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Equivalent Modal Damping of Short-Span Bridges Subjected to Strong Motion |
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| Authors: | Sungchil Lee Maria Q Feng Seung-Jun Kwon Seok-Hee Hong |
| Affiliation: | 1Assistant Researcher, Dept. of Civil and Environmental Engineering, Univ. of California, Irvine, CA 92617. E-mail: sungcl@uci.edu 2Professor, Dept. of Civil and Environmental Engineering, Univ. of California, Irvine, CA 92617. E-mail: mfeng@uci.edu 3Assistant Researcher, Dept. of Civil and Environmental Engineering, Univ. of California, Irvine, CA 92617. E-mail: juni98@yonsei.ac.kr 4Vice President, Naekyung Eng. Co., Anyang-Si, Kyungki-Do, Korea 431-060. E-mail: nk2900@empal.com |
| Abstract: | In this paper four different methods are investigated for estimating the equivalent modal damping ratios of a short-span bridge under strong ground motion by considering the energy dissipation at the boundary. The Painter Street Overcrossing (PSO) is investigated because of seismic data availability. Computed responses using the response-spectrum method with the equivalent damping ratios estimates are compared with the recorded responses. The results show that the four methods provide reasonable estimation of equivalent modal damping ratios and that neglecting off-diagonal elements in the damping matrix is the most efficient and practical method. The equivalent damping ratio of the PSO was nearly 25% under an earthquake with peak ground acceleration of 0.55g, which is much higher than the conventional assumption of 5%. |
| Keywords: | Bridges spans Response spectra Modal analysis Vibration California |