Optimum Criss Crossing Cables in Multi-span Cable-stayed Bridges using Genetic Algorithms

A multi-objective optimization approach in order to find the optimal cable overlap length in multi-span cable-stayed bridges with criss-cross cables is presented. The multi-objective optimization is solved by considering three objectives: 1) the cost of the cable system, 2) the displacement at the top of the pylon and 3) the alternate live load on the bridge. An unconventional criss-cross cable system configuration in which cables criss-cross at the center of intermediate spans is used for a bridge with five spans and four pylons. Taking into account both the cable overlap length and the different occurrences of alternate live load, the set of optimal solutions was obtained by the use of genetic algorithms. Results indicate that the optimal cable overlap length corresponds to three criss-crossing cables that corresponds to 0.28 times the length of the central span. Research on multi-span cable-stayed bridges with criss-cross cables allows the analysis of another solution for the problem of stabilizing the displacement of intermediate pylons in this kind of bridge.