Document Type : Original Article
Authors
1
M.Sc., Faculty of Civil Engineering, University of Tabriz, Tabriz, Iran
2
Associate Professor, Faculty of Civil Engineering, University of Tabriz, Tabriz, Iran
10.22065/jsce.2024.430478.3299
Abstract
The purpose of this article is to extract and evaluate the seismic fragility of braced steel building frames at different damage states by considering the effect of different seismic intensity measures. For this purpose, the finite element models of two steel frames with buckling-restrained braces (BRBs) have been used under 44 far-field earthquake records of FEMA-P695. Using incremental dynamic analysis (IDA) of models, seismic fragility curves of buildings as functions of four different seismic intensity measures including peak ground acceleration (PGA), peak ground velocity (PGV), spectral acceleration at the first mode of structural vibration (Sa (T1, 5%)) and weighted spectral acceleration with three modes (Sa (T123, 5%)) were obtained. Based on the criterion of interstory drift, four damage states including slight, moderate, extensive and complete damage were also considered to obtain fragility curves. The results show that the best seismic intensity measure depends on the desired damage states. At low damage states, where the response of the structure is mainly linear, the spectral parameters cause a significant reduction in the dispersion of the results compared to the other two intensity measures, and as a result, they are more efficient. However, at high damage states, where the nonlinear behavior becomes completely dominant, the difference in efficiency of different intensity measures decreases. Furthermore, the comparison of numerical values of probability of damage in two seismic hazard levels, i.e., design basis earthquake (DBE) and maximum considered earthquake (MCE) showed that the selection of the intensity measure can significantly affect the numerical values of the probability of damage.
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