ANALYSIS AND DESIGN OF BRIDGE ABUTMENT

Abstract

A bridge abutment acts both as retaining and load bearing structure. An abutment is generally checked for its stability and displacement criteria. Firstly the design of a conventional type of abutment for cohesion less soil is presented. The stability of the abutment is checked for overturning, sliding and base pressure. The effect of earthquake forces and the water table effect have also been considered. In the parametric study, the effect of earthquake forces, effect of position of water table and effect of surcharge have been shown. Secondly the design of a reinforced earth abutment for cohesion less soil is presented. It includes both external and internal stability analysis. Procedure of computing the tension in a reinforcement due to vertical and horizontal loads transferred from bridge deck have been discussed separately. The effect of Earthquake loading and the water table effect have also been considered. In the end parametric study has been presented. Lastly the displacement of the conventional abutment has been predicted. The displacement of an abutment under dynamic condition is estimated incorporating combined rotational and transitional movements. The backfill soil is replaced by closely spaced independent elastic springs. The backfill is treated as elasto-plastic material when the abutment moves away from the backfill and elastic material when the abutment moves towards the backfill. The effect of water table has been taken into consideration. In the end, parametric study has been presented.