4.0 seismic analysis (by the single pile analysis method) -using sacs

1. Create 5 directories under seismic analysis folder – Static, Pile, NatFreq, Earthqk and Post.
2. In Static folder, run a Linear Static analysis with PSI option for the In-place model.
3. From the ‘psilst’ file obtain the max. axial, lateral forces and moment for any pile group and the axial displacement from operating storm load cases only.
4. In Pile folder, Make a copy of the psiinp.* file and rename it as pilinp.*. In the datagen of the pilinp.* change the PSIOPT to PLOPT. At the end of the soil data, add PLSTUB card with the force values obtained in Step 3 above. (Note: Retain the soil prop. and a single pile group in the file, copied from the PSI input file).
5. Run Single Pile analysis ( In MISC in Runfile Wizard) and from the ‘pillst’ get the pile stub dimensions. Update the Inplace model by removing the pile group members and pilehead joints and adding the pile stubs instead to it. Also paste the pile stub section property line to the input file.
6. Copy the input (sacinp) file generated in Step 5 above to the NatFreq directory. Make all corner nodes of the various levels as ‘222000’. Delete all load cases except one combination for operating loads with suitable contingencies. This load case should not contain any environmental load data. Name it ‘SLE’ and ‘DLE’ for Strength Level and Ductility Level Earthquake runs respectively. Include DYN option in LDOPT card and DY in LCSEL card.
7. Create a ‘dyninp’ file with the number of mode shapes. Specify SA option in DYNOPT card and run a Dynpac analysis. Open the output file and check the period and total mass participation factors.
8. Copy the input file generated in Step 5 above to the Static directory. Add LCSEL card with load case ‘SLE’ or ‘DLE’ and specify ‘CMB’ option in the LDOPT card. Run a Linear static analysis.
9. Copy the updated model, the ‘dynmas’ and ‘dynmod’ files generated in Step 7 above to the Earthqk directory. Copy the ‘saccsf’ file generated in Step 8 above to the Earthqk directory.
10. Create a ‘dyrinp’ file specifying SLE as the primary load case in the STCMB card and a factor of 2.0 for Joint can check.
11. Run an earthquake analysis with the above files and generate the ‘dyrcsf’ file. Check the max. axial, lateral forces and moment under the ‘CQC SUMMATION FROM ALL DIRECTIONS’ column in the ‘dyrlst’ file.
12. These should be compared with the values added in Step 4. In case it is different, update the ‘pilinp’ file with these values.
13. Repeat Steps 5 to 12 till the values converge to a reasonable limit.
14. Create a ‘pstinp’ file in the Post folder. Select Load Case 1 and 2 only i.e., {Earthquake+ Static (Tension)} and {Earthquake + Static (Compression)} with a AMOD of 1.7 on the allowables.
15. Perform Element Code check and generate a Postvue Database file using the ‘dyrcsf’ file generated in Step 11 above.
16. Create a ‘jcninp’ file with AMOD as 1.7 for Load Cases 3 and 4 only i.e., {Earthquake + Static (Tension)} and {Earthquake + Static (Compression)} for joint check case. Run Joint Can analysis.

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5.0 VIBRATION ANALYSIS

1. The steps 1 to 9 specified in the Seismic Analysis section 5.0 above have to be first performed in the vibration analysis run.
2. Note : Retain relevant degrees of freedom including nodes present on equipment.
3. Create a dyrinp file and specify the run speeds of the reciprocating machines in the RSPEED card. Change the number of modes in the ENGVB card. Specify the unbalanced force and moments acting at various joints of the structure using the UNBAL card. The damping factor is 2% .
4. Run a dynamic response analysis using the dyrinp and the dynmas and dynmod files generated from the modal analysis steps.
5. Check the displacement levels in the joints versus the allowable specified in the dyrinp file.
6. In case the displacement is more than the specified value for some joint provide minor plate stiffening in the sacinp file and re-run all steps.

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STEP BY STEP GUIDE FOR JACKET DESIGN USING SACS SOFTWARE

RESEARCH & DEVELOPMENT
ENGINEERING & CONSTRUCTION DIVISION
LARSEN & TOUBRO LIMITED