Estimation of Seismic Capacity of Reinforced Concrete Skew Bridge by Nonlinear Static Analysis

Abstract

Skew bridges are constructed in situations where the supports need to be aligned in a non-orthogonal orientation with the direction of traffic. During strong earthquake shaking, the non-orthogonal orientation of deck leads to rotation in the deck and significant overall torsional response of the deck. Finally, this rotation may lead to unseating of the deck and failure in pier as observed during several past earthquakes. Based on a representative skewed bridge thirty five models of bridges with varying angle of skew and varying soil conditions having similar dimensions are modeled and analyzed using nonlinear static analysis . The bridges are modeled using the computer program SAP2000. Lumped plasticity model is adopted by assigning flexural plastic hinges at appropriate sections of the piers. The rotation of the deck, torsion in the piers, lateral force in bearings, lateral shear and displacement capacities of the various RC skew bridge are estimated and compared with each other and with those of a non-skew bridge with similar dimensions. The effect of soil structure interaction on the behavior of the bridge is also studied. It is observed that the rotation in the skew bridge with a smaller skew angle begins earlier either in the case of a seat type abutment or the case where there is a deterioration in the lateral capacity of the bearings at the abutment. The consideration of soil structure interaction shows that softer soils provide for greater deck rotations and smaller torsion in the pier. Comparison of various pushover curves with bearings fixed at abutments in the direction along the abutment, shows the trend in the contribution of the abutment with the skew angle and the effect of soil structure interaction in the longitudinal and transverse pushover cases.