Study On The Ultimate Strength Of Very Large Floating Structure Under Complex Loads

The very large floating structures(VLFS)are characterized by large scale,diverse configurations and complex structures.There are many structural failure modes that may occur under the long-term effects of wind,wave and current environment and storm weather conditions.Therefore,the prediction and evaluation of the strucaural safety of the VLFS is one of the key technologies for its design and manufacture.In this paper,the study is supported by the National Basic Research Program of ministry of science and technology of China,base on the main research object with connector surrounding structure and strut structure of the VLFS,the theoretical caluculation method and the nonlinear finite element method and model test technology for ultimate strength of structure under complex loads are systematically studied.The main research contents include:(1)According to the configuration and structure characteristics of the multi-module VLFS,the characteristics of the total wave load in the complex ocean environment are studied,and the load characteristics of the connector and strut structure are determined.(2)Based on the progressive failure method and the torsion theory of thin-walled beam,the theoretical method for ultimate strength of the VLFS under complex loads is studied.A method for evaluating the ultimate strength of the structure under the combined pressure and bending moment or torsion moment is proposed.(3)Taking the simple box girder and strut structure as the research object,the numerical simulation method of the ultimate strength of the structure under the complex loads is carried out,the factors such as grid scale,loading rate,material model,initial defects and loading sequence are included and a reasonable and feasible numerical simulation method for ultimate strength of structures under complex loads is established.(4)Based on the theory of mixed scale ratio and similarity condition of failure mode,the design technology of the ultimate strength model of structure under complex loads is carried out.Through theoretical analysis and numerical simulation,the model loading mode and control process under complex loads are proposed,and the overall failure mode of the structure is explored and the corresponding measurement scheme is formed.The results of the model test of the ultimate bearing capacity of the surrounding structure connector and strut structure under complex loads show that the failure process,failure mode and ultimate strength of the key structure of VLFS have new features.The theoretical calculation,numerical simulation and model test results are relatively consistent,and the proposed structure ultimate strength forecasting method and model test technology have practical engineering value.(5)Using the method of calculating the ultimate strength of VLFS under complex loads,the regularity of the ultimate strength of the surrounding structure of the connector base and strut structure was studied.The expression of the compressive ultimate bearing capacity of the surrounding structure of the connector base under bending and the strut structure under torsion moment is given by the curve fitting method.Some suggestions are given for the ultimate strength design of the related structures.Through the theoretical analysis,numerical simulation and model test of the VLFS,this paper systematically analyzes the failure mechanism and ultimate bearing capacity of the surrounding structure of connector base and strut structure of the VLFS under complex loads,and the ultimate strength model test technology for structures under complex loads is established.The theoretical method and numerical simulation method for the ultimate strength of VLFS under complex loads has been put forward.The research results are of great significance to the design of VLFS and checking of safety and reliability.