Nonlinear stochastic seismic dynamic response analysis of submerged floating tunnel subjected to non-stationary ground motion

Owing to the randomness of seismic excitations, the submerged floating tunnel (SFT), which is a new structure subjected to the combined action of self-weight, buoyancy, and anchorage under seismic excitation, is a nonlinear stochastic dynamic system and the evaluation of its dynamic performance is an issue that must be addressed. In this study, the nonlinear dynamic differential equation of an SFT subjected to seismic dynamic action was systematically derived by considering the wave–structure dynamic coupling interaction, and its numerical solution was obtained based on the Newmark-β integration algorithm. Furthermore, based on the theoretical framework of nonlinear stochastic dynamics and the stochastic seismic model reflecting the characteristics of the site-specific response spectrum, the probability density function (PDF) of the nonlinear seismic dynamic response of the SFT was analyzed, and its seismic dynamic performance was evaluated based on dynamic reliability. Thus, it was found that the randomness of ground motion propagates, fluctuates, evolves, and dissipates in the SFT, and finally reaches the nonlinear seismic dynamic response of the SFT. Additionally, the nonlinear dynamic response of the underwater suspension tunnel is highly sensitive to earthquake excitations. The proposed evaluation framework is an effective tool for evaluating the seismic performance of underwater tunnels.