Mid-American Highway Bridge Response to Near-field Ground Motions from New Madrid Seismic Zone

Abstract

The 1999 Taiwan earthquake caused severe damages of many highway bridges under near-field ground motions. In the Central and Eastern United States, most bridges are similar in structure type to those seen in Taiwan, although their soil deposits and rock compositions are quite different. Therefore, to understand how the highway bridges in the New Madrid Seismic Zone (NMSZ) respond to near-field ground motion is of great interest in the engineering community. In this paper, the responses of a multi-span simply supported bridge and a multi-span continuous bridge to near-field ground motions synthesized for the NMSZ have been investigated using future earthquake scenarios of moment magnitude, MW, of 6.5, 7.0, and 7.5. The scope of this work includes the modeling of two representative bridge structures, the understanding of their basic dynamic characteristics, and the significance of near-field and vertical ground motions in the response of bridges near an active fault. Site-specific investigations are recommended for the evaluation of highway bridges within 10 km of an active fault in the NMSZ. The rock motion(s) selected or synthesized should include all nearfield characteristics that are expected to influence the bridge response. In the NMSZ, forward rupture directivity effect is an essential feature, while fling step is unlikely seen in ground motions during future earthquake events due to the flexibility of deep soil deposits. For highway bridges located beyond 10 km from active faults in the NMSZ, a simple methodology based on the average directivity condition at the site can represent the near-field effects on design response spectra with an acceptable engineering accuracy.

Meeting Name

4th International Workshop on Seismic Design and Retrofit of Transportation Facilities (2006: Mar. 13-14, San Francisco, CA)

Department(s)

Civil, Architectural and Environmental Engineering

Keywords and Phrases

Bridges; Continuous girder bridges; Earthquake resistant design; Fault monitoring; Faults; Highway bridges; Seismicity; Soil deposits

Document Type

Article - Conference proceedings

Document Version

Citation

File Type

text

Language(s)

English

Publication Date

01 Mar 2006

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