Estimation of cumulative deformation capacity of buckling restrained braces

Recently, passive vibration control design has gained popularity. The aim of this design is to absorb most of the seismic energy by using additional dampers while maintaining the elasticity of the main structure. Buckling restrained braces (BRBs) are used as one of the elastoplastic dampers in this design and, therefore, the cumulative deformation capacity of BRBs to the point of fatigue fracture is an important benchmark for their performance. The estimation of this value under a random amplitude is complicated however, as this value is affected by the loading history. In this study, past experiments on BRBs are revisited in order to investigate the relation between the cumulative deformation capacity and the applied loading history. Based on these analyses, a simple method is proposed for predicting the cumulative deformation and energy absorption capacities of BRBs under random amplitudes. In contrast to Miner's method, the proposed method does not require analyses of the individual amplitudes, and the values of interest are directly determined from the response indexes.