ABUTMENT-PILE-SOIL INTERACTION OF A PSC BRIDGE UNDER SEISMIC LOADING

Abstract

The practical orientation of all the bridge structures are not straight, they may be skewed to some angles. A skewed bridge is one in which the major axis of the sub structure is not perpendicular to the longitudinal axis of the super structure.. The structural response of a skewed bridge to seismic loads gets significantly altered by the skew angles of the sub structure. Sub structure components consist of abutments, piers and foundations. These components always rest in the soil, hence the response of the structure caused by the flexibility of the foundation soil, as well as the response of the soils caused by the presence of the structure need to be assessed. Hence the study of soil structure interaction of sub structure (Interaction of Soil – Abutment - Pile) shows the behaviour of the sub structure and the soil due to seismic loadings. A Two span continuous prestressed concrete box girder bridge is selected as the super structure of the bridge and Finite element package SAP2000 V 14.2.4 software is used to model the bridge and to perform the analysis. The soil is modelled as five types of springs for which the spring stiffness are determined based on the guidelines given by American Petroleum Institute (API). These springs are modelled in SAP2000 as link elements. Earthquake record of the two major earthquakes Electro and Coalinga are collected from Pacific Earthquake Engineering Research (PEER). The input accelerations are scaled down to the acceleration of the Bangalore region and the time history analysis is performed. The super structure and the sub structure are modelled separately and the soil structure interaction is carried out. The response of the sub structure is obtained in the form of displacement, velocity, acceleration and spectral displacement, spectral velocity and spectral acceleration for the models with and without soil structure interaction.