Study On The Flexural Stability Load Capacity Of Duplex Stainless Steel Cold-formed Angle Cantilever Members

In recent years,the country advocates green development strategy,and the concept of green building has been promoted.Compared with carbon steel,stainless steel has the advantages of good corrosion resistance,stable mechanical properties,beautiful shape and low life-cycle maintenance costs,which fundamentally solves the problem of rust and corrosion of ordinary carbon steel,stainless steel is a high-performance green building materials.With the continuous improvement of stainless steel preparation and processing process,the cost of steel production gradually reduced,stainless steel products are widely used in various industries.Domestic and foreign research on austenitic and ferritic stainless steel is more concentrated,the nominal yield strength of the material is low and the price is high,while duplex stainless steel has the advantages of high nominal yield strength and good economy,more suitable for stainless steel structure,however,at this stage of its research is not perfect.Based on the above background,this thesis investigates the material static mechanical properties of duplex stainless steel and the stability performance of bending members.In this thesis,five specimens of duplex stainless steel S32001 were tested and the mechanical properties including initial modulus of elasticity,nominal yield strength,ultimate tensile strength and other mechanical properties were obtained.The test results show that the material has a high nominal yield strength and good ductility,and the yield strength is relatively large.For the fitting of the stress-strain relationship,Zheng’s three-stage model can simulate the mechanical properties of the tested material more accurately.A combination of experimental research and finite element analysis is used to systematically study the flexural stability of cold-formed angular steel cantilever members of duplex stainless steel.A series of test specimens were completed,and by comparing the flexural ultimate load capacity of the specimens,the influence of the length to slenderness ratio,limb length ratio β,etc.on the flexural ultimate load capacity of the specimens was obtained.The finite element software ABAQUS was used to simulate and study the test specimen,and the failure modes,load-displacement curve and ultimate bearing capacity of the simulation were compared with the test results,and it was found that the agreement between the finite element analysis results and the test results was good,which laid the test foundation for the subsequent parametric analysis of the flexural resistance of the member.On the basis of the verified finite element model,finite element parametric analysis of a large number of cold-formed thick angle section cantilever members was carried out,and its ultimate flexural capacity calculation formula was modified by using the finite element parametric analysis results on the basis of American single angle design code,so that it can be used for the calculation of ultimate flexural capacity of cold-formed angle members.The results of the study show that:two failure modes of section edge yielding damage and overall bending and torsional buckling occur in the thick section members;for the calculation of the flexural capacity of cold-formed angle steel,the calculation accuracy of the modified formula is better than that of the formula in the American single angle steel code.On the basis of the research on the ultimate flexural capacity of thick section,the calculation method of the ultimate flexural capacity of the member not involved in the U.S.single angle steel code when the local and overall torsion-related buckling failure occurs is carried out,and the calculation formula of the critical torsional buckling load of the member is modified by considering the effective section of the thin-walled member when the local buckling occurs,and the calculation formula that can be used for the local and overall torsionrelated buckling failure of the thin-walled member is proposed.The equation for the ultimate load carrying capacity in case of local and global buckling failure is proposed.Finally,by comparing the results of the finite element analysis,the design recommendations for the coldformed thin-walled angle steel rolled edge width-thickness ratio a/t are given on the basis of the minimum width-thickness ratio limits for rolled edges in the Technical Specification for Cold-Formed Thin-Walled Steel Structures(GB50018-2002).