Reliability Analysis On Vortex-Induced Vibration Of Single Span Of Submerged Floating Tunnel Subjected To Steady Current

The submerged floating tunnel (SFT) is a new traffic structure across water area. It has unparalleled technical and economic advantages compared with other types of traffic structure:such as has little effect on the environment surrounding the structures; more adaptable for water depth, seabed topography and geological conditions; reduce the length and the slope of approach linked to land transportation; reduce construction costs and polluttion, and so on. With the rapid development of technology related to immersed tube tunnels, offshore platforms and other structures, submerged floating tunnel construction has had a certain foundation. As a innovative technology, submerged floating tunnel has become a very attractive choice competing against conventional transportation technologies. This paper made some preliminary theoretical study on vortex-induced vibration and reliability of single span of submerged floating tunnel subjected to steady current in the vertical direction, the research work carried out are:1. The dissertation explained the causes, types and statistics law of ocean current, giving emphasis to coputational method of current loads on the SFT, mechanism of vortex-induced vibration and computational model of vortex lift force.2. The dissertation simplified single-span SFT as an Euler-Bernounlli beam simply supported at both ends, and derived partial differential equations of bending vibration when SFT is subjected to vortex lift force with a single vortex shedding frequency. Then transformed partial differential equations to ordinary differential equations by using separating variables method, and get the natural frequency of SFT and analytical solution of dynamic response (displacement, bending moment, shear force) under each mode. With calculating, the dissertation found first-order response play a leading role, and the dynamic study of SFT can only carried out when the first-order dynamic response.3. Considering the randomness of computational parameters, the dissertation assumed a normal distribution of lift force coefficient and velocity, then get Gumbel probability distribution of amplitude of vortex-induced lift force and exponential probability distribution of amplitude of mid-span moment and mid-span displacement in unit times (60s) by using Monte-Calor method.4. The dissertation discussed the establishment method of structural limit state expression, and calculated the corresponding reliability.