## 1 Introduction  
Submerged floating tunnels (SFTs) are tubular structures that float at a specified depth and are supported by mooring cables. The balance between pre-tensions in the mooring cables and net positive buoyancy (or residual buoyancy) maintains the structural stability of the SFT. The cost of an SFT per unit length remains almost constant with increasing length [1; 2]. Therefore, it is considered an economical alternative for waterway crossings in comparison to cable-supported bridges, underground tunnels or immersed tunnels, especially for deep and wide crossings. In addition, SFT is more advantageous, because it is not bound to geographic terrain and does not interfere with water surface traffic. The research efforts for development of the SFT began in 1923 when the first Norwegian patent was issued for it. Since then, many case studies and proposals have been made for different proposed projects, such as Hogsfjord in Norway [3], Funka Bay in Japan [4; 5], Messina Strait in Italy [6; 7], Qiandao Lake in China [8; 9] and Mokpo-Jeju SFT in South Korea [10]. The lack of experimental and model test results may be one of the reasons why an SFT has not yet been constructed. The work in [11] calculated the wave loads on a circular SFT using the boundary element method (BEM) and [PERSON]'s equation and compared the results with model tests. Wave loads on an elliptical SFT were calculated similarly by [12] using [PERSON]'s equation and compared with the test results. These studies indicated that both BEM and [PERSON]'s equation gave reliable estimates of wave loads on SFT. Researchers have focused the research developments on the behavior of SFT for more than three decades. A formulation for the dynamic analysis of the SFT under seismic and sea waves effects was presented by [13]. A primary attempt to analyze the fluid-structure interaction (FSI) of the SFT using a two-dimensional model was made by [14], followed by a more comprehensive presentation of FSI by [15] using the finite element implementation of the Navier-Stokes equation. The soil-structure interaction of SFT is another issue that needs to be investigated properly. Some SFT numerical models have idealized the soil-structure interaction as horizontal, vertical and rotational springs at the connecting points [16; 17; 18]. The vortex-induced vibrations of mooring cables caused by water currents can produce fatigue damage to the cables [19; 20; 21]. Since SFT is considered an alternative solution for transportation, moving load analysis or dynamic analysis under traffic loading is a key demand of the structure, but the research efforts are very limited regarding this problem. However, a primary attempt was made by [22], who investigated the effects of two- and three-dimensional added mass models on the response of SFT under single moving loads. The numerical models described above focused on the dynamic response of SFT, including some recent developments [10; 23; 24]. However, the global performance of the SFT under complex environmental conditions is not yet well understood. The determination of stable mooring cable configurations for the SFT is one of the challenges for its realization [12; 13]. Especially, the excessive lateral displacement of the SFT due to waves and currents make it questionable for safe transportation. Three different cable configurations were analyzed numerically by [PERSON] et al. [8] using the commercial software package ABAQUS/Aqua for the hydrodynamic conditions of Qiandao Lake (People's Republic of China). Similar configurations are evaluated further in the present study for an SFT with a cable inclination of 45\({}^{\circ}\), in order to check the performance of SFT. The mooring cables with this inclination are more stable [21; 25]. In addition, a comparison of the SFT responses for static, hydrodynamic and seismic loadings needs to be provided for SFT performance quantification under different conditions.