SCALING OF GROUND MOTION RECORDS BASED ON THE NONLINEAR BEHAVIOR OF STRUCTURES

Nonlinear time history analysis is the most accuratemethod for seismic response analysis of structures, andperforming it for designing and evaluating purposes isinevitable in some cases. The most important issue innonlinear time history analysis is the scaling method ofground motion records in order to have an accurate es-timation of structural responses. In this paper, a newmethod for scaling of ground motion records is proposed,in which the nonlinear behavior of structures is consid-ered. In the proposed method named SNSP (Scalingbased on Nonlinear Structural Properties), the scalingfactor of each record is determined in a way that the peakdisplacement of the equivalent single degree of freedom(SDOF) system subjected to the scaled record matchesthe target displacement. The target displacement is de-termined by averaging the values of the peak displace-ment of the equivalent SDOF system subjected to a largenumber of unscaled ground motion records. The charac-teristic parameters of the equivalent SDOF system aredetermined based on the modal pushover analysis, inwhich the load pattern is derived from the modal storyshear pro le of the structure. Thus, in the equivalentSDOF system, the e ect of higher modes and the in-teraction between them in the inelastic phase are con-sidered. Furthermore, the characteristics of the selectedground motion records are also considered using their re-sponse spectra in the proposed scaling procedure. Theaccuracy and eciency of the proposed method were ver-i ed through four 4-, 8-, 14- and 20-story buildings under21 near-fault records and was compared with the scalingmethod of the Iranian code of practice for the seismicresistant design of buildings, Standard No. 2800. Re-sults show that the structural responses obtained fromthe proposed scaling method are close to the averageresponses considering site-speci c records and the dis-persion of responses is low.