The Optimization Of Frame Without Horizontal Brace In Middle Cargo Tank Of VLCC

VLCC is the shortened form of Very Large Crude Carrier whose deadweight over 300 thousand tonnes.And the capacity is equal to 2 million barrels of crude oil.VLCC,ULCS(Ultra Large Container ship)and LNG(Liquefied Natural Gas)is the top standard of ship construction.In recent years,design institute and shipyard do a lot in research of VLCC optimization to win the competition in the bad market environment.The optimization is focus on environmental protection,energy conservation and construction technology.Now,frame without horizontal brace of VLCC is presented by Japan and Korea.This design is carried out with a idea that removing horizontal brace of frame except the stern frame and swash bulkhead.This design is advanced in construction technology,human cost and construction cycle.In this research,a optimization of frame without horizontal brace in middle cargo tan of VLCC is carried out.Main works are as follow:(1)Analyze the transmitting way of force,especially for the four steps of force transmission and the model of force.And then the optimization theory is carried out.(2)Project designs of frame without horizontal brace are carried out which by adding the height of vertical web,the height of beam under upper deck and the size of connection bracket.And these methods can improve the mechanical property of frame.(3)Eight project designs are carried out according to the mechanical property and every design is calculated according to the regulation.And then,comparison is done to find out the best design.(4)Finite element calculation is carried out to certify the yield strength and buckling strength.And the gridding of small structure is minishedto improve the structure.VLCC of frame without horizontal brace is advanced in cost of equipment,human cost and dock service cycle.This research is necessary and can provide technical support for design and construction of VLCC.