The Extension And Application Study Of Constrained Finite Strip Method Of Thin-walled Members

The physical properties of thin-walled member is quite different from those of common steel member,and the instability problem is even complicated and changeable.The basic buckling modes of thin-walled member can be categorized as global mode,local mode,and distortional mode.Sometimes,shear mode and transverse extension mode cannot be neglected either.The buckling mechanism of different buckling modes of thin-walled members is significantly different,and the influence and effects of defects,post-buckling and material elastic-plastic factors on different buckling modes are also different.Therefore,it is particularly necessary to define the basic buckling modes such as global,local and distorted buckling modes.At the present,the mainstream method for thin-walled members are generalized beam theory,constrained finite strip and constrained finite element.Among them,constrained finite strip method is used widely at home and abroad,but there are still some problems,such as round corner and closed section,which can not be solved well in the modal analysis of member buckling by the current constrained finite strip method.Under the frame of traditional theory,such as GBT and c FSM,those problems are solved by changing the derivation process.The current c FSM has been expanded in the paper to solve the problems,and the main research contents are as follows:(1)Derivation process of traditional c FSM is reconsidered.Without changing the definitions of basic modes and assumptions,the derivation process has changed based on the analysis of plane equivalent frame,and the mode algorithm has established.The comparison between the method in the paper and traditional method is carried out.(2)To solve the inaccurate of round corner by traditional c FSM,the paper explores the relationship between the parts of round corner and those of the whole cross section,and considers the reasonability of round corner from the point of degree of freedom,which eliminates the DOFs of parts of round corner.The round corner parts are treated specially,and the conclusions are relatively good.(3)The cuurent c FSM cannot be used to solve the buckling of closed section.The paper has demonstrated the compatibility between the Bredt shear flow and the definition of GBT,and the fluence of Bredt shear flow in the Global and Distortional modes have been considered.The buckling of closed section of thin-walled members are carried out in the paper.