3-D ANALYSIS OF CABLE-STAYED BRIDGES

Abstract

During the past two decades cable-stayed bridges have found wide applications. Their increasing popularity may be attributed to — the economy of the total design and construction, ease of maintenance and aesthetics. The significance of a cable-stayed bridge is the utilization of high strength cables, which supports the bridge girders, replacing the intermediate piers, thus enabling the girder to span a longer distance. A cable-stayed bridge is a statically indeterminate structure with a large degree of redundancy. It behaves as abeam on elastic foundation. The cables at their attachment points provide the elastic support for the girder. Because rigorous solution of the basic equations for a real deck is seldom possible, a much popular approximate, / grillage and finite—elements / methods of deck idealizations have been adopted in this work. The purposes of this work have been to make a comparative study between these two methods of deck idealization in a three-dimensional analysis of cable-stayed bridges. The behavior of cable-stayed bridges under lateral loads and dynamic loads has also been studied. A comparison of the 'grillage' and 'FEM' methods of deck idealizations shows that the positive and negative girder moments are higher in case of grillage method. However, deck idealization methods have little effect on maximum cable forces and lateral forces. In general, analyzing a bridge deck using grillage method is relatively simpler and needs comparatively less computer time. But it is observed that this method is highly conservative. Cable-stayed bridges are highly flexible; hence, the structure is little sensitive to seismic excitation. However, static wind forces cause higher shear forces at the Piers and Pylons.