Fatigue Assessment Method For Hull Structure Based On Strength Monitoring System

The ship is subjected to random wave loads throughout the operation period.Structural strength and fatigue problems could be caused by the random alternating load.In this paper,the extended application of the hull strength monitoring system was studied,and the feasibility of structural damage assessment based on the data from hull strength monitoring system was verified through simulation method.Taking a container ship as the research object,the fatigue damage of the container was calculated based on the hull strength monitoring system.Specific research contents are as follows:(1)According to a kind of hull strength monitoring system based on long base strain gauge,the composition of the system,including the function framework,hardware and software,was summarized.In view of the overall load monitoring,the internal bending and torsion moment decomposition algorithm of the system,and several monitoring schemes based on the system were analyzed..(2)In order to obtain the stress transfer function of the node under the effect of external moment,the whole model and cabin model of the container ship were established by using ANSYS software,and the wave load of the hull was calculated by AQWA software.According to the thin-walled structure mechanics,the calculation method of the torsional centre in the section was studied.(3)The software ANSYS combined with AQWA was used for calculation of regular wave in frequency domain when monitoring the section by a single long base strain gauge.The stress response transfer function and fatigue damage were calculated for the selected points of monitoring section based on the frequency domain results of total longitudinal bending moment,and the calculation results were analyzed.(4)The software ANSYS combined with AQWA was used for calculation of regular wave in frequency domain in the case of decomposing bending moment and torsion by double cross-sections monitoring.The stress response transfer function and fatigue damage were calculated for the selected points of monitoring section based on the frequency domain results of hull bending moment and torsion,and the calculation results were analyzed.