Torsional Response of Horizontally Curved Bridges Subjected To Earthquake-Induced Pounding

Abstract eng:
Horizontally curved bridges have been observed to be highly vulnerable to severe seismic damage, such as deck unseating, because of the strong tendency of their decks to in-plane rotation. The torsional demand of these bridges may dramatically increases when they are subjected to earthquake-induced pounding, as observed in Baihua and Huilan bridges during 2008 Wenchuan earthquake in China. This paper is focused on studying the influence of seismic pounding, deck-abutment collision, on the torsional response of horizontally curved bridges in strong earthquakes. For this purposes, a three-degreeof-freedom nonlinear model has been developed to capture key dynamic parameters affecting the seismic response of these types of bridges. In the model, the radial and azimuthal shear-displacement relations of the columns and their bilateral interactions are modeled by a coupled-biaxial bilinear hysteresis spring, but their torsional moment-rotation relations are molded by a linear spring; and the normal and tangential impact forces at the contact nodes between the deck and the abutments are modeled by Jankowski contact model and Karnopp friction model, respectively. Then, the nonlinear bridge model is utilized to perform a detailed parametric analysis on the torsional response of a prototype curved bridge based on variations of these key parameters of the model: (i) subtended angle of the deck, β; (ii) size of the gap between the deck and the abutments, δ g ; (iii) normalized static radial stiffness eccentricity, η sr . The results obtained from this numerical analysis indicate that the seismic pounding has a noticeable effect on the in-plane rotation of the curved bridge deck particularly when the distance between the stiffness center and the curvature center of the deck is increased.

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