Global Strength Study Of Very Large Floating Structure And Ultimate Strength Study Of Key Component

Very Large Floating Structure is made of several single modules which are connected through connectors, the structure of single module is similar to semi-submersible platform.It can be used to develop ocean oil and gas, logistics and reef fishermen’s life. It is one of research highlights in marine engineering at present. In recent years, research of VLFS is more and more attention in domestic. Single module of the VLFS is used to research in this paper, a long term prediction of wave loads to be cauculated, then global strength of single module of VLFS under four typical loading cases to be analyzed. Ultimate strength of key components are analyzed. The static strength of connector base is cauclated. The major works and conclusions are as follows:Firstly, a long term prediction of wave loads and global strength of single module of VLFS under four typical loading cases. Based on 3d potential flow theory, adopt Sesam to cauclate the long term prediction of wave loads, determine design wave parameters under typical loading cases. Analyzing global strength of the VLFS by load transfer analysis. The results show that the stress distribution of total structure is uniform, and there are three area of high stress. That is the joint of the columns and the upper box, the joint of the column and the pontoon, bell mouth position of brace. Brace structural strength is the most weak.Secondly, the ultimate bearing capacity of brace of single module of the VLFS under the state of tension, compression, shear and bending were calculated, and the failure mode is analyzed. At the same time, the influence of boundary condition, the initial defects and the corrosion of brace on the ultimate bearing capacity are studied. The failure mode of brace of the VLFS under the state of compression shows buckling failure and plastic deformation, and the failure mode of brace under the state of tensile, shear and bending show yielding and plastic flow. Initial deflection and corrosion have mainly an effect on the ultimate bearing capacity. They should be paid more attention.Thirdly, a static strength is analyzed, and the integral stress and the integral deflection of the connector base under the loading of different directions are studied. The integral stress of the two models are little, but there are two obvious areas of high stress, that is a joint of the connector and the upper box and a joint of the column and the upper box; There is almostly no obvious change of the maximum Von mises stress of the joint of the connector and the upper box, while the maximum Von mises stress of the joint of thecolumn and the upper box seems obviously change, and the stress of model 2 could be large than that of model 1. The influence of the loading of X dictection on the joint of the connector and the upper box is large, while the influence of the loading of Z upwards dictection on the joint of the column and the upper box is large. Moreover, the stress of the structure is largest under the common loading of X, Y and Z dictection.Finally, based on Quasi-Static method of nonlinear finite element method, to calculate ultimate strength of connector base under the load of different directions, and the ultimate bearing capacity and the location of first to be damaged could be analysed. There are almost the same of the ultimate bearing capacity of the two models. The value of calculation of the ultimate bearing capacity is far away from its loading.