Mobilization of Passive Earth Pressures Behind Abutments of Jointless Bridges

Abstract

Bridges without expansion joints are referred to as integral bridges. The abutment and the superstructure of integral bridges act as a single structural unit. As the temperature of an integral bridge changes, the length of the bridge increases and decreases. The changes push the abutment against the approach fill and pull it away and thus cause lateral deflections. The movement of the abutment into the approach fill develops passive earth pressure that is displacement dependent. Although earth pressures are detrimental for the substructure of a bridge, they are beneficial for the superstructure because they reduce the bending moments caused by the dead loads and the live loads in the bridge girders. Therefore, relying on the beneficial effects of the full passive earth pressures, regardless of the displacement, is not conservative. Charts are proposed to estimate the magnitude of the resultant force and the point of application of the resultant force as a function of the wall displacement. Medium-dense and dense granular backfill materials were considered in developing the charts. The need for estimating the maximum mobilized passive earth pressures for jointless bridges with cohesionless backfill may be fulfilled with the proposed charts.