Effect of Inelastic Behavior on the Code-Based Seismic Lateral Force Pattern of Buckling Restrained Braced Frames

Abstract

In recent earthquakes, the observed collapses have been mainly attributed to inappropriate distributions of stiffness and strength of structural members which result from using inefficient seismic lateral load distribution pattern in design phase. Using nonlinear time history analysis under 88 strong ground motions, this paper investigates the seismic lateral load distribution pattern of 3-, 6-, 12-and 16-story buckling restrained steel braced frames, which have been increasingly used during the past decade. Through comparing analytical results with those predicted by IBC-2009 lateral load distribution equation, it can be concluded that except for low-rise structures, code pattern lateral load is quite different from analytical lateral load pattern in particular for taller structures. Therefore, code pattern lateral load would not necessarily lead to efficient distribution of strength and stiffness within the structure; consequently, the structure does not response in a predictable and desirable manner.