Earthquake Engineering

Bridge Under Seismic Loads Conclusions

The objective of this study was to investigate the performance of the Confederation Bridge due to seismic excitations expected at the bridge location. A finite element model of a typical segment of the bridge was subjected to selected seismic motions representative of the seismic hazard for the bridge location. The response results obtained from the dynamic analysis of the model were compared with the seismic design parameters. The following are the main conclusions from this study:
 The responses from the linear time-history analyses (displacements and forces) were found to be smaller than those used in the design of the bridge.
 The longitudinal responses of some sections of the bridge obtained from the response spectrum analysis (i.e., for seismic actions represented by the horizontal and vertical  uniform hazard spectra) were found to be about 20% larger than the design values.

Considering the conservatism in the design through the use of factored material strengths and specified safety factors, as well as the characteristics of the uniform hazard spectra, the exceedance of the design responses by 20% does not represent any concern regarding the safety of the bridge.
 The general conclusion is that the seismic effects considered in the design are appropriate for the required safety during the service life of the bridge.
 A finite element model consisting of 3D beam elements is suitable for the Confederation Bridge provided that the foundation flexibility is taken into account in the modeling.
 The modeling method used in this study is considered to be applicable to single-box girder bridges in general.

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