The Local Stability Research On The Steel Polybeam’s Bending Node

With the progress of times and the continuous improvement of people’s aesthetictaste, a variety of light and lively facades form coming into the view, steel polybeams athome and abroad have begun to be more widely used. However, only a few countriesinvolved the study of the steel polybeam’s stability design, there is no clearly provisionof steel polybeam’s design in our current design codes, at the same time, there is lessliterature research on the local stability of the steel polybeam’s node. It is necessary tomake a systematic study on the local stability capacity of steel polybeams.First of all, this paper introduces three types of steel structure’s instability, six kindsof popular classical approximation method to calculate stability, as well as three typesof plate and the characteristics of thin plate’s buckling. Meanwhile, according to theclassification and analysis of commonly used methods for the stability of sheet, thispaper using thin plate theory to analyze the local stability of-beam. At the same time,it derives the elastic-plastic buckling stress of compressive flange in the bendingmembers. It also summarizes the three criteria to prevent local buckling of sheetmembers often used in current national codes. Based on previous studies on bendingangle, width-thickness ratio of flange, the initial geometric imperfection and weldingresidual stress, this paper reasonably applied them to the study of local stability analysisin the steel polybeam whose bending angle has no stiffener.In this paper, it makes the local buckling load and ultimate load of the I-sectionsteel polybeams whose bending site without stiffener as the research object. This paperuses finite ABAQUS as research and analysis platform, builds35finite element models,and the initial geometric imperfection and welding residual stress were taken into account, the stability capacity of each model by uniform load and concentrated load onthe flange is analyzed. It also compared each model’s local buckling load and ultimateload with angular as0°,10°,20°,30°,40°,50°,60°and width-thickness ratio offlange as8,10,12,13and15. After performed280operations, the paper draws thecorrelation curves of stability capacity about bending angle, width-thickness ratio offlange, the initial geometric imperfection and welding residual stress and ultimatelycomes to the following conclusions:Under the action of uniformly distributed load and concentrated load, the steelpolybeam’s local buckling bearing capacity decreases with the increasing of the ratio offlange’s width-thickness, but it improves with the angle increasing.Under the action of uniformly distributed load, the initial geometric imperfectionhas less effect on the local buckling bearing capacity, the adverse effect of the initialgeometric imperfection to the ultimate bearing capacity grows with the increasing ofangle; Under concentrated load, the adverse effect of the initial geometric imperfectionto the ultimate bearing capacity becomes bigger with the increasing of the ratio of theflange’s width-thickness and the angle. the reducing effect of the welding residual stressto the steel polybeam’s ultimate bearing capacity maintained at2%to6%.