Collapse analysis: Large inelastic deformations analysis of planar frames

In an attempt to trace the collapse of structures in seismic events, this paper discusses an alternative approach to the formulation and solution of the large deformation inelastic problem in planar frame structures. A beam-column element that includes the effect of geometric and material nonlinearities is developed using the flexibility approach. The formulation uses force interpolation functions and the principle of virtual forces in rate form. It is formulated in the context of the state space approach, where the global system of conservation equations and the local constitutive equations are solved simultaneously. The differential-algebraic system solver is used to solve the resulting system of equations. Numerical examples are presented to illustrate the functionality of the analysis using the newly formulated approach.