The Calculation And Analysis Of Mooring System

Sea contains giant oil and gas resources, facing the land resources is deficient day after day, the exploitation and usage of sea resources are receiving more and more attention. With the development of the deep ocean exploitation, submerged oil drilling platform and the floating production and storage offloading system (FPSO) are already becomes the main tool of the ocean exploitation. In order to guarantee the platform and other floating things working under the majority sea condition, the design of the mooring system of sea structure is especially important. The traditional method of mooring system design is the accurate static method which uses the safety coefficient to determine the anchor chain's working force. This method is fit in engineering, but it will bring in material the waste. So, for mooring system design, author has done several works as follow.(1) Analyzed and compared the component and its the characteristic of mooring chains.(2)Static analysis of mooring line. Author separately used catenary method and the lumped-mass method to establish the static equation of mooring line, produced discrete model and the iterated computation step. Taking a mooring chain as the example author calculated it's shape and force, and has carried on comparative analysis to two method's results.(3) Dynamic analysis of mooring line by lumped-mass method. Because the anchor chain works in under water circumstance, there are many affects to influence the dynamic response of the mooring chain. it decides the complexity of mooring chain's dynamic performance. The dynamic equation of motion chain is a group of high non-linear differential equations, the solution is difficulty. Author uses the lumped-mass method to carry on the theoretical analysis to the mooring chain's dynamic performance, and calculated by computer program made by author according to the theoretical analysis. The computation considered influence of each fluid force such as normal and tangential resistance, the added mass and the hydrostatic pressure. Adopted the Houbolt difference format to solve in time domain, obtained the force of the mooring line changing with time at given movement. Analyzed the influence of different frequency range to the force change tendency, obtained the biggest dynamic force change along with the frequency curve.(4) Produced the estimate step and formula of the strongest force in low frequency, obtained calculation result of upper-extreme point force of mooring chain change along with the frequency curve in the low frequency by this method, made the contrast with the lumped-mass computed result.