Investigation On Constitutive Model Of High-strength Stainless Steel And Lateral Torsional Buckling Behavior Of Flexural Members

With its strong corrosion resistance,excellent mechanical properties,good appearence and low life cycle cost,stainless steel has a broad application prospect in the field of engineering construction.It is a high performance environmental-friendly building material.It is in line with the national sustainable development strategy and becomes the best choice for the new material in the harsh environment.At present,some related studies have focused on the common austenitic and ferritic stainless steel.The nominal yield strength of the materials is low and the price is high,which limits the application of stainless steel structure to some extent.The high-strength stainless steel,represented by duplex stainless steel and soxhlet stainless steel which have high nominal yield strength and good economic performance,and have a wider application in the stainless steel structure.However,there are few related research at home and abroad.Based on the above background,the mechanical properties of high-strength stainless steel and the lateral torsional buckling behaviour of flexural members are studied in this paper.3 static material property tests on duplex stainless steel S22053 and 2 on soxhlet stainless steel have been carried out.The results show that compared with the common austenitic stainless steel,high-strength stainless steels show obvious nonlinearity.The materials have no obvious yield point,nominal yield strength and ultimate strength of which are higher,the elongation are lower,and the yield strength ratio are larger.The feasibility of the two stage model is verified by fitting the stress-strain curve.17 cyclic loading tests under 17 loading systems were carried out.The test obtained the skeleton curve under the cyclic loading,and the hysteresis loop of the curve were full,indicating that the material has good energy dissipation capacity.In addition,the material has strong nonlinear servo strengthening performance,and the isotropic strengthening performance is weak.The material circulation parameters are calibrated by using the isotropic strengthening/dynamic strengthening model in the finite element software ABAQUS.In order to reduce the constraints of the test loading and support devices,a new test installation for the lateral torsional buckling behavior of the flexural members is put forward on the basis of previous successful experience of other test devices.The lateral torsional buckling behavior tests of 7 duplex stainless steel S22053 welded I-shaped section flexural members were carried out.The bearing capacity and failure characteristics of duplex stainless steel S22053 welded I-section flexural members were obtained.In the bending tests,lateral torsional buckling and failure occurred to all of the flexural specimens except that one component failed of global-local interaction buckling.Based on the material properties obtained from tension tests,values of the calculation formula of the bearing capacity in the 3 specifications(?Specification for the Design of Cold-Formed Stainless Steel Structural Members?(SEI/ASCE 8-02),?Eurocode 3 –Design of Steel Structures-Part 1-4: General Rules-Supplementary for Stainless Steel?(EN 1993-1-4:2006),?Technical Specification for Stainless Steel Structures?(CECS410: 2015))as well as the calculated values of the design method proposed by Wang Yuanqing are compared with the experimental results.It shows that there are some differences between the test results and the calculated values of each design code and design method.The result of ?Technical Specification for Stainless Steel Structures? is the closest to the test results,and the formula proposed by Xin Lianchun could get more accurate results.numerical modeling of the test specimens were developed using the commercial finite element software ABAQUS,effects of material nonlinearity,geometric nonlinearity,residual stress,initial defect and constraints were considered in the finite element method modeling.Results of the experiments on the lateral torsional buckling performance of high strength duplex stainless steel S22053 flexural members are compared in the paper which indicates that the finite element analysis model is accurate.Then the factors which affect the carrying capacity of high-strength stainless steel members were investigated.The results show that the mechanical properties of the material has the greatest influence on the lateral torsional buckling capacity of the flexural members,the overall initial defect amplitude has little influence on the bearing capacity of the membrs,and the amplitude of the local initial defect has a greater influence on the small slendernessl members than large ones.Welded joints have an approximately 6% increase of bearing capacity,and the residual stress has little effect on the capacity of the flexural members.Based on the above analysis,an simplified model under pure bending is used to analyze the high-strength duplex stainless steel S22053 and soxhlet stainless steel S600 E fiexural members with regularized slenderness ratio ? and cross section height-width ratio h/b as main parameters.Based on the results of parameterized analysis,formulas in a simple form as well as of high precision applied to the high-strength duplex stainless steel as well as soxhlet stainless steel for the capacity of the flexural members are proposed respectively.The calculated values of the proposed formula for duplex stainless steel are compared with the experimental values at home and abroad.The results show that the proposed formula has a good prediction ability for the bearing capacity of the flexural member of the duplex stainless steel welded I-shaped section.The research results of this paper can provide experimental and theoretical basis for the establishment of the Technical Standard for High-strength Stainless Steel Structure.