Dynamic Response Evaluation of an Existing Bridge Structure Based on Finite Element Modeling

Abstract

Seismic excitation poses a serious risk to the road infrastructure network, particularly when it comes to the dynamic behavior of bridge structures. In order to assess the safety and serviceability of these structures, the dynamic response must be evaluated. In this regard, the finite element modeling is one of the widely used accepted methods which is equally applicable for the response evaluation of existing bridge structures. This paper focuses on the dynamic response evaluation of an existing highway bridge structure. The target system is a curved, box girder steel bridge, resting on soil type-II. For this purpose, a detailed 3D analytical modeling was carried out based on the recommended design guidelines, while considering the nonlinearities in the material and structural properties. The high intensity and low probability occurring, level-II type, accelerograms were retrieved and applied for dynamic response simulations. The parameters of interest analyzed were modal shapes, resonant frequencies, the response of substructure, and the laminated rubber bearings (LRBs). The resonant frequency associated with the fundamental mode observed was 0.978 Hz in the transverse direction. The displacement time histories were plotted at the selected node for the super and substructure. The reduction in relative displacement observed was ranging from 50.64% to 96.90%, which shows the effectiveness of LRBs in reducing the displacement demand on piers. It is worth mentioning, that despite a higher reduction rate in displacement, the bearings did not exceed the ultimate capacity limit state. Finally, the relative degree of vulnerability was described by developing the fragility functions for the pier and bearings, based on nonlinear time history analysis. The results showed that, for the given intensity demand, the reinforced concrete (RC) pier is highly sensitive to failure as compared to the rubber bearings.