Equivalent static evaluation of wave loads for the section design of concrete submerged floating tunnel

Abstract

Submerged floating tunnel (SFT) has many advantages of less excitation by wind load and earthquake owing to its positioning in the water compared to the sea-bridge or underground tunnel. Guarantee for the safety of the SFT is the primary request for the realization of the structure under the application of frequently varying wave load, complex interaction between the load and the structure, therefore, determination of the initial cross-section of the SFT requires repetitive iterations. However, numerical analyses of usual offshore structure are based on the beam elements, which gives only the information in the longitudinal direction, and the time-consuming process is required when the dynamic analysis is performed based on the solid elements. To overcome these limitations, an approach of the equivalent static load is introduced, which transforms a dynamic load at the time which induces the maximum response of the structure into an equivalent static load. After that, parametric studies with four parameters of outer diameter, outer thickness, wave parameters, and submergence depth of the SFT are performed. Reaction forces on mooring lines and three-dimensional compressive, tensile, and shear stresses can be evaluated and investigated with appropriate reinforcements. Through the rigorous analyses and verification of the numerical results, an initiative guideline for the optimal design of the SFT section can be suggested.