Lateral Torsional Buckling Of The Rectangular Hollow Flange Beams

With the rapid development of the construction industry,the light weight steel structures have been widely applied in engineering because of its light weight,good seismic performance,convenient construction technique and comprehensive economic benefits.Among them,cold formed thin walled steel components precisely have used as the main force components in lightweight steel structure due to the advantages of light weight,high strength,easy assembly.In this paper,the lateral torsional buckling of rectangular hollow flange beams under pure bending and uniform loading are mainly studied.As is known to all,the thin-walled I-beam under pure bending or uniform loading in engineering often buckles at bottom flange.In this paper,Enhancing the stability of the traditional I-beam and improving the empty flange beam proposed by Australian scholars,Rectangular hollow flange beam(RHFB)is used by changing the top and bottom flanges into rectangular hollow sections,in this case,the torsional stiffness and the warp stiffness of the hollow flanges of the RHFB section obviously increase,while the web stiffness will be obviously smaller.Thus,analysing the web deformation affects on the buckling performance solving the critical buckling load of RHFB are the main contents of this paper.This paper deduces the critical buckling load of RHFB under pure bending load and uniform loading by the principle of total potential energy,besides,finite element method and finite element method are respectively performed to carry out the linear buckling analysis and verify the correctness of the theoretical formula.It can be found that the difference between them decreases with the increase of the beam length but increases with increased section size.As a whole,the difference is within the allowable range.In addition,the torsion stiffness of the rectangular hollow flange is very large and the stiffness of the web is relatively weak,especially when the beam length is short and the flange is wide,The failure of the RHFB may include buckling of web distortion.Therefore,this paper defines the critical length of the beam(the critical point of web distortion and the total lateral buckling),and analyzes the influence of section geometry parameters on the critical length of RHFB by using the finite strip method.The parametric study testifies that the critical length of the beam defining the boundary of the buckling modes increases with the increase of the flange width or depth,or the increase of the section depth,or the decrease of the section thickness.