Structural Design And Analysis Of Submerged Floating Tunnel And Its Health Monitoring

Nowadays the increasingly busy traffic makes the connection between different region more and more important, and the long-span structures crossing large water area simultaneously become necessary for the world development, correspondingly, how to build suitable infrastructures utilizing limited resources which meet the requirements of social development and the principles of sustainable development is the core issue to face civil engineering technologists and technicians in the 21st century. Submerged floating tunnel (SFT), suspending in water and constrained by cable, is a innovate structure wisely employing the buoyancy to bear load. SFT have many advantages, such as exerting little influence on the surrounding environment, operating in any weather and great economic competitiveness for great connection, therefore, SFT is supposed to a new way out for realizing great spanning.This paper analyzed the static and dynamic behavior of SFT on the basis of Qiandao Lake SFT proposal, and did preliminary study on design of SFT borrowing ideas from design experience and codes standards of similar engineering projects, additionally, this paper explored to establish the health monitoring system for SFT with reference to the research results of health monitoring technology in civil engineering, and in the end of the paper, the guide for operation and monitoring of SFT was to put forward. The specific work carried out in the paper is as follow:(1) Based to the design technology of immersed tunnel, bridge and tunnel engineering, combining the current relevant design codes of civil and offshore engineering, the key technology of submerged floating tunnel design was presented, including load and combination of load, four ultimate states, tube design, layout form of cables, foundation design, ancilary system design, structural analysis method and so on.(2) Morison equation was applied to calculate the horizontal and vertical wave force acting on submerged floating tunnel by step by step integration from bottom to top of tube. The influence of the diameter of tube, the clearance between water surface and tube top, wave period factors etc. on calculation results was explored. In final, the wave forces were respectively obtained by the second-order nonlinear Stokes wave theory and linear wave theory. The variation of these results with wave period factors was studied, finally, spectral analysis method to calculate wave load of SFT was introduced.(3) Based on the structural characteristics and condition of circumstance Qiandao Lake SFT, its static and dynamic behavior under different action of combination of loads, which including the stress of each layer material of tube, the displacement, the cable tension and dynamic response under action of wave-current, were investigated using ANSYS software, finally, the security and rationality of the design proposal was evaluated.(4) The differential equation of vortex-induced nonlinear vibration under the action of current was deduced according to the mechanism of cable vibration in the water, and subsequently Runge-Kutta method was utilized to solve the equation after processed by Galerkin method. The dynamic response of cable was analyzed background of Qiandao Lake SFT, and the relationship between cable tension and vibration frequency was derived to realize the application of frequency method for monitoring the cable tension in health monitoring stage.(5) Refer to the existing research of health monitoring in civil engineering and background of Qiandao Lake SFT, the conceptual design of health monitoring system of SFT was carried out. At the end of the paper, the guide for operation and monitoring of SFT was further put forward.