Numerical comparison and optimization of force and displacement based elements for the analysis of the inelastic cyclic response of steel bracing members

Publisher Summary This chapter presents a comparison between force based elements (FBE) and displacement (DBE) based elements for the analysis of the seismic inelastic cyclic response of steel bracing members. In the force based element (mixed formulation), compatibility and equilibrium equations are satisfied in a weak sense. The implementation is based on the Hellinger-Reissner (H-R) variational principle with the weak form of the equilibrium equations. In the displacement based formulation, equilibrium equations are satisfied in a weak sense, with a displacement field assumed in each element. The chapter also presents two parametric studies. The first study compares the efficiency of both element formulations. The second study examines the influence of brace slenderness by carrying out analyses on three braces with different cross-sections and effective lengths. A co-rotational framework is used to model the nonlinear geometric behavior, and inelasticity was accounted for through fiber discretization of the cross-section with bi-linear hysteretic material behavior with isotropic and kinematic strain hardening. For both FBE and DBE models, optimal parameter configurations are first determined to achieve an acceptable level of accuracy with consideration of computational time.