Determining the Effective System Damping of Highway Bridges

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Determining the Effective System Damping of Highway Bridges

Author: Feng, Maria Q | Size: 1.93 MB | Format: PDF | Quality: Unspecified | Publisher: University of California, Irvine | Year: 2009 | pages: 312

This project investigates four methods for modeling modal damping ratios of short-span and isolated concrete bridges subjected to strong ground motion, which can be used for bridge seismic analysis and design based on the response spectrum method. The four methods are: complex modal analysis (CMA), neglecting off-diagonal elements in damping matrix method (NODE), composite damping rule (CDR), and optimization in time domain and frequency domain (OPT) and applied to a short-span bridge and an isolated bridge. The results show that the NODE method is the most efficient and the conventional assumption of 5 percent modal damping ratio is too conservative for shortspan bridges when energy dissipation is significant at the bridge boundaries. From the analysis of isolated bridge case, the effective system damping is very close to the damping ratio of isolation bearing.

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