On the importance of mooring cable dynamics in response analysis of submerged floating tunnel using quasi-static and fully coupled dynamic models

Submerged floating tunnels are considered an economical alternative to those conventional bridges in crossing deep and long-span water bodies. The development of accurate modeling methods and simulation tools is the primary requirement for the safe design of submerged floating tunnels. Mooring cables are the primary source of stability of submerged floating tunnels against hydrodynamic loadings, and are commonly modelled using the computationally efficient quasi-static catenary approach. The dynamics of mooring cables can be of significant importance in dynamic responses of the submerged floating tunnel. Therefore, in this study, a discrete catenary element is presented with the aim of its implementation in the fully coupled dynamic analysis of submerged floating tunnels. To study the effect of mooring cable dynamics, the prototype of Qiandao Lake submerged floating tunnel has been used in a comparative study between quasi-static and fully coupled dynamic models. The numerical examples show differences in displacements and cable tensions due to the mooring cable dynamics. Furthermore, the mooring cables dynamics have significant effect on the tunnel shear forces and bending moments. The quasi-static coupled modeling significantly underestimates the tunnel internal forces.