## 1 Introduction  
Submerged floating tunnels (SFTs) float underwater and have an innovative water-crossing typology, supported by Archimedes' principle [1]. While SFTs are placed underwater, they differ from the conventional immersed tunnels, which are placed directly on the seabed and are composed of segments. However, they have several structural or infrastructural issues. Several proposals for SFTs have been designed by different countries, after the concept was proposed by Sir [PERSON] of the United Kingdom in 1886, and are continuously being studied in the United States, France, Norway, Japan, Italy, Canada, Switzerland, Korea, China, and so forth. An SFT has its own weight and buoyancy, according to its immersion depth volume. Generally, the tunnel cross section is designed so that the buoyancy covers the structural weight, and the tunnel is then subjected to an upward force, which is exerted by a fluid [2]. Based on the vertical support, the current design alternatives for SFTs can be divided into two categories, as shown in Figure 1: a tether stabilized concept (Figure 1a) and a pontoon-stabilized concept (Figure 1b). In particular, Italy has been continuing its research on SFTs, as an alternative to crossing the straits, since the 1960s. Norway have advanced SFT technologies. The SJJLAB (Sino-Italian Joint Laboratory of Archimedes' Bridge) [3], as a Sino-Italian joint venture, was founded in 1998 and was co-financed by the Institute of Mechanics, Chinese Academy of Sciences, China and the \"Ponte di Archimede International\" company. The consortium has carried out the executive design of a prototype tunnel, with a length of 100 m, in Qiandao Lake in the eastern province of Zhejiang, China [3]. In addition, Norway is working on the world's first SFT project to cross the fjords. It is a long journey between Kristiansand and Trondheim, which is part of the E39 route, crossing the southwestern coast. The Norwegian Public Roads Administration (NPRA) aims to complete the construction by 2050 and plans to cut travel time by half [4]. However, this project focuses mainly on core technology research concerning a preliminary design and lacks experience in the practical application of an SFT, which involves, for instance, design standards and economic evaluation, and the tunnel has never been built (as of 2018). [PERSON] et al. (2019) [5] conducted an investigation on the vehicle-tunnel coupled vibration of SFT using tether vibration, and the Hamilton principle and D'Alembert's principle were used to define a theoretical model. [PERSON] and [PERSON] (2017) [6] researched the global dynamic performance of a submerged floating tunnel (SFT) under an impact load. [PERSON] et al. (2015) [7] presented a theoretical method, and tests using experimental models involving a wave were proposed for verification. [PERSON] et al. (2018) [8] studied the global dynamic response of an SFT under anchor-cable failure, considering the post-breakage performance. [PERSON] et al. (2011) [9] studied the dynamics of an SFT, when its behavior was affected by tether slack and snap force under wave conditions. [PERSON] and [PERSON] [10] studied time-domain hydro-elastic analysis of SFT using an finite element model under extreme wave and seismic excitations. [PERSON] et al. [11] researched coupled vibration performance of SFT in wave and current. [PERSON] and [PERSON] (2018) [12] proposed a concept design for an SFT with an inclined cable, as an application form. It is shown in Figure 2. The hydrodynamic characteristics of the SFT were studied, and a case study on the diameters, drafts, and BWR (buoyancy and weight ratio), as variables, was conducted. In this study, a feasibility study on the applicability of an SFT with suspension cables (Figure 3) was performed at an arbitrary site. Figure 4 illustrates two solutions concerning the components of SFTs with suspension cables, which consist of towers, main cables, hangers and anchorages.