Study On Slamming Load Of Connecting Bridge Of Large Trimaran

As one of the high-performance ships.,the trimaran has attracted extensive attention and has a broad development prospect because of the better stability,seakeeping and other advantages.When sailing in bad sea conditions,the relative motion between the ship and waves will cause severe slamming,for example,the bow slamming,the connecting bridge slamming and so on.At the moment of slamming,a huge impact force will occur and then the high-frequency vibration will happen,which is very unfavorable to the hull structure.The structure of the connecting bridge is relatively weak and the line is straight.With the development of trimaran to large-scale,the slamming problem of the connecting bridge becomes more serious,therefore it must be considered in the design.At present,only the British Bureau of shipping has published the trimaran specification according to the experiment data of Poseidon,but there is little mention of the slamming of the connecting bridge,and the actual navigation state of the trimaran cannot be taken into account.Therefore,it is necessary to deeply study the slamming law of trimaran connecting bridge and establish a calculation method of slamming load of trimaran connecting bridge.The main contents of this paper are as follows:(1)The load and motion data measured by the hydroelastic experiment are compared with the calculation results of the three-dimensional potential flow theory,to verify the applicability of the calculation method to the trimaran.On this basis,the influence of different layouts of the piece hull on the trimaran motion is studied.(2)The falling experiment is carried out based on a two-dimensional model of the cross section of a trimaran,the experiment conditions of different heights and angles are set,the slamming pressure sensors and displacement sensor arranged on the connecting bridge are used to analyze the dispersion of the measured value of slamming pressure and its relationship with speed and angle,and obtain the distribution law of slamming pressure force(slamming pressure coefficient)along the connecting bridge.(3)The falling-body slamming of the trimaran is simulated and calculated based on CFD method software.The key information such as water entry speed,slamming peak value at each measure position,slamming pressure time history and liquid level change at each typical time are compared to verify the effectiveness of numerical simulation,the slamming on the location where measuring points cannot be arranged is calculated and studied.Combined with simulation and experiment,the law of slamming pressure is given.(4)The equivalent design wave method is used to check the strength of the trimaran without considering the slamming load of connecting bridge.Several sections of connecting bridges along the X direction are selected to analyze the conditions of the connecting bridge slamming occurring,and the slamming design load calculation method of the connecting bridge of trimaran is proposed.The calculation results are compared with the calculation results of the specification.The response between considering the slamming of the connecting bridge and not considering are compared to study the influence of slamming load of connecting bridge on hull beam load.(5)Based on the strength analysis results without considering the slamming of the connecting bridge,the connection position between the main hull and the connecting bridge is optimized to reduce the stress concentration;At the same time,in order to improve the slamming-resistance ability of the connecting bridge,the slamming-resistance ability of different skeleton forms and different grid length width ratio are calculated and analyzed.Then,taking the force under the most dangerous working condition as the constraint condition,and the lightest structure as the objective function,the genetic algorithm is applied to further optimize the connecting bridge plate frame structure in order to achieve the purpose of the lightweight structure.