Improving the seismic performance of diagrid structures using buckling restrained braces

Abstract

The seismic performance of diagrids equipped with buckling restrained braces (BRBs) is investigated. In that regard, the effects of BRBs on the seismic performance characteristics of diagrids such as response modification factor, R, overstrength factor, Ω0, ductility ratio, μ, and median collapse capacity, S^CT, are evaluated. To this end, 6 three dimensional diagrid structures with various heights and diagonal angles are modeled using OpenSees program and are equipped with BRBs in a novel arrangement. Utilizing nonlinear static analysis, the seismic performance factors of models are evaluated. Subsequently, the median collapse capacity (S^CT) of the models are determined by performing nonlinear dynamic analyses. The results indicate that using BRBs improve the seismic performance of the considered models due to accumulation of plastic damages in BRBs and a better distribution of plastic hinges over those models. The nonlinear static analyses indicate that for the original diagrid models, the response modification factor, R, ranges from 1.7–2.5, while the ductility ratio, μ, varies between 1.2 and 2.5, depending on the diagonal angles. Also, the results show that the Ω0 remains fairly constant. However, in BRB equipped diagrids, the range of R increases to 2.4–3.3, while the ductility ratio μ varies in the range 2.1–3.1. Similar to regular diagrids, Ω0 remains constant for BRB equipped models. Furthermore, the output of the dynamic analyses indicates that the S^CT, which is a function of diagonal angles and generally increases by growing the diagonal angles, could rise up to 60% for diagrids equipped with BRB.