Investigation On Bending Resistance And Ductility Of Q690 High Strength Steel Welded H-section Beam

Steel structures are favored for their lightweight and high-strength material properties,simple and efficient construction methods,and a wide variety of architectural expressions and high-strength steel plays an important role.However,as the steel strength increases,its mechanical characteristics such as higher yield ratio,shorter yield platform and lower elongation exceed the limits in the specification.It is very important to verify the bending resistance and ductility for high strength steel.In this paper,the study on the flexural strength and rotation capacity of domestic 690 MPa high-strength steel welded H-shaped beam was carried out to evaluate the bending resistance and ductility of high-strength steel flexural members.Based on experimental research and finite element analysis,qualitative conclusions about the bending capacity and ductility of high-strength steel beams were obtained by the ultimate capacity and rotation capacity of the members,and the experimental and numerical analysis results were compared with the design provisions of some specifications to explore the applicability of the specification for high-strength steel ductile section classification values.The main contents of this paper are as follows:(1)The bending test was carried out on six welded H-shaped beams of 690 MPa domestic high-strength steel under two-point loading.Through the failure mode,loaddisplacement curve,load-strain curve,bending moment-rotation curve,ultimate strength and rotation capacity,the bending moment and ductility of high-strength steel beams with different section dimensions and lateral restraints were analyzed.Some qualitative conclusions were obtained by comparing the results with calculation results from different design specifications;(2)Finite element model was established using measured material properties and geometric dimensions.Ideal boundary conditions were set by considering real test conditions.Model correction was performed considering weld residual stress and initial geometric imperfections.Numerical simulation of the bending performance of highstrength steel H-shaped beam in this test and existing tests were carried out,and verification of the finite element model;(3)Parametric analysis was carried out using a validated finite element model.The effects of material properties,flange width-thickness ratio,web width-thickness ratio,lateral support on the bending capacity and ductility of the members were considered by changing parameters such as material parameters,section dimensions,and boundary conditions;(4)A large number of parameter analysis results were classified based on the bending capacity and ductility of the member.The applicability of the ductile section classification limit in the specification for high-strength welded H-shaped beam was explored.A new high-strength steel welded H-shaped beam ductile section classification formula was proposed.The innovations of this paper are as follows:(1)Through the experimental study,the bending moment and ductility performance test of the domestic 690 MPa high-strength steel beams under two-point loading were completed for the first time,and the bending capacity and rotation capacity were obtained;(2)Comprehensive analysis of the flexural capacity and ductile properties of highstrength steel beams was accomplished,and the influencing factors and laws were obtained on the flexural resistance and ductile properties of high-strength steel beams;(3)Based on the experimental data and a large number of parameter analysis data,the section classification methods in some design specification were evaluated,and a new ductile section classification design method suitable for the high-strength steel welded Hshaped beam was proposed.