Research On Flexural-torsional Buckling For Steel Beam Under Combined Loads

Due to its light weight,high strength,and good mechanical properties,steel is widely used in various building structures.However,for steel structural members,if the technical design is not properly handled under lateral load and without sufficient lateral support,local buckling and overall buckling of the steel structural members may easily occur.At present,the theoretical research on the stability of I-shaped steel beams under a single load is relatively mature,and the relevant design standards are also given in the steel structure design specifications.However,in actual engineering,the building structure may act in two or more load forms.Due to the mutual influence between different kinds of loads,the influence of the state of the component is different from that of a single load and is more complicated.This is also an important reason why the current steel structure design codes do not give relevant design standards.Therefore,the theoretical research on the stability of I-shaped steel beams under various loads has certain value.For this reason,this paper carried out related theoretical studies on the flexural-torsional buckling of single-axisymmetric I-shaped simply supported steel beams,fixed steel beams and cantilevered steel beams under several common combined loads.The main research content of this article is as follows.(1)Based on the energy variation method,The total potential energy equations for flexural-torsional buckling of single-axisymmetric I-shaped simply-supported steel beams subjected to uniformly distributed load and concentrated load at mid-span,uniformly distributed load and symmetrical concentrated load across the center,combination of end moment and uniformly distributed load,combination of end moment and concentrated load at mid-span,combination of end moment and symmetrical concentrated load across the center are derived respectively.And the displacement and torsion angle mode function of the flexural-torsional deformation are selected as one-term,two-term and infinite-term Fourier series.According to the principle of potential energy standing and the introduction of related dimensionless parameters,the analytical solution of the dimensionless critical bending moment of flexural-torsional buckling under corresponding load is obtained.The exact solution can be obtained by converging the analytical solution of the dimensionless critical bending moment of the infinite series of solutions.The finite element software ANSYS was used to numerically study the flexural-torsional buckling of I-shaped simply-supported steel beams under combined loads,which compared with the theoretical exact solution in this paper.(2)Based on the energy variation method,The total potential energy equations for flexural-torsional buckling of single-axisymmetric I-shaped fixed steel beams subjected to single uniformly distributed load,concentrated load at mid-span,symmetrical concentrated load across the center and uniformly distributed load and concentrated load at mid-span,uniformly distributed load and symmetrical concentrated load across the center are derived.And the displacement and torsion angle mode function of the flexural-torsional deformation are selected as one-term,two-term and infinite-term Fourier series.According to the principle of potential energy standing and the introduction of related dimensionless parameters,the analytical solution of the dimensionless critical bending moment of flexural-torsional buckling under corresponding load is obtained.The exact solution can be obtained by converging the analytical solution of the dimensionless critical bending moment of the infinite series of solutions.The finite element software ANSYS was used to numerically study the flexural-torsional buckling of I-shaped fixed steel beams under five load conditions,which verified the theoretical solution of this article.(3)Based on the energy variation method,The total potential energy equations for flexural-torsional buckling of single-axisymmetric I-shaped cantilevered steel beams subjected to uniformly distributed load and concentrated load at end is derived.And the displacement and torsion angle mode function of the flexural-torsional deformation are selected as one-term,two-term and infinite-term Fourier series.According to the principle of potential energy standing and the introduction of related dimensionless parameters,the analytical solution of the dimensionless critical bending moment of flexural-torsional buckling under corresponding load is obtained.The exact solution can be obtained by converging the analytical solution of the dimensionless critical bending moment of the infinite series of solutions.The finite element software ANSYS was used to numerically study the flexural-torsional buckling of I-shaped cantilevered steel beams,which verified the theoretical solution of this article.