능력스펙트럼을 이용한 최대 비탄성 변위 응답의 정확성 평가

In the capacity spectrum method (CSM) using a linear response spectrum, the peak response of an inelastic system under a given earthquake load is estimated transforming the system into the equivalent elastic one. The CSM for estimating the peak inelastic response is evaluated in this paper. The equivalent period and damping ratio are calculated using the A TC-40, Gulkan, Kowalsky, and Iwan methods, and the performance points are obtained according the procedure B of ATC-40. Analysis results indicate that the ATC-40 method generally underestimates the peak response resulting in the unsafe design, while the Gulkan and Kowalsky methods overestimate the responses. The Iwan method produces the values between those by the A TC-40 method and the Gulkan and Kowalsky methods, and estimates the responses relatively closer to the exact ones.