Dynamic response analysis for submerged floating tunnel due to fluid-vehicle-tunnel interaction

Vibration of submerged floating tunnels due to moving loads

Tunnel-mooring-train coupled dynamic analysis for submerged floating tunnel under wave excitations

Global dynamic analysis of a 700-m-long SFT section considered in the South Sea of Korea is carried out for survival random wave and seismic excitations. To solve the tunnel-mooring coupled hydro-elastic responses, in-house time-domain-simulation computer program is developed. The hydro-elastic equation of motion for the tunnel and mooring is based on rod-theory-based finite element formulation with Galerkin method with fully coupled full matrix. The dummy-connection-mass method is devised to conveniently connect objects and mooring lines with linear and rotational springs. Hydrodynamic forces on a submerged floating tunnel (SFT) are evaluated by the modified Morison equation for a moving object so that the hydrodynamic forces by wave or seismic excitations can be computed at its instantaneous positions at every time step. In the case of seabed earthquake, both the dynamic effect transferred through mooring lines and the seawater-fluctuation-induced seaquake effect are considered. For validation purposes, the hydro-elastic analysis results by the developed numerical simulation code is compared with those by a commercial program, OrcaFlex, which shows excellent agreement between them. For the given design condition, extreme storm waves cause higher hydro-elastic responses and mooring tensions than those of the severe seismic case.

https://www.mdpi.com/2076-3417/8/12/2386/pdf

Time-Domain Hydro-Elastic Analysis of a SFT (Submerged Floating Tunnel) with Mooring Lines under Extreme Wave and Seismic Excitations

Wave interaction with a submerged floating tunnel in the presence of a bottom mounted submerged porous breakwater

Submerged Floating Tunnel (SFT) is a new structural concept for crossing water. The purpose of the present study is to develop a dynamic analysis program for SFT and investigate dynamic response characteristics of SFT subjected to external environmental wave load. The structure is modeled with 3-dimensional beam element and the fluid is assumed incompressible, invicid and irrotational and is analysed by boundary element method applying linear potential theory. Using the hydrodynamic coefficients of added mass, radiation damping and wave excitation force obtained by solving 2-dimensional diffraction problem, 3-dimensional structural analysis of SFT is performed in time domain and results are presented. The depth effect of SFT location on the hydrodynamic coefficients are illustrated as well as the effect of the frequency dependency of the coefficients which is taken into account in the analysis program.

Analysis of wave force induced dynamic response of submerged floating tunnel

Nonlinear behavior of flexible offshore structures governed by Morison's equation is studied in frequency domain through an application of higher order transfer functions. Nonlinearities included in the analysis are the drag nonlinearity considering relative velocity between wave and a structure and the additional effect of current. Nonlinearity in the equation of motion of the syste em is expanded in polynomial series by using statistical method, the polynomially expanded equation converted to sequentially ordered differential equations using Volterra series and the nonlinear transfer functions acquired by transforming these equations to fequency domain. The characteristics of the nonlinear transfer function models are investigated through the analysis of the nonlinear re sponse of SDOF system subject to harmonic wave input. The response spectrum analysis is also performed using the 3rd, 5th and modified 3rd order transfer function model and the reliability of the modified 3rd order model proposed in this study is presented through numerical examples.

Jang Sub Kwon

Papers

Analysis of wave force induced dynamic response of submerged floating tunnel

Nonlinear frequency domain analysis of flexible offshore structures using volterra series