SIPC - A practical geometric nonlinear analysis method for the design of metal structures

Geometric nonlinear or second-order effects are the changes to forces, moments, and displacements that result when solving the equations of equilibrium on the actual deformed shape rather than the undeformed shape of a structure. For most civil engineering structures constructed of steel or aluminum and designed for serviceability, these additional nonlinear effects are significant enough to warrant consideration when designing for strength, but are often not substantial enough to require an extremely accurate numerical solution scheme. With this in mind, this paper proposes the use of an approximate second-order elastic solution method that utilizes only two linear analyses within a single load increment. Further contributing to the method's efficiency is its use of analysis results from the serviceability design process in the initial or predictor step, thereby requiring only one linear corrector analysis per load combination investigated. Through comparisons with a more exact solution scheme, twenty-two steel benchmark frames have been used to demonstrate the method's ability to maintain sufficient accuracy while significantly improving computational efficiency. Consideration is given to the advantages and limitations of the method, leading to a more general discussion regarding frame sensitivity to second-order effects.

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