PRELIMINARY TOOLS FOR ANALYSIS AND DESIGN OF CABLE STAYED BRIDGES

Abstract

The use of cable stayed system in modem bridge engineering was due to the tendency of bridge engineers in Europe, primarily Germany, to obtain optimum structural performance from material which was in short supply during the post war years. Cable bridges are constructed along a structural system which comprises an orthotropic deck and continuous girders which are supported by stays, i.e. inclined cable passing over or attached to towers located at the main piers. The cables of a cable stayed structure work solely in tension. The cables must not only have sufficient capacity to carry the dead load, but must also have enough reserve capacity to carry the live load. Otherwise, the horizontal surface may suffer serious deformations. The horizontal surface must be sufficiently stiff to transfer and / or resist the lateral and torsional stresses induced by wind, unbalanced live loads, and the normal force created by upward pull of the stays. The stays are usually attached symmetrically to the column or tower with an equal number of stays on both sides. This is so that the horizontal force component of the inclined cables will cancel each other out and minimize at the top of the tower or column. Wide and successful application of cable stayed systems was realized only recently, with the introduction of high strength steels, orthotropic type decks, development of welding techniques and progress in structural analysis. The development and application of computers opened up new and practically unlimited possibilities for the exact solution of these highly statically indeterminate systems and for precise statically analysis of their three dimensional performance.....