Effect of bay-span length on ductility demand in steel-core buckling restrained braces under near-field seismic disturbances

• Main Authors: Anand, T.P., Safeer Pandikkadavath, Muhamed
• Format: Conference Proceeding
• Language: English
• Subjects: Brace ductility; Buckling restrained braces; Near-field seismicity; Nonlinear time history analysis
• ISSN: 2214-7853; 2214-7853
• DOI: 10.1016/j.matpr.2022.04.697

Buckling-restrained braces (BRBs) represent effective passive control systems to improve the seismic response of newly designed and existing buildings. In BRBs, a sleeve provides buckling resistance to an unbonded core that resists axial stresses. As buckling is prevented, BRBs behave similarly in tension and compression, allowing for the development of stable hysteretic cycles, providing significant energy dissipation capacity. BRB frames have been widely investigated through experimental and numerical studies, demonstrating their capacity to improve the frame’s seismic performance. However, most of the studies focused on the seismic response considering Far-Field ground motions only. Conversely, there is still a lack of knowledge on the seismic performance of BRB frames under Near-Field pulse dominant seismic actions, and additional studies are required in this direction. In the present paper, several case study BRB frames characterized by different span lengths, with BRB devices designed according to the Equivalent Lateral Force Analysis Method, are numerically investigated by considering the effect of Near-Field ground motions. The frames are modelled in OpenSees, and Nonlinear Time History Analyses are carried out under a selected suite of Near-Field seismic records. Local Engineering Demand Parameters (EDPs) for the BRBs, such as the Maximum Brace Ductility and Maximum Cumulative Brace Ductility, are considered to evaluate the structural response. Probabilistic Seismic Demand Models (PSDMs) are successively developed for these EDPs and used to derive fragility curves. The results are compared for the different BRB frames to evaluate the influence of the design method and the BRB lengths (due span variation) on the structure’s seismic performance under the considered set of Near-Field ground motions.