| Rectangular concrete-filled steel tubular flange I-beam is a new type of composite beam which uses rectangular concrete-filled steel tubular flange instead of the flat flange of traditional I-shaped steel beam.It has the characteristics of higher strength,greater torsional stiffness and better stability.At present,the I-shaped beam with concrete-filled steel tube flange is mainly used in bridge structure.When the I-shaped beam with concrete-filled steel tube flange forms the bridge deck structure,there is an I-shaped section connecting beam or steel truss between the beam and the beam,which plays the role of lateral bracing and is beneficial to the stability of the beam.The research on this kind of beam at home and abroad mainly focuses on the single-span simply supported beam,while the research on the elastic flexural-torsional buckling of the two-span concrete-filled rectangular steel tube flange I-beam is rare.Based on this,this paper selects the two-span rectangular concrete-filled steel tube flange I-beam with or without lateral bracing as the research object,and uses theoretical and finite element numerical simulation methods to study its elastic flexural-torsional buckling.1.Based on the energy method to analyze the elastic torsional buckling of the lateral bracing simply supported beam,the critical moment value of the elastic torsional buckling obtained from the theoretical analysis and the finite element analysis solution are compared with the critical moment equation of the lateral bracing simply supported beam given by Prof.Genshu Tong,and the correctness of the theoretical analysis and finite element modeling method of this paper is verified.2.Based on the energy variational method,the total potential energy equations of flexural-torsional buckling of two-span concrete-filled rectangular steel tubular flange I-beams with or without lateral bracing under concentrated load and uniform load are established respectively.Six trigonometric series are selected to express the displacement and rotation functions of the flexural-torsional deformation of the section.3.According to the principle of potential energy standing value,the relevant dimensionless parameters are introduced to solve the buckling equation of the dimensionless critical bending moment of the two-span concrete-filled rectangular steel tube flange I-beam with or without lateral bracing under two kinds of loads.The analytical solution of the critical bending moment of elastic bending-torsional buckling of the beam is calculated,and use Matlab to write a program,input different values of a(4)、a(4)_L、k(4)_L、K,you can calculate the dimensionless elastic bending torsional bending critical moment,which lays the foundation for the regression of elastic torsional buckling critical moment equation.4.Based on the dimensionless elastic torsional flexural critical bending moment data,a nonlinear fitting of the elastic torsional flexural critical bending moment was performed using 1st Opt software to obtain the elastic torsional flexural critical moment calculation formula.The error is less than 5%when compared with the calculated critical moment of elastic torsional flexural using ANSYS.5.The effects of concrete strength,web height-to-thickness ratio,flange steel ratio and span-to-depth ratio on the elastic flexural-torsional buckling of two-span concrete-filled rectangular steel tubular flange I-beams with lateral bracing are investigated.The results show that concrete strength and web height-to-thickness ratio have little effect on elastic flexural-torsional buckling properties of rectangular concrete-filled steel tubular flange I-beams,while span-to-depth ratio and flange steel ratio have a greater effect on elastic flexural-torsional buckling properties of rectangular concrete-filled steel tubular flange beams,which provides a theoretical reference for the practical engineering design of such beams. |
