Finite element modeling of concentric HSS braces under cyclic loading

Braced frame construction is advantageous in reducing earthquake-induced displacements, but is susceptible to loss of ductility, attributed to brace behaviour. A three-dimensional, nonlinear, elastoplastic finite element model has been developed to simulate the hysteresis behaviour of bracing members subject to reversed axial displacements. The model was able to simulate the hysteresis behaviour of previously tested bracing members in terms of the peak loads and displacements, energy dissipation, and the degradation of both strength and stiffness. The finite element model was refined to include a damage accumulation model for low cycle fatigue and was then used to simulate a second series of experimental tests. The model provided new insight for analysis of the load-displacement hysteresis curves. New fracture life and energy life equations are thus proposed, based on a better understanding of the important parameters influencing brace behaviour.