Study On The Lifting Forces Computation And Simulation In The Process Of Wreck Salvage With Double Barges

With the increase of sunken ships’ tonnage in salvage,the method of raising large-tonnage sunken ships entirely with double barges using hydraulic synchronous lifting system has been applied more and more widely.It is inevitable that the floating process in salvage will be affected by waves and this effect will lead to six degree of freedom motion of barges,and it can also make sunken ship produce corresponding movement through wire ropes.Hundreds of tonnes’ lifting forces will change the lengths of the wire ropes,and the relative motion of barges and sunken ship will result in a very complicated change of lifting forces.The main objective of this paper is to study the process of salvage with double barges,and to analyze the changes of lifting forces and the motion of the sunken ship under the wave conditions.The whole salvage process was analyzed by dividing the salvage process into three stages:uprighting,lifting and coming out.The static analysis of each stage and the wave influence were carried out.GHS software was then used to simulate the three stages.The general changing rules of grounding forces,lifting forces,maximum longitudinal shear and maximum longitudinal bending moment have been obtained.Based on three-dimensional potential flow theory,the motion equations of ships in regular wave were introduced.And combined with the method of solving ship motion response in irregular waves,the time domain motion response calculation of barges in mooring state was carried out.Motion response laws of barges under the conditions of different wave incident angles and significant wave heights were analyzed.By establishing a dynamic model of the salvage process with double barges,the influence of adsorption force acting on the lifting forces has been analyzed.According to the results of the calculation response of barges,the dynamic simulation of salvage process under the action of wave was carried out.The change of the sunken ship’s motion and the lifting forces of wire ropes were analyzed under the conditions that the significant wave height was 2m,the wave incident angle was 90 degrees and 45 degrees respectively,it also provides a basis for the controls of lifting forces and safety.