8th ASCE Specialty Conference on Probabilistic Mechanics and Structural Reliability PMC2000-145 Song and Wen 1 REDUNDANCY OF DUAL SYSTEMS UNDER EARTHQUAKE LOADS

Damage investigations from past earthquakes such as Northridge and Kobe indicate that severe structural failure occurred due to lack of redundancy, which has since become a serious concern of both researchers and practitioners. As suggested in ATC 19 and 34, buildings with a small number of lateral resisting components for a given floor area are penalized by an increase in design force to compensate for the lack of redundancy. Recently, such a reliability/redundancy factor is introduced in NEHRP 97 and UBC 97 based largely on engineering judgement. In this paper, two types of building structure, a 5-story dual system and a 3- story special moment resisting frame, are investigated. The redundancy factor in NEHRP 97 and a uniform risk redundancy factor based on nonlinear analyses and proper consideration of the uncertainty in the excitation are compared. The shortcomings of the former are pointed out