Wave Load Calculation And Motion Response Analysis Of Large Crane Ships

Since the beginning of the 21 st century,with the increasing efforts of various countries in the development of marine energy,large offshore lifting ships have also developed rapidly as an important offshore engineering lifting equipment.For large tonnage crane ships,one of the square coefficients is large and the ratio of the ship’s breadth B to the draught T will exceed the provisions of the conventional ship rules B/T≤2.5,L/B>5,and the other is due to the excessive lifting tonnage.And the high center of gravity,coupled with a series of uncertainties in operating sea conditions,requires relatively high stability,so as to reduce the risk of offshore operations and improve safety.Therefore,the research on the dynamic performance of large-tonnage crane ships has become the key research field of many scholars at home and abroad in recent years.In this article,the finite element model of each structure of a 3600 t large floating crane is established,and each structure is studied separately.The specific research contents are described as follows:(1)First,the three-dimensional model of the upper boom structure of the crane was established by using the beam element BEAM 188,the lumped mass element MASS 21 and the rod element LINK 10,and the boom structure was analyzed by the analysis software ANSYS 16.0.Modal analysis is carried out to obtain the natural frequency and mode shape of the boom structure under the first ten modes,so as to understand the dynamic stiffness and the influence of various frequency loads on the boom when it is in the working state.(2)Three-dimensional modeling of the hull is carried out according to the given hull parameters,and the displacement is estimated.Secondly,the direct calculation method and the standard calculation method are used to calculate the lateral and longitudinal impact forces on the crane ship respectively,and the results are calculated.For comparison,the above calculation results and displacement are verified by the hydrodynamic analysis software Workbench/AQWA,which provides a theoretical basis for the structural design and stability calculation of the crane ship.(3)Based on the potential flow theory and radiation/diffraction theory of waves,the AQWA-LINE hydrodynamic analysis module is used to calculate the hydrodynamic coefficient of the main hull with six degrees of freedom under different wave frequencies and wave angles,and the motion amplitude in the free-floating state Response operator RAO,wave excitation force and wave drift force.(4)The influence of different working conditions(6 water depths,3 speeds and JONSWAP wave spectrum)on the dynamic stability of the crane ship in waves was studied,and the results provided reliable forecast for the wave load when the crane ship was operating.theoretical basis.