Nonlinear structural dynamics

What this module covers

• Describe a bilinear hysteretic system and state what each of its three parameters controls
• Explain why a nonlinear step needs iteration and what the tangent stiffness is for
• Compute ductility demand, hysteretic energy and residual displacement from a response
• Use the equal-displacement and equal-energy rules, and say where each applies
• Explain why superposition, modal analysis and response spectra all stop being valid
• Recognise when a nonlinear analysis is genuinely needed and when it is not

Lessons

1. 16.1

   When the restoring force remembers

   Hysteresis, the bilinear model, tangent stiffness and the iteration inside every nonlinear time step.

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2. 16.2

   Ductility, and what it buys

   Strength reduction factors, the equal-displacement and equal-energy rules, equivalent damping, and the demand that peak displacement does not describe.

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