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• Twelve pin-ended compression tests on austenitic stainless steel flat–oval hollow section columns were conducted. • Their flexural buckling behaviour about the cross-section major and minor principal axes was studied. • FE models were developed to simulate the test results and then used to perform parametric studies. • The codified buckling curves were evaluated. The flexural buckling behaviour and resistances of cold-formed austenitic stainless steel flat-oval hollow section columns are studied in this paper, based on experiments and numerical modelling. An experimental investigation was firstly conducted and included tensile coupon tests, initial geometric imperfection measurements and major-axis and minor-axis pin-ended compression tests on ten column specimens. The experimental investigation was followed by a numerical investigation, where the column test results were used to validate finite element models; upon validation, parametric studies were conducted to generate additional numerical data over a wide range of cross-section dimensions and member effective lengths. The obtained test and numerical data were adopted to assess the applicability of the relevant buckling curves for cold-formed austenitic stainless steel circular and elliptical hollow section columns, as specified in the European code, American specification and Australian/New Zealand standard, to cold-formed austenitic stainless steel flat-oval hollow section columns. It was revealed from the assessment results that the buckling curves of the European code and American specification led to overall accurate and consistent flexural buckling resistance predictions, while the flexural buckling resistance predictions from the buckling curve of the Australian/New Zealand standard were slightly conservative. [ABSTRACT FROM AUTHOR]

• The flexural buckling behaviour of austenitic stainless steel semi-oval hollow section columns was studied. • Twelve pin-ended column tests were conducted. • FE models were developed to validate against the test results and then adopted to conduct parametric studies. • The codified buckling curves were evaluated and led to an overall good level of design accuracy. Semi-oval hollow section is an innovative cross-section profile and consists of one semi-circular flange, one flat flange and two flat webs. While the semi-circular flange (exposed to fluid or wind) offers a low level of hydrodynamic or aerodynamic drag, the flat elements facilitate connections with other members. The flexural buckling behaviour and resistances of austenitic stainless steel semi-oval hollow section columns are investigated in this paper. An experimental programme was firstly conducted on two austenitic stainless steel semi-oval hollow sections, with six column specimens of varying member lengths adopted for each cross-section, and included tensile coupon tests, initial geometric imperfection measurements and pin-ended column tests. Both 'C'-shaped flexural buckling (with failure specimens bowing towards semi-circular flanges) and 'reverse C'-shaped flexural buckling (with failure specimens bowing towards flat flanges) were observed upon testing. The experimental programme was accompanied by a numerical modelling programme, with finite element models developed to simulate the test results and then adopted to conduct parametric studies to generate further numerical data. On the basis of the test and numerical data, the relevant buckling curves for austenitic stainless steel circular hollow section columns, as provided in the European code, American specification and Australian/New Zealand standard, were evaluated for their applicability to austenitic stainless steel semi-oval hollow section columns. The evaluation results generally revealed that the codified buckling curves led to overall accurate and consistent flexural buckling resistance predictions when used for austenitic stainless steel semi-oval hollow section columns. [ABSTRACT FROM AUTHOR]

This paper presents experimental and numerical investigations into the web crippling behaviour and load-carrying capacity of stainless steel built-up I-section members under End-Two-Flange (ETF) concentrated transverse loading. An experimental programme was conducted on 23 austenitic and duplex stainless steel built-up I-section specimens, with each consisting of two identical press-braked channel sections assembled back-to-back by means of self-tapping screws. Following the experimental programme, a numerical modelling programme was performed, where finite element models were firstly developed to replicate the tests and then used to conduct parametric studies. Based on the test and numerical data, the existing design rules for stainless steel built-up I-section members failing by web crippling, as set out in the current European, American and Australian/New Zealand design standards, were assessed. The comparisons indicated that the European and Australian/New Zealand design standards resulted in overly conservative and rather scattered failure load predictions, while the American design standard led to less scattered failure load predictions, but with many predictions on the unsafe side. Therefore, an improved design approach was proposed and shown to provide substantially improved failure load predictions for stainless steel built-up I-section members under End-Two-Flange loading. • The web crippling behaviour of stainless steel built-up I-sections under ETF loading was studied. • Tests were conducted on 23 stainless steel built-up I-section specimens. • FE models were developed and validated against test results and then used for parametric studies. • The existing codified design rules were assessed and a new design approach was proposed. [ABSTRACT FROM AUTHOR]

• The compressive behaviour of square RACFSST stub columns after exposure to fire is investigated. • Twelve post-fire compression tests are conducted. • The influences of heating durations and RCA replacement ratios are discussed. • Thermal and mechanical FE models are validated against test results and then used to conduct parametric studies. • The relevant design codes are assessed against the test and FE data. Experimental and numerical studies on the cross-section compressive behaviour and residual resistances of square recycled aggregate concrete-filled stainless steel tube (RACFSST) stub columns after exposure to fire are reported in this paper. An experimental programme was firstly carried out on twelve stub column specimens with three recycled coarse aggregate replacement ratios (0%, 35% and 70%) after exposure to the ISO-834 standard fire for 0 min (i.e. at ambient temperature), 15 min, 30 min and 45 min. The test results, including load–end shortening curves, failure loads and failure modes, were presented, with the initial compressive stiffness and confinement effect analysed. The experimental programme was followed by a numerical modelling programme, where thermal and mechanical finite element models were developed and validated against the test results and afterwards used to conduct parametric studies to generate additional numerical data over a wide range of cross-section dimensions. Based on the test and numerical data, the relevant design rules for square natural aggregate concrete-filled carbon steel tube stub columns at ambient temperature, as specified in the European code, Australia/New Zealand standard and American specification, were evaluated, using post-fire material properties, for their applicability to square RACFSST stub columns after exposure to fire. The evaluation results generally revealed that the European code and Australian/New Zealand standard led to a good level of design accuracy, while the American specification resulted in slightly conservative post-fire cross-section compression resistance predictions. [ABSTRACT FROM AUTHOR]

This paper presents experimental and numerical investigations into the post-fire cross-section compressive behaviour and resistances of circular recycled aggregate concrete-filled stainless steel tube (RACFSST) stub columns. Twelve stub column specimens, fabricated from concretes with three recycled coarse aggregate replacement ratios (0%, 35% and 70%), were tested after exposure to the ISO-834 standard fire for 0 min (i.e. at ambient temperature), 15 min, 30 min and 45 min. The experimental investigation included heating and cooling of specimens, cylinder tests and post-fire tensile coupon tests and stub column tests. The test results, including load–end shortening curves, failure loads and failure modes, were fully reported and the initial compressive stiffnesses and confinement effect were discussed. The numerical investigation was subsequently conducted, where thermal and mechanical finite element models were developed and validated against the test results and then used to perform parametric studies to generate further numerical data. Given the absence of design codes for stainless steel–recycled aggregate concrete composite structures after exposure to fire, the relevant design rules for circular natural aggregate concrete-filled carbon steel tube stub columns at ambient temperature, as set out in the European code, Australia/New Zealand standard and American specification, were assessed, using post-fire material properties, for their applicability to circular RACFSST stub columns after exposure to fire, based on the test and numerical data. The assessment results generally revealed that the European code and the Australian/New Zealand standard led to an acceptable level of design accuracy and consistency, while the American specification resulted in rather conservative and scattered post-fire cross-section compression resistance predictions. • The compressive behaviour of circular RACFSST stub columns after exposure to fire is investigated. • Post-fire compression tests on twelve circular RACFSST stub column specimens are conducted. • The influences of heating durations and RCA replacement ratios are analysed. • Thermal and mechanical FE models are validated against test results and then used to conduct parametric studies. • The relevant design codes are assessed against the test and FE data. [ABSTRACT FROM AUTHOR]

This paper reports experimental and numerical investigations into the structural behaviour and resistances of high strength concrete-filled stainless steel tube (HCFSST) beam-columns under combined compression and bending. An experimental investigation was conducted on sixteen HCFSST beam-columns specimens fabricated from stainless steel tubes with two cross-section sizes and high strength concretes with four material grades, and included concrete cylinder tests, tensile coupon tests, initial global geometric imperfection measurements and eccentric compression tests. The test setups and procedures were fully reported and the experimental observations were discussed and analysed in detail. It was found that the plane cross-section assumption was valid for eccentrically loaded HCFSST sections and the lateral deflection distribution patterns for HCFSST beam-columns were approximately half-sine wave shapes. The test results were used in a subsequent numerical investigation for the validation of finite element models, which were then employed to conduct parametric studies to generate additional numerical data over a wide range of cross-section dimensions, member lengths and loading combinations. Based on the experimental and numerical results, the relevant design rules, as set out in the European code, American specification and Australian/New Zealand standard, were evaluated for their applicability to HCFSST beam-columns. The evaluation results revealed that the European code provided accurate but scattered failure load predictions when used for HCFSST beam-columns, while the American specification and Australian/New Zealand standard resulted in conservative and scattered failure load predictions. • The behaviour of high strength concrete-filled stainless steel tube (HCFSST) beam-columns is investigated. • Eccentric compression tests on sixteen HCFSST beam-column specimens are conducted. • The ductility, strength, longitudinal strain development and lateral deflection distribution are analysed. • FE models are developed to validate against the test results and then used to conduct parametric studies. • The applicability of relevant design codes is assessed against test and FE data. [ABSTRACT FROM AUTHOR]

The flexural buckling behaviour and resistances of press-braked stainless steel Z-section columns are investigated in this paper, based on experiments and numerical modelling. An experimental investigation was conducted on two press-braked stainless steel Z-sections and included material testing, initial geometric imperfection measurements and twelve fixed-ended column tests. Minor-axis flexural buckling was observed for all press-braked stainless steel Z-section column specimens upon testing. The key obtained fixed-ended column test results, including failure loads, load–deformation histories and failure modes, were fully reported. Following the experimental investigation, a numerical investigation was performed, with finite element models developed to validate against the fixed-ended column test results and then used to conduct parametric studies to generate additional numerical data. On the basis of the test and numerical data, the relevant buckling curves, as specified in the European code, American specification and Australian/New Zealand standard, were evaluated and shown to provide accurate and consistent flexural buckling resistance predictions for press-braked stainless steel Z-section columns. • The flexural buckling behaviour of press-braked stainless steel Z-section columns was studied. • Twelve fixed-ended column tests were conducted. • FE models were developed to validate against the test results and then used to perform parametric studies. • The codified buckling curves were assessed, showing good design accuracy and consistency. [ABSTRACT FROM AUTHOR]

This paper reports laboratory testing and numerical modelling on the cross-sectional behaviour and resistances of press-braked S690 high strength steel slender channel section stub columns under combined compression and minor-axis bending. A testing programme, including initial geometric imperfection measurements and ten minor-axis eccentric compression tests, was firstly conducted. This was accompanied by a numerical modelling programme, including a validation study, where finite element models were developed and validated against test results, and a series of parametric studies, where the validated finite element models were used to generate further numerical data. The obtained test and numerical data were then adopted to evaluate the current codified design interaction curves for press-braked S690 high strength steel slender channel section stub columns under combined compression and minor-axis bending, as provided in the European code, North American specification and Australian/New Zealand standard. The evaluation results revealed that the codified design interaction curves led to conservative and scattered resistance predictions, mainly due to the conservative end points (i.e. the cross-section compression and bending resistances). Finally, a new design interaction curve, anchored to more accurate end points, was proposed and shown to result in a higher level of design accuracy and consistency than the codified design interaction curves. • The behaviour of S690 high strength steel slender channel sections under minor-axis combined loading was studied. • Minor-axis eccentric compression tests were carried out. • FE models were developed and validated against the test results and then used to perform parametric studies. • The codified design interaction curves were evaluated, revealing a high level of conservatism. • A new interaction curve, anchored to the CSM end points, was proposed and shown to yield higher design accuracy. [ABSTRACT FROM AUTHOR]

This paper presents experimental and numerical investigations into the cross-sectional behaviour and resistances of press-braked S690 high strength steel channel sections under combined compression and minor-axis bending. An experimental programme was firstly conducted and included initial local geometric imperfection measurements and ten minor-axis eccentric compression tests. The experimental programme was accompanied by a numerical modelling programme, where finite element models were developed and validated against the test results and then employed to perform parametric studies to expand the test data pool over a wider range of cross-section dimensions and loading combinations. The obtained test and numerical data were then used to assess the relevant codified design interaction curves, as provided in the European code, North American specification and Australian/New Zealand standard. The assessment results revealed that all the codified design interaction curves led to excessively conservative and scattered resistance predictions for press-braked S690 high strength steel channel sections under combined compression and minor-axis bending, mainly owing to the conservative linear shapes and inaccurate end points. Finally, a new design interaction curve, with more accurate end points and nonlinear shape, was proposed and shown to offer more accurate and consistent resistance predictions than the codified design interaction curves. • The behaviour of S690 high strength steel channel sections under minor-axis combined loading was studied. • Minor-axis eccentric compression tests were conducted. • FE models were developed and validated against the test results and then used to perform parametric studies. • The codified design interaction curves were assessed, revealing a high level of conservatism. • A new design interaction curve was proposed and shown to provide much improved design accuracy. [ABSTRACT FROM AUTHOR]

• Determination of the temperature distribution of an IPT-asphalt system while energizing an emulator IPT pad. • Five ambient temperatures, ranging from 15 to 50 °C, four power losses of the pad, ranging from 5 to 30 W, and three experimental configurations were considered. • Acceptable agreement between the results of the experimental and simulation models was found. • Higher thermal conductivity of the asphalt mixture lowers the temperatures inside the experimental setup. • Change in the asphalt mixture's specific heat by 20% mainly affected the heating and cooling rates. This paper utilises experimental and numerical methods of determining the temperature distribution in an asphalt slab containing an energized embedded emulator Inductive Power Transfer (IPT) pad. In the series of experiments, five different ambient temperatures from 15 to 50 °C, four IPT pad power loss values from 5 to 30 W, and three pavement layer configurations were considered. A thermal camera was used to measure the surface temperature distribution of the asphalt slab, while a Fiber Bragg Grating (FBG) sensor and six thermistors were used for point temperature measurements. A numerical simulation, using a combination of experimentally determined, and literature-sourced thermal properties was developed for the experimental set-up, which was validated against the measured temperatures. Results show good agreement between the experimental and the simulation models with a maximum point-wise differential of 12.9%. It was found that increasing the ambient temperature from 15 to 50 °C, at a constant pad power loss of 30 W, increased the simulated asphalt surface temperature (25 mm offset from the pad) from approximately 32 to 65 °C. Moreover, varying the IPT pad power loss from 5 to 30 W, at an ambient temperature of 50 °C, increased the simulated asphalt surface temperature at the same location from approximately 53 to 65 °C. However, changing the asphalt thickness from 43 mm to 86 mm, or adding a compacted aggregate base course layer below the IPT-asphalt slab, only marginally decreased the temperature values. An increase in the thermal conductivity of the asphalt from 1 to 3 Wm−1°K−1, results in the temperatures reducing by a maximum of approximately 21% at the bottom of the pad. However, changing the specific heat has a very small effect on the heating and cooling rates. A numerical study of an in-service New Zealand asphalt pavement, containing an emulator IPT pad and utilising a three-day period of recorded New Zealand summer climatic data is presented. The method can be used to identify IPT-pavement hotspots and aid in the design of thermally robust IPT-pavement systems. [ABSTRACT FROM AUTHOR]

Aluminium alloy has recently become popular in New Zealand's construction sector as a sustainable building material. However, in roll-formed aluminium alloy (RFA) channel beams, particularly those having web holes, cripples at points of concentrated or localised loading. In this paper, end-two-flange (ETF) web crippling behaviour of RFA unlipped channels having web holes was investigated using experimental tests, numerical simulations and a deep learning model referred as deep belief network (DBN). A total of 1080 data points was generated to train the DBN, using a finite element (FE) model that was validated using 30 new experimental results reported in this paper. Compared to the test data, the DBN predictions were conservative by around 6%. Using the DBN predictions, a comprehensive parametric study was undertaken which used the validated FE model in order to explore the effects of hole size, hole location, section thickness, and bearing plate on the web crippling strength of RFA channels having web holes. Web crippling strengths obtained from the DBN, tests and finite element analysis (FEA) were utilised to evaluate the performance of current design specifications from the American Iron and Steel Institute (AISI), Australian/New Zealand Standards (AS/NZS 1664; AS/NZS 4600:2018) and Eurocode (CEN 2006, 2007). It is shown that the current design rules are not reliable to predict the web crippling strength of RFA unlipped channels with web holes. As a consequence of the parametric analysis, new web crippling strength and web crippling strength reduction factor formulae for perforated RFA unlipped channels were proposed. A reliability analysis was then conducted, which confirmed that the proposed equations are capable of predicting the ETF web crippling strength of perforated RFA unlipped channels. • ETF web crippling behaviour of roll-formed aluminium alloy channels was studied experimentally and numerically. • Finite element analysis was conducted and validated against test results. • A deep-learning model was developed to predict the web crippling strength. • A parametric study was conducted to investigate the effects of different parameters. • New design equations were proposed for web crippling strength of roll-formed aluminium alloy channels. [ABSTRACT FROM AUTHOR]

Cold-formed steel (CFS) is a popular form of construction in New Zealand and the developed world because it can be cost-effective, durable, sustainable, resilient to extreme environmental and seismic loads and easy to install. When used in domestic and medium-rise buildings, T-Stub connection between CFS channel sections is formed by using self-drilling screws which connect the flanges. In the literature, no prior investigation on the tension capacity of such connection has been reported. Therefore, this paper describes a novel test procedure for determining the tension capacity of such CFS T-Stub connection and the associated mechanism of failure. An experimental test program that comprises thirty experimental tests is reported in this paper. Three channel section thicknesses were examined: 0.55 mm, 0.75 mm, and 0.95 mm. All specimens failed as a result of tilting of the screws and bearing failure. Non-linear elasto-plastic finite element (FE) models were developed, and the predictions were validated against the experimental test results. It was adjudged that there was reasonable agreement in terms of connection strength and failure mode prediction. Finally, the design strengths derived from current design standards were compared with the experimental failure loads. It was found that the American Iron and Steel Institute (AISI 2016) and Australian and New Zealand Standard (AS/NZS 2018) are conservative by 6% and unconservative by 10% for the initial and final failure loads of T-Stub CFS connections, respectively. • A novel cold-formed steel T-stub connection was studied experimentally and numerically. • The results of a total of 30 new experimental tests were reported. • Finite element analysis was conducted and validated against the test results. • The prediction accuracy of current design standards was evaluated. [ABSTRACT FROM AUTHOR]

Cold-formed steel sections are used in many different shapes based on their applications. Recently, a new C-section known as SupaCee was introduced in Australia with higher flexural capacities compared to traditional channel sections. However, all cold-formed steel sections are vulnerable to web crippling failures due to their higher plate slenderness. Australian/New Zealand (AS/NZS 4600) and North American (AISI S100) Standards use a unified web crippling design equation with four coefficients while Eurocode 3 Part 1.3 uses different design equations to predict the web crippling capacities of cold-formed steel sections. The web crippling coefficients were developed based on the experimental studies undertaken since the 1940s. These experimental studies utilised different test set-ups and specimens lengths and hence the accuracy of predictions using these coefficients may be inadequate. No coefficients are available for unlipped channel sections with fastened supports and high strength SupaCee sections while the same coefficients are used for lipped channels with fastened and unfastened supports. To address these shortcomings, the web crippling behaviour of unlipped and lipped channel and SupaCee sections was experimentally investigated based on recently developed AISI S909 web crippling test guidelines. Finite element analyses were then performed to extend the range of cold-formed steel sections. Using the web crippling capacity results from both experiments and finite element analyses, new equations were proposed to determine the web crippling capacities of lipped and unlipped channel and SupaCee sections. Suitable direct strength method based web crippling design equations were also developed. This paper presents the important details of several detailed web crippling studies undertaken recently including a suite of web crippling design equations that can be adopted in relevant cold-formed steel standards. • Investigated web crippling behaviour of several cold-formed steel sections. • Developed advanced finite element models, validated and used in detailed parametric studies. • Proposed improved web crippling coefficients for AS/NZS4600/AISI S100 equations. • Developed predictive equations for the buckling loads for DSM based design. • Developed DSM equations for the web crippling design of cold-formed steel sections. [ABSTRACT FROM AUTHOR]

• The structural behaviour of cold-formed steel T -stub connections with HRC and screws was studied experimentally and numerically. • The results of a total of 15 new experimental tests were reported. • Finite element analysis was conducted and validated against the test results. • The prediction accuracy of current design standards was evaluated. Cold-formed steel (CFS) T -Stub connections are widely used in single-story buildings, and their use is increasing in multi-story and long-span buildings. Recently, an innovative CFS T -Stub connection was developed using self-drilling screws and the Howick Rivet Connector (HRC), and such a newly-developed connection demonstrated excellent structural performance in the building industry. In this paper, a comprehensive experimental and numerical investigation was conducted to investigate the failure mechanism and structural behaviour of CFS T -Stub connections with a combination of HRC and screws under tension force, considering the effects of screw numbers. Firstly, a total of 15 new experimental tests were conducted on the CFS T -Stub connections with various numbers of screws. From the experiments, it was observed that the HRC was subjected to shear failures, while screws failed primarily due to tilting and bearing failures in all investigated specimens. Then, a non-linear elasto-plastic finite element (FE) model was developed and validated against the experimental results in terms of connection strength and failure modes. Finally, the design strengths obtained from the American Iron and Steel Institute (AISI 2016) & Australia/New Zealand standards (AS/NZS 2018) and Ahmadi et al. (2016) were compared with the test and FEA results, showing that the ultimate design strength of CFS T -Stub connections was overestimated by 16% and 14%, respectively. However, for T -Stub connections with HRC alone and with HRC and one screw, these design guidelines were unconservative by 5%. [ABSTRACT FROM AUTHOR]

• The structural behaviour of press-braked austenitic stainless steel slender channel section beam-columns was studied. • Ten beam-column tests were performed. • FE models were developed to simulate the test results and then adopted to conduct parametric studies. • The codified design interaction curves were assessed, indicating conservatism. • A new improved design interaction curve was proposed. The present paper reports experimental and numerical studies of the structural behaviour and resistances of press-braked austenitic stainless steel slender channel section beam-columns under combined compression and minor-axis bending. An experimental programme, including initial geometric imperfection measurements and ten beam-column tests, was firstly performed. The test procedures, setups and results were fully reported. The experimental programme was accompanied by a numerical modelling programme, including a validation study, where finite element models were developed and validated against the test results, and a series of parametric studies, where the validated finite element models were used to generate further numerical data. The obtained test and numerical data were adopted to assess the current design interaction curves for press-braked austenitic stainless steel slender channel section beam-columns, as provided in the European code, American specification and Australian/New Zealand standard. The assessment results revealed that all the three codified design interaction curves led to conservative and scattered resistance predictions, due to the conservative compression and bending end points and inappropriate shapes. To address these shortcomings, a new design interaction curve has been proposed and shown to yield a higher level of design accuracy and consistency for press-braked austenitic stainless steel slender channel section beam-columns than the codified design interaction curves. [ABSTRACT FROM AUTHOR]

The strength and stiffness of cold-formed steel portal frames are heavily related to the performance of their joints; these joints are normally formed through brackets, bolted to the webs of channels. They should have adequate strength to ensure the frame fails within the members, and the design moment capacity of a joint should be equal to or exceed the moment to which the joint is subjected. For apex brackets, based on the results of a non-linear elasto-plastic finite element study, the authors have recently proposed design guidance in the form of equations for predicting the moment capacity. However, this prediction was limited to fully restrained apex joints against lateral torsional buckling, which is an arrangement not commonly used in practice. Furthermore, the joints considered were composed of back-to-back brackets connecting back-to-back channels. The design recommendations were further limited to apex joints under bearing gravity load, equivalent to the opening moment applied to the bracket. This paper extends the previous work by now considering both single and double apex brackets, which are partially restrained, consistent with New Zealand practice, and considering both opening and closing moments on apex joints (or gravity and wind uplift load on portal frames). This study proposes unified design equations from a parametric study comprising 5,040 finite element models. • Validate finite element model of apex joints under bearing pure bending moment. • Propose design equations to predict the moment capacity of both the single and double apex brackets, used in practice. • Validate the proposed equation against the finite element analysis results of the practical portal frames. [ABSTRACT FROM AUTHOR]

Cold-formed steel (CFS) weatherboard claddings are popular in industrial and housing applications, and CFS weatherboard claddings with spans of up to 1500 m are now being used in New Zealand. However, there are limited experimental data on their behaviour under uplift and cyclic wind loading. This paper presents a detailed experimental investigation to investigate the wind-uplift capacity of clip-fixed CFS weatherboard cladding. A total of 24 new tests were carried out on a series of weatherboard claddings under static wind uplift and cyclic pressure using a Pressure Loading Actuator (PLA). Two different cladding thicknesses (0.48 mm and 0.55 mm) were considered in the experimental investigation. The material properties of the claddings were determined using tensile coupon tests and the initial geometric imperfections were measured using a laser scanner. Tests revealed that the weatherboard clips are susceptible to local failure in the region of the tek screws where two adjacent cladding sheets are connected, followed by the global failure of the cladding assembly at ultimate wind pressure. The global failure was initiated by the shear failure of the weatherboard clips. A nonlinear finite element model was also developed for weatherboard claddings under static wind uplift pressure, which showed reasonable agreement with the experimental results. The non-linear material properties and initial imperfections were included in the finite element model. A parametric study was conducted comprising 264 finite element models to investigate the effect of thickness, yield stress and cladding span on the wind uplift capacity of such weatherboard claddings. It was found that the width of pan, yield stress and cladding thickness are important factors in influencing the wind-uplift capacity of such weatherboard cladding profiles. The experimental results and the numerical model can be used by the researchers and practising engineers to predict the wind-uplift capacity of such weatherboard claddings under static wind uplift and cyclic wind pressures. • An experimental program was carried out on a series of weatherboard claddings under static wind uplift and cyclic pressure using a Pressure Loading Actuator (PLA). • A total of 24 tests were conducted and reported herein. Two different cladding thicknesses (0.48 mm and 0.55 mm) were considered in the experimental investigation. • A nonlinear finite element model was also developed for weatherboard claddings under static wind uplift pressure, which showed good agreement with the experimental results. • A parametric study was conducted comprising 264 finite element models. • Load-span tables are also proposed for ultimate limit state of failure for weatherboard claddings. [ABSTRACT FROM AUTHOR]

Cold-Formed Steel (CFS) members are highly susceptible to several structural instability phenomena, involving either individual (Local — L, Distortional — D and Global — G) or interaction (LD, LG, DG, and LDG) buckling modes. The buckling mode interaction of CFS columns and beams may lead to strength erosion compared to isolated modes and must be considered in structural design. The North American, Australian/New Zealand and Brazilian standards incorporated the Direct Strength Method (DSM) that provides accurate design approach for columns and beams affected by L, D, G, and LG buckling modes. However, the coupled LD, DG, and LDG buckling modes are not currently considered in the DSM and many recent research projects have been focused on these topics. The procedure adopted by DSM estimates the CFS member strength through experimentally calibrated design strength equations and curves, based on the relationship between the member elastic stability and the steel yielding property, respectively the elastic critical buckling load and the plastic load, represented by the slenderness factor. The more accurate the buckling load, the more improved will be the result of the column strength by the DSM equations. In this context, the present paper presents the main results of the investigation, based on both experimental and finite element method numerical results, that conducted to calibrated strength curves for CFS unstiffened sections columns without holes covering LD interaction buckling mode. To take into account the effect of the LD buckling, the proposed procedure for design purposes incorporates the slenderness factor ratio R λ D L = λ D / λ L as the main variable, and λ L , λ D , λ G as the local, distortional and global slenderness factors, respectively. • Local–Distortional buckling mode interaction of thin-walled steel cold-formed columns. • General method for the design of columns under Local–Distortional buckling mode. • Structural design rules according to the Direct Strength Method principles. • Shell finite element method model for the analysis of steel thin-walled columns. [ABSTRACT FROM AUTHOR]

This paper reports an experimental and numerical investigation into the buckling behaviour and resistance of press-braked ferritic stainless steel slender channel section beam–columns under combined compression and minor-axis bending moment. An experimental programme was firstly performed, including material coupon tests, initial global and local geometric imperfection measurements and ten beam–column tests. The experimental programme was followed by a numerical modelling programme, where finite element models were developed and validated against the experimental results and then adopted to conduct parametric studies to generate additional numerical data. Based on the obtained test and numerical data, the existing design interaction curves, as set out in the European code, American specification and Australian/New Zealand standard, were evaluated and found to result in conservative and scattered resistance predictions. An improved design interaction curve, anchored to more accurate end points and featuring more appropriate shape, was then developed and shown to offer more accurate and consistent resistance predictions for press-braked ferritic stainless steel slender channel section beam–columns over the codified design interaction curves. Statistical analyses were also performed to confirm the reliability of the new proposal. • The behaviour of press-braked ferritic stainless steel slender channel section beam–columns was studied. • Ten beam–column tests were conducted. • FE models were developed to validate against the test results and then used to conduct parametric studies. • The codified design interaction curves were evaluated, revealing conservatism. • A new improved design interaction curve was developed. [ABSTRACT FROM AUTHOR]

This paper presents an experimental and numerical investigation into the flexural–torsional buckling behaviour and resistance of pin-ended press-braked S690 high strength steel angle section columns. An experimental programme was firstly conducted and included initial geometric imperfection measurements and twelve pin-ended column tests. The column test results, including the failure loads and deformations at the failure loads, load–mid-height torsional rotation curves and failure modes, were fully reported and discussed. The experimental programme was accompanied by a numerical modelling programme, where finite element models were developed and validated against the test results and then employed to perform parametric studies to expand the test data pool over a wider range of cross-section dimensions and member lengths. The obtained test and numerical data were then used to assess the relevant codified design rules, as provided in the European code, North American specification and Australian/New Zealand standard, and a DSM-based design approach. The assessment results revealed that all the codified design rules lead to excessively conservative and scattered resistance predictions for pin-ended press-braked S690 high strength steel angle section columns susceptible to flexural–torsional buckling, while the DSM-based design approach yields substantially improved resistance predictions, owing to the rational consideration of the length-dependent characteristic of flexural–torsional buckling and the interaction of flexural–torsional buckling with minor-axis flexural buckling. • The flexural–torsional buckling of pin-ended press-braked S690 high strength steel angle section columns was studied. • Twelve pin-ended compression tests were conducted. • FE models were developed and validated against test results and then adopted to perform parametric studies. • The accuracy of the codified design rules was assessed, indicating inaccuracy. • A new DSM-based design approach was evaluated and shown to yield improved design accuracy. [ABSTRACT FROM AUTHOR]

• 1. The local–flexural interactive buckling of press-braked stainless steel slender channel section columns is studied. • 2. Ten pin-ended column tests are conducted. • 3. FE models are developed and validated against the test results and then adopted to conduct parametric studies. • 4. The codified design rules are assessed and shown to yield inaccurate interactive buckling resistance predictions. • 5. A new design method is proposed, showing improved design accuracy. The present paper reports experimental and numerical studies of the local–flexural interactive buckling behaviour and resistance of press-braked stainless steel slender channel section columns. A testing programme was firstly performed, including tensile coupon tests, initial geometric imperfection measurements and ten pin-ended column tests. The pin-ended column test setup, procedures and results were fully reported and analysed. The progression of local buckling and flexural buckling was discussed in detail. Following the testing programme, a numerical modelling programme was conducted, where finite element models were developed to replicate the test responses and then employed to perform parametric studies to generate further numerical data over a wide range of cross-section dimensions and member effective lengths. The obtained test and numerical data were employed to assess the accuracy of the relevant design rules for press-braked stainless steel slender channel section columns, as set out in the European code, American specification and Australian/New Zealand standard. The assessment results revealed that the European code leads to conservative and scattered interactive buckling resistance predictions, while the American specification and Australian/New Zealand standard result in many unsafe and scattered interactive buckling resistance predictions. A new design approach was then developed, based on the Eurocode column buckling curve and the continuous strength method, and shown to lead to accurate, consistent and safe interactive buckling resistance predictions for press-braked stainless steel slender channel section columns. The reliability of the new design approach was confirmed by means of statical analyses. Besides, the relevant design rules for press-braked carbon steel slender channel section columns, as given in the North American specification, were assessed, and shown to result in unsafe though consistent interactive buckling resistance predictions, when used for their stainless steel counterparts. [ABSTRACT FROM AUTHOR]

A new high-chromium grade EN 1.4420 stainless steel, which possesses higher material strength and better corrosion resistance but lower material price than the currently most commonly used grade EN 1.4301 stainless steel, has been recently developed, with a good potential in engineering practice. The present paper reports experimental and numerical investigations into the structural behaviour and resistance of concrete-filled high-chromium stainless steel tube (CFHSST) stub columns under combined compression and bending. The experimental investigation was conducted on twelve CFHSST stub column specimens fabricated from high-chromium grade EN 1.4420 stainless steel tubes with three cross-section sizes and concretes with two grades. The failure loads, mid-height lateral deflections, evolution of neutral axis and confinement effect were analysed and discussed. Numerical modelling was subsequently carried out, where finite element models were developed to simulate the test results and then employed to conduct parametric studies to generate further numerical data. The relevant design interaction curves, as set out in the European code, American specification and Australian/New Zealand standard, were assessed for their applicability to CFHSST stub columns under combined compression and bending, based on test and numerical data. The assessment results revealed that the European code and Australian/New Zealand standard provide overall accurate failure load predictions, while the American specification underestimates the failure loads for CFHSST stub columns under combined compression and bending, due to the conservative shape of the design interaction curve. • The structural behaviour of CFHSST stub columns under combined compression and bending is studied. • Twelve eccentric compression tests on CFHSST stub columns are conducted. • The test results, including the neutral axis and the confinement effect, are discussed. • FE models are developed to validate against the test results and then used to conduct parametric studies. • The relevant codied design interaction curves are assessed against the test and FE data. [ABSTRACT FROM AUTHOR]

This paper presents an experimental and numerical study of eccentrically loaded circular recycled aggregate concrete-filled stainless steel tube (RACFSST) stub columns. The testing programme was conducted on twelve specimens designed with different stainless steel tube section sizes and recycled coarse aggregate replacement ratios, and included tensile coupon tests, concrete cylinder tests and eccentric compression tests. The test results, including the failure loads and modes, load–mid-height lateral deflection curves and evolution of neutral axis, were reported and discussed. Following the testing programme, a numerical modelling programme was conducted, with finite element models developed and validated against the test results and then employed to perform parametric studies to generate further numerical data. The confinement effects were analysed based on the numerical data. The relevant design interaction curves, as set out in the European code, American specification and Australian/New Zealand standard, were assessed for their applicability to circular RACFSST stub columns under combined compression and bending. On the basis of the quantitative and graphical assessments, it has been found that (i) each set of codified design interaction curve leads to similar assessment results for eccentrically loaded circular RACFSST stub columns with different recycled coarse aggregate replacement ratios and (ii) the failure load predictions from the codified design interaction curves are conservative. • The structural behaviour and resistance of circular RACFSST stub columns under combined loading are investigated. • Twelve eccentric compression tests are conducted. • FE models are developed to validate against the test results and then used to conduct parametric studies. • The confinement effects of different types of RACFSST composite sections are discussed. • The applicability of the relevant codified N–M interaction curves is evaluated. [ABSTRACT FROM AUTHOR]

• The structural behavior and capacity of RACFSST stub columns under combined loading are studied. • Twelve eccentric compression tests on RACFSST stub columns are conducted. • The evolution of neutral axis in RACFSST composite section as well as the confinement effect are discussed. • FE models are developed to validate against the test results and then used to conduct parametric studies. • The relevant design codes are assessed against the test and FE data. This paper reports experimental and numerical investigations into the behaviour and resistance of recycled aggregate concrete-filled stainless steel tube stub columns under combined compression and bending. Eccentric compression tests were conducted on twelve stub column specimens fabricated from austenitic stainless steel tubes with two cross-section sizes and concretes with three recycled coarse aggregate replacement ratios (0%, 35% and 70%). The test results, including the failure loads, load–mid-height lateral deflection curves, evolution of neutral axis and confinement effect, were discussed in detail. The testing programme was followed by a numerical modelling programme, where finite element models were developed and validated against the test results and then used to perform parametric studies to generate further numerical data over a wide range of cross-section dimensions and loading combinations. Given that there are no existing design codes for recycled aggregate concrete–stainless steel composite structures, the relevant codified design rules for natural aggregate concrete filled-carbon steel tube stub columns under combined compression and bending, as set out in the European code, American specification and Australian/New Zealand standard, were evaluated for their applicability to recycled aggregate concrete filled-stainless steel tube stub columns, based on the test and numerical data. The evaluation results revealed that the European code and Australian/New Zealand standard generally provide an acceptable level of design accuracy, while the American specification yields unduly conservative failure load predictions. [ABSTRACT FROM AUTHOR]

• The local–flexural interactive buckling of S690 high strength steel slender channel section columns was studied. • Twelve pin-ended compression tests were conducted. • FE models were developed and validated and then adopted to perform parametric studies. • The accuracy of the codified design rules was assessed, revealing inaccuracy. • A new design approach was proposed, showing a high level of accuracy. This paper reports an experimental and numerical investigation into the local–flexural interactive buckling behaviour and resistance of press-braked S690 high strength steel slender channel section columns. An experimental programme was firstly conducted and included initial geometric imperfection measurements and twelve pin-ended column tests. Interaction between local buckling and flexural buckling was observed for all specimens upon testing and discussed in detail. The experimental programme was accompanied by a numerical modelling programme, where finite element models were developed and validated against the test results and then employed to perform parametric studies to generate further numerical data over a wide range of cross-section dimensions and member effective lengths. The obtained test and numerical data were used to assess the accuracy of the codified design rules for press-braked S690 high strength steel slender channel section columns failing by local–flexural interactive buckling, as set out in the European code, North American specification and Australian/New Zealand standard. The assessment results revealed that the European code leads to excessively conservative and scattered resistance predictions, while the North American specification and Australian/New Zealand standard result in a higher level of design accuracy and consistency, but still with many conservative resistance predictions for columns with short to intermediate lengths. Finally, a new design approach was proposed and shown to yield substantially more accurate and consistent resistance predictions for press-braked S690 high strength steel slender channel section columns over the design codes. [ABSTRACT FROM AUTHOR]

This paper reports experimental and numerical investigations into the structural behaviour and residual capacity of concrete-filled high strength steel tube (CFHST) stub columns after exposure to fire. The experimental investigation was conducted on twelve square CFHST stub column specimens after exposure to the ISO-834 standard fire for 15 min, 30 min and 45 min and four reference specimens at ambient temperature. The test results, including failure loads, load–end shortening curves, initial compressive stiffnesses and failure modes, were fully reported and discussed. A numerical investigation was subsequently conducted, where thermal and mechanical finite element models were developed and validated against the test results, and afterwards used to performed parametric studies to generate further numerical data over a wide range of cross-section dimensions. Owing to the absence of design codes for composite structures after exposure to fire, the relevant ambient temperature design rules, as set out in European code, American specification and Australian/New Zealand standard, were evaluated, using post-fire material properties, for their applicability to post-fire CFHST stub columns, based on the test and numerical data. The evaluation results revealed that all the three design codes generally yield accurate failure load predictions for CFHST stub columns after exposure to fire. • Post-fire tests on concrete-filled high strength steel tube (CFHST) stub columns were conducted. • The behaviour and residual resistance of CFHST stub columns after exposure to fire were analysed. • FE models were validated against the test results and then used to conduct parametric studies. • The applicability of the ambient temperature design codes to post-fire CFHST stub columns was demonstrated. [ABSTRACT FROM AUTHOR]

• A total of 41 cold-formed steel built-up I-sections were tested under ETF, ITF, EOF and IOF loading conditions. • Finite element models were developed to replicate the experiments. • Parametric study of 258 specimens was performed. • The existing codified web crippling design provisions were assessed. • Design rules were proposed based on the unified equation and direct strength method. This paper reports the experiments, numerical modelling and design of cold-formed steel built-up I-sections subjected to localised loadings. The built-up I-sections were made up of two equal-sized plain channels fastened back-to-back in the web. The web crippling tests were undertaken on 41 built-up I-section members under Interior-Two-Flange (ITF), End-Two-Flange (ETF), Interior-One-Flange (IOF) and End-One-Flange (EOF) loading conditions. The effects of the arrangement of screws along the web height were investigated. After the experiments, finite element (FE) analyses considering the initial local imperfections of the web of the specimens were performed and the validity of the FE models was assessed using the test results. A parametric investigation including 258 numerical simulations was conducted to expand the database and evaluate the influences of the screw arrangements in the web height. The test and numerical results indicated that the failure modes of the specimens with different screw arrangements were generally similar in each loading condition, and the screws located close to the flange-web junctions of the sections could generally provide maximum web crippling resistances of the built-up I-sections. The design recommendations on the arrangements of screws along the web height were proposed. The experimentally and numerically generated web crippling resistances were utilized to assess the current North American specification (AISI S100), Australian and New Zealand standard (AS/NZS 4600) and European code (EN1993-1-3). The results show that the existing codified design formulas lead to either conservative or highly unsafe results. Therefore, two sets of design formulas were derived on the basis of unified equation and direct strength method. [ABSTRACT FROM AUTHOR]

This paper describes the development of a three-dimensional constitutive model for laminated veneer lumber (LVL) needed for new developments using this material. The LVL was manufactured in New Zealand from Radiata Pine. Experimental testing has been performed according to European timber testing standards. Block compression testing has resulted in modulus of elasticity values in the three material directions. Digital image correlation (DIC) technique has been used to determine the six Poisson's ratios. Shear testing, whereby timber specimens were glued between two steel plates, has given stiffness values using DIC measurements. Experimental testing results have been compared with values found in literature. Results from this experimental testing programme have made it possible to create a three-dimensional elastic material model of LVL for the use in finite element analysis programmes. Although the material properties do not result in a symmetrical constitutive matrix, only minor adjustments are needed to gain the benefits of a symmetrical matrix. [ABSTRACT FROM AUTHOR]

In the latest North American Specification S100:2016 Edition and the most up-to-date Australian/New Zealand Standard AS/NZS 4600:2018, the Direct Strength Method (DSM) shear design rules for unperforated channel sections have been adopted. To date, for perforated sections, there is no DSM design rule for shear in the current Specification/Standard while the conventional reduction factor method is still in use to calculate shear strengths for these sections. This paper summarises the test results in an experimental program aiming to determine the ultimate shear strengths of high strength cold-formed C-sections with square holes centrally cut from the webs. A total number of 24 tests were performed using lipped channel sections in which 18 tests were conducted with central square holes of variable thicknesses and sizes, and the remaining 6 were tested with no holes in the webs. Three different section thicknesses and square hole sizes were chosen for investigation in this study. In addition, Finite Element Method (FEM) analysis was initially developed to validate against test results, and the accurate results from the FEM were then employed in a parametric study for the extension of test data by varying the section thicknesses and the hole sizes. In the DSM shear design equations, two inputs namely the shear buckling load, V cr , and the shear yielding load, V y , are required. The numerical solutions for V cr for whole sections with central square holes have been proposed by first author in previous research studies. For V y in this paper, a new and simplified model is proposed based on net web areas. Recommendations for an extension to the DSM shear design rules for channel sections with square holes up to certain hole size limit are given. • An experimental program of high strength cold-formed steel channels with square holes in shear is carried out. • Numerical simulation using Finite Element Method (FEM) program is performed for test validation and parametric study. • Elastic shear buckling loads of channel sections with square holes are computed using numerical solutions. • A new simple and simplified equation based on net web area of the channel to calculate shear yield loads is proposed. • Extension of the DSM shear design rules is proposed for cold-formed channels with square openings up to hole size limit. [ABSTRACT FROM AUTHOR]

Aluminium alloys are increasingly popular in structural engineering applications because they have high strength, low weight and great durability. However, the mechanical properties of aluminium alloy material may be significantly affected by high temperature. This paper presents a numerical study on the behaviour of aluminium alloy channel section columns at elevated temperatures. A non-linear finite element (FE) model was developed and validated against 27 experimental results at high temperature. The validated FE model was used to conduct an extensive parametric study, in which a total of 360 aluminium alloy channel section columns were generated at elevated temperatures. The key parameters for the parametric study include two types of aluminium alloys (6061-T6 and 6063-T5), three lengths (360 mm, 1000 mm and 2000 mm) of columns and ten temperatures (range from 24 °C to 600 °C). The design strengths were calculated using American, Australia/New Zealand and European Standards and compared with the numerical results generated from parametric study. In addition, a reliability analysis was used to assess the reliability level of the considered design methods. • Review of test data on aluminium alloy columns at elevated temperatures. • Development and validation of aluminium alloy column models at elevated temperatures. • Parametric studies to generate numerical results on aluminium alloy channel columns at elevated temperatures. • Comparison of test/FE results with existing design methods. • Assessment of existing methods by reliability analysis. [ABSTRACT FROM AUTHOR]

Cold-formed steel (CFS) channel beams are an increasingly popular choice as load-carrying members in building structures. Such channel beams often include web holes for installation of services. Traditional web holes are normally punched and are un-stiffened. This can restrict the size and spacing of web holes. Recently, a new generation of CFS channel beams with edge-stiffened web holes has been developed and used widely in New Zealand. However, no experimental investigation has been reported in the literature for such channel beams under bending. In this paper, a total of 215 results comprising 16 four-point bending tests and 199 finite element analysis (FEA) are reported on the moment capacity of CFS channel beams with both edge-stiffened and un-stiffened web holes. For comparison, channel beams without web holes were also tested. For all specimens, initial imperfections were measured using a laser scanner. A nonlinear elasto-plastic finite element (FE) model was also developed, and the results showed good agreement with the test results. A parametric study was conducted using the validated FE model to investigate the effects of beam length, hole diameter, stiffener length and fillet radius on the moment capacity of CFS channel beams. It is shown that for the case of a channel beam with five edge-stiffened web holes, the moment capacity increased by as much as 14.5%, compared to that of a plain channel beam. For comparison, the same section with un-stiffened web holes had a 13.6% reduction in moment capacity, compared to that of a plain channel beam. Furthermore, the accuracy of current design guidelines in accordance with the American Iron and Steel Institute (AISI) and Australia/New Zealand (AS/NZ) standards were verified by comparing the tests and FEA results against the design strengths for moment capacity of CFS channel beams without web holes. On the other hand, for CFS channel beams with web holes, the moment capacity obtained from tests and FEA were compared against the moment capacity calculated from the design equations of Moen and Schafer. Upon comparison, it was found that the AISI and AS/NZS can closely predict the moment capacity of CFS channel beams without web holes. The Moen and Schafer design equations were found to be over-conservative by around 11% and 28% for moment capacity of CFS channel beams with un-stiffened and edge-stiffened web holes, respectively. • A new generation of cold formed steel channel beams with edge stiffened holes is examined. • Results from an experimental regime and elasto-plastic finite element are reported. • A parametric study involving 199 FE models was conducted. • Variables included beam length, hole size, stiffener lengths and stiffener fillet radius. • Edge stiffened hole-sections can outperform plain sections in terms of moment capacity. [ABSTRACT FROM AUTHOR]

Cold-formed steel (CFS) back-to-back channels are becoming a popular choice for use in load-carrying members in building structures. These built-up channels often include web holes for installation of services. Traditional web holes are un-stiffened, which can restrict the size and spacing of holes. Recently, a new generation of CFS channels with edge-stiffened holes has been developed and used widely in New Zealand. No research has been reported in the literature to investigate the axial strength of back-to-back channels with edge-stiffened holes. Experiments are required on back-to-back channels with edge-stiffened holes so to understand the effects of composite actions between the back-to-back channels on the axial strength of such channels. This paper presents a total of 162 new results comprising 27 axial compression tests and 135 finite element analysis (FEA) results on the axial strength of back-to-back channels with edge-stiffened holes, un-stiffened holes and plain webs. Prior to compression tests, initial geometric imperfections were measured using a laser scanner. Tensile coupon tests were also conducted to determine the material properties of both the flat and corner portions of the channels. The test results show that for the case of back-to-back channels with edge-stiffened holes, the axial strength increased by 6.6% on average, compared to a back-to-back plain channel. For comparison, the same section with un-stiffened holes had a 12.4% reduction on average in axial strength, compared to a back-to-back plain channel. A nonlinear elasto-plastic finite element (FE) model was then developed, and the results showed good agreement with the test results. The validated FE model was used to conduct a parametric study involving 135 FE models to investigate the effects of column slenderness, diameter of hole, screw spacing, stiffener lengths and stiffener fillet radius on the axial strength of such channels. Finally, the tests and parametric study results were compared against the design strengths calculated in accordance with the American Iron and Steel Institute (AISI) (2016) and Australian and New Zealand Standards (AS/NZS) (2018) for back-to-back plain channels and against the design equations of Moen and Schafer (2011) for back-to-back channels with un-stiffened holes. It was found that the AISI (2016) and AS/NZS (2018) are only 3% conservative to the test results. The Moen and Schafer equations (2008, 2009, 2011) are conservative by 21% on average for back-to-back channels with un-stiffened holes. Deformed shapes at failure from experiments and FEA. Unlabelled Image • A new generation of back-to-back CFS channels with edge-stiffened holes is examined. • Results from an experimental regime and elasto-plastic finite element are reported. • A parametric study involving 135 FE models was conducted. • Variables included column slenderness, hole size, screw spacing, stiffener lengths and stiffener fillet radius. • Edge stiffened hole-channels can outperform plain channels in terms of axial strength. [ABSTRACT FROM AUTHOR]

Recently, a new generation of cold-formed steel (CFS) channel sections with edge-stiffened circular holes have been developed by industry in New Zealand. No previous research, however, has considered the web crippling strength of CFS channel sections with edge-stiffened circular web holes under the interior-two-flange (ITF) loading conditions. In this paper, a combination of experimental investigation and non-linear finite element analysis (FEA) are used to investigate the effect of edge-stiffened holes under ITF loading conditions; for comparison, channel sections without holes and with unstiffened holes are also considered. In total, 30 web crippling test results are reported. A non-linear finite element (FE) model is described, and the results were compared against the test results, which showed a good agreement in terms of both the web crippling strength and failure modes. The results indicate that the stiffened web holes can significantly improve the web crippling strength of CFS channel sections. Using the validated FE model, a parametric study was conducted which include 1116 FE analyses, covering the effect of different hole sizes, edge-stiffener lengths and fillet radii, length of the bearing plates and position of the holes in the web. From the results of the parametric study, design recommendations in the form of web crippling strength reduction factors are proposed, that are conservative to both the experimental and FE results. • Web crippling tests of cold-formed channel section with edge-stiffened web openings was conducted. • The results indicate that the stiffened holes can significantly improve the web crippling strength. • Non-linear finite element (FE) models were developed and validated against the test results. • A parametric study involving 1116 FE analyses was performed. • Design recommendations in the form of web crippling strength reduction factors were proposed. [ABSTRACT FROM AUTHOR]

This paper describes an investigation of web crippling behaviour of aluminium alloy plain and lipped channels with flanges restrained. A total of 340 data is presented that include 52 test results and 288 numerical results. A series of tests was conducted on plain and lipped channels fabricated by extrusion using 6063-T5 and 6061-T6 heat-treated aluminium alloys under end-two-flange (ETF) and interior-two-flange (ITF) loading conditions. The concentrate loads were applied by means of bearing plates. The flanges of the channels were either bolted (fastened) to one or two bearing plates. A finite element model was developed and verified against the experimental results. Geometric and material non-linearities were included in the finite element model. It was shown that the finite element model closely predicted the web crippling strengths and failure modes of the tested specimens with flanges restrained. Hence, the finite element model was used for an extensive parametric study of cross-section geometries, and the web slenderness value ranged from 24.0 to 207.3. The test results and the web crippling strengths predicted from the finite element analyses were compared with the design strengths obtained using the American, Australian/New Zealand and European specifications for aluminium structures. A unified web crippling equation with new coefficients for aluminium alloy channels with flanges restrained under ETF and ITF loading conditions is proposed in this study. Since two failure modes of web buckling and web yielding were also observed in the aluminium plain and lipped channels with flanges restrained, design rules of web crippling strengths are also proposed by considering the lesser of the web buckling strength and web yield strength. • Web crippling tests were conducted on aluminum alloy channels with flanges restrained. • A finite element model was developed for aluminium alloy channels undergoing web crippling. • The effect of flange-restrained condition on the web crippling strengths of aluminium alloy channels was examined. • The current web crippling design rules for aluminum structures were assessed. • Two web crippling design approaches are proposed for aluminium alloy channels with flanges restrained. [ABSTRACT FROM AUTHOR]

The use of cold-formed steel (CFS) channel sections are becoming popular as the load-carrying members in building structures, and such channel sections often include web openings for the ease of installation of services. Traditional web openings are normally punched, and are unstiffened which can restrict the size and spacing of web openings. Recently, a new generation of CFS channel sections with edge-stiffened web openings has been developed, and is widely used in New Zealand. However, no experimental investigation has been reported in the literature for such channel sections under compression. In this paper, a total of 75 results comprising 26 axial compression tests and 49 finite element analysis results are reported on the compression resistance of CFS channel sections with both edge-stiffened and unstiffened web openings. For comparison, channel sections without web openings were also tested. For all specimens, initial imperfections were measured using a laser scanner. A nonlinear elasto-plastic finite element model was also developed, and the results showed good agreement with the test results. A parametric study was conducted using the validated finite element model to investigate the effect of opening spacing and column length on compression resistance of channel sections. It is shown that for the case of a channel section having seven edge-stiffened web openings, the compression resistance increased by as much as 22%, compared to a plain channel section. For comparison, the same section having unstiffened web openings had a 20% reduction in compression resistance, compared to a plain channel section. • A new generation of cold formed steel sections with edge stiffened holes is examined. • Results from an experimental regime and elasto-plastic finite element are reported. • Local and overall imperfections are considered in FE models. • Edge stiffened hole-sections can outperform plain sections in terms of axial strength. • A parametric study demonstrating the effect of opening spacing and column length was conducted. [ABSTRACT FROM AUTHOR]