SEISMIC AND SECONDARY EFFECTS IN INTEGRAL BRIDGES

Abstract

Over the Iast three decades, engineers have become aware of the problems associated with the use of expansion joints and bearings. One of the best solutions to overcome these problems is the Integral Abutment and Jointless Bridges, commonly known as Integral Bridges. The concept of Integral Bridges is now gaining ground in India. In spite of the growing popularity of the integral bridge concept in some countries, this is consistently being overlooked or avoided by many bridge design practitioners in many parts of the globe. At last, the concept of jointless bridges has come into reckoning in India. Few structures are being constructed and some are being planned in the urban areas with this concept. The aim of the dissertation is to study the seismic and secondary loadings i.e. effects of temperature, creep and shrinkage in integral bridges. By studying these effects an attempt made to recommend some design considerations for integral bridges, for which no such guidelines are available in the current Indian standards. For the analysis twenty models of integral bridges with varying span lengths from 25m to 60m and number of spans from single span to five spans are modeled using two commercially available structural analysis software packages namely SAP 2000 and RM2004. SAP 2000 has been used for seismic load analysis where as RM2004 has been used for studying the secondary effects. In this study it is assumed that abutments are rigidly connected with founding soil and abutting soil, piers are completely rigid at foundation level. Furthermore, an extensive study of available literature related to seismic, thermal, creep and shrinkage effects on integral bridges is included in the dissertation. The report concludes that integral bridges are most suitable for the seismic regions, for small and medium span bridges. Shrinkage effects are not significant, can be neglected. However, the temperature and long term creep effects are significant and there is an urgent need to formulate a unified code or proper guidelines should be incorporated in bridge codes.