Determining the behavior factor of irregular steel buildings in plan using pushover analysis

This study tries to determine the behavior factor of irregular steel buildings in plan using pushover analysis.In order to examine the irregular effect in plan on the bahavior factor of steel buildings, three numerical models of irregular steel buildings in plan and also a regular 8-storey building are simulated using Sap 2000. Analysis of structures was performed using non-linear pushover static method and the way how plastic hinges are formed in each model are examined according to seismic rehabilitation of existing buildings (Publication No. 360). Then, parameters for determining the behavior factor of structures were extracted using load-displacement graphs which were obtained from non-linear pushover static method. Finally, behavior factors of each simulated structure was determined using Miranda and Bertero method and they were compared with the behavior factor proposed by Iranian seismic standard (2800). Numerical models of three irregular 8-storey building in plan and also a regular building are simulated using Sap2000 software. Analysis of structures was performed using non-linear pushover static method and the way how plastic hinges are formed in each model are examined according to seismic rehabilitation of existing buildings (Publication No. 360) Then, parameters for determining the behavior factor of structures were extracted using load-displacement graphs which were obtained from non-linear pushover static method. Finally, behavior factors of each simulated structure was determined using Miranda and Bertero method and they were compared with the behavior factor proposed by Iranian seismic standard (2800). In this study, comparing the obtained behavior factors in the examined irregular structures with the introduced behavior factors in the seismic standard (2800) shows a significant difference between the mentioned cases so that even this difference is about 37/48 percent. Although the editors of Iranian seismic standard (2800) have proposed R for special structural system based on significant and influential parameters and then with some restrictions, they have considered other destructive factors such as irregularity; but due to this considerable difference and due to various irregularities (such as geometric irrregularity, massive irregularity and etc.), it seems that its is necessary to present separate behavior factors in the fourth edition of the seismic standard (2800). As a result, the design engineers can make accurate and appropriate predictions about the real behavior of the structure

Keywords:

irregularity in plan , steel moment frame , SAP 2000 , non-linear static analysis