Dynamic behavior of a long-span cable-stayed bridge with floating towers after the sudden failure of tethers and cables under irregular waves

Cable-supported bridges with floating towers do not require fixed piers at the seabed. Therefore, innovative conceptual models have been continuously developed to overcome the limitations of conventional bridges in deep waters. The main floating tower that supports superstructures using stay cables is balanced by the buoyancy of floaters moored by tethers. The applicability of floating bridges should be verified by evaluating the overall stability considering the tether design. Here, various cases of the sudden failure of tethers and stay cables under the environmental conditions of a 100-year return period are simulated in a time-domain. The floating cable-stayed bridges are subjected to constantly changing environmental loads such as wind, waves, and current. The dynamic analysis of these loads was performed, applying the irregular wave load generated by the Joint North Sea Wave Project (JONSWAP) spectrum model. The structural responses of the floating bridges were evaluated via hydrodynamic analysis after the sudden failure was simulated. In this study, various cases were evaluated considering the number of failed tethers and stay cables. When the four tethers suddenly failed in the 100-year return period wave conditions, some of them exhibited structural stress exceeding the yield stress, and others even suffered compression. The effects of the sudden failure of the tethers and stay cables on the change in structural responses and states were directly compared in an intensive parametric study. According to the analytical study, the sudden failure of the tethers induces a significant increase in the dynamic responses of the floating bridges.