Modeling of Qiandao Lake submerged floating tunnel subject to multi-support seismic input

The modeling and seismic analysis of Qiandao lake submerged floating tunnel (SFT) is addressed with particular attention to the mooring system, to dissipation issues and to the spatial variability of the excitation, within a numerical procedure developed by the research group to perform the step-by-step dynamic analysis of iscretized non-linear structural systems. The procedure, which can handle arbitrary external loading allowing for multiple-support seismic excitation, is enhanced by enriching the mooring cables model adding non-linear hydrodynamic loads. Different dissipation models account for hydrodynamic damping, structural damping and radiation damping which are included, respectively, as non-linear forces, as linear viscous damping equivalent to linear hysteretic by means of an iterative procedure, and as linear viscous damping. A possible solution is here studied to define an adequate cable discretization in order to correctly model nonlinear geometric effects and to avoid fictitious compressions. A uniformly modulated random process, whose spatial variability is governed by a single coherency function, is deemed adequate to model multi-support seismic input for the given structure. A novel method to obtain response spectrum compatible accelerograms is here proposed.