The Analysis And Research Of Multiple Crack Interference Of The Jacket Platform

Jacket platform is the most widely used kind of fixed platform and suffers wind,wave and other loads all the time.There is stress concentration at the jacket nodes,so that crack defects often occur,which have serious impacts on the life of platform.Methods of analysis of stress intensity factor are summarized.After comparing,finally the node displacement method and element stress method of finite element method are chosen.First,influence of wall thickness and length of crack on stress intensity factor of T tube node poles is analyzed.Then two different-face and circumference penetrated crack are analyzed and the interference law is summarized.The influence of the existence of chord member crack on pole crack with different length or different load or different crack distance is also discussed.By comparing the stress intensity factor with or without chord member interference,the stress intensity factor ratio is yielded.Single crack analysis shows that the greater the wall thickness is,the smaller the stress intensity factor is.When the wall thickness is greater than 20 mm,stress intensity factor almost stays constant.When the wall thickness is smaller than 5mm,stress intensity factor changes distinctly.The analysis of different-face crack shows that the existence of pole crack inhibits the extension of pole crack.As the crack length increases,the inhibition decreases.As the wall thickness increases,the inhibition increases.The crack distance change has nearly no impact on inhibition.Stress intensity factor will increase gradually as wall thickness increases with the interference effect.The maximum stress of crack tip will occur at the crack tip of the chord member.Besides the stress intensity factor is higher.