INFLUENCE OF SOIL STRUCTURE INTERACTION ON DYNAMIC RESPONSE OF BRIDGES

Abstract

Bridges are regarded as important civil infrastructures and life line of transportation network of a country. Their safety in earthquakes is vital because of post-earthquake importance in relief and rescue operations. The response of bridge and its safety is rather more important under seismic conditions as these cannot be inspected and repaired in the event of distress. Soil-structure interaction is one of the main factors affecting the behaviour of bridges under dynamic loading and thus it has been a very active field for research from many years. The importance of the nature of the subsoil, its natural period of vibration is demonstrated in many past earthquakes. A As is well known, there are two main methods, which are being used in the soil-structure interaction analysis, namely, Substructure and Direct Method. This dissertation presents an evaluation of the effects of soil-structure interaction (SSI) on the dynamic response of bridges. The study was carried out by studying the change in parameters of bridge while applying the soil foundation interaction. The responses were obtained by performing response spectrum analysis and Time History analysis using a commercial analysis program. The dynamic responses of the prototype bridges were computed with and without consideration of SSI (i.e. flexible-base versus fixed-base piers). This work explores the efficient implementation and practical application of the direct methods of SSI analysis. It presents the seismic demands of the prototype bridge foundations, and provides a quantified picture of the effects of SSI on the response and the total displacement demands of the bridge as functions of their natural period