| Submerged floating tunnel is a new type of traffic structure,which has strong adaptability to the terrain,water depth,weather and other environments,and has large crossing capacity and relatively low construction cost.Therefore,it has strong competitiveness in the construction of cross-strait channels in the future.Submerged floating tunnel is usually in a complex wave and current environment.When the water flows through the tube or the section of the anchor cable,the phenomenon of ’vortex-induced vibration’(VIV)will occur.At present,domestic and international research on vortex-induced vibration of submerged floating tunnel tube and anchor cable is carried out in the construction state,and research on vortex-induced vibration response of submerged floating tunnel during construction stage is insufficient.In this paper,considering the length and dynamic characteristics of submerged floating tunnel with the construction,a simplified calculation model is established for the structural characteristics of the construction stage,the eddy excitation response and vibration suppression measures of submerged floating tunnel are studied,and the dynamic response of the tube segment during the sinking stage is calculated.The main contents are as follows:(1)According to the construction method of submerged floating tunnel,the SFT system during the construction stage is simplified as an elastically supported cantilever beam.Based on the modified Timoshenko beam and Euler beam theories,the dynamic characteristic equations are derived using the transfer matrix method,and the characteristic equations are solved using numerical examples to obtain the natural frequencies and vibration modes of each mode of the tube during the construction stage.The results obtained are compared with the elastic foundation beam theory and ABAQUS numerical simulation results,and the applicability of the simplified model is compared.The effects of the length of the tube,relative stiffness and floating weight ratio on the dynamic characteristics of submerged floating tunnel are analyzed.(2)The orthogonality conditions for the vibration modes of the Timoshenko beam with cantilever boundary correction are derived,and the vibration modes of each stage of the suspension tunnel during construction are calculated using the transfer matrix method.Based on the modified Timoshenko beam theory,the vibration equation of the tube is established,and the vibration mode superposition method is used to solve the dynamic response of the tube during the construction stage of the submerged floating tunnel under the action of water flow.At the same time,numerical simulation was conducted in ABAQUS with a numerical example to verify the correctness of the theoretical model and calculation method of the mode superposition method.Finally,the effects of tube length,anchor stiffness,and flow velocity on the dynamic response of the tube are discussed.(3)Taking the additional anchor cable as the vibration reduction measure of the tube in the construction stage,the influence of the additional anchor cable on the dynamic characteristics,displacement and internal force of submerged floating tunnel tube is analyzed,and the influence of the additional anchor cable spacing,inclination angle and tube length on the vibration reduction effect is discussed.(4)The overall dynamic response of submerged floating tunnel segment during sinking is analyzed.The submerged floating tunnel segment is regarded as a rigid body with six degrees of freedom.Morison equation is used to calculate the wave and current loads,and the relaxation of the cable is considered.The catenary method is used to solve the mooring line tension.Based on Newton’s second law,the six-degree-of-freedom motion equation of the tube segment is established and solved.The effects of immersion depth,incident angle,wave parameters and current velocity on the dynamic response of the tube segment and cable are analyzed. |
