Local And Local-overall Buckling Behaviour Of Welded Stainless Steel Members Under Axial Compression

The key advantages of stainless steel structures are their remarkable corrosionresistance and durability, which can offer a fundamental solution to the long termcorrosion and maintenance problems for carbon steel structures, raising their promisingprospect in structural engineering applications. In view of the disparities in materialproperties and residual stress distributions between stainless steel and carbon steelsections, the buckling capacities of welded structural stainless steel members may differsignificantly from carbon steel ones. The majority of the previous research on structuralstainless steel has focused on the behaviour of cold-formed sections. However, far lessexperimental work have been carried out on welded stainless steel sections, which maybe more suitable for meeting the strength requirements of heavier load bearingapplications. There is currently no design standard for structural stainless steel in China,the use of stainless steel in structures is thus limited. This research forms part of thefundamental work to underpin the development of the first Chinese design code forstructural stainless steel. By means of a considerable amount of experimental tests andnumerical results, combined with the theoretical research on structural stabilityproblems, the residual stress distributions, the local and local-overall bucklingbehaviour of welded stainless steel members under axial compression were investigated,with new design proposals presented. The following four sections were covered in thisdissertation,(1) Using the sectioning method, a total of18structural stainless steel built-upsections of austenitic grade S30408and duplex grade S22253, including ten I-sections,four square hollow sections (SHS) and four rectangular hollow sections (RHS) wereexamined to acquire the level and distribution of residual stresses present in suchsections. Based upon the acquired test data, new simplified predictive models forresidual stress distributions in stainless steel built-up I-sections and box sections weredeveloped. Following comparisons with other available residual stress test data, theapplicability of the proposed models was also extended to the three broad families ofaustenitic, duplex and ferritic stainless steels.(2) A total of72tensile and compressive coupon tests and28stub columns tests onwelded stainless steel sections were carried out, revealing material non-linearity, anisotropy and asymmetry in tension and compression, and the local buckling behaviourof the stub column specimens. The test results were subsequently used to validate thefinite element (FE) models set up using the ABAQUS software package.(3) Interactive buckling tests on a total of18welded stainless steel columns withI-sections, SHS and RHS were conducted, exploring the local-overall bucklingbehaviour and resistances. Based on the obtained experimental results, FE models weregenerated and carefully validated, with the material properties, welding residual stresses,initial local and global geometric imperfections, and initial load eccentricity all takeninto consideration.(4) Using the validated FE models, systematic parametric studies were carried outto assess the impacts of the key input parameters on the local and local-overall bucklingbehaviour. Numerical simulations on a total of844stub columns and654columns withintermediate overall slenderness were performed. Based on the obtained test andnumerical results, new validated slenderness limits for both internal and outstandelements subject to compression have been presented. Modifications to the two designapproaches, the effective width method (EWM) and the direct strength method (DSM),have been proposed for treatment of local buckling. Together with the classicalPerry-Robertson formula, both the EWM-Perry and the DSM-Perry design methodshave been developed for predicting the local-overall buckling resistances of weldedstainless steel members under axial compressions.