Influence of modeling parameters on seismic response of steel moment resisting frames

Abstract

The purpose of this work is to identify the building response to variations in modeling parameters and assumptions for the steel mid-rise buildings. The behavior and response of 9-story building in Los Angeles are studied. The building that was designed according to the UBC 1994 provisions was used in the analysis. Different models for this structure were developed and analyzed dynamically. The models investigated involved the use of centerline dimensions of elements, or clear length dimensions (rigid zone effect), nonlinear springs for the beam connections, and nonlinear springs for the panel zones. Also, P-delta effects on the system response to the ground motions were investigated. Nonlinear time-history analysis was used to assess the performance of buildings subjected to strong earthquake ground motions. The global (roof) and story level displacement demands, story drift ratio demands, beam and panel zone plastic rotation demands, location of plastic rotations of the systems, and the story shears were obtained by subjecting the six models to set of 10 ground motions representative of a 10150 (10% probability of being exceeded in 50 years) hazard level. The results are compared to evaluate the influence of modeling assumptions on the nonlinear dynamic response of the structures. As a result it is concluded that, the effect of analytical modeling is intrinsic to understanding the response of the structure. The overall effect of the different models can result in significant changes in the demands. Moreover, structure P-delta effects are found to have a potentially severe influence on the response of steel moment resisting structures.