Article Article
Inferring Dynamic Characteristics of a Bridge through Numerical Simulation and and Low-Magnitude Shaking as a Global NDE Method

Boundary conditions of a structure affect its response to dynamic excitations. In most highway bridge designs, the dynamic soil-structure interaction is not considered, with an underlying assumption that bridge piers have fixed-ends. Foundation flexibility, and more importantly radiation damping from the foundation, whether it is a shallow or deep foundation, can significantly influence the response of substructure/superstructure system. This may lead to deviations of the actual response compared to the design assumptions, depending on soil properties and geometrical and structural characteristics of the bridge. Low-magnitude shaking can be used as the means of evaluation of actual dynamic characteristics of a bridge. Moreover, numerical simulations of the same bridge with the same low-magnitude shaking load on the bridge can be used to model the dynamic response of the bridge, with the consideration of the dynamic soils structure interaction. In this paper, a comparison between the actual response of a bridge in Hamilton Township, New Jersey, and results from numerical simulations is presented. The shaking of the bridge was done using T-Rex, a large mobile shaker from NHERI Experimental Facility at University of Texas at Austin. The test setup, and results from both numerical simulations and field-testing are presented and discussed. Experimental results confirm that the FEM model developed is adequate to infer dynamic characteristics through the eigenmode analysis.

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