Cold-formed High Strength Stainless Steel Research Articles

Web crippling behaviour of cold-formed duplex stainless steel tubular sections at elevated temperatures

This paper reports a numerical investigation of cold-formed high strength stainless steel square and rectangular hollow sections subjected to web crippling at elevated temperatures. Finite element analysis was conducted on cold-formed high strength austenitic and duplex stainless steel material. Four loading conditions specified in the American Specification and Australian/New Zealand Standard for cold-formed stainless steel structures were investigated in the numerical study. A non-linear finite element model which includes geometric and material non-linearities was developed and verified against experimental results. It was shown that the finite element model closely predicted the web crippling strengths and failure modes of the tested specimens under the four loading conditions. Hence, parametric study was carried out to investigate the web crippling behaviour of cold-formed high strength stainless steel square and rectangular hollow sections at elevated temperatures. The web crippling strengths predicted from the finite element analysis were compared with the design strengths obtained using the American, Australian/New Zealand and European specifications for stainless steel structures by substituting the reduced material properties in the current web crippling design equations. A unified web crippling equation for cold-formed high strength stainless steel square and rectangular hollow sections at elevated temperatures is proposed. It is demonstrated that the web crippling strength obtained using the proposed equation is safe and reliable using reliability analysis.

Cold-formed high strength stainless steel cross-sections in compression considering interaction effects of constituent plate elements

This paper presents a numerical investigation of cold-formed high strength stainless steel square and rectangular hollow sections in compression. A non-linear finite element model which includes geometric and material non-linearities was developed and verified against experimental results. The model was then used for an extensive parametric study to investigate the interaction effects of constituent plate elements on Class 3 slenderness limit and section capacities of cold-formed high strength stainless steel square and rectangular hollow sections in compression.The numerical investigation shows that the interaction effects of constituent plate elements on cross-section response are quite obvious particularly for slender sections. The design provisions on Class 3 slenderness limit and effective width equations specified in the EC3 Code and proposed by Gardner and Theofanous are suitable for square hollow sections, but not for rectangular hollow sections since they do not take into consideration of interaction effects of constituent plate element. Hence, the new Class 3 slenderness limit and the section capacity design equations based on the whole cross-section response are proposed in this study, which carefully consider the interaction effects of constituent plate elements.

Experimental and numerical investigation of high strength stainless steel structures

The paper summarises research on high strength stainless steel tubular structures conducted at the University of Hong Kong, and the Hong Kong University of Science and Technology. Square and rectangular hollow sections were investigated. The test specimens were cold-rolled from high strength austenitic and duplex stainless steel sheets. The material properties of the test specimens were determined by tensile coupon tests at normal room and elevated temperatures. The initial geometric imperfection and residual stress of the specimens were measured. The experimental and numerical investigation focused on the design and behaviour of cold-formed high strength stainless steel structural members. The results were compared with design strengths calculated using the American, Australian/New Zealand and European specifications for cold-formed stainless steel structures.

Experimental Investigation of Cold-Formed High-Strength Stainless Steel Tubular Members Subjected to Combined Bending and Web Crippling

This paper presents a test program on cold-formed stainless steel tubular sections subjected to combined bending and web crippling. A series of tests was performed on square and rectangular hollow sections fabricated by cold-rolling from high strength material of duplex and high strength austenitic stainless steel sheets. The concentrated load was applied by means of a bearing plate which acted across the full flange width of the section. The flanges of the hollow section specimens were not fastened to the bearing plates during testing. The specimens were tested using the interior-one-flange loading condition specified in the American Specification and Australian/New Zealand Standard (AS/NZS) for cold-formed stainless steel structures. Different specimen lengths were tested to obtain the interaction relationship between moment and concentrated load. The combined bending and web crippling test results were compared with the design strengths obtained using the current American Specification and AS/NZS for cold-formed stainless steel structures. Generally, it is shown that the American Specification and AS/NZS Standard conservatively predicted the strengths of cold-formed high strength stainless steel square and rectangular hollow sections subjected to combined bending and web crippling.

Cold-Formed High-Strength Stainless Steel Tubular Sections Subjected to Web Crippling

A series of tests on cold-formed high-strength stainless steel square and rectangular hollow sections subjected to web crippling is presented in this paper. The types of stainless steel investigated in this study were high strength austenitic and duplex material. The measured web slenderness value of the hollow sections ranged from 16.5 to 49.7. The tests were carried out under four loading conditions considered in the American Specification and Australian/New Zealand Standard for cold-formed stainless steel structures, namely end-one-flange, interior-one-flange, end-two-flange, and interior-two-flange loading conditions. The web crippling test strengths were compared with the design strengths obtained using the American, Australian/New Zealand, and European Specifications for stainless steel structures. In addition, the North American Specification for cold-formed carbon steel structural members was also used to predict the web crippling strengths and compared with the test results. It is shown that the ...

Buckling analysis of high strength stainless steel stiffened and unstiffened slender hollow section columns

This paper investigates the buckling behaviour of cold-formed high strength stainless steel stiffened and unstiffened slender square and rectangular hollow section columns. The high strength duplex material is austenitic-ferritic stainless steel approximately equivalent to EN 1.4462 and UNS S31803. The columns were compressed between fixed ends at different column lengths. A nonlinear finite element model has been developed to investigate the behaviour of stiffened slender square and rectangular hollow section columns. The column strengths, load-shortening curves as well as failure modes were predicted for the stiffened and unstiffened slender hollow section columns. An extensive parametric study was conducted to study the effects of cross-section geometries on the strength and behaviour of the stiffened and unstiffened columns. The investigation has shown that the high strength stainless steel stiffened slender hollow section columns offer a considerable increase in the column strength over that of the unstiffened slender hollow section columns. The column strengths predicted from the parametric study were compared with the design strengths calculated using the American Specification, Australian/New Zealand Standard and European Code for cold-formed stainless steel structures. It is shown that the design strengths obtained using the three specifications are generally conservative for the cold-formed stainless steel unstiffened slender square and rectangular hollow section columns, but slightly unconservative for the stiffened slender square and rectangular hollow section columns.

Tests of cold-formed high strength stainless steel compression members

The paper describes a test program on cold-formed high strength stainless steel compression members. The duplex stainless steel having the yield stress and tensile strength up to 750 and 850 MPa, respectively, was investigated. The material properties of the test specimens were obtained from tensile coupon and stub column tests. The test specimens were cold-rolled into square and rectangular hollow sections. The specimens were compressed between fixed ends at different column lengths. The initial overall geometric imperfections of the column specimens were measured. The strength and behaviour of cold-formed high strength stainless steel columns were investigated. The test strengths were compared with the design strengths predicted using the American, Australian/New Zealand and European specifications for cold-formed stainless steel structures. Generally, it is shown that the design strengths predicted by the three specifications are conservative for the cold-formed high strength stainless steel columns. In addition, reliability analysis was performed to evaluate the current design rules.

Design and behaviour of concrete-filled cold-formed stainless steel tube columns

This paper presents a nonlinear finite element model to investigate the behaviour and design of axially loaded concrete-filled cold-formed high strength stainless steel tube columns. The study was conducted over a wide range of concrete cylinder strengths from 20 to 100 MPa. The depth of flat portion-to-plate thickness ( d / t ) ratio of the square and rectangular hollow sections ranged from 16 to 96, covering compact and slender sections. The columns had different lengths so that the length-to-depth ratio remained a constant of 3. Nonlinear material models for confined concrete and stainless steel tubes were used in the finite element model. The results obtained from the finite element analysis were verified against experimental results. An extensive parametric study was conducted to investigate the effects of cross-section geometry and concrete strength on the behaviour and strength of the columns. The column strengths obtained from the finite element analysis were compared with the design strengths calculated using the American specifications and Australian/New Zealand standards. A design equation was proposed for concrete-filled stainless steel tube columns. It is shown that the design strengths obtained using the proposed modified equation are more accurate compared to the American and Australian/New Zealand predictions.

Behavior of Cold-Formed High Strength Stainless Steel Sections

This paper presents the behavior of cold-formed high strength stainless steel sections. The test specimens were cold-rolled from flat strips of duplex and high strength austenitic stainless steel. The material properties of high strength stainless steel square and rectangular hollow sections were determined. Tensile coupons at different locations in cross section were tested. Hence, the distributions of 0.2% proof stress and tensile strength measured in the cross section of cold-formed high strength stainless steel sections were plotted. The material properties of the complete cross section in the cold-worked state were also obtained from stub column tests. Detailed measurements of initial local geometric imperfections of the sections were obtained. The initial local plate imperfection profiles were plotted. Residual stress measurements of the high strength stainless steel sections were also conducted. The membrane and bending residual stress distributions in the cross section of the specimens were obtained. Furthermore, the stub column test strengths were compared with the design strengths.

Experimental investigation of concrete-filled cold-formed high strength stainless steel tube columns

This paper presents an experimental investigation of concrete-filled cold-formed high strength stainless steel tube columns. The high strength stainless steel tubes had a yield stress and tensile strength up to 536 and 961 MPa, respectively. The behaviour of the columns was investigated using different concrete cylinder strengths varied from 40 to 80 MPa. A series of tests was performed to investigate the effects of the shape of the stainless steel tube, plate thickness and concrete strength on the behaviour and strength of concrete-filled high strength stainless steel tube columns. The high strength stainless steel tubes were cold-rolled into square and rectangular hollow sections. The depth-to-plate thickness ratio of the tube sections varied from 25.7 for compact sections to 55.8 for relatively slender sections. The columns had different lengths so the length-to-depth ratio generally remained at a constant value of 3. The concrete-filled high strength stainless steel tube specimens were subjected to uniform axial compression. The column strengths, load–axial strain relationships and failure modes of the columns were presented. The test strengths were compared with the design strengths calculated using the American specifications and Australian/New Zealand standards that consider the effect of local buckling using an effective width concept in the calculation of the stainless steel tube column strengths. Based on the test results, design recommendations were proposed for concrete-filled high strength stainless steel tube columns.

Structural performance of cold-formed high strength stainless steel columns

This paper describes an accurate finite element model for the structural performance of cold-formed high strength stainless steel columns. The finite element analysis was conducted on duplex stainless steel columns having square and rectangular hollow sections. The columns were compressed between fixed ends at different column lengths. The effects of initial local and overall geometric imperfections have been taken into consideration in the finite element model. The material nonlinearity of the flat and corner portions of the high strength stainless steel sections were carefully incorporated in the model. The column strengths and failure modes as well as the load-shortening curves of the columns were obtained using the finite element model. Furthermore, the effect of residual stresses in the columns was studied. The nonlinear finite element model was verified against experimental results. An extensive parametric study was carried out using the verified finite element model to study the effects of cross-section geometries on the strength and behaviour of cold-formed high strength stainless steel columns. The column strengths predicted from the parametric study were compared with the design strengths calculated using the American Specification, Australian/New Zealand Standard and European Code for cold-formed stainless steel structures. The results of the parametric study showed that the design rules specified in the American, Australian/New Zealand and European specifications are generally conservative for cold-formed high strength stainless steel square and rectangular hollow section columns, but unconservative for some of the short columns.