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- For symmetrical structures, you may need to introduce some geometric or loading imperfections to initiate buckling.
- In the load case (V11 analysis case) definition, request multiple output steps to help convergence and so you can see the buckling.
- Using displacement control rather than load control may be necessary if the structure loses load-carrying capacity. This is referring to the control defined in the load case (V11 analysis case), not to how the load is actually applied.
- You may need to tighten the Convergence tolerance, say to 1e-6.
- Make sure your elements are small enough to capture geometric nonlinear effects. Typically 4 to 8 frame or shell elements per span is needed.
- Some buckling cases require converting the nonlinear static analysis case to direct-integration time-history if the instability is severe.
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We would recommend you to review the following sections of the CSI Analysis Reference Manual that provide good insight into this topic:
- chapter Load Cases, section Linear Buckling Analysis
- chapter Geometric Nonlinearity, section Overview
- chapter Geometric Nonlinearity, section The P-Delta Effect
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