Study Of Plate-Beam Theory On Flexural-Torsional Buckling Of CFST Truss Arches

The concrete-filled steel tube truss arch structure not only has the characteristics of balanced stress and strong economy,but also has the high bearing capacity of the arch structure and the high strength of the CFST structure.But at present,there are few researches on the section parameters of CFST Truss and the out of plane stability of arch structure.In order to make the CFST Truss Arch Structure easy to calculate and use in practical engineering,based on the "Plate-Beam Theory" of Professor Zhang Wenfu,this paper uses the method of continuous model to comprehensively consider the role of various components of the truss beam and arch structure,and manages the bending and torsional buckling of the single axis symmetric and double axis symmetric CFST plane truss beam and arch and the rectangular section truss beam and arch.The finite element analysis software ANSYS is used to establish multiple groups of models and verify the theoretical analysis results.The main contents of this paper are as follows:(1)Based on the "Plate-Beam Theory" and the equivalent principle of torsion stiffness of web members,the bending and torsional buckling of CFST plane truss beams with uniaxial and biaxial symmetry are analyzed and studied.The total strain energy of CFST plane truss beam under bending and torsional buckling is obtained,and the calculation formulas of flexural rigidity,free torsional rigidity and restrained torsional rigidity are obtained.Through the solution of the initial stress potential energy of the CFST plane truss with uniaxial symmetry,the section asymmetry coefficient is obtained.The finite element models of nine CFST plane truss beams are established,and the correctness of the section properties is verified by comparing the critical load formula of flexural-torsional buckling with the finite element solution.(2)Based on the "Plate-Beam Theory" and the equivalent principle of shear stiffness of web members,the bending and torsional buckling of CFST rectangular section truss beam structure with uniaxial symmetry and biaxial symmetry is analyzed and studied.For the closed section,the in-plane bending deformation of the plate is applicable to Timoshenko beam theory,and the shear deformation is included in the analysis.The total strain energy of CFST rectangular section truss beam under bending and torsional buckling is obtained.The calculation formulas of flexural rigidity,free torsional rigidity and restrained torsional rigidity are obtained by analyzing the formula of total strain energy.In order to obtain the section asymmetry coefficient of the concrete-filled steel tubular rectangular section truss with uniaxial symmetry,the initial stress potential energy of the truss under load is solved and analyzed.The finite element models of six CFST Truss beams with rectangular section are established.The correctness of the section properties is verified by comparing the critical load formula of flexural-torsional buckling with the finite element solution.(3)According to the total potential energy of flexural-torsional buckling of CFST Truss Arch Structure,the equilibrium equations of flexural-torsional buckling of simply supported CFST Truss Arch under pure bending moment and axial pressure are given,and the calculation formula of critical load of flexural-torsional buckling is obtained.Using the finite element analysis software ANSYS,the truss arch models with different model parameters and loads are established respectively.First,the static analysis is carried out,then the modal analysis is carried out,and the characteristic value of bending and torsional buckling is obtained,which verifies the correctness of the section parameter formula of truss arch structure and the calculation formula of the critical load of bending and torsional buckling.