Load Balancing Analysis of Cable Stayed Bridges

The cable stayed bridge is a structure well suited for load balancing, that is for reduction of bending moments and displacements throughout the structure by post-tensioning the cables. The problem was approached frist from the point of view of reducing bending moments. A procedure was developed to achieve this reduction. The first step of this method consists of determining the bending moments due to a unit force applied successively along each cable of the bridge system. Next, a system of equations is written to express the condition that the sum of the bending moments due to unknown post-tensioning forces in the cables, shall be opposite in sign and equal to a fraction of the bending moment caused by the action of the dead load. By solving this system of equations, the post-tensioning forces in cables are determined. A computer program was written in FORTRAN language to carry out the computations.