROGRAM STA LIFTBOAT is the PROGRAM descibed above The OWNER of this PROGRAM is Stewart Technology Associates who are also the program developers The USER referred to above is the organization who purchased the PROGRAM from Stewart Technology Associates and who have a valid License Agreement for STA LIFTBOAT Stewart Technology Associates 1988 and onwards STA LIFTBOAT USER MANUAL and THEORY Ver 4 01 Page iii CONTENT
76. ection 49 pad 1 2 height 41 Pad Data 41 pad length 41 Pad max angle 49 Pad max calc bend mom 46 Pad mean angle 47 Pad Moment Results 53 Pad penetration 32 Pad Restraint 62 Pad Ultimate Moment Capacity 49 pad width 41 PAD1 before environmental load 45 PAD2 before environmental load 45 PAD3 before environmental load 45 PadMax Id corrected 47 PadMax Id uncorrected 46 PadMin ld corrected 49 PadMin Id uncorrd 49 P delta effect 59 PDelta leg BM max 46 Penetration ft 32 Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 72 phase angles 61 Poison s ratio 37 Print all graphs 19 Print all results 29 44 Print all tables 19 44 Print this screen 15 18 44 Printer 4 Quick Start 5 rack ht to top teeth 42 Rack width 42 radius 37 Rational Stress Check 57 Rational Unity str chk 50 51 resonance 67 Results Summary 45 rotational spring stiffness 61 secondary bending amplification 59 SECONDARY DATA INPUT 36 Shear 62 shear flexibilities 64 shear modulus of steel 63 shear stress 51 sidesway 59 SIGN CONVENTION 33 slenderness ratio 59 soil shear modulus 62 Soil Structure Interaction 61 soil su needed to support pad 36 Stabilizing Moment 68 stiffeners 41 43 stochastic DAF 66 stochastic dynamic amplification factor 39 stochastic dynamic amplification factor SDAF 67 Stresses 16 Stru
77. eeeeee 61 9 4 Shear and Bending Kn 62 9 5 Pad Restraint erst 62 9 6 Jacking Mechanism Sliffiess ci conet te pei E n Ip EES 62 9 7 Bending Moment Coefficients Beta and Mu 63 9 8 E ler Leg Load EE 64 9 9 Equivalent EE 65 9 10 Natural EE 65 9 11 Dynamic Amplification Factors DAF 66 9 12 Dynamic Response Analysis errore erreur hes 67 9 13 Corrected Stabilizing Moment 67 9 14 Corrected Pad ETH io io ce eegene egener 69 9 15 MomoefbAmbplifICatiOn eebe 69 Stewart Technology Associates 1988 and onwards STA LIFTBOAT USER MANUAL and THEORY Ver 4 01 Page iv 10 0 Ee INDEX ee Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 1 1 0 INTRODUCTION Stewart Technology Associates STA has developed a suite of programs for the analysis of certain types of offshore structures STA LIFTBOAT is the program offered by STA for the analysis of liftooats in the elevated and afloat transit modes The program was originally developed in 1990 and has undergone continuous further development since that time Initially the program ran in the environment of Lotus Symphony Since release 2 01 in 1992 the program has been available running in the environment of Microsoft Windows and Microsoft Excel Instructions for loading and operating the program are given in Section 2 of this manual The purpose of STA LIFTBOAT is to calculate the structural response and pad
78. eg1 1 61 ksi Uncorr O T SF 3 65 ratio Max axial stress at lower guide Leg2 2 02 ksi Corrected O T SF 2 13 ratio Max axial stress at lower guide Leg3 2 43 ksi DnV O T Safety F 2 37 ratio Max bend str at lower guide Leg1 23 15 ksi ABS pre 88 unity str chk leg 1 0 71 ratio Max bend str at lower guide Leg2 24 41 ksi ABS pre 88 unity str chk leg 2 0 80 ratio Max bend str at lower guide Leg3 24 59 ksi ABS pre 88 unity str chk leg 3 0 86 ratio fa Fa ABS leg 1 K effective 0 23 ratio fb Fb ABS leg 1 K effective 0 48 ratio fa Fa ABS leg 2 K effective 0 29 ratio fb Fb ABS leg 2 K effective 0 51 ratio fa Fa ABS leg 3 K effective 0 35 ratio fb Fb ABS leg 3 K effective 0 51 ratio Rational Unity str chk leg 1 0 74 ratio PadMax Id corrected 434 51 kips Rational Unity str chk leg 2 0 80 ratio PadMin Id corrected 248 46 kips Rational Unity str chk leg 3 0 86 ratio FIGURE 15 Input Summary and Summary Results Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 25 Leg section properties are permitted to vary along a liftboat leg with up to five different sections being specified The diagram below shows how stiffeners are defined inside the leg A single pair of stiffeners on the x axis and up to 3 sets
79. es the user to the MASTERINPUT xls workbook where up to 50 load cases can be stored and edited e File Management This button takes the user back to the Liftboatopen xls workbook where another set of files for another boat may be opened a new boat may be saved etc Most of the other information contained on the first input data screen is technical and is described in the next section of this manual However it is worth noting that there is one switch on this screen which is in the bottom row of the screen near the left hand side This cell is labeled Wind force switch f the value is set to one then the program seeks to find a wind force on the left hand side of the screen in the cell labeled wind force kips If the Wind force switch is set to two the program uses the wind areas and velocities specified by the user to calculate wind loads on the boat Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 16 5 2 Lift001 XLS Buttons Figure 7 below shows the screen that is presented to the user after clicking on the button on the first screen labeled Go on to Structural Response A series of buttons is shown in the upper part of this screen The actions of the buttons are generally intuitive but for completeness are described below 8 12 98 Date File Management Stewart Technology Associates Boat Name Dennis Doyle 5 Width Added Input Leg Data Licenced User US Coast Guard
80. f The soil su value will be set to 160 psf and the total damping value will be set to 296 of critical Both terms can be changed to other values by the user NOTE If impossible input conditions are given for example negative length of leg sections the automatic coefficient calculation routines will fail The program will show a warning message to the user advising that the Manual Coefficients button must be clicked after the input has been corrected The user should also click the Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 30 button Set 5 Penetration if this has not been clicked and the Auto Calc Penetration button has been clicked The Auto Coefficients button may be clicked only after input errors have been rectified In addition to the operational features described above using the in built macros that are invoked when the various buttons are clicked the experienced user may make use of some of the Excel functions that are still provided within the normal Excel main menu that is available when STA LIFTBOAT is run From the File menu the experienced user may choose to save certain sets of results in separate files or to print separate sections of the screen without using the STA macros Users are cautioned not to make modifications to any of the main program files that would normally be used by STA LIFTBOAT For inexperienced users the normal Excel Help facility can
81. f 2 whenever an instruction box to do So appears e Program group box will appear Click ok e Close the installation file e A Liftboat box should appear on the windows screen 2 2 Install Icon You should set up an icon to run the software An icon file is available inside the liftboat box You can simply drag that icon to the windows screen in order to create a short cut If by accident you close the liftboat box you may create the short cut icon through following An icon file is available inside the liftboat subdirectory Right click the mouse on a blank area of the main Windows 95 desktop screen You then select new followed by shortcut You will then be prompted to provide a command line Here you should give the path to the liftboat directory and to the file liftboatopen xls This will probably be as follows CALIFTBOATWiftboatopen xls Having completed the command line click finish The new shortcut will appear on your desktop Right click on it with the mouse and select properties Select the tab Shortcut and then left click on the button Change icon Another dialogue box will open and give you an option to browse for alternative icons Click on the Browse button and select the Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 4 file LIFTBOAT ICO from the list of files that should be displayed in the Liftboat directory in drive C The icon for STA LIFTBOAT
82. foot rather than the value computed by the program Otherwise the data is ignored USER SPEC gyrad ft This is the hull excluding legs gyradius in feet If the third switch in this input data block see above is set to 1 the program will use this user specified leg weight per foot rather than the value computed by the program Otherwise the data is ignored total damping crit Percentage critical damping e This is an important term if wave period and natural boat sway periods are close Values in the range 2 to 7 are appropriate The term e is used to compute the dynamic amplification factor DAF The method for calculating the DAFs is conventional being based upon an equivalent single degree of freedom system The equation involves the vessel s natural period and the period of the waves together with the damping value selected The dynamic amplification factor is found from DAF 1 Tg T 22 2 e Tg T 2 2 Where Tg is the vessel natural period and T is the period of the wave The above equation is appropriate to response evaluation in long crested regular waves and may be unreasonably conservative in real sea conditions To account for this DnV introduced the concept of a stochastic dynamic amplification factor SDAF The accepted result of this approach is to compute DAFs Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 39 with twice the equivalent linear d
83. ge buoyancy of the legs which is a vertically upwards force having the effect of decreasing the weight on the pads It is the average of the three leg buoyancy forces which may each be different if the user has specified a different diameter for each leg It is calculated for each leg from water depth pad penetration x leg diameter x weight density of water Note that the weight density of the water in STA LIFTBOAT is taken as 0 064 kips per cubic foot Lateral Stiffness used This is the effective lateral stiffness of the unit in kips foot The physical explanation of this term can be understood by considering the horizontal force applied to the hull needed to displace the hull horizontally by a distance of one foot Wind force This is the calculated wind force acting on the exposed areas of the legs and hull for the particular loading direction under consideration Note that this term will not be displayed if the user has set the wind force switch to 1 and given a specific wind force in the first data input screen The user specified wind force will then appear in the Input Summary Max wave current force This is the maximum force found during the wave cycle by the program on the legs coming from wave and current drag and inertia terms on each leg element Wind O T moment This is the overturning moment coming from the wind force The moment is taken about the center of the pads Amplitude wave current O T moment This is the amplit
84. gram then finds a rotational spring stiffness at the pad and hence an applied moment from the soil resisting leg rotation together with the global response of the vessel Then the maximum pad vertical reaction is found If the bearing capacity required to support this reaction is greater than the soil can provide based on the soil shear strength and classical bearing capacity formulae the program increases the soil shear strength This increases the soil shear modulus and the rotational spring stiffness reducing global response as pad moments increase The program iterates until a solution is found see Section 9 for further details If Auto Calc Penetration has been selected then the pad penetration depth is increased decreased as the iterative calculations proceed If the Set 5 Penetrn button has been clicked the pad penetration will remain at 5 or any other constant value selected by the user in the Liftinpt xls workbook Next the program changes the damping term until the calculated response is matched with the correct damping see Section 9 for further details NOTE If impossible input conditions are given for example negative length of leg sections the automatic coefficient calculation routines will fail The program will show a warning message to the user advising that the Manual Coefficients button must be clicked after the input has been corrected The Auto Coefficients button may be clicked only after input errors have been
85. heck The figure below illustrates the output from the program in a case where the local buckling stress check is required Note that the results shown in below indicate that the factor of safety against local buckling is not satisfactory since the unity stress checks for both cases aft leg and forward legs exceed 1 00 Either the leg section properties must be increased or the loads reduced Note that if the leg section properties are increased until D t gt E 9Fy then the leg section will be compact and local buckling will not be a problem whether or not the local buckling unity stress check is greater or less than 1 00 D t gt E 9Fy No hence no local buckling check required sigma_b sigma_b0 sigma_cr legs2 amp 3 0 249 sigma_b sigma_b0 sigma_cr leg2 sigma a sigma cr legs1 amp 3 0 152 sigma a sigma cr leg2 DnV usage factor legs 1 amp 3 0 402 DnV usage factor leg2 rational unity stress chk legs1 0 502 rational unity stress check leg2 1 030 max sigma a sigma cr DnV legs1 amp 3 Safety factor of 1 25 used against local buckling 1 079 max sigma a sigma cr DnV leg2 9 573 lambda lambda 0 15 081 i average radius of gyration in 0 343 mu coeff for calc sigma cr 169 037 KI effective length to 1 2 pad ht ft 0 243 sigma cr sigma F 134 503 lambda k column slenderness 0 105 sigma a sigma cr legs1 amp 3 16 367 sigma E Euler stress ksi 0 226 alpha sigma b 1 sigma a sigma
86. hich are exposed to beam winds See the Appendix on wind loading WB ft This is the equivalent width of the solid structures typically including the hull deck houses etc which are exposed to beam winds See the Appendix on wind loading Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 32 Distance from aft to fwd legs ft This is the leg spacing from center of leg to center of leg between the center of the aft leg with the line joining the center of the forward two legs Distance bet fwd leg centers ft This is the spacing from center to center of the fwd pair of legs Pad penetration ft This is the average penetration of each pad from sea bed surface to pad tip Note that the average distance must be used and that it is to the pad tip from the sea bed surface Wind force kips This term is only used if the wind force switch on the last line of the main input data screen is set to 1 This term represents a total wind force to be used in the analysis This can be useful if wind tunnel test data or other data is known The exposed wind areas WH1 WB lattice area etc are then no longer used The wind velocity v2 see below is not used either but the user must specify a wind elevation on the right hand side of the main input data screen at which the specified wind forces acts WH2 ft This is the average height of the solid area exposed to head wind force
87. his button will cause the computer to print the data screen as shown in Figure 10 Note that depending upon the display monitor you are using you may be able to see all of this data screen or just a part of it You may use the scroll bars to move around in the spread sheet to view different parts of this and any other screen Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 19 8 12 98 Date File Management Stewart Technology Associates Boat Name Dennis Doyle 5 Width Added Input Leg Data Licenced User US Coast Guard Run Ref 40kn 2kn 14 10s 120 15 4 Tabular Results Input Summary Back to Input File UC Stresses Auto Calc Penetration Go to Master Graphical Results Print this screen Print graphs Print all tables Print all results Set 5 Penetrn Input 4 02 DE equiv leg diam ft EDIT USER DEFINED VARIABLES deflection multiplier 1 normal Young s Modulus leg steel ksf MomSwitch 0 off 1 40 K equivalent nat period multiplier norm 1 no dyn 01 1037 Average maximum allowable pad moment yield stress for leg steel Cu surface 871 pad moment amplitude accept calc wt ft 1 no 2 yes add mass coef 1 normal accept hull gyrad 1 no 2 yes 12 46 ft pad pen VCG excluding legs ft for transit su needed to support pad psf 12 46 ft pad pen input 10 56 pad equiv radius ft su soil und shear str below pad 0 577 calculated leg ki
88. ibuted to Shell Changing the cylinder drag coefficient will change the result for the equivalent leg drag coefficient and will change the graph of drag coefficient produced by the program However these calculated values are reported to the user but not used in the response calculations The user must specify the drag force coefficient to be used in the analysis at the first data input screen for each leg see Section 5 page 15 Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 38 marine growth thickness inches This term is used to increase the diameters of the cylindrical portion only not the rack dimensions of the leg The resulting leg equivalent diameter is reported to the user As with the cylinder drag coefficient above it is necessary for the user to tell the program what equivalent leg diameter is to be used at the first data input screen for the purposes of wave loading and buoyancy calculations However there is an important difference in changes to the leg diameter which affects structural response The program uses the calculated leg equivalent diameter not the input leg diameter in order to calculate leg added mass Leg added hydrodynamic mass is used in the calculation of the boat s natural periods deflection multiplier 1 normal This term is normally to be set to 1 00 However the user may investigate the importance of secondary bending effects by varying this
89. ing combined axial and bending stresses on a slender column is used The formula for this rational stress check is adopted from DnV Reference 2 This formula is usually stated by DnV in the form of a Usage Factor n which should not exceed 0 8 for storm load conditions in the intact condition A value of unity for n is used to evaluate structural integrity in a damaged condition The maximum value of is found from the following two equations n falter fb fpo 1 P Pg fo n Est fp fbo fer Where fa axial stress due to design loadings fp bending stress due to design loadings not including secondary bending fp B bending stress due to design loadings including secondary bending amplification and dynamic effects for local critical stress see below too bending stress induced by P x eg P average axial load on leg due to self weight only Pe Euler buckling load as defined below for leg total axial stress yield stress leg von Mises stress PE nEl K 2 K effective length factor I leg length extended ep static horizontal offset of the leg at the elevation of the lower guide caused by the legs not being perfectly straight the hull not being perfectly level and the guides not being perfectly tight The same type of formula can be derived by a combination of the AISC plastic design formula N4 2 on page 5 95 of Reference 9 and the simple prior to 1988 unity check adopted by the AB
90. ion within the guides d is the vertical distance between the guides and kj is the jack stiffness defined above For leg models where the shear area varies along the leg the program automatically selects the correct value for Agg depending upon the leg length extended in the particular run For single rack legs Beta is always zero Mu determines the bottom leg bending moment and is a function of two other coefficients as shown below a Aq 1 Beta Ago i 1 1 Beta 1 3b d 3 b d 2 2 lo Where is the average moment of inertia of the leg Ag is the average shear area of the leg lg is the average moment of inertia of the leg portion within the guides and d is the height of the jack support point above the lower guides To get Mu we have numerator 1 2id 3 2a E l d G Ag denominator 1 2E l ks Mu numerator denominator Where is the leg length from the lower guide to the mid height of the pad and all other terms are defined above The transverse overall stiffness of one leg is then given by k 1 fg fg Where fg and fo are the bending and shear flexibilities of the leg and are given by fg Beta B 1 3Mu 2 1 Mu id 1 Mu 3El fq 1 a d 1 Mu GAg Alternatively the overall transverse stiffness of one leg may be represented by Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 64 k 3El cB Where c 1 3Mu 2 1 Mu id 1
91. is is the lateral deflection amplitude of the hull during a wave cycle and includes both static and dynamic effects Offset deflection This is the maximum lateral deflection of the hull found during a wave cycle including the initial static offset If the static offset is zero this term will be equal to the max hull deflection Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 49 Euler leg load This is the Euler load of the leg the axial load that would theoretically cause Euler buckling It accounts for the top and bottom leg fixity conditions as well as the bending and shear stiffness of the leg Max base shear This is the maximum horizontal force that must be resisted by soil reactions on the pads during a wave cycle It is the total of the force resisted by all three pads Max low gde reac This is the maximum horizontal force applied by the lower guides to the legs during a wave cycle Max horizontal pad reaction This is the maximum horizontal soil pad reaction found during a wave cycle and is equal to one third of the maximum base shear as the program considers the pad horizontal reactions to be shared equally BM hull max w oPD This is the maximum bending moment found in the legs at their connection with the hull during a wave cycle before P delta effects and dynamics are applied In other words it is the bending moment that would be found for a structure without an
92. l by specifying soil strength and a coefficient used by the program to find a soil shear modulus Alternatively the user may allow the program to calculate the minimum cohesive undrained shear strength of the soil necessary to give bearing support to each pad The user specified soil stiffness may be varied from zero representing a pin joint through to completely fixed if desired In version 2 0 and onwards of the program the ultimate moment capacity of the soil is reported based upon either the user specified value for the soil strength or based upon the minimum soil strength necessary to provide bearing support to the pads If the user specifies a large degree of fixity at the sea bed or a rather stiff rotational spring the Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 2 program will calculate large moments at the pads If the calculated moment exceeds the theoretical ultimate moment capacity of the soil beneath the pad the program will issue a warning In the a future release of the program the DnV formulae for allowable moments in either sand or clay soils will be used These maximum allowable moments are a function of the preload applied on each leg and the maximum leg reactions found during the analysis run In both cases the program has an iterative solution option which permits the user to maximize the soil stiffness in the analysis to either just meet the ultimate soi
93. l foundation capacity in combination with moment Fy moment capacity of foundation Vio maximum vertical foundation load during preloading Hio A Cuo Cuo Cu1 As the maximum sliding capacity factor in clay occurring at V 0 5 Vio and M 0 Mo 0 1 Vio B maximum moment capacity occurring at V 0 5 Vig and H 0 A spudcan effective bearing area based on cross section taken at uppermost part of bearing area in contact with soil A spudcan laterally projected embedded area B effective spudcan diameter at uppermost part of bearing are in contact with the soil for rectangular footing B width Cuo undrained cohesive shear strength at maximum bearing area D below mudline Gu undrained cohesive shear strength at spudcan tip D distance from mudline to spudcan maximum bearing area The load combination vertical horizontal and moment lies outside the yield surface if the left hand side of Equation 2 is less than zero and inside the yield surface if greater than zero Equation 2 can be rewritten so that the maximum permissible spudcan moment on the yield surface becomes a function of the horizontal and vertical loads as is shown in Equation 3 2 0 5 Qy Qy Qy Qy Fy M 16 1 EE Equation 3 2 l el 2 E where Qy applied vertical load Qu applied horizontal load Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 54
94. l gyrad 1 no 2 yes 12 46 ft pad pen VCG excluding legs ft for transit 190 psf su needed to support pad psf 12 46 ft pad pen input 10 56 pad equiv radius ft su soil und shear str below pad 0 577 calculated leg kips ft coef on su to get soil G modulus 39 45 calculated hull gyrad 1 55E 05 ks calc rot stiff soil kip ft rad Maximum pad SER SPEC leg kips foot 800000 kj rot stiff jack hull kip ft rad moment USER SPEC gyrad ft Ke0 horiz offset coef 1585kpft 0 00 Beta calculated cylinder drag coef w marine growth Mu calculated marine growth thickness inches 2 461778867 total damping crit FIGURE 5 Structural Response Screen in Workbook LiftO01 xls Step 10 Edit soil strength data if required Edit pad penetration if required Edit coefficient on su to get soil G modulus if required Edit pad and leg data these data are in the Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 14 structural file below the data shown in Figure 5 Once you have finished editing data you can look at the results in either tabular or graphical form However there are now some important controls to consider Button controls in the various program screens are described in the next section of this manual Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 15 5 0 BUTTON CONTROLS 5 1 STAINPT XLS But
95. l moment capacity or to just satisfy the maximum allowable moment according to the DnV formulae Leg stresses typically limit liftboat operational envelopes STA LIFTBOAT computes unity stress checks based upon both ABS MODU Rules both pre 1988 and post 1988 and based upon a more rational stress check for slender axially loaded columns as used by DnV The US Coast Guard will accept any of these unity stress checks subject to certain conditions see Section 9 STA LIFTBOAT also evaluates leg stresses induced by vessel roll and heave motions plus lateral wind loads in transit The user may opt to use standard ABS criteria for MODUS or use any combination of roll amplitude and natural roll period or roll amplitude and roll period Other special features have been included in some versions of the program including the calculation of maximum stresses induced in the pads for certain boats A single page of results can be produced from each run which summarizes all important input data as well as all important response results including environmental forces calculated Generally the user is concerned with factors of safety against overturning maximum vertical pad reactions induced which should not usually exceed values achieved during preload bending moments and unity stress checks in the leg at the lower guide In addition to the tabular results the user may optionally print graphical results Stewart Technology Associates 1
96. lysis data entry Step 6 Any time the File Management button is clicked the user is returned to the liftboatopen xls workbook If a new boat is to be created see Step 5 above the user should now click on the button Save New Liftboat Files in New Directory as illustrated in Figure 3 below ate of this run 08 12 98 Licenced User US Coast Guard Copyright 1988 and onwards Close and Save Close and Save S ve All Open Active Liftboat Active Files in Files In New Files New Directory Directory Close Open Files Not Saving Data Open Existing Liftboat Files This worksheet keeps track of up to 50 Liftboat File Sets edited T Boat number Number of boats in libraray 1 1 by the user selected Name of active boat Dennis Doyle 5 Width Added 1 Dennis Doyle 5 Width Added 1 Begin Editing Data FIGURE 3 Top Part of LIFTBOATSTART XLS Screen Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 11 If the new boat name you gave in Step 5 does not exist in the present Boat Name list this will be the new name that will show up in the list after the new files have been saved If the name already exists a 1 will be added to the existing name and a new set of files for Existing Name for example will be created The directory or folder structure used by STA OG Littboat LIFTBOAT is shown to the right In this example the OC Projects Dennis Doyle
97. m will double the natural period A value of 0 5 for the natural period multiplier will halve the natural period Tnyy sway period This is the same as for Tnxx above but for sway in the fore aft direction Natural torsional period This is the natural period of the vessel in torsion The vessel is assumed to twist about the leg geometric center Note that the torsional natural period is reported but not used in the calculations associated with leg forces or moments Mean hull deflection This is the mean lateral deflection of the hull It is caused by the wind loads which are treated as steady and the mean value of the wave current load There is no contribution in this term from an initial static offset Max hull deflection This is the maximum deflection of the hull caused by environmental forces It is made up of the mean hull lateral deflection and a dynamic component of deflection which is influenced by the dynamic amplification factor There is no contribution to this term from any initial static offset Uncorrected stabilizing moment This is equal to the weight acting on the sea bed through the pads multiplied by the distance of the center of weight to the center line of the nearest pair of pads This term is calculated with the vessel in the undeflected position meaning before application of environmental loads Corrected stabilizing moment This is the stabilizing moment computed from the weight of the vessel acting through the
98. maximum allowable bending stress Fb calculated according to ABS Rules pre 1988 The effective leg length or K factor used to calculate Fb is that shown in the right hand column of the Results Summary If leg 2 is heavier loaded than either legs 1 or 3 the fb Fb value for leg 2 will be shown Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 48 Weight buoyancy This is the total weight reaction on the pads resisted by the soil It is equal to the total weight of the boat specified by the user in the main data input minus the buoyancy on each of the three legs Note that the effect of water inside the legs see leg buoyancy option in input data is not to increase leg weight but to reduce leg buoyancy However water inside the legs adds mass to the vessel and increases natural sway periods Total buoyancy This is the force calculated by summation of buoyancy accounting for leg internal flooding on each of the three legs Lateral x stiffness This is the effective lateral stiffness of the unit in kips foot in the x direction fore aft sway The physical explanation of this term can be understood by considering the horizontal force applied to the hull needed to displace the hull horizontally by a distance of one foot Lateral y stiffness This is the effective lateral stiffness of the unit in kips foot in the x direction side sway The physical explanation of this term can
99. nd most derivatives were written with structural steel buildings in mind with relatively stiff frames The second unity stress check above is designed to take account of secondary bending stresses in frames subject to sidesway but this stress check is meant to be applied to first order stresses which are calculated from a linear analysis and do not include secondary bending effects When stresses are rigorously calculated to include secondary bending effects caused by the P delta effect this stress check is incorrect and overly conservative Furthermore because the sidesway of liftboats is generally much larger than the sidesway of normal building frames and the leg slenderness ratio is very large the AISC stress check may give unpredictable results even if applied as it is intended to be to first order stresses only Since STA LIFTBOAT computes secondary bending amplification effects the ABS stress check in use prior to 1988 is used instead of the second stress check above However although the results of this ABS AISC stress check are reported they are generally overly conservative and rather misleading The procedure for computing the ABS unity check is described below Allowable axial stresses F4 are computed which are to be the least of a yield stress divided by appropriate factor of safety b overall buckling stress divided by appropriate factor of safety C local buckling stress divided by appropriate factor of safety The
100. ntal forces including dynamics and the additional overturning moment that results from the deflection of the structure Pad Ultimate Moment Capacity This is the calculated ultimate moment that the soil can apply to the pad based upon a cohesive soil an circular pad of equivalent area to the actual rectangular pad and a hemispherical failure surface with the same radius as the equivalent circular pad The center of rotation is assumed at the pad center and the soil shear strength is assumed to increase beneath the pad at 4 psf ft of depth If this maximum calculated moment at the pad exceeds this value a warning is printed at the top of the Results Summary In the Version 4 0 STA LIFTBOAT program this ultimate moment is no longer used and the methodology described in the 1997 City University Jack Up Conference paper by Stewart is now implemented This Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 50 paper is included as an appendix to this manual This method involves Pad Soil Yield Surface Checks Combined vertical horizontal and rotational pad loads are considered See Section 8 3 of this manual K Equivalent This is the effective leg length factor or K factor which is calculated by the program based upon leg top and bottom fixities and relative flexural and shear stiffnesses This term is used in the calculation of allowable stresses in the unity stress checks Uncorr
101. nwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 35 Min leg length to be above hull bottom ft This is the minimum acceptable length of the legs to be above the hull bottom It will usually be the distance from the hull bottom to the top of the jacking towers plus around one foot so that the top of the leg can still be seen above the jacking tower Cell A20 shows the calculated value of this term If the calculated value is less than the minimum acceptable value the legs have been extended too far Note this term is not included in the data pasted from MASTERINPUT xls Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 36 7 0 SECONDARY DATA INPUT 2nd Data Screen The secondary data that may be edited by the user is in the workbook Lift001 xls on the data screen that appears after the button Go on to Structural Response has been clicked by the user on the main first data input screen Only the cells highlighted in yellow containing bold text can be edited The first of these cells are shown shaded in Figures 5 and 10 which is a print out of the second data screen The input data terms are described below 7 1 Control and Miscellaneous Data Young s Modulus leg steel ksf Normally 4248000 ksf this term can be changed by the user to simulate special steels or other leg materials if required natural period multiplier This term permits the user to inves
102. of 4 stiffeners only 2 sets shown may be defined at angles relative to the x axis as shown below An additional stiffener may be defined behind the rack and another stiffener may be opposite this For each stiffener the area amp radius of the center of area from the leg center must be defined The area input is that for a single stiffener Hence if there are four ou stiffeners in a group the Stiffener opposite rack e 1 of 4 stiffeners at group area will be four j 62 times the single Y axis 2nd rack if specified 1 of 4 stiffeners at A stiffener area input 01 d 1 of 2 stiffeners on x axis 1 of 4 stiffeners at TA 02 Stiffener inside rack otal leg lengtt Pad height Number of Rack width rack ht to Rack ht to No racks appendage OD inc pad ft ft sections in top teeth in bot teeth in 1 or 2 wt factor in 170 2 Boat Name Dennis Doyle 5 Width Added Run Ref 40kn 2kn 14 10s 120 15 4 om length Tabular Results Input Summary Home _ Graphical Results Ga Print this screen T cick butane to move rand washed ose esr are st RS amp bottom bplengh 85 000 Click buttons to move around worksheet or use scroll bars at RHS amp bottom Stiffener properties bottom sect epzetesl average Thickness in Stiff area inside rack sqin Inside rack area radius in Stiff area opposite rack sqin Opp rack area radius in Stiff area x axis sqin X axis area radius in
103. ogy Associates Close Open Close and Save Close and Save Save All Open Files Not Active Liftboat Active Files in Files In New Saving Data Files New Directory Directory Open Existing Liftboat Files This worksheet keeps track of up to 50 Liftboat File Sets edited Boat number by the user selected Name of active boat Dennis Doyle 5 Width Added Dennis Doyle 5 Width Added Begin Editing Data Dennis Doyle 5 Width Added1 Use the control buttons to select existing or add new vessels to Liftboat Library The list can be manually edited but the directory structure may become corrupted The root directory is CALIFTBOAT The directory containing the individual boat directories is C LIFTBOAT PROJECTS Each set of boat files is then found in the projects directory ina directory or folder with the boat s name This library is setup to hold up to 50 liftboats Each boat has a GE 09 m ay seen ss 0 O0 imaster input file where up to 50 load cases can be stored o Eg o o0 o a Ss ees H o0 EO ee Sep Number of boats in libraray 2 1 To enter a new boat into the library select a new boat change its name click the File Management button and come back to this sheet Then press Save New Liftboat Files in New Directory Directory Name User MUST give drive letter and Directory name where Liftboat Files are located Boat f 9 2 1 13 3
104. omatically calculates these terms based upon the user specified water depth pad penetration and leg diameter LCG ft to forward legs This is the distance of the longitudinal center of gravity of the boat to the center line of the forward legs see Figure 4 Note that the longitudinal center of gravity is defined in this case as being related to the total boat weight specified above In other words the weight of the legs and cans excluding water in the cans must be included TCG ve towards L1 This is the distance of the transverse center of gravity of the boat from the boat center line Note that it also relates to the total boat weight as for the LCG above TCG is positive towards the port side see Figure 4 Init phase ang deg In most cases the user will set this to zero meaning that the wave crest will be at the center line of leg 1 at time t 0 seconds Any phase angle may be specified This can be useful as some of the graphs are drawn to show hydrodynamic forces on the legs at time t 0 seconds Wind elevation ft This term is only used if the wind force switch is set to 1 and a user specified wind force has been given The elevation is relative to the bottom of the hull or the keel line It is the elevation at which the wind force is assumed to act Total leg length ft This is the length of the legs of the boat from the bottom of the pad pad tip to top of the legs Stewart Technology Associates 1988 and o
105. on ft4 Graphical Results 2 3672 2 3672 lateral bending direction ft4 Print this screen 2 3672 2 3672 results used for this loading direction elevated 1 2587 1 2587 lt lt results for bottom leg section for transit calcs For definition of K equivalent see manual K 2 for stress check K equiv 1 40 181 52 lt lt F2y 4Pi2E KI r 2 gt gt KI r 244 37 with K 2 00 4 96 lt lt Pi2E KI r 2 gt gt Kl r 171 57 with K equiv 48 00 leg outer diameter D in Cc 99 35 SQRT 2PiPiE Fy 1 124 wall average equiv thickness t in Fer 4 96 ksi crit overall buckling str ABS Fer from DnV method for K value 10 06 F S 1 44 combined loads 60 00 Fy for leg ksi F S 1 44 D t avg 42 72 ratio D t 25 2 56 D t to power 25 D t at low guide 28 33 E 9Fy 55 56 ratio 4320000 Young s modulus for leg ksf E 9Fy 55 56 Is D t gt E 9Fy No hence no local buckling check required 5 lt lt leg section lower guide 0 12Et R lt lt ksi Younger value for K 2 shown left K equivalent shown right gt gt 2CEt D lt lt ksi Fxe elastic local buckling str API with C 0 3 gt gt Fxc ksi inelastic local buckling stress API gt gt Faa lt lt ksi ABS allowable axial stress 1 Para 3 11 4 gt gt Fab lt lt ksi ABS allowable axial stress 2 Para 3 11 4 gt gt Fac lt lt ksi ABS allowable axial stress 3 Para 3 11 4 gt gt Fa lt lt ksi min val of above 3 ABS allow
106. orkbook by clicking the button Go to Master Input Each of the 50 load cases in the MASTERINPUT xls workbook looks like the Liftinpt xls main screen The buttons are a little different An example is shown in Figure 4 overleaf You can either use the button Select Load Case or you can display sheet tabs and move from one load case to another When you want to use a load case in your analysis simple press the button Paste Data and the load case data will be automatically pasted to the Liftinpt xls workbook From there it is automatically linked to the Lift001 xls workbook where the main analysis takes place Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 13 08 12 98 Date of this run LC1 Licenced User US Coast Guard Rig Name Copyright 1990 and onwards Stewart Technology Associates Loadcase description This data set will be pasted into the LIFTINPT XLS file when the user presses the Paste Data button The user may then immediately examine the results by pressing the Go on to Structural Response button Go on to Structural Response Print this screen Paste Data Go back to Input File Only data in shaded yellow cells can be edited Last data used is displayed AvShield Wave attack angle deg Leg diams 1 2 3 ft Input wave height ft Input wave period sec Cm1 Cm2 Cm3 Input water depth ft 7 7 0 70 CD1 CD2 CD3 Lattice area sqft lattic
107. ps ft coef on su to get soil G modulus 39 45 calculated hull gyrad 1 55E 05 ks calc rot stiff soil kip ft rad USER SPEC leg kips foot 800000 kj rot stiff jack hull kip ft rad USER SPEC gyrad ft Ke0 horiz offset coef Beta calculated 0 78 CDEaverage 0 86 CDEmax max drag coef Maximum pad moment 1585 kp ft cylinder drag coef w marine growth marine growth thickness inches 2 461778864 VCG lower guide ft b jack vcg ft h jack support spacing ft used only if two racks guide space multiplier 1 or 0 Mu calculated total damping crit geometry select switch d guide spacing ft 1 OR 2 RACK SWITCH pad 1 2 height ft pad length ft weight of 1 pad kips pad width ft pad buoyancy 6 67 ft spare leg length FIGURE 10 Printout Resulting From Clicking Print This Screen Button e Print graphs This will print all eleven of the graphs They print on four separate pages as shown on the next four pages e Print all tables Clicking on this option will print both the data screen shown in Figure 10 the Input Summary and Results Summary table shown in Figure 15 the Leg Structural Input Data shown in Figures 16 and 17 the Stress Check Intermediate Results table shown in Figure 18 and the Transit Condition Leg Stress Check table shown in Figure 19 Stewart
108. s See Appendix on wind loading WL ft This is the average width of the solid area of the boat exposed to beam wind forces See Appendix on wind loading Leg buoy 1 dry 2 flood If this term is set to 1 the program considers the legs to be dry internally If this term is set to 2 the program assumes the legs to be flooded up to the still water level The weight of the water inside the legs is not included in the total weight input term Air gap ft This is the distance beneath the bottom of the hull to the still water level In this area the wind force is calculated on each of the legs This term is also used to calculate the total leg length extended in combination with the pad penetration and water depth input terms AvShield This term describes the average amount of leg which is hidden by the solid components of the boat At a minimum it should be equal to the hull thickness However there may be shielding from other structures such as the jacking towers which may have been described by the user in computing the terms WH1 WB etc In addition there may be justification in providing larger amounts of shielding for different wind directions such as when the wind is on the stern and the main accommodation block and other deck houses shield the aft leg significantly The program calculates wind force on the leg sections which remain above the bottom of the hull from the tops of the legs down to a distance equal to AvShield above th
109. s case the guide horizontal reactions will be high See section on theory for further explanation For single rack liftboats the value of beta is always zero Mu bottom fixity coefficient This term describes the relative magnitude of the moment at the pads compared to the moment at the hull for the legs A value of Mu 0 implies that the pads are pinned A high value of Mu implies that the pads are nearly fully fixed See section on theory for further explanation Wave crest elevation This is the elevation of the wave crest above the still water level Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 45 8 2 Results Summary Pad1 before environmental load This is the vertical soil reaction on pad 1 port fwd pad see sign convention Figure 4 Page 16 before environmental loads or any static offset due to hull not being level or legs not straight are applied Pad3 before environmental load This is the vertical soil reaction on pad 3 stbd fwd pad see sign convention Figure 4 Page 16 before environmental loads or any static offset due to hull not being level or legs not straight are applied Pad3 before environmental load This is the vertical soil reaction on pad 2 stern pad see sign convention Figure 4 Page 16 before environmental loads or any static offset due to hull not being level or legs not straight are applied Average leg buoyancy This is the avera
110. s is the area of one of an optional set of four stiffeners arranged symmetrically about the x axis as shown in Figure 16 in each of the leg sections you have defined Theta1 radius in This is the radial distance from the leg cylinder center to one of the centers of area of the Theta1 stiffeners Theta2 Theta3 input as for Theta1 Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 44 8 0 TABULAR RESULTS For maximum efficiency in program operation and results reporting STA has made concerted efforts to try and keep to a format of a single page of data which describes all important input and output for a single analysis run As the capabilities of STA LIFTBOAT have expanded the amount of results produced and required input and control data has grown Nevertheless a single page summarizing all critical input data and results is still produced For complete reporting on a run the user will probably wish to print the main input data screen the second data input screen which also contains pad moment results the single page Input Summary and Results Summary the detailed leg section properties the intermediate stress check results the transit stress checks and the ten standard graphs The following pages describe the tabular results in detail 8 1 Input Summary The input summary table is printed with other results on one page with the Results Summary when the user cli
111. ses equiv leg 3 0 86 Rational DnV unity check Leg 3 Home Transit Graphical Results Tabular Results Print local buckling FIGURE 18 Stress Check Intermediate Data Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Run ref Page 28 08 12 98 Date printed TRANSIT CONDITION ROLL MOTION STRESS CHECKS ON LEGS 40kn 2kn 14 10s 120 15 4 roll angle sing amp deg 33 33 Boat name Dennis Doyle 5 Width Addeq Z0 reference height wind vel ft roll period sec 174 72 ZH top of leg abv SWL ft leg length extended 0 fully raised ft 0 00001 wind force coefficient on leg gravity force multiplier from ABS 33 5 d half distance bet fwd legs ft vessel draft ft 145 50 leg length abv up guide ft VCG for boat excluding legs amp pads ft 29 22 distance b ft VCG calculated including legs ft Tabular Results STA copy ML weight one leg above upper guide kip 0 60 Graphical Results leg weight ft inc appendages kip ft Print this screen Vwind1 kt user selected wind velocity parameter c FTS stat trans force w ABS multiplier kip parameter zW xS vertical lever arm for FTS ft FW1 wind force on leg in Vwind1 kip FTD inertia transverse force kips FW70 wind force on leg in 70 kt wind kip xD vertical lever
112. t leg length ft 22 54 ft leg length above hull bottom min leg length to be above hull botta Now you can open any available liftboats by clicking Open Stored Liftboat Files To create a new liftboat you can edit the available liftboat that you ve opened change the name and save it by clicking the Save New Liftboat Files in New Directory liftboatopen xls can contain up to 50 liftboats Once you have selected a vessel and the program has opened the appropriate files you simply click the Begin Editing Data button This will bring the screen to Liftinpt xls Once you have edited the data that you require for your first run or at any time you will see a table of calculated wind moments and forces will be displayed Click on the Print Input Screen and Wind Loads button to print the input data and wind loads assuming that your printer is hooked up correctly Click on the button marked Go on to Structural Response to move to the main results section of the program Another data screen will be displayed Along the top of this you will see the words Microsoft Excel LiftO01 xls Your screen should appear as shown overleaf Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 7 8 12 98 Date Stewart Technology Associates Boat Name Dennis Doyle 5 Width Added Input Leg Data Licenced User US Coast Guard Run Ref 40kn
113. te for design storm loading fer is determined from the yield criterion see Note 2 below as for Del fy Where f actual value of axial stress component in the leg fe von Mises equivalent stress component fy yield stress of leg steel In practice the von Mises stress is almost identical to the axial stress component as shear stress is small and in any case the point of maximum shear stress is at 90 degrees around the leg circumference from the point of maximum bending stress Consequently the critical stress fcr is generally approximately equal to the leg yield stress see Note 2 below Note 1 In STA LIFTBOAT version 1 the value for P the average axial leg load was put equal to the average axial leg load at the point of maximum response This was overly conservative and was in part due to some ambiguity in the 1984 version of the DnV Classification Note 31 5 In the 1992 version of this Classification Note the definition of P has been clarified In STA LIFTBOAT the value for P calculated for each leg is equal to the load coming onto the leg through the pinions plus half the weight of the leg beneath the lower guide in the absence of environmental loads Note 2 The above stress checks are governing only if the legs are proportioned and stiffened in such a way that local buckling is excluded If the effective D t internal diameter divided by average equivalent thickness for the leg beneath the lower guide ratio exceeds th
114. tigate the effect of dynamics on the response of the structure The natural period of the structure is multiplied by this term Hence a value of 0 5 for the term will reduce the natural sway period by 50 Hence dynamic amplification will generally be reduced and results will tend towards the static solution as the DAF tends towards 1 0 For dynamics to be correctly calculated this term should be set to 1 0 However experimenting with this term can give an immediate and useful insight into how changes in the natural sway period can either increase or decrease response results See the discussion on dynamic response results later accept calc wt ft If this term is set to 1 the user specified leg weight per foot is used see below If the term is set to 2 the programs calculated equivalent weight per foot is used for the legs The user specified weight per foot may be useful if additional non structural weight is added to the legs Or the term may simply be used for parametric variation studies of boat responses accept hull gyrad If this term is set to 1 the user specified hull gyradius is used see below If the term is set to 2 the gyradius estimated by the program is used The hull gyradius is used by the program to calculate the torsional natural period of the boat soil su needed to support pad psf input in cell below This term is reported by the program and indicates to the user based upon the pad geometry and maximum calculated p
115. ton jumps the user to the top of the leg force moment and stress calculations associated with vessel roll and heave motions in transit Use the scroll bars and the mouse to move down this section to investigate the leg stress while in transit calculations e Auto Calc Penetration Clicking on this button causes the program to iterate until it has penetrated all pads to a depth needed to get the bearing capacity equal to the maximum pad load computed in this run The soil undrained shear strength is used as input by the user in cells D13 and D14 on this sheet The pad penetration depth is modified in the Liftinpt xls workbook and reflected in the Lift001 xls workbook on this sheet in cells D15 and D16 The assumption made with this approach is that all Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 17 three legs will be preloaded to this same level and all three legs will penetrate the same amount during preloading e Auto coefficients Clicking on this button causes the program to perform two sequential sets of iterative calculations First the program iterates until the induced pad moments balance with the soil rotational stiffness The soil shear strength is set initially to the minimum value calculated to be necessary to provide the maximum calculated pad vertical reaction during the wave cycle With this value and the user defined coefficient on cu to get soil G modulus the pro
116. tons In the upper part of the screen on the right hand side the boat name and run reference can be edited by the user The run reference and boat name will appear on the graphs that are automatically produced when the program executes Note that the date of the run shown in the upper right hand corner of the screen is taken from the computer s own system clock Hence if this is incorrect the date will appear to be wrong 08 12 98 Date of mist run Licenced User US Coast Guard i E Copyright 1990 and onwards Stewart Technology Associates THIS IS THE MAIN DATA INPUT SCREEN CLICK Run Per GO TO RESPONSE Go on to Structural Response Print Input Screen and Wind Loads Go to Master Input File Management Only data in shaded cells can be edited Last data used is displayed Build New Boat Master Input File FIGURE 6 Buttons on STAINPT XLS Screen The buttons which appear gray on the screen appear white in the hard copy as seen in Figure 6 above Clicking the mouse once on any of the five buttons seen in Figure 6 will perform the following tasks e Go On To Structural Responses This will move the user from the input data screen to the first screen of response data where further parameters that the user may edit are contained e Print this screen This will instruct the system through the printer that has been set up in Windows in the control panel to print the data displayed on the screen e Go to Master Input This tak
117. ts in larger sway response from vertical than would be found for a perfectly level boat with perfectly straight initially legs Typical values for this term are in the range 0 001 to 0 006 resulting in offsets of 0 196 to 0 696 of extended leg length A value of zero results in no initial offset A value of 0 003 is suggested cylinder drag coef w marine growth This is the drag coefficient to be applied to a clean cylindrical leg with no rack The hydrodynamic leg model accounts for mass volume displaced and drag force on the cylindrical portion of the leg and on the rack s This detailed model is used to compute the equivalent hydrodynamic volume of a unit length of the leg from which the equivalent leg diameter is found The drag coefficient for the cylindrical portion of the leg alone is provided for the user to experiment with The cylinder drag coefficient will strongly influence the total drag coefficient found for the equivalent leg The normal drag force coefficient used by STA for cylindrical members of liftboat legs is 0 64 Lower values may be achieved for new clean cylinders and higher values may be appropriate for members with excessive marine growth The larger the rack the higher will be the maximum drag coefficient when flow is perpendicular to the rack direction The graph of leg drag coefficient shows two formulae for the drag coefficient as influenced by the rack The formula attributed to DnV is suggested rather than that attr
118. ual to a maximum usage factor of 0 80 appropriate for design storm loading fer is determined from the yield criterion see Note 2 below as for f f f Where f actual value of axial stress component in the leg fe von Mises equivalent stress component fy yield stress of leg steel In practice the von Mises stress is almost identical to the axial stress component as shear stress is small and in any case the point of maximum shear stress is at 90 degrees around the leg circumference from the point of maximum bending stress Consequently the critical stress fcr is generally approximately equal to the leg yield stress see Note 2 below Rational Unity str chk leg 2 This is the rational stress check used by DnV for jack up rigs with tubular legs applied to leg 2 aft The interaction equation for this stress check is given by the maximum of either Stress check value 1 25 t Mor fo kal J Stress check value 1 25 JA fy keet x 1 1 P Pg Where fp is as defined above and includes secondary bending stress components fa and fy are defined as above but f does not include secondary stress components Gi local critical stress average axial leg load due to functional or self weight loads only see Note 1 below Pe Euler load for leg using weakest axis The safety factor of 1 25 is equivalent to making the unfactored interaction equation equal to a maximum usage factor of 0 80 appropria
119. ude of the wave and current force overturning moment Note that this term is subsequently multiplied by the dynamic amplification factor DAF This is the only term which is treated dynamically on the forcing function side of the dynamic response equations Tnxx sway period This is the natural period of the vessel in beam direction sway This term is influenced by the mass of the hull the distributed mass of the legs the added mass of the legs the stiffness of the pad rotational springs the flexural and shear stiffness of the legs the stiffness of the hull leg connection and the leg length extended Note that the added hydrodynamic mass of the legs is a function of the leg diameter found in the leg hull file rather than the leg diameter specified by the user Note also that the natural sway period can be altered in the second data input screen by the user selectable term natural period multiplier the first term in this second data screen For correct dynamics the natural period multiplier should be set to 1 If the user wishes to completely remove dynamics the natural period multiplier may be set to any value less than 0 1 If the user wishes to investigate the effect of arbitrary changes in the Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 46 natural period on the overall response of the structure the natural period multiplier may be set to any value A value of 2 for this ter
120. uently equal there are many times when it is more appropriate to use different drag coefficients for different wave loading directions For example if the boat has twin racks on each leg with the racks in the fore and aft direction on the forward legs and in the side to side direction on the aft leg then the drag on the two forward legs will be lowest when the drag on the aft leg is highest wind and waves on the bow or stern A graph of leg drag coefficient variation with wave attack angle is drawn by the program From this graph it can be seen that there is often a large variation in the leg drag coefficient for different wave attack directions Wind v2 kn This is the wind velocity to be used in conjunction with the user specified wind areas in order to compute wind loading on the vessel Total weight kips This term is the total boat weight in air excluding water in the pads and legs if flooded but including the weight in air of the cans and legs plus all variable loads any drill string loads light ship weight crane loads if required etc If the user wishes to study the boat during preload then the weight of all preload water should be included in this term If the user wishes to study the operational weight of the boat or the boat condition under any storm loading then preload weight should not be included but all other weight must be included in this term No deductions for buoyancy of the legs should be made as the program aut
121. uide spacing ft h jack support spacing ft used only if two racks 1 OR 2 RACK SWITCH There are around 30 extra items of data that you may optionally edit in the cells with a yellow background and bold black or red characters within them In the section below this you will see INPUT LEG STRUCTURAL DATA BELOW The leg structural definition including internal stiffening and up to 5 different leg sections is then defined You may jump to the main table of results simply by clicking on the gray button near the top of this screen labeled Tabular Results Alternatively you may jump to the input summary by clicking on the button labeled nput Summary Other buttons at the locations around the screen that you jump to will permit you to either print the data displayed or to jump back to the home point in the upper left hand portion of the screen At any time you may click on the gray button Go back to Input File This will jump you immediately back to the main input data file and you may change for example wave height or wind speed and jump back immediately to the structural response file by clicking the Go on to Structural Response button Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 8 Master Data Input Sheet A separate workbook with 50 worksheets is provided MASTERINPUT xls in order to set up numerous load cases for a single vessel 08 12 98 Date
122. ure assumes that the pads will bed down during a storm as has been suggested by Hambley Reference 12 The geotechnical portion of Reference 9 was verified and improved upon in 1996 1997 following a study performed by SINTEF Reference 13 commissioned by SNAME SINTEF cited Hambley s work and noted that he suggested this condition may be approached analytically by calculating the deformations due to the static wind current loads with a pinned foundation and then evaluate the rotation foundation stiffness for the wave loads only The dynamic analysis would then only include wave loads In STA LIFTBOAT it is now assumed that the mean pad inclination angle should correspond to the mean angle during a wave cycle given the full environmental load wind current and waves and a cyclically degraded soil shear modulus for rotational loading As the pad rotates to this mean angle there will be some further penetration The cyclic motions of the pad caused by further wave loading will then result in pad moments oscillating about a zero mean value with pad rotations oscillating about a nonzero value An iterative trial and error process is used to find an allowable stiffness for the equivalent linear rotational spring representing the soil Where the leeward leg induces soil moment amplitudes which peak outside the yield surface but the windward legs have load conditions inside the yield surface then the average of the maximum allowable moments are
123. us divided by nine times yield stress ratio then a local buckling check must also be performed in order to ensure local buckling will not occur ABS Stress Checks In addition to the rational stress checks described above STA LIFTBOAT also computes unity stress checks according to ABS Rules Reference 4 which follow the AISC stress check convention Reference 3 Prior to the 1988 ABS Rules the stress check required for structures similar to liftboat legs was the simple interaction equation fa Fa fg Fp gt 1 0 Where fa actual axial stress Fa allowable axial stress fb actual bending stress Fa allowable bending stress In 1988 the ABS modified their rules to follow the AISC rules more closely and introduced the interaction equation fa Fa Cmfb 1 fa F e Fp gt 1 0 Where Fo 12p E 23 K r Fe ABS AISC defined Euler buckling stress and may be increased under ABS rules by 1 3 for combined static and environmental loadings Stewart Technology Associates 1988 and onwards STA LIFTBOAT v4 0 USER MANUAL and THEORY ver 4 01 Page 59 K Cm effective length factor coefficient which relates to joint translational freedoms For liftboats this coefficient is to be taken as 0 85 This second unity stress check is to be applied if fz Fa is greater than 0 15 which is usually the case for liftooats under design maximum conditions However the AISC allowable stress design rules Reference 3 a
124. using Morison s equation see results later Input wave period sec This is the wave period that is used in the analysis The wave length and water particle kinematics are influenced by both the water depth and the selection of this wave period Input water depth ft This is the water depth to be used in the analysis from the sea bed to the still water level If the analysis is to account for a change in water elevation because of storm surge or tidal elevation changes the user should incorporate all terms within this one input value In the ABS wave theory used the wave crest is generally further above the still water level than the wave trough is below the still water level The value of crest elevation above the mean water level is reported in the input summary see Figure 5 Lattice area sqft This is the area of all structures on the boat which are not solid but present significant wind area This typically includes the crane boom s if of the lattice type and may include a lattice structure supporting the helideck The area should be equivalent to the projected outline of these structures They are assumed to have two sides and ABS Rules to calculate wind viscous drag forces on these areas are used See the Appendix on wind loading calculations WH1 ft This is the average height of the solid structures typically the hull jacking towers if appropriate and deck houses plus other equipment for example including the crane base w
125. will then be shown as a picture in this dialogue box and you can click on OK to close the box Click on OK to finish the process 2 3 Program Files On Distribution Diskettes The files on your diskettes should be Setup exe on Disk 1 and Setup 001 on Disk 2 After you have run setup the files on your hard drive should be as listed in the table below FileName Deseripten Liftboat ico Icon for STA LIFTBOAT The icon is displayed by WINDOWS Double click on the icon to start STA LIFTBOAT after program is installed liftboatopen xls This is the first file displayed to the user by Excel The vessel to be analyzed is selected Its files are then opened If a new vessel is desired an existing vessel is selected its files are opened then saved with a new boat name Up to 50 sets of vessel files can be stored Liftinpt xls This is the first file displayed to the user after a set of vessel files has been opened The environment and other principal input data is specified in this file This data is automatically linked to other files LiftOO1 xls This is the rig hull file with the structural data for the rig This is the file displayed with the table of results and graphs when STA LIFTBOAT is running Readme txt The latest information on installation and running procedures and program updates not included in manual are in this text file MASTERINPUT xls This file is used to enter and store up to 50 input data sets or load cases
126. y deflections BM hull max w PD This is the maximum leg bending moment computed at the hull connection including all response effects Max axial leg load lower guide This is the maximum axial load found in a leg at the lower guide during a wave cycle including all response effects PadMin Id uncorrd This is the minimum pad vertical reaction found during the wave cycle before structural response is accounted for PadMin Id corrected This is the minimum vertical pad reaction found during a wave cycle accounting for static and dynamic structural response If this term goes to less than zero it indicates that there would be uplift on one or more of the pads during the wave cycle This does not necessarily imply that the structure would topple for several reasons Firstly the structure has significant inertia and the forces applied to it during a wave cycle are oscillatory Unless the mean value of the pad reaction during a wave cycle is less than zero it is unlikely that the structure can topple Secondly especially in soft cohesive soils there is generally a significant force required to extract the pad quickly within a wave cycle from the sea bed The extraction force may be negligible if the pad is sitting on hard sand and is not fully penetrated Pad max angle This is the maximum angle to which the pad is computed to rotate during a wave cycle Max OT mom w PD This is the maximum overturning moment computed from the environme

lift401 - Stewart Technology Associates

Contents

Download Pdf Manuals

Related Search

Related Contents