Numerical Assessment of Seismic Earth Pressures for Integral Abutment Bridges

Integral abutment bridges (IAB) consist of a continuous concrete deck integrated with abutments generally supported by a row of piles and they are cost-effective with less maintenance efforts. However, the abutment walls of the these bridges are subject to significant seismic loads during strong seismic shaking as opposed to the bridges with joints separating deck and abutments and there are limited guidelines available in the literature to evaluate the seismic loads on the abutments walls. The paper presents the results of the dynamic soil-structure interaction (SSI) analysis carried out for a typical two-span bridge with integral abutments using the computer program FLAC^2D. The bridge structure has been represented by a series of beam and pile elements that interact with the continuum medium through normal and shear soil springs. The slippage between abutment and soil has been accounted for by introducing interface elements in the model. The piles supporting the abutment walls are driven on to the bedrock and the middle pier is support by rock sockets extended into the bedrock. The bedrock is classified as “Class A” in accordance with the 2014 Canadian Highway Bridge Design Code (CHBDC). The seismic loads computed from the SSI analyses were compared with those estimated from the simplified analyses available from the literature.