Development of a New Response Spectrum Analysis Approach for Determining Elastic Shear Demands on Shear-Dominated Steel Building Frames

This research is focused on improving the conventional response spectrum analysis (CRSA) method for the elastic shear demands estimation of shear-dominated steel building frames. An alternative approach named the improved response spectrum analysis (IRSA) method is proposed and validated in this paper. A simplified procedure to capture the dynamic features of a continuous shear beam (CSB) with stepped stiffness is first presented, and then validated. The CSB is employed in IRSA to replace the original eigenvalue analysis in CRSA to provide the modal parameter estimation for the considered system. A modified SRSS (MSRSS) mode superposition based on a genetic algorithm is then proposed and employed in IRSA. Based on the analyses conducted in this research, it is found that using first three modes in MSRSS to execute mode superposition could provide a great estimation of the elastic shear demands distribution. The amplification of weighting coefficients for the second and third mode contribution indicates the underestimation of the high mode effect in CSRSS. Further, response history analyses (RHA) are performed on two demonstration building frames to evaluate the improvement of the IRSA. The results indicate that IRSA provides a more precise estimation on the elastic shear force demand distribution in shear-dominated steel building frames under seismic effects compared with that which was achieved by CRSA.

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