Effects of moving loads and wave excitations on a 900-m-long SFT (submerged floating tunnel) are presented and discussed. Floater-mooring coupled dynamic analysis is done by a time-domain numerical simulation program. Hydro-elasticity of the tunnel and mooring lines are considered with the clamped-clamped end-boundary condition. The result of modal analysis is included to investigate natural frequencies of the entire structure. Effects of the BWR (buoyancy to weight ratio) and velocity of a moving vehicle are discussed. In addition, moving-load effects coupled with wave excitations are also analyzed. Finally, the effect of the same moving weight on smaller SFT is also assessed. Time histories of horizontal and vertical responses of the tunnel and mooring tensions at the middle span are presented with the corresponding spectra.
SFTs are considered as one of alternatives for crossing sea straits and fjords of relatively large water depth. Research has been conducted for several decades, which includes Hogs fjord in Norway, the Strait of Messina in Italy, and the Funka Bay in Japan (Skorpa, 1989; Fujii, 1996; Remseth et al., 1999; Faggiano et al., 2001). In particular, Norwegian Public Road Administration (NPRA) has been considering the first construction of the SFT crossing fjords in Norway and initial research has been carried out (Engebretsen et al., 2017; Xiang et al., 2017).
Major topics of SFT-research with respect to its global performance included dynamic/structural responses under wave/seismic excitations and accidental loads by collision/explosion. However, there were little research regarding the effect of train-like-moving-load on its global dynamics. Tariverdilo et al. (2011) studied the vibration of a SFT due to moving loads with simplified approach and mainly investigated the influence of moving-vehicle velocity and mooring stiffness. They considered moving load as point force and mooring lines are simplified by continuous elastic foundation. Yuan et al. (2016) investigated how the speed of a single moving load (i.e., point mass) affects the dynamic responses of a SFT, and they reported that adjusting vertical stiffness of mooring lines has a positive effect on reducing dynamic responses. Similar studies can also be found in the floating bridge. Shixiao et al. (2005) and Fu and Cui (2012) compared experimental results with numerical simulations for a floating bridge. In their research, they mainly studied the effect of moving-mass velocity on vertical responses. In those researches, the non-linearity of mooring lines and moving loads coupled with wave excitations were not considered.
