Numerical Modelling of a Four-Span Bridge, Bi-Axially Tested on Three Shake Tables

Abstract eng:
Most of existing experimental investigations of bridges were under slow cyclic loading. Data about the dynamic response of bridge components are relatively rare. The experiments investigating the response of the whole bridge are only few. One of these very rare (dynamic) tests of the whole bridges was recently performed at the University of Nevada, Reno. Large scale model (scale 1:4) of an asymmetric, four-span, torsionally sensitive bridge was bi-axially tested on three shake tables. Additionally, the influence of the abutments to the seismic response of the whole bridge was also investigated, exciting the bridge in the longitudinal direction simultaneously with actuators attached to the abutment seats. The response of the bridge was very complex, exhibiting large in-plane deck (torsional) rotations. The results of this test were used to evaluate the existing numerical models of different bridge components, and their interaction. The 3D analytical study of the bridge was performed using the OpenSees programme platform. Beside the standard existing fibre models of columns, different models of less investigated bridge components were evaluated. The crucial elements, having the significant influence on the overall response were the abutments. Two types of elements (zeroLengthContact3D and zeroLengthImpact3D), which were capable of modelling the impact as well as the friction between the superstructure and the abutments, were tested. It was found that the impact between the abutments and the superstructure was one the most important parameters influencing the response. Although the bridge was straight, the centre of its rotations was significantly changing, due to the impact between the abutments and the superstructure, substantially amplifying its in-plane rotations.

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