Research On The Characteristics Of Wave Loads For Very Large Floating Structure

Very Large Floating Structure(VLFS) is a kind of large-scale offshore integrated support bases. In recent years,it has become a new research hotspot for offshore platforms in the world.Accurate and reasonable environment loads prediction,especially the design wave load evaluation, is very important to ensure the safety of the VLFSin operation.Therefore,it is very significant to investigateits characteristics of dynamic responsesin waves and the method in determining design wave load for the engineering application of the VLFS and the development of ocean engineering.A VLFS with transverse pontoons is selected as the research object in the paper. Based on the three dimensional potential theory in frequency domain, the hydrodynamic performance of single module floating structure and multiple-module floating structure is analyzed with the software of ANSYS/AQWA, and then the design wave loadsarededuced. The main contents and results are as follows:(1)The hydrodynamic responses of the single module of VLFS are predicted and analyzed. The hydrodynamic responses of the single module arecalculated in frequency domain with the hydrodynamic software—AQWA-Line. The transfer functions of motions, vertical shear forcesand bending momentsfortypical cross sections of VLFS indifferent wave directionsare predicted. The basic rule of the motion and the wave load responsesforthe single module of VLFS is obtained.(2)With regard to the single module of VLFS, the short-termand the long-term response of the vertical bending moment amidship,in extreme sea statesand the environment of wave statistical data of South China Sea respectively, are analysis. The design wave load and design wave parameters are given after analysis.(3)The hydrodynamic interference effect amongmodules in multi-module VLFS is analyzed, and the motiontransfer functions ofthe multi-module and the single-module structures are compared. For the extreme sea states of South China Sea, the transfer functions of longitudinal force and vertical shear force,and the extreme loads on the connectorsbetween modules are analyzed. The direct calculation method of the VLFS with the vertical bending moment as a main design parameter is proposed.Some conclusions such as the characteristics of motion and the load transfer functions of VLFS, the design wave parameters and the direct calculation method are obtained, and it provides a valuable reference to the research and development of VLFS.