Study On Vehicle-SFT-Fluid Coupling Spatial Vibration Of Submerged Floating Tunnel

The submerged floating tunnel(SFT)is a novel underwater traffic hub facing the long and deep waterway crossing project,where the structure is to bear the complex external water environment and internal traffic load during the operation stage.The existing researches of the SFT are mostly focused on the engineering structure design and parameter optimization,the fluid-structure coupling simulation method under ultra-high Reynolds number,the vibration response analysis and safety evaluation of the structure under the wave-flow field and extreme actions,which are limited to the plane analysis.This paper takes the cable-moored multi-span SFT as the research object,and carries out theoretical research on its vehicle-SFT-fluid coupling spatial vibration behavior during the operation stage to propose more efficient and adaptive analysis methods.The main research results are as follows.(1)Based on the classical dynamics theory and the support characteristics of the SFT,the vehicle is simulated as the 7-DOF three-dimensional model,and the vehicle-SFT coupling spatial analysis model of the SFT under the vehicle eccentric load is established by using Hamilton principle and the spatial elastic foundation beam assumption.Besides,the nonlinear effect of the fluid environment is considered,and the numerical integration method is applied to solve the vibration differential equation.Furthermore,ABAQUS numerical simulation is used to verify the effectiveness and efficiency of the theoretical method,and the effects of motorcade layout,vehicle speed and anchoring stiffness on the vehicle-SFT coupling vibration behavior and torsional amplification effect are discussed.(2)Based on the plane vibration model of tube-cable coupling model and the 12-DOF three-dimensional vehicle model,the displacement coordination relationship between the different DOFs of each component is constructed,and the differential equation of the SFT spatial vibration of the vehicle-tube-cable coupling vibration under uniform current considering geometric nonlinearity is derived.Moreover,the overall vibration total value(OVTV)standard for evaluating the ride comfort is introduced,and the influence of coupling parameters related to the tube,the cable,the vehicle and the current on the dynamic behavior and vehicle ride comfort of the SFT is discussed.The results indicate that through reasonable structural design to avoid parametric resonance,the cables can still be considered as equivalent elastic supports during analyzing spatial vibration response of the tube.(3)In the actual engineering of the SFT,the elastic boundary constraints,the connection effect between the tube and the cable,the stiffness change in the segmental joint and other factors are converted to the equivalent stiffness,while the interaction between the structure and the fluid is simulated based on the spatial wake oscillators model coupling in the cross-flow and in-line directions.In this case,the mode superposition Galerkin hybrid method(MSGHM)is proposed to solve the vehicle-SFT-fluid coupling spatial vibration problem of the multi-span SFT with arbitrary boundary and continuous conditions.Furthermore,the convergence of the theoretical model and the reliability of the self-compiled program are verified by numerical examples.Through comparison,it was also found that the MSGHM can better balance computational accuracy and efficiency.(4)The finite difference scheme and corresponding iterative solution flow for solving the vehicle-SFT-fluid coupling spatial vibration of the SFT are derived and the calculating results are compared with the proposed MSGHM.Moreover,the effects of vortex-induced vibration characteristics,the end restraint properties,the arrangement of segmental joints and cables on the coupling vibration response of the tube and internal vehicles are discussed,so as to provide references for the project plan,the component design and the vibration optimization of the SFT.