An approach for adjusting the tensile force coefficient in equivalent static cable-loss analysis of the cable-stayed bridges

The sudden rupture of cable is one of the factors that can threaten the bridge safety; causing progressive collapse due to severe vibrations along with numerous changes in the internal forces of all bridge members. Therefore, analyzing the bridge behavior after the sudden cable rupture and estimating the maximum response of the bridge members is of great importance. According to Post-Tensioning Institute (PTI), the sum of the static analysis responses of two models can be used instead of dynamic analysis of cable rupture. In one of these models, the ruptured cable should be removed and twice its tensile force should be applied at the two ends of the cable. In this study, an approach proposed for investigating the tensile force coefficient (TFC) of the ruptured cable in the model of cable rupture effect. For this purpose, an optimization problem was defined to minimize the difference between the static and the maximum dynamic analysis results. The performance of the proposed approach is illustrated with a three-span cable-stayed bridge. This problem was solved for the rupture of each of the bridge cables under examination at different durations of cable rupture using ECBO meta-heuristic algorithm. Moreover, this meta-heuristic algorithm was used to adjust the tensile forces of the cables. Based on the results, a general form of equations was found between cable rupture duration and TFC, which the maximum of it, is in accordance with the PTI coefficient. According to this equation, increasing the cable rupture duration reduces this coefficient.