INFLUENCE SURFACES FOR CABLE STAYED BRIDGES

Abstract

This thesis describes a numerical method for the . direct determination of influence fields or surfaces for the generalised stress resultants in the Cable Stayed Bridges, These stress resultants include bending moments, twisting moments, shears and reactions per unit length at a specified position in the deck slab, Influence surface techniques have their well _ established identity in the cases where effects of moving loads are to be studied for the determination of critical design moments, shears and in plane forces in bridges. The finite element method -provides a-unified approach to--- the determination of influence field in general for elastic continua. The theoretical treatment is based on the ' 'elastic pinch' procedure whereby a set of prescribed forces are applied around the observation point under -consideration and the resulting deflected shape provides the influence fields for the stress computations at the observation point. The influence surface results can be used for estimating the stresses due t o multiple wheel load con-figurations, temperature and -sh inkage effects. The method is also useful for establishing the critical load pos t.ions, Apart from the application of the influence surface technique to the analysis of simple bridge structures, its utility has been high-lighted for a.nalyffising the 'Cable Stayed Bridges', The method has significant importance essentially when the bridge is supported at several points by means of cables passing through the supporting towers and the deck is of complex nature. Several influence surfaces of different stress resultants such as N~, M and TMX~. are presented.