Theoretical And Experimental Investigations On High Strength Welded Stainless Steel Members Under Axial Compression

With its remarkable corrosion resistance,good appearance and excellent mechanical properties,stainless steel has promising prospect in structural engineering applications.As a high performance environmentalfriendly building material,it fits the country's medium and long-term development strategy and becomes the best choice for the new material in the harsh environment.At present,the related research and application of stainless steel structure mainly focus on austenitic and duplex stainless steel.This kind of material has strong corrosion resistance,but the price is high and the strength is low,which causes the initial investment of stainless steel structure to be high and difficult to promote.In recent years,new high-strength stainless steels(S600E,304 D,etc.)have been developed at home and abroad.The outstanding characteristics of this kind of materials are high strength and low price,and they have strong competitiveness and popularization and application prospects in stainless steel structures.Based on this situation,this paper studies the residual stress distribution,local stability and overall stability of the new high-strength stainless steel S600 E welded axial compression box and I-shaped components through experimental research and numerical calculation,and puts forward reasonable design suggestions.The following three sections were covered in this dissertation,(1)The composition analysis of S600 E stainless steel was carried out and 24 groups of tensile tests were carried out in different directions.The important parameters of the mechanical properties of the new highstrength stainless steel S600 E tensile material were obtained.The feasibility of the two-stage R-O constitutive model was verified.(2)The residual stress magnitude and distribution pattern of 10 I-shaped sections and 6 box-section stainless steel members welded by S600 E were tested by cutting strip method(1000 strips).The nominal yield strength of the material is higher than the peak residual stress of the welded stainless steel member,and there is a wide residual tensile and compressive stress transition region in the cross section.The peak value of the residual compressive stress of the I-sections does not change significantly with the width-to-thickness ratio of the plate.The distribution range of the residual tensile stress is related to the width of the plate and is independent of the thickness.The peak value of the residual compressive stress of the cross-section is directly related to the width-thickness ratio of the plate.The larger the aspect ratio of the plate,the smaller the peak value of the residual compressive stress.Based on the measurement results,a simplified model for residual stress recommendation for S600 E is proposed.(3)16 stub columns tests on welded stainless steel sections were carried out,and the local stable bearing capacity and failure characteristics of the stainless steel S600 E welded members were obtained.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+A1:2015),“Technical Specification for Stainless Steel Structures”(CECS410: 2015))are compared with the experimental results.It indicates that “Technical Specification for Stainless Steel Structures” and European norms are conservative,and American standards should not be directly used for the design calculation of S600 E welded stainless steel axial members.The accuracy of the short-column finite element model is verified by comparing the finite element with the experimental results.Numerical simulations on a total of 186 stub columns of the local stability of welded stainless steel axial members were carried out.The evaluation of the existing design method was used to propose new validated slenderness limits for both internal and outstand elements subject to compression have been presented.Modifications to the effective width method(EWM)have been proposed for treatment of local buckling.(4)The overall stability test of two welded stainless steel columns was carried out,and the applicability of the finite element model was verified by comparison.According to the finite element results,the domestic and foreign normative calculation methods are evaluated,which shows the limitations and shortcomings of the normative calculation formula.The numerical analysis of the main factors affecting the overall stability was carried out,and the column curve suitable for the S600 E material was obtained.The research results of this paper can provide experimental and theoretical basis for the revision of "Technical Regulations for Stainless Steel Structures"(CECS410:2015)and the preparation of "Technical Standards for High-strength Stainless Steel Structures".