Study On Dynamic Characteristics Of Connectors Of Very Large Floating Structure In Deep Water

Currently, it is seen that the development and application of ocean resources have been progressed from the coast to the deep sea gradually. Under this background, the research of very large floating structure(its simple name is VLFS) is shown increasingly significant. This paper takes Mobile Offshore Base(simple name is MOB) as a research object, which is the typical model in VLFS of semi-submersible. The time domain analysis for the displacement of MOB modules and the constraint load of elastic connectors have been conducted under the random wave excitation, and the connectors are optimized designed aimed at the engineered example. The specific study contents and innovative conclusions show as follow:(1) Based on “Rigid Modules-flexible Connectors” calculation model, this paper obtain the simple formulas about MOB structure’s modules of hydrodynamic coefficients matrix, wave force matrix, and the constraint load matrix of elastic connectors. It can provide the foundation for solving the displacement and corner of MOB modules, constraint force of connectors in time domain.(2) The model of “three rigid modules” as an typical engineered example has been used to test and verify whether the theory formulas are right or not. This paper obtained the time-change process of hydrodynamic coefficients, wave force, the dynamic response displacement or corner and the constraint load of elastic connectors in every module in the sea state of six grade. The results are almost similar to test data in the references, which can prove the effectiveness of theory formulas in this paper.(3) This paper studied the dynamic characteristics of instance structure deeply based on above-mentioned theory formulas, such as aiming at the different stiffness of connectors, the various of sea state(the six, seven and eight grade) and wave corner(0°~90°) et al. At the same time, the distinguishes and change rules of every module are researched in this paper.(4) This paper has processed the optimal design for the stiffness and installation site of connectors under the premise of the same quantitative ones based on the example, which can gain the value range of optimal stiffness in every elastic connector. It is shown that the stress of connectors has nothing to do with its installation site.This paper researched on the connectors in VLFS which is the part of weaknesses relatively, and it obtained the practical formulas that can evaluate the dynamic characteristics of modules in the typical VLFS named MOB. The effectiveness of calculation has been proved in the engineered example. Ultimately, this paper tried to process the optimal design for connectors. The conclusions can provide some theory supports on dynamic response of modules in VLFS and the design of elastic connectors.