Structural Redundancy of Dual and Steel Moment Frame Systems Under Seismic Excitation

摘要

The extensive investigation of structural failure after the Northridge and Kobe earthquakes showed poor structuralperformance due to brittle member behavior and improper design. The lack of ductility capacity and redundancy hasbecome a serious concern. Most reliability and redundancy studies in the past have been limited to ideal simplesystems. As a result, structural redundancy under stochastic loads such as earthquakes has not been well understood,which could lead to misunderstandings among structural engineers. In this study, the redundancy of dual systems andspecial moment resisting frames (SMRF) is investigated in terms of system reliability under SAC ground motions.Major factors considered include structural configuration (number and layout of shear walls and moment resistantframes), ductility capacity, uncertainty in demand and capacity including correlation of member strength. Dualsystems of five and ten stories, equal lateral resistance, and different configurations are first investigated. Interactionbetween walls arid moment frames is considered. Ductile special moment resistant frames (SMRF) of three and ninestories, equal floor area and strength but different numbers of bays and different beam and column sizes are thenanalyzed. Furthermore, three SMRF systems of 1 x 1, 2 x 2, and 3 x 3 bay, equal strength, and brittle beam-columnconnections are investigated to examine the effect of ductility capacity and torsion. A uniform-risk redundancy factoris then proposed and compared with the redundancy factor (p) in the NEHRP-97, UBC-97, and IBC2000. The p factoris found to be inconsistent. It overestimates the effect of configuration and underestimates the effects of ductility andtorsion.