Seismic performance of steel frames designed using different allowable story drift limits

Abstract

The design of Moment Resisting Steel Frames (MRSFs) is usually governed by drift limits rather than strength because of their high flexibility. The purpose of this study is to evaluate the seismic performance of a 6-story MRSF designed according to the Egyptian code with three different levels of allowable story drift limits: 0.5%, 0.75% and 1.0%. Seismic evaluation in this study has been carried out by static pushover analysis and time history earthquake analysis. Ten ground motions with different PGA levels are used in the analysis. The mean plus one standard deviation values of the roof-drift ratio, the maximum story drift ratio and the maximum beam- and column-strain responses are used as the basis for the seismic performance evaluations.The results obtained indicated that the strength and the initial stiffness of the designed frames decrease as the allowed story drift limit of the frame increases. Two of the designed frames exhibit maximum story drifts that are higher than the allowed limits specified by the code. The maximum story drift and beam-strain responses of the designed frames under the earthquake loading increase with the increase in the allowable story drift limits.