Second-order, buckling and dynamic methods

What this module covers

• Explain geometric stiffness physically and say why it depends on the load
• Compute the amplification a compression load applies to deflections and to imperfections
• State why P-delta results may not be superposed
• Set up linear buckling as an eigenvalue problem and read its output correctly
• Back-calculate an effective length, and say what it is meaningless without
• Distinguish a local buckling mode from a global one
• Say what a dynamic analysis needs from a model that a static one does not

Lessons

1. 10.1

   Geometric stiffness: why load changes stiffness

   The second matrix. Where it comes from, why it scales with force rather than with EA, and what that costs you.

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2. 10.2

   Buckling as an eigenvalue problem

   Finding the load factor that cancels the stiffness, and reading what comes back without over-claiming.

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3. 10.3

   What these analyses need from the model

   Mesh density for buckling, mass for dynamics, and the modelling decisions that a static analysis lets you get away with and these do not.

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