The Overall And Local Stability Analysis Of Hybrid Castellated Beams

The hybrid castellated beams is that according to the stress state and failure modes,applying the combination with different strength grades of steel.The material properties can be fully utilized,simultaneously the structural weight and project cost will be economized by adopting the two types of steel legitimately.This paper mainly makes analysis of overall stability and local stability of hybrid castellated beams.First,for the overall stability problem.Theory of hybrid castellated beams was deduced formula for bending torsional buckling.second, researching the mechanical behavior of elastic-plastic bending and deformation. then calculating the ultimate bearing capacity of hybrid castellated beams and general girders with I-section by the finite element program ANSYS,Studying the differences in the aspects of ultimate bearing capacity and economic benefits.The results show that the rational application of hybrid castellated beams will optimize the collocation of steel and reduce the project cost while meet the requirements of bearing capacity.For the local stability problem,Web of castellated beams is treated as simply supported plate with opening.The stability of plate with openings is studied under pure bending and uniform shear by using ANSYS and the characteristics of buckling are described.When plate length、height、thickness and the number of openings keep constant,a series of finite element analyses are carried out by using ANSYS to achieve the variation relationship of resistance capacity with diameter-depth ratio and space-depth ratio of web.The buckling coefficient of web with openings is obtained and an expression of it is brought forward with linear fitting method to correlate with diameter-depth ratio andspace-depth ratio of web.The formula for buckling of thin plate is adopted by substituting the original buckling coefficient.At last,the stability of web is analyzed under lateral loads.A simplified method is presented to check the local stability of web.