Abstract
Abstract In this study, the seismic behavior of regular and irregular composite moment resisting frame (CMRF) buildings was investigated. To this aim, 5, 8, 10, 13 and 15-story CMRFs having concrete filled steel tube columns and composite beams were designed at high ductility level and their performances were evaluated comparatively. The case study CMRF structures were categorized into two groups as regular and irregular in elevation. Examined irregular structures have setbacks in different story levels. During the design and performance analysis, SeismoStruct software was employed. Nonlinear static pushover and incremental dynamic analyses were used in the seismic performance assessment. The uniform and triangular load distributions were considered in the pushover analysis while a total of 22 earthquake acceleration records were utilized in the dynamic analysis. The variation in the lateral response, global yielding value, interstory drift, behavior factor, inherent strength factor, overstrength factor, and ductility factor were examined for the regular and irregular CMRF structures. It was observed that the regular CMRFs were more consistent with the design assumptions as compared to the irregular ones. Moreover, the former exhibited more uniform non-elastic demands over the building height according to the results of the incremental dynamic analysis. Under the seismic scenario adopted, all the building types yielded higher values of the behavior factor complied with the limits available in the code.
Highlights
Composite steel and concrete building systems are widely used in areas with high seismic risk such as in North America and Japan
The incremental dynamic analysis (IDA) was performed by using selected time history (TH) records to obtain the seismic response of the case study composite moment resisting frame (CMRF)
According to the PO analysis results for CMRFs, the Ωi values obtained for uniform load distribution (ULD) were mostly greater than 1.0 and all Ωi values obtained for triangular load distribution (TLD) were less than 1.0 (Figure 16)
Summary
In another study by Wang et al (2017), the composite frames with square or circular CFST columns and steel-concrete composite beams with steel-bars truss deck were tested and their analysis results were examined in terms of various response parameters. Duan and Chandler (1995) examined the seismic response of a setback framework structure class, taking into account the inelastic behavior of the structural elements, but considering a representative setback frame model. They stated that both static and modal spectral analysis were insufficient to predict and prevent damage concentration in the members close to the level of irregularity. One or two sided setback configurations with symmetric or asymmetric around the vertical axis of the structure are a key factor on the performance assessment (Karavasilis et al 2008)
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