In the capacity spectrum method (CSM), the peak response of an inelastic system under a given earthquake load is estimated transforming the system into the equivalent elastic one. This paper presented estimating the peak inelastic response is evaIuated by the CSM. The equivalent period and damping are calculated using the ATC-40, Gülkan, 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 generaIly underestimates the peak response, while the Gülkan and Kowalsky methods overestimate the responses. The Iwan method produces the values between those by the ATC-40 method and the Gülkan and Kowalsky methods, and estimates the reponses relatively closer to the exact ones. Further, it is found that the Kowalsky method gives the negative equivalent damping ratios depending on the hardening ratios, and thereby can not be used to estimate the responses in some cases.

• 김홍진(단국대학교 건축대학 초빙교수, 공학 박사) | Kim, Hongjin
• 민경원(단국대학교 건축대학 부교수, 공학박사) | Min, Kyung-Won
• 이상현(서울대학교 공학연구소 객원 연구원, 공학 박사) | Lee, Sang-Hyun
• 박민규(단국대학교 건축대학 석사과정) | Park, Minkyu
• 정란(단국대학교 건축대학 정교수, 공학 박사) | Chung, Lan