Strength Evaluation Of Hull And Special Structure On The Light Falling-net Fishing Vessel

Coupled with the overfishing on the offshore fishery resources and seriously increasing of the environment problem,the world began to strengthen their own exclusive economic zone of management and protection of fishery resources,and actively carry out the development and utilization of fishery resources on the high seas and polar.At present,the transformation and upgrading of marine fishery from offshore to ocean has become the current trends of international marine fishery development.For this reason,preferential policies of pelagic fishing vessel construction as well as the fuel were issued in China to promote the rapid development of ocean fishing in China.With the practice and improvement of many years,the light falling-net fishing vessel has gradually become the main form of deep-sea fishing,and the structure design for this type of deep sea fishing vessel is based on the Specification for the construction of a steel marine fishing vessel 2015,where the determination of wave loads is still followed by the traditional empirical static formula.However,with the increasing of sailing speed of pelagic fishing vessel,the extension of working area,the variation of structural form and the improvement of fishing methods,the safety problem of the light falling-net fishing vessel under the actual dynamic load are paid more and more attention by the industry.Using the software COMPASS WALCS-Basic based on the three-dimensional potential flow theory that issued by CCS in 2013,this thesis focuses on the investigation on the wave loads in the dangerous condition and corresponding stress response of a light falling-net fishing vessel in service.The calculation results of normal wave bending moment and corresponding stress are compared and analyzed with those in Rules.On this basis,considering the actual existence of uncertainty of wave loads and ultimate strength,the reliability analysis on the longitudinal strength of the pelagic fishing vessel under the dangerous condition are performed,and the specific evaluation theory and procedure are given.In this thesis,the local strength of poles structures on the light falling-net fishing vessel are also calculated and analyzed using Finite Element Methods,and an evaluation method of a kind of poles structure is recomlended.The working contents and conclusions obtained in this thesis can provide a theoretical reference for structure design and further revision of construction specification of pelagic fishing vessels.