Feasibility Study of Submerged Floating Tunnels Moored by an Inclined Tendon System
- 169 Downloads
Concepts of submerged floating tunnels (SFTs) for land connection have been continuously suggested and developed by several researchers and institutes. To maintain their predefined positions under various dynamic environmental loading conditions, the submerged floating tunnels should be effectively moored by reasonable mooring systems. With rational mooring systems, the design of SFTs should be confirmed to satisfy the structural safety, fatigue, and operability design criteria related to tunnel motion, internal forces, structural stresses, and the fatigue life of the main structural members. This paper presents a feasibility study of a submerged floating tunnel moored by an inclined tendon system. The basic structural concept was developed based on the concept of conventional cable-stayed bridges to minimize the seabed excavation, penetration, and anchoring work by applying tower-inclined tendon systems instead of conventional tendons with individual seabed anchors. To evaluate the structural performance of the new type of SFT, a hydrodynamic analysis was performed in the time domain using the commercial nonlinear finite element code ABAQUS–AQUA. For the main dynamic environmental loading condition, an irregular wave load was examined. A JONSWAP wave spectrum was used to generate a time-series wave-induced hydrodynamic load considering the specific significant wave height and peak period for predetermined wave conditions. By performing a time-domain hydrodynamic analysis on the submerged floating structure under irregular waves, the motional characteristics, structural stresses, and fatigue damage of the floating tunnel and mooring members were analyzed to evaluate the structural safety and fatigue performance. According to the analytical study, the suggested conceptual model for SFTs shows very good hydrodynamic structural performance. It can be concluded that the concept can be considered as a reasonable structural type of SFT.
KeywordsSubmerged floating tunnel Hydrodynamics Motion Mooring Fatigue
This research was supported by a grant (18CTAP-C133500-02) from technology advancement research program funded by Ministry of Land, Infrastructure and Transport of Korean government.
- American Petroleum Institute. (2010). Planning, designing, and constructing tension leg platforms (API RP 2T). Washington DC: API Publishing Services.Google Scholar
- Det Norske Veritas. (2011). Fatigue design of offshore steel structures (DNV-RP-C203). Oslo: DNV.Google Scholar
- Korea Institute of Ocean Science and Technology. (KIOST). (2012). “Submerged floating tunnel with a cable-stayed super long-span and a construction method thereof capable of reducing construction costs.” Korea Patent, 10-1211491.Google Scholar
- Kunisu, H., Mizuno, S., Mizuno, Y., & Saeki, H. (1994). Study on submerged floating tunnel characteristics under the wave condition. In Proceedings of the fourth international offshore and polar engineering conference. ISOPE-I-94-096.Google Scholar
- Lu, W., Ge, F., Wang, L., Wu, X., & Hong, Y. (2011). On the slack phenomena and snap force in tethers of submerged floating tunnels under wave conditions. Material Structures, 24(4), 358–376.Google Scholar
- Østlid, H. (2010). When is SFT competitive? Dynamic response and structural integrity of submerged floating tunnel due to hydrodynamic load and accidental load. In Procedia engineering, first international symposium on archimedes bridge (ISAB-2010), 4, pp. 3–11.Google Scholar