Comparative Evaluation of Behavior Factor of SMRF Structures for Near and Far Fault Ground Motions

Abstract

In common design codes, earthquake loads are reduced by a coefficient (behavior factor) which depends on nonlinear seismic performance of structure during earthquake event. Nonlinear performance of structures depends on structural properties and ground motion characteristics. There are different methods for estimation of seismic response parameters such as behavior factor. One of the approaches is using incremental dynamic analysis. This paper gives estimations of behavior factor for special moment-resisting steel frames under near and far fault records using incremental dynamic analyses. Three moment resisting frames with, 3, 6, and 10 stories, are considered for evaluations employing two performance levels (Life Safety and Collapse Prevention). One aspect of difference among earthquake records is existence of velocity pulse in their time-history. This issue is investigated through evaluation of R factor for three frames. It is shown that behavior factor for near fault records is averagely 23% less than far fault records.