A Study On The Wave Load Characteristics Of Damaged And Flooded Ships Considering Actual Sea States

Nowadays,the trend of economic globalization is becoming more and more obvious,the demand and scale of international trade are increasing quickly,and the shipping industry has been developing rapidly.At the same time,because of various reasons such as reef,collision,grounding and improper human operation,the accident of ship structure damage is also gradually increasing.The damaged ship was listed to varying degrees as a result of flooding on one side.The residual bearing capacity,survivability and stability of damaged ships are greatly reduced compared with intact ships.If the damage and residual strength of the ship cannot be evaluated,proper rescue measures cannot possibly be taken,and the hull is likely to continue to collapse,resulting in marine accidents.Therefore,it is very important to accurately predict the motion and load response of damaged ships in waves when waiting for rescue at sea.The main research work of this thesis is as follows:(1)Firstly,the load prediction method of damaged ship is studied,and a simplified method to determine the design load-equivalent design sea state method is introduced.Based on this method,the frequency domain analysis of the target ship is carried out.After the longterm statistical analysis of the load is carried out according to the specified wave scatter diagram,the short-term sea states with the largest contribution of the long-term results are selected as the design sea state.(2)Then,a damaged hull is used as the research object to calculate the center of gravity of the damaged flooded tank and the mass of water flooded into the tank,and the influence of these factors on the floating state is considered in the numerical calculation using a fully nonlinear potential flow based method.Using irregular waves to simulate the selected shortterm design sea states,the nonlinear time domain curve of wave load on damaged ships is calculated,and the load characteristics of damaged ships are studied.(3)The load amplitude of the entire time history curve is extracted,and the histogram obtained after statistics is fitted with the Weibull distribution.The design load is obtained by taking the corresponding probability of exceedance,and compared with the linear long-term statistics,finally we can find when considering the combined action of multiple loads,the critical load condition of the damaged ship occur in the oblique wave.