Performance And Design Calculation Formula Of Castellated Beams Experiencing Distortional Buckling Behavior Considering Residual Stress

With the rapid development of steel structures,castellated beams have entered the field of engineering practice as a form of component that has advantages such as light weight,high strength,economic benefits and aesthetics.As being similar to solid web beams,castellated beams mainly occur buckling failures when subjected to loads.The principal buckling modes include global torsional buckling,local web buckling,and cross-section distortion buckling,a kind of buckling mode between the first two.In recent years,domestic and foreign researchers have paid more attention to the research on distortion buckling.Domestic research on distortion buckling of castellated beams is still in its preliminary stage.The relevant content of bearing capacity calculation and design method is relatively scarce,so this paper does the following works:(1)The manufacturing process of castellated beams is complicated,including multiple cutting and welding processes,so the residual stress distribution of the components is greatly different from that of solid web beams.In order to obtain the accurate actual stress state of the castellated beam,this paper carried out a residual stress test on each step of the castellated beam processing steps,analyzed the generation process of the residual stress,and proposed a residual stress distribution model of the castellated beam.(2)Load-carrying capacity test of 6 castellated beams with moderate slenderness ratio under the constraint of mid-span upper flange.By observing the web deformation of the half-span cross-section and the quarter-span cross-section,it was confirmed that the component had deformed and buckled.(3)Based on experimental components,a numerical analysis model was established and verified by ANSYS software.After that,the parameters were analyzed including the slenderness ratio of the member,the geometric characteristics of the cross section,the yield strength of the steel,the stiffness of the support constraint,and the initial defects.The influence of each parameter on the bearing capacity and buckling mode of the castellated beam member was considered.The degree of residual stress influence on the stable bearing capacity in each condition of the castellated beam was compared.(4)Combined with the results of numerical simulation of the castellated beams distortional buckling mechanical properties model,the calculation formulas for the stability coefficients of beam members in the current GB50017-2017 "Steel Structure Design Standards" and the existing theoretical calculation formulas for the overall bending elasticity of castellated beams are analyzed and compared The revised formula for the stability coefficient is proposed,which provides a reasonable and reliable reference for the future application practice and scientific research of castellated beams members.