Effect of Bearing Stiffness and Skew Angle on Performance of Precast Concrete Bridge

Reinforced elastomeric bearing pads generally support precast concrete bridge girders. The condition of these bearing pads and the pad-bridge interface defines the support boundary conditions of the bridge super-structure. The interface between bearing pads and bridge girders affects the performance of the superstructure and the substructure. The pads are designed to carry vertical loads and to accommodate horizontal movements of the bridge girders. A study was conducted to determine the effects of various parameters on bridge superstructure performance and to compare the girder performance with simple support conditions corresponding to the current Florida Department of Transportation design. A parametric study on the interaction of the support boundary conditions and bridge girders was performed. The parameters studied included the skewness of the bridge and the effect of the bearing stiffness on the bridge system. A finite element model of a bridge superstructure containing Florida bulb tee 78 girders was created using ANSYS software. The model was subjected to an HL93 truck load according to the AASHTO load and resistance factor design specifications. The results indicate that pads with higher bearing stiffness are beneficial to bridges with higher skew angles. However, the reductions in deflections and stresses are smaller for increasing skew angles.