Dynamic Response Of Submerged Floating Tunnel Research Articles

Dynamic response analysis of submerged floating tunnel - canyon water system under earthquakes

Submerged Floating Tunnel (SFT) is one new type of infrastructure, representing a challenge in structural engineering, both on the theoretical and operational fields. Several research work focused on this innovative structure, especially on effects of dynamic loadings such as earthquakes and sea waves. So far, the dynamic response of SFT under vertical seismic ground motion input and secondary hydrodynamic pressure has been studied deeply using theoretical and numerical methods. However, the dynamic response characteristics of SFT-Canyon water system under surging caused by the canyon horizontal sloshing motion remain unclear. In this paper, a new mathematical model for analyzing the dynamic response characteristics of SFT-Canyon water system caused by horizontal sloshing motion was proposed, which considered the transmission effect of canyon water to the original horizontal seismic wave input. Firstly, the canyon was simplified as a rectangular water tank and hydrodynamic potential flow theory was used to study the dynamic input to SFT through canyon water. After that, based on the theory of structural dynamics, SFT was simplified as an elastic support beam, and the action of horizontal seismic input was considered as the load transmitted through the fluid in the canyon to study the response of SFT transmitted through water. Finally, we used verified MATLAB coding to achieve Duhamel integration to solve the mathematical model of the system dynamic response under the action of sine wave and seismic wave respectively. Besides, the factors affecting the maximum vertical displacement response of SFT under hydrodynamic pressure caused by horizontal seismic input to the canyon were discussed.

Numerical investigation of dynamic responses and mooring forces of submerged floating tunnel driven by surface waves

Based on Navier–Stokes equations, a numerical model for studying the dynamic responses and mooring forces of the moored Submerged Floating Tunnel (SFT) driven by surface waves is presented in this paper. The mechanics models of the vertically and inclinedly moored floating body under wave forces are built, and the overset meshing method is employed to dynamically configure the computational meshes. Two laboratory experiments are used for validating the numerical model in terms of motion responses and mooring forces of the SFT, indicating the proposed model is capable of accurately simulating the instantaneous position of the body under the wave action. This hydrodynamic model is then utilized to simulate the wave–structure interaction of the prototype SFT designed for Qiongzhou Strait located between Mainland China and Hainan Island. The effects of the fundamental structure parameter, or the inclined mooring angle (IMA), on the dynamic responses of SFT are analyzed. The numerical experiments not only shed light on the mooring forces, as well as pitch, sway and heave responses of the SFT with various values of IMA, but also provide guidance for the choice of IMA in engineering design. The range of IMA is separated into five zones, and Zone 2 is regarded as the best choice for the design of IMA for both motion displacements and mooring forces are relatively small in this zone. Zone 3 is considered to be the worst choice as not only are motion responses of SFT severe in this zone, but also the mooring chains are at the risk of going slack under severe wave conditions.

Effect of Cable Stiffness and Waves Parameters on the Dynamic Responses of Submerged Floating Tunnel

Submerged floating tunnel (SFT) is a new structural solution for waterway crossings compared to the classical solutions such as cable supported bridge, immersed tunnel or underground tunnel. An SFT is subjected to extreme waves, currents, earthquakes and other environmental loadings. The effect of key structural and waves parameters are important from the design perspective for an SFT. This study, the dynamic responses of SFT are evaluated using truss and catenary cables to check the effect of cable stiffness. The second part of this study deals with the effect of wave height and wave period on the dynamic responses of SFT. 3D truss and 3D catenary cables give very similar dynamic responses under waves and vertical ground motions. The wave height and wave period mainly control the dynamic behavior of SFT.

Effect of Cable Stiffness and Waves Parameters on the Dynamic Responses of Submerged Floating Tunnel

Submerged floating tunnel (SFT) is a new structural solution for waterway crossings compared to the classical solutions such as cable supported bridge, immersed tunnel or underground tunnel. An SFT is subjected to extreme waves, currents, earthquakes and other environmental loadings. The effect of key structural and waves parameters are important from the design perspective for an SFT. This study, the dynamic responses of SFT are evaluated using truss and catenary cables to check the effect of cable stiffness. The second part of this study deals with the effect of wave height and wave period on the dynamic responses of SFT. 3D truss and 3D catenary cables give very similar dynamic responses under waves and vertical ground motions. The wave height and wave period mainly control the dynamic behavior of SFT.

On the slack phenomena and snap force in tethers of submerged floating tunnels under wave conditions

Under severe sea wave conditions, the mooring tethers of submerged floating tunnel (SFT) might go slack. It may cause the structure failure during the service lifetime of SFT. The paper investigated SFT dynamics when going through tether slacking and the related snap force under wave conditions. Besides the nonlinearity of fluid drag and of structural geometry for a relative large structure displacement, the problem is characterized by the nonlinearity due to the discontinuity in axial stiffness of the tethers. To include these nonlinearities, the method of Lagrange energy is used to build the governing equations of SFT motion, and a bilinear oscillator is introduced to simulate the mooring tether operating in an alternating slack-taut state. The sensitivities of the occurrence of tether slacking to wave height and wave period are investigated. Results show that at a large wave height SFT tether will go slack and snap force occurs. SFT responses are categorized into three types of state according to the dynamic response characteristics of tether tension. Effects of two fundamental structure parameters, buoyancy-weight ratio (BWR) and inclined mooring angle (IMA), on the dynamic responses of SFT are analyzed. A slack-taut map of SFT tethers is built. It intuitively describes the occurrences of slack and snap force with different combinations of the two parameters. An analytical approach for slack prediction by deriving the slack criterion is provided to reveal the mechanism of the presented slack-taut map. By present research, the authors tried to make their effort to provide an alternative philosophy for SFT structural design on concerning preventing the occurrence of tether slacking and snap force.