COMPLEX INTERACTION AMONGST SEVERAL PARAMETERS OF A CABLE STAYED BRIDGE

Abstract

A bridge is a structure providing passage over an obstacle without closing the way beneath. Since the dawn of civilisation many types of bridges and their methods of construction has been evolved. Cable stayed bridges with their great structural advantage for medium and long span highway bridges fall under the category of modern bridge system. The idea of using the cables to support bridge spans is by no means new. Unfortunately, not very many cable stayed bridges were developed in the past. This was due to the fact that the statics were not fully understood and that unsuitable materials such as bars and chains were used to form the inclined supports or stays. Wide and successful applications of cable stayed system was realised only recently with the introduction of high strength steels, orthotropic type decks, development of welding techniques and progress in structural analysis through electronic computers. The significance of cable stayed bridges has increased so rapidly that they are about to take their rightful place among other classical bridge systems. The future applications of the various types of cable stayed bridges are countless and will no doubt dominate the intermediate and long span ranges of ravines and river crossings. In the present study, twin pylon cable stayed bridge has been studied for their three well known configurations namely radial, harp and fan with a view to find the comparative change in girder moments, girder deflections, pylon moment and pylon forces and cable tensions in these configurations with a change in sectional areas of the cables for different main span to side span ratios. The study has been done in progressive manner starting from cantilever beams supported by increasing number of cables to existing single pylon bridge at Centre Canal, Obourg, Belgium, and finally to a twin pylon bridge of 268 m of span. Analysis has been carried out using ANSYS 4.5 software program by generating 2-D models of bridge profiles in radial, harp and fan configurations. Results have been presented both in tabular and x-y plot form so as to arrive at appropriate conclusions.