Finite Element Modelling of Buckling Restrained Braces under Combined In-Plane and Out-of-Plane Loading

During earthquakes, buckling restrained braces (BRBs) are likely subjected to both in-plane (INP) and out-of-plane (OOP) loadings simultaneously, therefore, BRBs are required to act robustly under combined INP and OOP loading. It is believed that the OOP loading will reduce the energy dissipation ability of BRBs. The intent of this study is to numerically investigate the performance of BRBs under combined INP and OOP loading with a finite element model of BRB with circular cross-section. Restraining concrete within the BRB is modeled as connector elements in the model and is proven to be an effective way. Simulation results show that the performance of BRBs under combined INP and OOP loading is not as good as that under the INP loading only and the energy dissipation ability is decreased by about 15% when the magnitude of OOP loading is equal to that of INP loading. Furthermore, the results give a deeper insight into the behaviour of BRBs under different combined OOP and INP loading histories.