EFFECT OF GROUND MOTION DURATION ON SEISMIC RESPONSE OF STEEL MRF STRUCTURES

Steel Strong ground motion duration of earthquake input has profound effect on seismic behavior and safety of structures. Some of the important processes such as stiffness degradation, reduction in strength and fatigue, depend on the number of load or stress cycles occur during the earthquake loading. Effect of ground motion duration on seismic behavior of steel structures has been studied in this research work. Horizontal components of 19 recorded accelerograms from ten earthquakes having moment magnitude ()wM of 6 s.5-7.5 and recorded on sites of type B ( 360 750 /)sV m = − according to USGS classification, have been selected in this study. In order to examine solely the effect of ground motion duration on response, the selected accelerograms have been scaled to be compatible with a site specific design response spectrum. For all of records the ground motion duration has been determined according to four very well known definition of duration namely, bracketed duration, uniform duration, significant duration and finally effective duration. Nonlinear time history analysis of three MRF steel buildings of three bay with four, six and eight stories have been conducted. All of the model buildings have medium ductility and have been designed according to UBC97-ASD. For all of analyses the scaled ground motions have been used as input motions