Modal analysis may be used to troubleshoot the convergence failure of a staged-construction load case. If the model fails to converge in stage X of a staged-construction case named Staged, modal analysis may indicate the convergence problem through the following process:
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- To locate disconnected elements, try assigning unit mass to all DOF and running a modal analysis. The modal shapes will identify disconnected elements that cannot support load and prevent convergence in nonlinear analysis.
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NOTE: A variation of this process may be used to troubleshoot convergence problems which occur during time-history analysis. When a certain step fails to converge, run analysis until that step, then run modal analysis using stiffness at that step to check for instabilities. |
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