Nonlinear Dynamic Response of the Tension-Leg Submerged Floating Tunnel Segment Models Under Lateral Seismic Excitations

Tension-leg submerged floating tunnels (SFTs) are significantly affected by earthquakes, which can act through boundary excitations, cable propagation paths, and seaquake-induced effects. In super-long tension-leg SFTs, where mooring cables are the dominant constraint, seismic energy transmitted along the cable paths poses a significant threat to safe operation. This study experimentally investigates the nonlinear dynamic behavior of a scaled tension-leg SFT segment model subjected to lateral seismic input via cable propagation paths. Structural response characteristics are analyzed under both harmonic and transient excitations, with particular emphasis on the effects of cable inclination and buoyancy-to-weight ratio (BWR). The results indicate that the nonlinear resonance mechanism is the primary mechanism responsible for the extreme displacement and cable force observed under lateral seismic input via the cable propagation path. Increasing cable inclinations enhances lateral seismic resistance, but angles exceeding 60° substantially reduce this beneficial effect. Configurations with reduced BWRs suppress overall vibration amplitudes but lead to amplified roll responses compared with higher BWR designs.