Analysis On Mechanical Behavior Of Tube Joints Of Submerged Floating Tunnel

Submerged Floating Tunnel (SFT) is a new type of traffic structure which can traverse waterways, and nowadays there is no case history in the world. Under some special conditions, SFT has much more technical and economical advantages than other traffic structure means, so it has future expansive prospects.Tube joints is an important component in SFT structural system, this thesis mainly proceed the mechanial behavior analysis and research on tube joints of SFT, combining with the ministry of education HuoYing Dong fund and the National Natural Science Foundation of China.Firstly, the mechanical model is established according to that the steady flow's effect is simplified as the static load and the long-period wave is approximated to harmonic load through analysing the fluid load. The static and dynamic analysis on the SFT' structural system are dealed with by using the Bernoulli-Euler beam to simulate the tube and the elastic ream to simulate the tube joints.The finite element method (FEM) and transfer matrix method are used to analyze the structure to research the influence of bending stiffness of tube joints on the SFT's static response and dynamic characteristics and harmonic response. The FEM is achieved through the software ANSYS while the transfer matrix method is achieved through editing Visual Basic program.The thesis finally focuses on the analysis on mechanical characteristic of tube joints, in which the analytic formula is deduced and the numerical method is achieved to discuss the factors and laws on the mechanical characteristic of the tube joints.Through the previous analysis and research, the main conclusions are drawn and sumed up as follows:(1) The influence of bending stiffness of tube joints on the SFT's static response is mainly externalized at offshore site with the steady flow's effect. The stiff joint means bigger internal force while the flexible joint follows bigger displacement and distortion.(2) The natural vibration frequency of SFT's tube can enlarge when the bending stiffness of tube joints rise, and the amplitude of the higher frequency is more obvious than that of low order frequency.(3) The long-period wave does not arouse the resonance vibration on the SFT's tube. The influence of bending stiffness of tube joints on the amplitude value of harmonic response of SFT's structural system is conform to that of static response.(4) The main factors which influence the mechanical characteristics of tube joints include physical dimension and the materical characteristics of joint parts and the initial condition of tube' water pressure.