Ultimate Bearing Capacity Of Thin-walled Stainless Steel Members In Axial Compression

Stainless steel is characterized by its outstanding corrosion resistance, aesthetics virtue, ease of forming and good mechanical performances, which make it an excellent construction material with great appearance and behavior. However, its material properties and mechanical behavior are distinct form carbon steel, featuring for non-linear stress-strain curve, no yield plateau, low proportionality stress, and significant strain-hardening capability. Domestically, there are no sufficient researches or design codes on mechanical behavior of stainless steel members, which limits the development of stainless steel application in structure engineering. The ultimate bearing capacity of thin-walled stainless steel members in axial compression is systemically researched in this paper.Firstly, the paper reviews the researches in strain-stress relations models home and abroad, after introducing, analyzing and comparing, presents the best stress-strain model for stainless steel material. It is shown that the three-stage stress-strain model proposed by Quach, which is defined by the three basic Ramberg-Osgood parameters, is the most accurate stress-strain model for stainless steel material.Next, by incorporating modifications into the conventional Generalized Beam Theory, the paper derives the equilibrium equation which could be used in non-linear elastic metallic materials, and the expressions are formulated to calculate the local buckling loads of stainless steel plates, the distortional buckling loads of stainless steel lipped channels section columns and the global buckling loads of stainless steel box section columns. Comparing with the existed test results, it is shown that the modified GBT method produces reliable results, which could be used in determining the buckling strength of thin-walled stainless steel members in compression.Then FE models are established for analyzing the local buckling behaviour of stainless steel plates in compression, which is based on the results of existing test. After revising the winter curve through the parametric analysis, the expressions are proposed for determining the local buckling strength of stainless steel thin-walled plates and rectangular hollow section members in compression. And then, the paper presents tests on thin-walled stainless steel tubular members in compression, including material tensile property, stub column and long column tests. Based on the tests results, analysis is conducted on material properties, failure modes, displacements, strain distribution and initial imperfection.After developing a consistent FE model based on the tests results, extensive parametric studies are carried out to investigate the effect of slenderness, diameter, thickness, diameter-thickness ratio, initial imperfection and material properties on the buckling strength of thin-walled stainless steel tubular members in compression. The formulas are proposed to calculate the critical modified slenderness and limiting diameter-thickness ratio.Finally, the paper presents theoretical analysis on buckling behavior of thin-walled members in axial compression, as well as introduces several methods of determining buckling resistance in stainless steel structures design code of foreign country. At last, the expressions are proposed for determining the ultimate bearing capacity of thin-walled stainless steel tubular long columns and stub columns. Comparing with the numerical analysis results, it is shown that the expressions, which produce more reliable results than the existing design code, could be used in determining the ultimate bearing capacity of thin-walled stainless steel members in compression.