Question
1. I have combined 2 CSFs for the analysis below, but the load summation in cmblst is zero.
- Jacket Inplace Static Analysis with PSI
- Jacket Inplace Static Analysis with environment load only
2. I am performing Spectral Earthquake Analysis (Static PSI + Seismic), and I found that the forces and moments are all zero.
Answer
1. When a PSI analysis is included in the static analysis, there are no restrained joints as the piles are connected to the support joints. Hence, the reaction forces at these joints from a PSI analysis are zero.
When the CSF from PSI runs are combined, the forces and moments summed about the origin are zero because there are no reaction forces. This does not signal that an error has occurred during the combine run.
2. The 'Force and Moments Summary' report adds the reaction forces in the static csf to those from the earthquake analysis.
In the Dynamic-Spectral Earthquake analysis run in the Analysis Generator, you are using a csf generated from a PSI analysis; there are no joints with fixity in the model. Hence, there are no joint reactions in the CSF from the PSI analysis (psicsf.ele), resulting in zero values in the table.
Earthquake analysis is usually combined with a basic static dead load analysis (without PSI).
Refer to Sample 05 - Spectral Earthquake analysis in the SACS Executive Projects tab for the correct execution of seismic analysis combination.