The Second-order Inelastic Analysis Of High-strength Steel Welded Section And Its Application

High-strength structural steel(high-strength steel)refers to steel with a yield strength greater than 460 MPa,which has superior weldability,higher yield strength and good toughness.Compared with ordinary steel,the use of high-strength steel can reduce the weight of the structure,reduce the cross-sectional area of the component,and increase the use space,which brings significant economic benefits and becomes a symbol of modern urban construction.With the progress of social economy,high-strength steel is widely used in engineering,and its mechanical properties need further research.Due to the rapid development of computer technology,a direct analysis method based on the second-order inelastic analysis method is gradually applied to modern engineering.Although there have been many studies on second-order inelastic analysis at home and abroad,considering that the material properties and residual stress models of high-strength steel are different from ordinary steel,the existing second-order inelastic analysis method is not suitable for calculation of high-strength steel.Therefore,the paper takes high-strength steel with welded cross-section as the research object.Through a large number of theoretical analysis and numerical simulations,a second-order inelastic analysis method suitable for high-strength steel is proposed and applied to the stability analysis of high-strength steel axial compression members and frames.High-strength steel engineering design provides reference.The research content and conclusions of this article are as follows:(1)A second-order inelastic analysis method suitable for welding I-shaped and box-shaped sections of high-strength steel with a yield strength of 460-960 MPa is proposed.Based on the uniform distribution model of high-strength steel residual stresses,the tangent modulus and the progressive development process of section plasticity under different strengths are obtained through the section analysis method and theoretical derivation.From this,the simplified tangent modulus formula,the ultimate yield surface formula and the stiffness degradation function are established.The second-order inelastic analysis method uses the beam-column theory based on the stability function for the axial compression component,considers the progressive yield effect caused by bending,and combines the influence of the development of plastic hinge on the equilibrium differential equation to further establish the elastoplasticity of the beam-column element Stiffness matrix,thus obtained the second-order inelastic design method suitable for high-strength steel.(2)The high-strength steel axial compression components with welded cross-sections are calculated using the second-order inelastic analysis method,including 46 axially compressed components with welded box section and 27 axially compressed components with welded I-shaped section.Compare the calculated and tested load-displacement curves and the ultimate bearing capacity results.The ultimate bearing capacity results show that the calculation results of the second-order inelastic analysis are generally smaller than the test results,and the error between most of the calculation results and the test value is less than 10%.The results of the load-displacement curve show that the second-order inelastic analysis is similar to the test curve and can more accurately predict the mechanical behavior of high-strength steel axially compressed components.Therefore,the second-order inelastic design method is suitable for the stability calculation of such members.(3)For the high-strength steel axial compression members with welded cross-sections considering local stability,the corresponding second-order inelastic analysis methods are proposed based on the AISC360-16 design method,the effective section method and the effective yield strength method.At the same time,the existing partial buckling high-strength steel axial compression component test is used for verification,including 15 box-shaped cross-section components and 25 I-shaped cross-section components.The comparison results of the ultimate bearing capacity and the load displacement curve show that for the box section,the calculation results based on the AISC360-16 design method are in good agreement with the experimental values.For the I-shaped section,the second-order inelastic analysis results and the test based on the effective section method The values are in good agreement and the degree of dispersion is low.Therefore,when considering local stability,the second-order inelastic analysis method based on AISC360-16 is recommended for box-shaped sections,and the second-order inelastic analysis method based on effective section method is recommended for I-shaped sections.(4)Stability analysis of welded cross-section high-strength steel frame.Second-order inelastic analysis and finite element numerical simulation were carried out on three types of steel frames,including single-story single-span,double-story single-span,and six-story double-span.The results of load-displacement curves at different nodes were compared.The results show that the finite element and second-order inelastic analysis load-displacement curves of different structural forms of high-strength steel frames with a yield strength of 460～960MPa are in good agreement.The proposed second-order inelastic analysis method is suitable for the analysis of welded cross-section high-strength steel frames.It is convenient for frame design and has certain reference significance for actual engineering.