Load Balancing Analysis of Cable Stayed Bridges

by Benjamin E. Lazar, Asst. Prof. of Civ. Technol. and Head of Constr. Program; Univ. of Houston, Houston, TX,
Michael S. Troitsky, Assoc. Prof. of Civ. Engrg.; Sir George Williams Univ., Montreal, Canada,
Matthew McC. Douglass, Assoc. Prof. and Chmn.; Dept. of Civ. Engrg., Sir George Williams Univ., Montreal, Canada,

Serial Information: Journal of the Structural Division, 1972, Vol. 92, Issue 8, Pg. 1725-1740

Document Type: Journal Paper


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.

Subject Headings: Cable stayed bridges | Cables | Moment (mechanics) | Bending (structural) | Tension | Load factors | Bridge tests | Dead loads

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