Investigation of the Distribution of Cumulative Ductility Demand Parameter in Various Storeys of Buckling Restrained Braced Frames

Document Type: Regular Paper

Authors

1 Department of Civil Engineering, University of Qom, Qom, Iran

2 Department of Civil Engineering, Faculty of Engineering, University of Tehran, Tehran, Iran

Abstract

Due to the fact that the buckling-restrained brace core yields subject to both tension and compression, it can adsorb energy and exhibit high ductility rendering it proper for tolerating earthquake loads. One of the important objectives of seismic standards is safeguarding the appropriate ductility for the structures because the structures, in case of being ductile, can dissipate a considerable amount of earthquake energy. According to the importance of the issue, the present study makes use of cumulative ductility parameter as a scale that is practically applied for describing the plasticity demand of the buckling restrained brace (BRB) member to investigate the cyclic behavior of the braces and buckling restrained braced frames (BRBF). To do so, nonlinear time history analysis was run on three steel buckling restrained braced frames in three different height rates, namely 5-storey, 10-storey and 15-storey, subject to seven earthquake records in OpenSees Software. Using the results of the analysis, hysteretic curves were delineated for the storeys and cumulative ductility demand and hysteresis energy parameters were calculated for each of the obtained curves. The results indicated that the cumulative ductility demand distributions of the storeys of the buckling restrained braced frames, designed corresponding to AISC360 guidelines are not identical and that higher ductility demands were scored for the upper storey. The storeys with more cumulative ductility demand should be considered in the design of a larger brace cross-section, although resistance does not require a larger brace cross-section.

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