| The asymmetric semi-submersible lifting platform studied in this paper has super capacity of hoisting.The structure of the asymmetric semi-submersible lifting platform in this paper is very novel.Different from the traditional semi-submersible platform,it has an asymmetric lower hull structure.On the right side of the main platform,it is equipped with a heavy crane.At present,the semi-submersible platform has been widely used in the field of ocean engineering.It has the characteristics of strong wind and wave resistance,large deck area and variable load,large water depth range and various operation functions.In this paper,potential flow theory and relevant numerical calculation are adopted to conduct in-depth research on the coupled dynamic response of a new type of asymmetric semi-submersible lifting platform and mooring system.Specific related work is as follows:First,three-dimensional hydrodynamic model is established,according to the three dimensional potential flow theory of asymmetric semi-submersible lifting platform hydrodynamic performance analysis,to obtain the motion response of asymmetric semi-submersible lifting platform amplitude RAO,a first order and second order wave forces acting on the wave force,added mass,such as calculation results,the analysis of the effect of asymmetric on the platform hydrodynamic performance.Considering the influence of viscous damping on the motion response of the platform,the viscous damping was calculated through Fine/Marine simulation static water attenuation experiment,and the difference between the added damping and the non-added damping was compared.The results show that the sway,roll and sway of the platform are most affected by the asymmetric structure.The RAO value of the sway motion of 90°and-90°has a certain deviation,the peak value of 90°is1.308m/m,and the peak value of-90°is 1.302m/m.The maximum downward wave of roll 90°is 0.700°/m,and the maximum downward wave of-90°is 0.657°/m.The rocking motion mainly occurs at 60°and-60°in oblique waves,which are 0.287°/m and 0.271°/m respectively.Secondly,In this paper,the characteristics of the mooring system of asymmetric semi-submersible crane platform are studied.the mooring system is arranged,and the mooring system parameters,such as the number of mooring cables and the slack degree of mooring cable catenary,are studied.The influences of these parameters on the platform motion and mooring cable stress are calculated and analyzed.The results show that,in the analysis of mooring cable number parameters,the platform motion and mooring cable tension under 8 and 12 root mooring cables are compared,and it is found that the economy of 8 root mooring cables is better when both meet the requirements of the code.In the study of the catenary relaxation,five different kinds of mooring cables with different degree of relaxation were selected,and it was found that the moveable and economical performance of the mooring cables with the degree of relaxation was the best.Finally,the asymmetric semi-submersible lifting platform and the mooring time3 hours for time domain short-term forecast,symmetric arrangement of mooring system under different working conditions,to get through the curve when the motion response of mooring tension statistics,analysis summary different direction of sea condition of cable distribution and statistical characteristics of motion response,and the three kinds of working conditions of mooring system for the security check.The results show that when the height of the sense wave is 6m and the direction of wave inflow and discharge is-180°,the largest mooring rope of the asymmetric semi-submersible crane platform is no.8 cable.The mooring tension is 8.29×10~6N and the safety factor is 5.33.When the height of the implied wave is 2.5m and the direction of the incoming wave is-90°,the mooring rope of the asymmetric semi-submersible crane platform has the largest stress of no.4 cable,the mooring tension is 3.75×10~6N and the safety factor is 11.77.The mooring system under both conditions can meet the requirements of the specification.When the height of the sense wave is 13.5m,the direction of the incoming wave is 180°,the maximum tension of the 8#cable is 3.467×10~7N,and the safety factor is 1.28,which is less than the safety factor of 1.67 required by the specification.The mooring system in this limit sea condition can no longer meet the operation requirements,but does not exceed the breaking strength,and can still be in the survival state.Therefore,in general,the mooring system under three working conditions can basically meet the requirements. |
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