Vertical Plane Analysis Theory Research For The Moored Submerged Floating Tunnel And Structural Design Analysis

Submerged Floating Tunnel(SFT)will be a new type of underwater traffic structure and its environmental conditions are different from the current traffic structure like bridges and tunnels.The research on the SFT needs to establish accurate analysis model,but most of the current theoretical research was based on the beam on elastic foundation(BOEF)model or just analysis the single-span SFT.In this paper,on the basis of current research,the plane theoretical analysis models is further improved,which is called the SFT of multi-pipe mechanical model with discrete elastic supports.The vibration response of the SFT under different loads is analyzed by theoretical method and finite element method.Finally,a preliminary scheme of SFT at Dongwuyang fiord is designed and its structure is analyzed.The main research contents are as follows:(1)According to the elastic assumed conditions of anchored SFT,the SFT of multi-pipe mechanical model with discrete elastic supports is established based on Euler-Bernoulli beam theory.The model can be applied to any elastic boundary constraint,any elastic support stiffness of anchor cable and any elastic flexural stiffness of tunnel joint in the SFT.The modal function of the analysis model is solved by transfer matrix method,and the dynamic response of the SFT under moving load is analyzed by MATLAB calculation program based on the modal superposition method and the fourth order Runge-Kutta method.The influence of boundary conditions,cable stiffness,joint stiffness and other parameters on the structural response is discussed.(2)The dynamic characteristics and vibration responses of the continuous beam on elastic foundation(BOEF)model and the beam on elastic supports(BOES)model under the moving loads are analyzed and compared.The differences of the two models under three different boundary conditions,including the simply supported condition,the fixed condition and the elastic supported condition at two ends,are studied respectively.The analysis results show that the displacement and bending moment of the two models are obviously different even when the first-order frequency difference between the two models is small(1.84%).(3)The finite element numerical model is established based on the universal finite element program ABAQUS.The dynamic response of the structure is analyzed by simulating the vehicle load and marine environment of SFT based on the self-programmed *DLOAD subroutine and AQUA module respectively,and the results were compared with the theoretical analysis,so as to verify the accuracy of the multi-pipe mechanical model with discrete elastic supports.The structural response of SFT under the wave,current and vehicle is analyzed and the influence of boundary conditions on wave load effect is investigated.(4)Based on the hydrogeological data of the Dongwuyang fiord and the current research on the SFT,a preliminary design scheme of suspension tunnel in this sea area is put forward,including overall layout design,tunnel section design,anchor cable layout design,tunnel joints and revetment section design,etc.The environmental design load of Dongwuyang fiord is summarized and the internal force and deformation of the SFT under the dead load,environmental load,traffic load and the most unfavorable load combination are investigated.According to the analysis results,the preliminary design scheme is optimized in order to improve the safety redundancy of the structure.