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Recently, a new generation of roll-formed aluminium sections have been produced by BlueScope Permalite Australia and utilized in structural systems. However, limited research has been conducted to investigate their buckling instabilities including web crippling failure. The empirical nature of the current design guidelines may also lead to inaccurate estimation to their web crippling capacities. Therefore, this study aims to investigate the web crippling behaviour of and the design considerations for roll-formed aluminium lipped channel (ALC) sections using a combination of experimental study and finite element analysis (FEA). In total, 40 ALC specimens were tested under one-flange loading conditions with flanges being restrained to the supports (Fastened). Non-linear finite element models were also developed and validated against the experiments. An extensive parametric study was subsequently conducted to extend the range of geometrical dimensions and aluminium alloy grades of ALC sections. Further, the applicability and accuracy of the design rules given in the American, Australian, and European specifications were assessed. It was found that most of these guidelines yield either unconservative or over-conservative predictions of the ultimate web crippling capacities, and hence suitable modifications were proposed. Predictions due to the modified design rules showed a good agreement with both experimental and numerical results, and are hence recommended to be incorporated in relevant aluminium standards.

Occupying a substantial proportion of the overall building expense, building envelopes are the subject of ongoing research and improvement in both aesthetic and structural aspects. The aluminium window wall frame, consisting of vertical members (mullions) and horizontal members (head and sill transoms), is placed between sub-heads at the top and sub-sills at the bottom of the wall. These window walls are designed to carry lateral wind loads. Of particular importance to design stability is the bearing behaviour of aluminium sub-heads. The bearing behaviour and capacities of C-shaped sub-heads were recently investigated through a detailed experimental study at Griffith University for the development of strength prediction equations. To allow for easier assembly of facade panels, a kind of sub-head section known as sub-head with removable bead is used in aluminium window wall system. Two parts of this sub-head are connected together without any external mechanisms. The present research places emphasis on assessing the bearing behaviour of aluminium sub-heads with removable beads through comprehensive experimental testing. A total of 36 tests were conducted using six section geometries, two engagement lengths, and three bearing widths. The bearing strengths obtained from tests of aluminium sub-heads with removable beads were compared with the bearing capacities predicted using the design rules developed by the authors for conventional C-shaped aluminium sub-heads and available cold-formed steel design provisions (AISI S240 2015, TI 809-07, and SSMA 2000 specifications). As a result of the investigation, the current design equations were found to be unreliable for estimating the bearing capacity of aluminium sub-head sections with removable beads. Hence, new design expressions have been developed which accurately predict the strengths of aluminium sub-heads with removable beads under out-of-plane loads. Furthermore, the influence of the removable beads on the bearing behaviour and capacity is discussed in detail.

Cold-formed stainless-steel (CFSS) sections are increasingly popular for architectural and structural applications, especially in the corrosive environment due to its resistance to corrosion and other various benefits. The combination of stainless-steel material properties and the lightweight section properties makes the CFSS section the right choice for offshore steel structures. The demand for the stainless-steel sections in the construction industry is limited to a certain extent due to the higher cost; thus, the optimal use of stainless steel is vital. Openings to the web of CFSS Lipped Channel Beams (LCB) are introduced to facilitate the building services to reduce the floor height. Subsequently, the shear capacity is reduced due to the reduction of the web area. However, only very limited researches have been conducted so far to predict the reduced shear capacity of CFSS LCBs with circular web opening. Hence, this paper addresses a numerical study to investigate the shear behaviour and strength of cold-formed austenitic grade 1.4301 and duplex grade 1.4462 stainless steel LCB sections with unreinforced circular web openings. A detailed parametric study was carried out by developing 180 Finite Element Analyses (FEA) models to establish a wide-ranging shear strength database following the validation process with available shear test results. The analysis of the numerical results showed that the currently available reduction factor equations are either conservative or unsafe to use for the CFSS LCBs with circular openings. Hence, three sets of equations with different approaches to predict the shear capacity of CFSS LCBs with circular web opening are developed and presented in this paper.

Aluminium sections are significantly used as primary load bearing members in the building industry due to its corrosion resistance, ease of fabrication and erection, and high strength-to-weight ratio. Roll-formed aluminium lipped channel beam (LCB) is one of these sections which are typically used as roof purlins, floor joists and rafter. However, LCBs are vulnerable to buckling failures due to the increased web slenderness and low elastic modulus compared to steel. Hence an experimental study was conducted at Griffith University to investigate the shear behaviour of these sections. Finite element models of aluminium LCBs were then developed and validated with test results. A detailed parametric study was also undertaken with different sections, web slenderness, aluminium grades and aspect ratios to obtain the shear strengths and shear buckling characteristics of aluminium LCBs. The ultimate shear capacities of aluminium LCBs obtained from the tests and finite element analyses (FEA) were compared with the current shear design rules of Australian/New Zealand Standard and Eurocode for both aluminium structures and cold-formed structures as well as direct strength method (DSM). The comparison showed that these current shear design rules are not suitable to predict the shear capacities of aluminium LCBs. Hence new design rules were proposed in this study to accurately predict the shear capacities of roll-formed aluminium LCBs. This paper presents the details of the experimental and numerical studies and the development of shear design rules based on Australian/New Zealand Standard, Eurocode and DSM.

Aluminium alloys have recently been utilised in the fabrication of thin-walled members using a roll-forming technique to produce purlins, floor joists and other structural bearers. Such members are often subjected to transversely concentrated loads which may possibly cause a critical web crippling failure. Aluminium specifications do not explicitly provide clear design guidelines for roll-formed members subjected to web crippling actions. Therefore, this study was conducted to investigate the mechanism of web crippling for roll-formed aluminium lipped channel (ALC) sections with flanges attached to supports (fastened) under two-flange loading conditions. Based on the experimental works presented in a companion paper, numerical simulations were conducted including an extensive parametric study covering a wide range of ALC geometrical dimensions, bearing lengths, and 5052 aluminium alloy grade with H32, H36 and H38 tempers. The acquired web crippling data were then used to investigate the influence of the flange restraints on the web crippling mechanism of the ALC sections. Furthermore, a detailed assessment of the consistency and reliability of the currently available design rules used in practice was carried out. The predictions of the web crippling design guidelines given in the Australian, American and European specifications were found to be unsafe and unreliable, whereas a good agreement was obtained between the predictions of our recently proposed design guidelines and acquired web crippling results. Further a suitable Direct Strength Method (DSM)-based design approach was developed in this study with associated equations to predict the elastic bucking and plastic loads of fastened ALC sections under two-flange loading conditions.

Nailplated timber trusses are widely used in residential housing. However, there is limited evidence of use or research on the application of nailplated trusses in exposed environments. It is common knowledge to the nailplated truss industry that weather-exposed trusses experience a phenomenon referred to as “nailplate backout”, where the nailplates separate from the timber surface due to the shrink-swell mechanism of the timber in response to its varying moisture content. This paper investigates the performance of innovative nailplated joints on: (1) stopping moisture-driven backout and (2) increasing the capacity of the joints, when compared to currently used joints, after exposure to severe moisture cycling. Three different experimental sets of joints were manufactured to achieve these outcomes, with Set 1 and Set 2 containing 100 splice and 100 butt joints while Set 3 had 40 splice and 40 butt joints. Sets 1 and 2 have a re-designed tooth profile where: (1) Set 1 combined a polyurethane adhesive with a modified nailplate tooth designed to allow the adhesive to penetrate the timber and (2) Set 2 implemented a hook in the middle of the nailplate teeth to grab the timber when the nailplate tries to separate from the timber, either from moisture induced backout or from loading. Polyurethane adhesive was also used in Set 3 but on an un-modified tooth profile. To evaluate the efficiency of the new nailplates, control joints with unmodified nailplates were manufactured for each set and tested. All joints were subjected to severe accelerated moisture cycles inside an air-driven kiln with the temperature being kept constant 70 °C and the relative humidity varied between 15 and 95%. The cycles consisted of a 7-h wetting and an 18-h drying period. For Sets 1 and 2, the tensile capacity of the joints was measured after 0, 3, 6, 9 and 12 moisture cycles, while for Set 3, it was only measured after 0 and 12 cycles. The backout was recorded after each moisture cycle for Sets 1 and 2 and after 12 cycles for Set 3. The average backout of Set 1 and Set 2 control joints after 12 severe cycles was 1.13 mm and 1.01 mm, respectively, while the addition of glue and a hook reduced the backout to 0.56 and 0.92 mm, respectively. In terms of capacity, the adhesive in Set 1 increased the capacity for the splice joints and butt joints by 43% and 13%, respectively. In Set 2, the hook only marginally increased the capacity of the splice joints by 13% and reduced the average butt joint capacity. Observations were made regarding the failure modes of the joints. The addition of the adhesive and hook to the nailplate teeth resulted in more joints failing due to the capacity of the timber rather than due to the nailplate separating from the timber during the tensile testing.

Stainless steel is a high‐performance construction material that combines the strength and stiffness associated with ferrous alloys with the corrosion resistance derived principally from the high chromium content. Its unique combination of properties usually comes at a cost, which puts increased emphasis on ensuring that the material is utilized to the upmost in structural applications. Consequently, in the recent years, an increase in the use of stainless steel in the construction industry has been witnessed, more specifically in exposed architectural applications and where total life economics, durability, improved resistance to aggressive environment, etc. are prime deciding criteria. However, the shear behaviour and capacity of cold‐formed stainless steel beams has not been investigated adequately in the past. Hence, detailed finite element analyses (FEA) were undertaken to investigate the shear behaviour and strength of stainless steel lipped channel beams (LCBs). The developed finite element models were first validated using the shear test results. They were then used in a detailed parametric study to investigate the effects of various influential parameters such as section thickness, depth and grade. Moreover, a parametric study was conducted to emphasize the beneficial effect of strain hardening of stainless steel on shear capacity of LCBs, in particularly for compact sections. FEA results showed that currently available design equations (EN1993‐1‐4) are inadequate to capture the available inelastic reserve capacity of compact stainless steel LCBs, thus suitable equations were proposed to enhance the predictions. This paper presents the details of finite element modelling and analyses of stainless steel LCBs and the development of these new shear design rules.

Cold-formed steel (CFS) members, when subjected to optimisation, can significantly increase their ultimate load carrying capacity leading to a more economical and efficient structural system. This paper presents the details of an investigation on optimisation of CFS beams subjected to bending capacity and an investigation of shear and web crippling capacities of optimised sections. The optimisation was aimed to meet construction constraints reported in Eurocode 3 (EC3). In this research, 4 different CFS sections were considered including the introduction of 2 novel sections (Super Sigma and Smart Beam) which has closer shear center to the web and less susceptible to web buckling. The bending capacity of the available sections were obtained based on the effective width method reported in EC3, while the optimisation procedure was performed using particle swarm optimisation (PSO). The capacities of the optimised CFS beams were also obtained using the nonlinear finite element (FE) analysis and the FE results were compared with EC3. The FE results showed that the Smart beam and Super Sigma claim dual advantage of increase in section moment capacity and restrain against torsional effect than the conventional CFS channel sections with the same amount of material. These optimised cold formed steel beams can be employed in light gauge steel building constructions.

The application of aluminium alloy members in building construction has considerably increased in recent years due to their appealing advantages such as corrosion resistance and high strength-to-weight ratio. However, the elastic modulus of aluminium is only one-third of that of steel, making aluminium members being susceptible to various buckling modes including web crippling. To date, only a limited amount of research study has been conducted to investigate the web crippling failure phenomenon in aluminium structural members, and no research has been carried out on the web crippling behaviour of roll-formed aluminium lipped channel sections. Hence, an experimental study was conducted to assess the web crippling behaviour and capacities of unfastened aluminium lipped channel sections under two flange load cases (End-Two-Flange (ETF) and Interior-Two-Flange (ITF)). Forty tests were performed with different bearing lengths, web heights and thicknesses. The results obtained from this study were then compared with the nominal web crippling strengths predicted using the design rules provided by the Australian, European and American Standards. The comparison showed that the current design equations are potentially unsafe and unreliable to estimate the capacity for aluminium lipped channel sections under both ETF and ITF load cases. Hence, suitable modifications were proposed to the available design equations based on the experimental results to accurately predict the web crippling capacities of aluminium lipped channel sections. Generally, it is shown that the web crippling results acquired from the modified equations agreed well with the test results.

This paper presents a finite element analysis based study of web crippling failures in cold-formed steel unlipped channel sections with their flanges fastened to supports under one-flange load cases (EOF and IOF). Currently no design equations are available in the current cold-formed steel specifications to determine the web crippling capacities of unlipped channel sections with restrained flanges under one flange load cases. Hence the web crippling behaviour of unlipped channel sections was first investigated experimentally using 28 tests and suitable coefficients were proposed for the current web crippling design equation. However, the applicability of the proposed coefficients was limited to the tested channel sections. In this study advanced finite element models were developed in ABAQUS/CAE and validated in terms of ultimate failure loads, load versus deflection curves and failure modes. The developed models were analysed using nonlinear static and quasi-static analysis based on implicit and explicit integration schemes. This study addressed the effects of mesh size, element type, mechanical property model and inertia of support and loading plates. Also, the effects of two enhancement techniques of explicit analysis such as mass scaling and artificial loading rates with different thicknesses were investigated and the results are presented. A detailed parametric study was then conducted using the validated finite element models. New and improved design equations were proposed to determine the web crippling capacities of unipped channel sections using the results from both finite element analysis based parametric study and experiments.

The bending-shear interaction response of cold-formed stainless steel lipped channel sections has been given inadequate attention in the past. Therefore, this paper investigates the bending and shear interaction behaviour of cold-formed stainless steel lipped channel sections using numerical studies. Finite element (FE) models were developed and validated against the experimental results found in the literature for three-point and four-point loading tests of lipped channel sections of both cold-formed stainless steel and cold-formed steel. The elaborated FE results were used for a comprehensive parametric study that was conducted comprising 60 FE models of three-point loading simulations of stainless steel lipped channels with five different aspect ratios to study the shear response and the bending-shear interaction response. Another 12 FE models of four-point bending simulations were developed to study the bending response. The numerical results were analysed and it is found that the sections with aspect ratios of 1.5 and 2.0 are subjected to the interaction of bending and shear while there is no interaction effect observed in the sections with other aspect ratios. Eurocode 3 and American specifications interaction equations were then evaluated using the numerical results. These design provisions are found to be too conservative for a higher level of applied shear force. Therefore, revised design equations for bending and shear interaction were proposed aiming better prediction accuracy. Further, a statistical evaluation was conducted for the proposed interaction equations and results suggest improved and consistent predictions.

Stainless steel offers a range of benefits over conventional carbon steel in structural applications. This paper presents the detailed numerical modelling of shear response of cold-formed stainless steel hollow flange sections using finite element software package, Abaqus. The effect of geometric parameters such as section height and section thickness, and the influence of different steel grades were investigated following the validation of finite element models. From numerical results, the formation of diagonal tension fields can be clearly observed in the webs of rectangular hollow flange sections while more even distribution of the stresses in the webs is seen in triangular hollow flange sections. Further, a plastic hinge type mechanism is formed in triangular flanges at the post-failure region. The evaluation of Eurocode 3 and the direct strength method shear design provisions for stainless steel hollow flange beams is found to be significantly conservative. Therefore, modified provisions were proposed and the comparison of those with finite element results confirmed the accurate and consistent shear resistance predictions over the codified provisions.

The shear response of the cold-formed stainless steel lipped channel sections with longitudinal stiffeners has not been investigated adequately in the past. Therefore, this paper presents the details of numerical investigations conducted to study the shear behaviour of longitudinally stiffened cold-formed stainless steel lipped channel sections. Following a validation study of the finite element models of lipped channel sections, the effect of return lips and web stiffeners on the shear response of lipped channel sections was examined through comprehensive numerical parametric studies. In addition, numerical investigations were conducted to study the elastic shear buckling response of the sections and the shear buckling coefficients were back-calculated. It was found that the longitudinal web stiffeners enhance the shear buckling resistance of lipped channel sections considerably with increased stiffener depth. However, the shear capacity increment is not significant compared to plain lipped channel sections. The presence of the web stiffeners is found to be not preventing the out-of-plane buckling of the sections. The evaluation of Eurocode 3 and the direct strength method shear provisions for stainless steel channel sections with longitudinal stiffeners illustrates inaccurate capacity predictions. Therefore, modifications were proposed and comparisons reveal that the proposed provisions enhance the shear resistance predictions with good accuracy over the codified provisions.

The load carrying capacity of cold-formed steel (CFS) beams can be enhanced by employing optimisation techniques. Recent research studies have mainly focused on optimising the bending capacity of the CFS beams for a given amount of material. However, to the best of authors’ knowledge, very limited research has been performed to optimise the CFS beams subject to shear and web crippling actions for a given amount of material. This paper presents the optimisation of CFS lipped channel beams for maximum bending, shear, and web crippling actions combined, leading to a novel conceptual development. The bending, shear and web crippling strengths of the sections were determined based on the provisions in Eurocode 3, while the optimisation process was performed by the means of Particle Swarm Optimisation (PSO) method. Combined theoretical and manufacturing constraints were imposed during the optimisation to ensure the practicality of optimised CFS beams. Non-linear Finite Element (FE) analysis with imperfections was employed to simulate the structural behaviour of optimised CFS lipped channel beams after successful validation against previous experimental results. The results demonstrated that, the optimised CFS sections are more effective (bending, shear, and web crippling actions resulted in 30%, 6%, and 13% of capacity increase, respectively) compared to the conventional CFS sections with same amount of material (weight). The proposed optimisation framework can be used to enhance the structural efficiency of CFS lipped channel beams under combined bending, shear, and web crippling actions.

Cold-formed steel (CFS) members have been used significantly in light-gauge steel buildings due to their inherent advantages. Optimizing these CFS members in order to gain enhanced loadbearing capacities will result in economical and efficient building solutions. This research presents the investigation and results of the optimization of CFS members for flexural capacity. The optimization procedure was performed using the particle swarm optimization (PSO) method, while the section moment capacity was determined based on the effective width method adopted in EN 1993-1-3 (EC3). Theoretical and manufacturing constraints were incorporated while optimizing the CFS cross-sections. In total, four CFS sections – lipped channel beam (LCB), optimized LCB, folded-flange and super-sigma – were considered in the optimization process, including new sections. The section moment capacities of these sections were also obtained through non-linear finite element (FE) analysis and compared with the EC3-based, optimized section moment capacities. The results show that, compared with a commercially available LCB with the same amount of material, the new CFS sections possess the highest section moment capacity enhancements (up to 65 %). In addition, the performance of these CFS sections when subjected to shear and web-crippling actions was also investigated using non-linear FE analysis.

Lipped channel beams are commonly used in buildings for load-bearing components such as floor joists and roof purlins. The typical practice is to use one-sided web side plates (WSPs) to attach beams from their webs to the supports at the connections, through bolts. In such realistic conditions, it is not practical to use WSPs over the full height of the webs, thus only a part of the web height is restrained at the supports. This controls the mobilising of diagonal tension field in the web and also provides less restraint to the lateral movement of the web. Therefore, realistic support conditions affect the shear capacity due to the lack of restraint of the web at the supports. On the other hand, the current shear design rules are based on ideal support conditions which do not represent the true scenario. Therefore, it is critical to investigate the effect of reduced support restraints on the shear capacity since it has been given less attention in the literature. This paper presents the effect of reduced support restraints on the shear capacity of stainless steel lipped channel beams. Finite element models were developed to study the effect with regard to various influential parameters. From the finite element results, it was found that the shorter the WSP—the higher the shear capacity reduction, where about 50% shear capacity reduction was observed for 60% reduction in WSP height. Furthermore, it was concluded that compact sections exhibit more significant capacity reduction than slender sections when reducing the WSP height. Therefore, a reduction factor was introduced to the current direct strength method shear design rules considering the effect of reduced support restraints on the shear capacity.

Use of aluminium sections as primary load bearing members has recently expanded considerably in the building industry. Aluminium as a new constructional material has several advantages in building structures including corrosion resistance, durability, high strength-to-weight ratio, reduced cost of transportation and ease of erection and fabrication. The popularity of aluminium structures has attracted attention regarding the efficiency and design of many sections, and roll-formed lipped channel beam (LCB) is one of these commonly used sections. However, aluminium LCBs are prone to shear buckling failures due to its increased web slenderness and low elastic modulus compared to steel. Hence an experimental study was conducted to investigate the shear behaviour of LCBs and to verify the current design rules to accurately predict the shear strengths. Shear tests have been conducted using ten different generally available roll-formed aluminium LCBs. The test sections were loaded at mid-span at the shear centre until failure. The results obtained from the tests were then compared with the predictions using the current shear design rules in the Australian/New Zealand standards and Eurocodes for both aluminium structures and cold-formed steel structures as their shear behaviour are quite similar. This paper presents the details and results of this experimental study and comparison with shear design rules based on current design rules.

The demand for highly structurally efficient stainless steel is limited to a certain extent by its high initial cost. Therefore, the utilisation of material to the optimum possible level is important. In achieving this, further consideration should be given to enhance the design rules where beneficial effects such as pronounced strain hardening in stainless steel should be taken into account in the design process. In addition to that, a thorough understanding of the structural behaviour of stainless steel sections is also required. However, the shear behaviour and capacity of cold-formed stainless steel lipped channel beams (LCBs) have not been thoroughly investigated previously. Therefore, experimental and detailed finite element (FE) modelling were undertaken to investigate the shear behaviour and strength of stainless steel LCBs. A comprehensive parametric study was also conducted by developing 100 FE models. From the results, the available post-buckling strength in slender stainless steel LCBs was highlighted. Furthermore, the beneficial strength increment due to the strain hardening effect of stainless steel, particularly for compact LCBs in shear, was investigated. Comparisons indicated that current EN1993-1-4 and direct strength method (DSM) shear design rules are too conservative in particularly for compact sections. Thus, existing shear design rules were modified to enhance the overall prediction accuracy for stainless steel LCBs while attention was given to capture the available inelastic reserve capacity.

Cold-Formed Steel (CFS) members with slotted perforations in webs are used in civil construction to amplify the thermal and energy performance of structures. However, the slotted webs reduce the structural performance of the element, prominently their shear, bending and combined bending and shear strengths. Many research studies have been undertaken to examine the behaviour of CFS channel sections subject to bending. Yet, no research has been performed to investigate the distortional buckling behaviour of slotted perforated CFS flexural members. Finite Element (FE) models of CFS channels with staggered slotted perforations were developed herein to investigate their distortional buckling under bending stress. A parametric study was conducted in detail by developing 432 slotted perforated CFS FE models based on the validation process with available experimental results. In particular, this paper presents the FE analysis details of CFS flexural members with slotted perforations subject to distortional buckling and results. The reliability of the current Direct Strength Method (DSM) for CFS flexural members with web holes subject to distortional buckling in accordance with the North American Specification (AISI S100) (2016) and the Australian/New Zealand Standards (AS/NZ 4600) (2018) was investigated. Modified DSM formulae for slotted perforated CFS flexural members subject to distortional buckling were also proposed.

Thin-walled members in structural systems are highly vulnerable to buckling instabilities, including web crippling. Aluminum alloy members are more prone to this kind of failure due to thei...

This paper focuses on the web crippling performance of staggered slotted perforated Cold-Formed Steel (CFS) channels under Interior-One-Flange (IOF) load case, highlights the web crippling strength reduction, and provides reliable design guidelines. Finite Element (FE) analysis was employed to represent the IOF load case web crippling behaviour of staggered slotted perforated CFS channels. The developed FE models were then validated against laboratory tests on web crippling of CFS channels with both solid web and web openings under IOF load case. A parametric study (288 models) was conducted using the validated models to assess the effect of staggered slotted configurations and the corresponding degree of reduction in web crippling strength. It is shown that staggered slotted perforations play an important role in defining performance and may lead to a considerable reduction (up to 49%) in web crippling strength. Based on the results of the parametric study, new web crippling design equations were developed for IOF load case accounting the staggered slotted perforations. The web crippling strength predictions using the proposed equations yielded at a much higher level of accuracy, enhancing the commercial aspects of slotted perforated channels.

The development of new Cold-Formed Steel (CFS) channels with staggered slotted perforations has led to advances in improved thermal efficiency of buildings. These new generations of CFS channels reduce the thermal bridging effect interrupting the direct heat transfer across the web. However, the integration of these staggered perforations creates challenges in terms of reduced structural capacity. It is therefore vital to study the structural behaviour under various loading scenarios. Therefore, the web crippling performance of staggered slotted perforated channels under End-One-Flange (EOF) loading condition and flanges unfastened to bearing plate was investigated in the present paper. Finite Element (FE) models were developed to capture the web crippling strength and failure mechanism of these staggered slotted perforated channels. The validity of the FE modelling techniques was ensured by comparing the web crippling experimental results of CFS channels with solid and perforated webs under the EOF loading. Upon validation, an extensive parametric study comprising 360 FE models was then performed with the aim of (i) examining the effect of staggered slotted configurations and (ii) the corresponding degree of web crippling strength reduction. The results provided a direct mean of notable web crippling strength reduction up to 74%. The numerically derived data points were used to develop a reduction factor based new design equation, which can directly be applied to predictive equations of web crippling. The proposed approach yields more accurate and consistent strength predictions and improves the understanding of CFS channels with staggered slotted perforations.

A sub-head refers to the horizontal member at the top of an aluminium window wall system. Under wind load, bearing failure of the aluminium sub-head (ASH) flange due to its long length is a common failure mode, being subjected to high concentrated load transferred from the vertical members (mullions). The bearing behaviour of ASH sections was previously investigated experimentally by the authors and suitable equations (DRA I ) were proposed to predict the bearing capacities. These design rules were manufacturer and product specific and only applicable for sections considered in the test plan. To address these limitations, the present study further investigates the behaviour and design of ASH sections through non-linear static analyses using ABAQUS, based on implicit integration schemes. The effects of mesh size, element type, and loading plates on the bearing behaviour of ASH section under different loading and boundary conditions was addressed. The finite element models were validated against the test results in terms of ultimate loads, load–displacement curves and failure modes, and the validated model was then used to perform an extensive parametric study. A broad range of ASH sections covering flange widths ranging from 40 to 100 mm, thicknesses varying between 2 and 4 mm, bearing widths ranging from 50 to 150 mm, and six engagement lengths (5 to 30 mm) was considered in the parametric study. It should be noted that the ultimate loads obtained from the parametric study are not product nor manufacturer specific. Since no aluminium design rules exist to predict the bearing capacities of ASH sections, the accuracy of the current cold-formed steel design rules (DRSs) and that of DRA I were assessed. Both DRSs and DRA I were found not to be suitable for ASH sections in window walls, hence appropriate modifications were made in this study and the proposed design rules (DRA P ) predicted accurate bearing capacities which agreed well with the numerical results.

A window wall is a lightweight external wall composed of glass and aluminium, which does not carry any gravity loads from the building except for its own weight. Wind load is transferred to the main structural system through the connections of sub-frames (consisting of sub-heads and sub-sills) with slabs. An aluminium sub-head with a removable bead (ASHWRB) is a common type of sub-head consisting of two parts: a base and a bead. Under wind load, the bead flange is directly loaded by the mullion and undergoes bearing failure due to its long length. This paper presents a detailed numerical study on the bearing capacities of the ASHWRB sections subject to wind loading. For this purpose, finite element models were simulated using ABAQUS/CAE and validated with our previously conducted experimental work in terms of ultimate loads, load-displacement curves, and failure modes. Validated finite element models of the ASHWRB sections were then used for an extensive parametric study covering a wide range of thicknesses, flange widths , bearing widths, and engagement lengths. Notably, the ultimate loads obtained from the parametric study are not product nor manufacturer specific, whereas, the data obtained from experimental study is specific to the manufacturer products. The acquired bearing database was used for a detailed assessment of the consistency and reliability of the previously proposed design rules by the authors (DRA) based on the experimental tests as well as currently available cold-formed steel design rules (DRSs). It was found that the bearing capacities determined by both DRA and DRSS are unreliable for predicting the bearing capacities of the ASHWRB sections in the window wall. Thus, modifications were made to DRA and DRSS. Consequently, new design rules were proposed in this paper (DRA P), which accurately predicted the bearing capacities and correlated very well with the numerical results.

Roll-formed aluminium sections have recently been utilised in structural systems as load-bearing members. Commonly used as flexural members, these sections are vulnerable to various buckling instabilities including web crippling failure. The current web crippling design guidelines are imperial in nature and their suitability for newly developed sections may not be accurate and reliable. Therefore, this study aims to investigate the web crippling behaviour of and design considerations for unfastened roll-formed aluminium lipped channel (ALC) sections under one-flange loading conditions. An experimental investigation was conducted for this purpose based on the AISI S909 web crippling test guidelines. Numerical simulations were subsequently conducted to extend the range of geometrical dimensions and aluminium alloy grades. A detailed assessment of the design rules given in the American, Australian, and European specifications was carried out using the acquired experimental and numerical results. Most of these guidelines were found to yield unsafe and unreliable predictions of the ultimate web crippling capacities, and therefore suitable modifications and improvement were proposed. The modified design rules predictions showed a good agreement with both experimental and numerical results. Hence it is recommended to adopt these improved design guidelines in relevant aluminium standards.

Cold-formed steel (CFS) unlipped channel sections are commonly used as bearers in floor systems while rectangular hollow sections (RHS) are used as joists. The transverse loads from the joists do not pass through the shear centre of channel bearers due to different joist to bearer and bearer to column connections. Hence, the channel bearers are subjected to torsion in addition to concentrated loads and bending. This study investigated the effects of two joist to bearer (bolted/welded) connections, two bearer to column (cap plate/angle cleat) connections and fly braces on the structural behaviour of channel bearers. Eight full-scale tests were performed using simplified floor arrangements, made of two unlipped channel bearers with eight and six RHS joists located at 450 mm spacing. Suitable finite element models of tested channel bearers including their connections were developed and validated in terms of ultimate failure moment, failure mode and deflections. A parametric study was then performed using the validated finite element models. The effects of bolted/welded joist to bearer connections and cap plate/angle cleat bearer to column connections on the behaviour of channel bearers were determined and discussed based on the experimental and numerical results. Suitable recommendations were then made to the design methods based on the observed failure modes, and the most suitable combination of connections for the CFS floor systems investigated in this study.

Aluminium members are recently being used as main structural elements in residential, commercial and industrial buildings. Aluminium Lipped Channel Beam (LCB) is one of the popular thin-walled sections used in different applications in construction. Web openings are incorporated in these sections to accommodate building services when they are used as beams. Even though the bending, shear and web crippling behaviours of these sections were investigated in the past, their structural behaviour with web openings have not been investigated. Hence, experimental and numerical studies were conducted in this research to investigate the shear behaviour of these aluminium LCBs with web openings. An aspect ratio of one was considered in this study. A total of 17 tests were conducted first to investigate the shear behaviour of aluminium LCBs with circular web openings using three-point loading arrangement. Finite element models were developed with appropriate loading and boundary conditions and validated using the experimental results. A detailed parametric study was then undertaken using the currently available roll-formed aluminium LCBs with different thicknesses, grades and web opening sizes. The ultimate shear capacities and the shear capacity reduction factors obtained from the tests and finite element analyses were compared with the currently available design rules. This paper presents the details and results of the experimental and numerical studies on the shear behaviour of aluminium LCBs with circular web openings and the comparison with current and recently proposed design rules.

The facade, as the exterior cladding of a building, is an essential component which provides waterproofing, thermal isolation, light transparency and structural independence against environment actions. The vertical member, named mullion, is the dominant wind load-bearing structural member in this facade system. Even though aluminium is a durable material, the conventional aluminium frame is weak in thermal performance. On the other hand, timber frames are preferred by architects due to their aesthetic appearance and sustainability. Therefore, an innovative composite mullion was developed in this study using aluminium and timber to achieve the best features of both materials. An experimental study was also conducted to verify the structural performance of the composite mullion. Four-point bending tests were performed to investigate the bending behaviour of the newly developed product. The test results showed that the section moment capacities of the composite mullions are greater than the traditional aluminium mullions. © 2019 Taylor & Francis Group, London, UK.

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.

Cold-formed steel studs and purlins with staggered slotted perforations in webs are used in building structures to produce a better thermal performance of the profiles and for the energy efficiency of structures. On the other hand, the slotted webs result in an unfavourable effect in terms of the structural performance of the element, prominently their shear, bending and combined bending and shear strengths. Relatively little research has been reported on this subject despite its importance. Many research studies have been undertaken to examine the behaviour of conventional cold-formed steel (CFS) channel sections subject to combined bending and shear. To date, however, no research has been carried out to investigate how CFS channels with staggered slotted perforations behave under combined bending and shear actions. An extensive study on this area is therefore essential. Finite element (FE) models of CFS channels with staggered slotted perforations were developed to investigate their combined bending and shear capacity. A parametric study was conducted in detail by developing FE models based on the validation process with available experimental data. This paper presents the FE analysis details of CFS channels with staggered slotted perforations subject to combined bending and shear actions and the FE results. New design equations were also proposed to predict the combined bending and shear capacity of steel channels with staggered slotted perforations.

Cold-formed steel members are becoming increasingly popular in the building industry due to their superior strength to weight ratio and ease of fabrication as opposed to hot-rolled steel members. However, they are susceptible to various buckling modes at stresses below the yield stress of the member because of their relatively high width-to-thickness ratio. Web crippling is one of the failure modes that occurs in steel channel sections under transverse concentrated loads or reactions. Recently a test method has been proposed by AISI to obtain the web crippling capacities under both one-flange and two-flange load cases. Using this test method 21 tests were conducted in this research to investigate the web crippling behaviour and strengths of an unlipped channel section with stocky webs known as DuraGal Channels under end-one-flange (EOF) and interior one-flange (IOF) load cases. DuraGal channels with different web slenderness and bearing lengths were tested with their flanges unfastened to supports. In this research the suitability of the currently available design rules for unlipped channels subject to web crippling under one flange load cases was investigated, and suitable modifications were proposed where necessary. This paper presents the details of this experimental study and the results.

The facade, as the exterior cladding of a building, is an essential element which provides waterproofing, thermal isolation and structural resistance against environmental actions. The vertical members in curtain wall facade systems, referred to as mullions, are the dominant load-bearing structural members. Despite aluminium being a durable material, conventional aluminium facade frames are weak in thermal performance, and hence thermal breaks are often used in the industry to provide the required insulation. In addition, timber frames may be preferred by building designers due to their aesthetic appearance and sustainability. Therefore, an innovative composite mullion was developed using aluminium and timber to combine the best features of both materials and is presented in this study. Experimental studies were also conducted to verify the structural performance of the composite mullion. The first series of tests was performed to investigate various aluminium-timber connections to ensure composite action. Four different connection types were considered in this study and the optimum connection was chosen and discussed. Four-point bending tests were performed next to investigate the bending behaviour and strength of the newly developed mullion as well as traditional aluminium mullions under positive and negative wind loading scenarios. It was found that the new composite mullions achieved higher section moment capacities than the traditional aluminium mullions, while being energy-efficient, aesthetically pleasing and more sustainable.

Cold-Formed (CF) structural members have recently drawn significant attention in light gauge steel construction. The employment of the different materials, for example CF carbon steel, stainless steel and aluminium, are becoming more common. These structural members are often subjected to concentrated loading conditions, which ultimately leads to failure through web crippling. A plethora of experimental and numerical studies have investigated the web crippling strength and behaviour of CF carbon steel lipped channel sections. However, only limited studies are available for CF stainless steel and aluminium members. This paper presents the investigation of the web crippling strength of CF lipped channel beams under End Two Flange (ETF) loadings and aims to propose a unified equation considering strength factor. Finite Element (FE) models of CF carbon steel, aluminium, and stainless steel lipped channel beams were developed and validated against the available web crippling ETF load case experimental data. Subsequently, a detailed parametric study was performed based on the validated FE models, to establish a wide-ranging data set. New ETF load case web crippling unified design guidelines were proposed for the CF lipped sections made of carbon steel, stainless steel, and aluminium.

Mid-rise to tall mass timber buildings are becoming internationally popular and are required, for instance in the Eurocode or the Australian building code, to be designed against progressive collapse. Designing against progressive collapse is especially important for mass timber buildings as, when compared to reinforced concrete and steel, timber is a more brittle construction material and mass timber buildings are deemed to be more elastic and have limited rotational capacities at the beam-to-column connections. However, whilst the ability of reinforced concrete and steel buildings to resist such an extreme event has been widely researched, limited studies were carried out on mass timber buildings. Their load transfer mechanisms and structural response after the loss of a load-bearing element are currently unclear. Consequently, this paper presents the outcomes of three experimental tests performed on three scaled-down, 2 × 2-bay, post-and-beam mass timber substructures under an edge column removal scenario. The capacity of the 3D substructures to resist progressive collapse was investigated for two types of beam-to-column connectors, namely two tests performed with a connector type commonly used in Australia in mass timber buildings and one test with a proposed novel connector. In the tests, Uniformly Distributed Pressures (UDP) were applied to the floors in two stages: (i) a constant UDP of 4.8 kPa was first applied to the bays not adjacent to the removed column and (ii) an idealised UDP was then increasingly applied to the remaining two bays through a hydraulic jack connected to a six-point loading tree. The load redistribution mechanisms or alternative load paths, structural response and failure modes were recorded and are presented in this paper. Results showed that the applied load was principally transferred to the three columns closest to the removed column and that the Cross Laminated Timber (CLT) panels spanning over two bays were efficient in resisting and transferring the load. The substructure with the proposed novel connector showed an 8.5% increase in capacity and higher ductility than the substructures assembled with the commonly used connector. A simplified theoretical model consistent with the methodology currently used by industry to predict the collapse resistance capacity of post-and-beam mass timber buildings was compared to the test results. The model underpredicted the test capacity by 53%.

In the building sector, the application of aluminium alloys in load carrying structures as well as building envelopes has received attention over the past decades. Under wind loading, the vertical members of window walls known as mullions, carry the horizontal load transferred from the glass panels. This load is then transferred to the sub-heads at the top and the sub-sills at the bottom which are connected to the structure. The aluminium sub-head flange due to its long length is susceptible to bending (bearing failure) under this loading condition, a phenomenon that has hitherto not been adequately researched. Hence the performance of aluminium sub-head sections subjected to bearing failure was investigated through a series of 42 tests. This study mainly explores the impacts of parameters such as the bearing width, the loading and boundary conditions, as well as various geometric sections, on the bearing failure of aluminium sub-heads. The significant failure modes observed in the tests were yielding at web-flange junction and slipping of the bearing plate. Currently, no design rules are available to predict the bearing capacity of aluminium sub-heads. Hence a comparison of the ultimate bearing capacities of the test results and the design capacities obtained using the available cold-formed steel design specifications was performed. The code-predicted design strengths were found to be overly conservative for aluminium sub-head sections in window walls. Therefore, new design equations were developed to ensure safe, economic and reliable design of aluminium sub-heads using a wide range of bearing capacity data obtained from the experimental studies. The proposed design rules were found to be in precise agreement with the experimental values.

Quality and productivity are both important in 3D printing products and processes. However, it is quite challenging to control the quality and productivity of each product due to several parameters involved in this additive manufacturing process. Most of the parameter settings depend on trial and error techniques which consume a lot of time and material waste. Therefore, in this study, the application of optimization approach which is Full Factorial Design (FFD) approach which has been employed on 3D printed housing part made from Polylactic Acid (PLA) which were printed using Fused Deposition Modelling (FDM) 3D printer to minimize shrinkage on the 3D printed parts. Based on the optimization work, the results showed the performance of FFD approach provides a good dimensional accuracy compared to the drawing specification for the printed part. Therefore, this research provides beneficial scientific knowledge and alternative solution for the additive manufacturing process in industries application to enhance the quality of the 3D printed parts produced using FDM 3D printer machine.

Mid-rise to tall mass timber buildings, which are constructed from engineered solid wood products, such as Laminated Veneer Lumber (LVL), Glued laminated timber (Glulam) and Cross Laminated Timber (CLT), have recently gained international popularity. As the height of timber buildings increases, so do the consequences of a progressive collapse event. While collapse mechanisms of concrete and steel buildings have been widely researched, limited studies have been carried out on mass timber buildings. This paper presents and discusses the experimental results performed on a series of 2D timber frame substructures, used in post-and-beam mass timber buildings and scaled down to fit the purpose of this research, under a middle column removal scenario. The behaviour of the frames and the ability of three types of commercially available beam-to-column connections and a proposed non-commercial novel connection, to develop catenary action under large deformations are reported. Furthermore, the system capacity in terms of the uniformly distributed pressure is also discussed. The test results showed that only the proposed connector was able to sustain the design pressure in international design specifications if no dynamic increase factor was considered, and therefore presented a potential solution to improve the robustness of post-and-beam timber buildings.

To fully understand the structural behaviour of large structural systems under given loading scenarios, experimental testing of the entire system or of a representative part of it is often required. However, due to limited laboratory space and budget restrictions, tests are frequently performed on scaled down systems. The scaled tests allow investigating the influence of a large number of parameters, therefore providing in-depth understanding of the structural system response, an opportunity rarely achievable in full-scale testing due to cost related issues. As timber is known to be sensitive to size effects, it is unclear (i) how accurately tests performed on a scaled down timber structure would reproduce the full-scale system response and (ii) how scaled tests results must be interpreted to consider the scaling effect. This paper experimentally investigates the full-scale and quarter-scale moment and shear non-linear responses of three types of beam-to-column connectors currently used in post-and-beam mass timber buildings. Moreover, the paper discusses (i) how tests performed on scaled down timber buildings can be extrapolated to full-scale structures, and (ii) presents recommendations for the scaled down specimens to best replicate the response of the full-scale ones. A total of 12 full-scale and 18 quarter-scale tests were performed. Considering the scaling factor, results show that the overall non-linear responses of the quarter-scale connections closely match the full-scale responses. However, still taking into account the scale factor: (i) the average ratio of the quarter-scale to full-scale elastic stiffness is 0.74 and (ii) the tests performed on the scaled down connections typically result in a capacity 1.2 times higher than the capacity of the full-scale systems. Results also demonstrate the importance of using steel or aluminium connectors with similar material ductility in both the scaled down and full-scale connectors.

Bearing failure is a form of localized failure that occurs when thin-walled cold-formed steel sections are subjected to concentrated loads or support reactions. To determine the bearing capacity of cold-formed channel sections, a unified design equation with different bearing coefficients is given in the current North American specification AISI S100 and the Australian/New Zealand standard AS/NZS 4600. However, coefficients are not available for unlipped channel sections that are normally fastened to supports through their flanges. Eurocode 3 Part 1.3 includes bearing capacity equations for different load cases, but does not distinguish between fastened and unfastened support conditions. Therefore, an experimental study was conducted to determine the bearing capacities of these sections as used in floor systems. Twenty-eight web bearing tests on unlipped channel sections with restrained flanges were conducted under End One Flange (EOF) and Interior One Flange (IOF) load cases. Using the results from this study, a new equation was proposed within the AISI S100 and AS/NZS 4600 guidelines to determine the bearing capacities of cold-formed unlipped channels with flanges fastened to supports. A new design rule was also proposed based on the direct strength method.

Cold-formed steel members have many advantages over hot-rolled steel members. However, they are susceptible to various buckling modes at stresses below the yield stress of the member because of their relatively high width-to-thickness ratio. Web crippling is a form of localized failure mode that can occur when the members are subjected to transverse high concentrated loadings and/or reactions. The four common loading conditions are the end-one-flange (EOF), interior-one-flange (IOF), end-two-flange (ETF) and interior-two-flange (ITF) loadings. Recently a test method has been proposed by AISI to obtain the web crippling capacities under these four loading conditions. Using this test method 42 tests were conducted in this research to investigate the web crippling behavior and strengths of unlipped channels with stocky webs under ETF and ITF cases. DuraGal sections having a nominal yield stress of 450 MPa were tested with different web slenderness and bearing lengths. The flanges of these channel sections were not fastened to the supports. In this research the suitability of the currently available design rules for unlipped channels subject to web crippling was investigated, and suitable modifications were proposed where necessary. In addition to this, a new design rule was proposed based on the direct strength method to predict the web crippling capacities of tested beams. This paper presents the details of this experimental study and the results.

Cold-formed steel members have been widely used in residential and commercial buildings as primary load bearing structural elements. They are often made of thin steel sheets and hence they are more susceptible to local buckling. The buckling behaviour of cold-formed steel compression members under fire conditions is not fully investigated yet and hence there is a lack of knowledge on the fire performance of cold-formed steel compression members. Current cold-formed steel design standards do not provide adequate design guidelines for the fire design of cold-formed steel compression members. Therefore a research project based on extensive experimental and numerical studies was undertaken to investigate the local buckling behaviour of light gauge cold-formed steel compression members under simulated fire conditions. First a series of 91 local buckling tests was conducted at ambient and uniform elevated temperatures up to 700oC on cold-formed lipped and unlipped channels. Suitable finite element models were then developed to simulate the behaviour of tested columns and were validated using test results. All the ultimate load capacity results for local buckling were compared with the predictions from the available design rules based on AS/NZS 4600, BS 5950 Part 5, Eurocode 3 Parts 1.2 and 1.3 and the direct strength method (DSM), based on which suitable recommendations have been made for the fire design of cold-formed steel compression members subject to local buckling at uniform elevated temperatures.

Current design rules for the member capacities of cold-formed steel columns are based on the same non-dimensional strength curve for both fixed and pinned-ended columns at ambient temperature. This research has investigated the accuracy of using current ambient temperature design rules in Australia/New Zealand (AS/NZS 4600), American (AISI S100) and European (Eurocode 3 Part 1.3) standards in determining the flexural–torsional buckling capacities of cold-formed steel columns at uniform elevated temperatures using appropriately reduced mechanical properties. It was found that these design rules accurately predicted the member capacities of pin ended lipped channel columns undergoing flexural torsional buckling at elevated temperatures. However, for fixed ended columns with warping fixity undergoing flexural–torsional buckling, the current design rules significantly underestimated the column capacities as they disregard the beneficial effect of warping fixity. This paper has therefore recommended the use of improved design rules developed for ambient temperature conditions to predict the axial compression capacities of fixed ended columns subject to flexural–torsional buckling at elevated temperatures within AS/NZS 4600 and AISI S100 design provisions. The accuracy of the proposed fire design rules was verified using finite element analysis and test results of cold-formed lipped channel columns at elevated temperatures except for low strength steel columns with intermediate slenderness whose behaviour was influenced by the increased nonlinearity in the stress–strain curves at elevated temperatures. Further research is required to include these effects within AS/NZS 4600 and AISI S100 design rules. However, Eurocode 3 Part 1.3 design rules can be used for this purpose by using suitable buckling curves as recommended in this paper.

Cold-formed steel members are widely used in residential, industrial and commercial buildings as primary load-bearing elements. During fire events, they will be exposed to elevated temperatures. If the general appearance of the structure is satisfactory after a fire event then the question that has to be answered is how the load bearing capacity of cold-formed steel members in these buildings has been affected. Hence after such fire events there is a need to evaluate the residual strength of these members. However, the post-fire behaviour of cold-formed steel members has not been investigated in the past. This means conservative decisions are likely to be made in relation to fire exposed cold-formed steel buildings. Therefore an experimental study was undertaken to investigate the post-fire mechanical properties of cold-formed steels. Tensile coupons taken from cold-formed steel sheets of three different steel grades and thicknesses were exposed to different elevated temperatures up to 800 °C, and were then allowed to cool down to ambient temperature before they were tested to failure. Tensile coupon tests were conducted to obtain their post-fire stress–strain curves and associated mechanical properties (yield stress, Young׳s modulus, ultimate strength and ductility). It was found that the post-fire mechanical properties of cold-formed steels are reduced below the original ambient temperature mechanical properties if they had been exposed to temperatures exceeding 300 °C. Hence a new set of equations is proposed to predict the post-fire mechanical properties of cold-formed steels. Such post-fire mechanical property assessments allow structural and fire engineers to make an accurate prediction of the safety of fire exposed cold-formed steel buildings. This paper presents the details of this experimental study and the results of post-fire mechanical properties of cold-formed steels. It also includes the results of a post-fire evaluation of cold-formed steel walls.

Cold-formed steel sections are commonly used in low-rise commercial and residential buildings. During fire events, cold-formed steel structural elements in these buildings are exposed to elevated temperatures. Hence after such events there is a need to determine the residual strength of these structural elements. However, only limited information is available in relation to the residual strength of fire exposed cold-formed steel members. This research is aimed at investigating the residual distortional buckling capacities of fire exposed cold-formed steel lipped channel sections. A series of compression tests of fire exposed, short lipped channel columns made of varying steel grades and thicknesses was undertaken in this research. Test columns were exposed to different elevated temperatures up to 800 oC. They were then allowed to cool down at ambient temperature before they were tested to failure. Suitable finite element models of tested columns were also developed and validated using test results. The residual compression capacities of tested columns were predicted using the ambient temperature cold-formed steel design rules (AS/NZS 4600, AISI S100 and Direct Strength Method). Post-fire mechanical properties obtained from a previous study were used in this study. Comparison of results showed that ambient temperature design rules for compression members can be used to predict the residual compression capacities of fire exposed short or laterally restrained cold-formed steel columns provided the maximum temperature experienced by the columns can be estimated after a fire event. Such residual capacity assessments will allow structural and fire engineers to make an accurate prediction of the safety of buildings after fire events. This paper presents the details of these experimental and numerical studies and the results.

Taylor's spatial frame (TSF) and Ilizarov external fixators (IEF) are two circular external fixator commonly used to address complex deformity and fractures. There is currently no data available comparing the biomechanical properties of these two external fixators. This study looks into the mechanical characteristics of each system. TSF rings with 6 oblique struts, 4 tube connectors, 4 threaded rods, and 6 threaded rods were compared to a standard IEF rings with 4 threaded rods. Compression and torsional loading was performed to the frame as well as construct with Polyvinylchloride tubes. TSF rings with 4 tube connectors had the highest stiffness (3288 N/mm) while TSF rings with 6 struts was the least stiff. The situation was reversed for torsion where TSF rings with 6 oblique struts had the highest torsional stiffness (82.01 Nm/Degree) and frame Ilizarov rings with 4 threaded rods the least. Standard TSF construct of two ring with 6 oblique struts have better torsional stiffness and lower axial stiffness compared to the standard IEF. KEY WORDS Taylor's Spatial Frame, Ilizarov External Fixator, Biomechanical properties.

Recent research at the Queensland University of Technology has investigated the structural and thermal behaviour of load bearing Light gauge Steel Frame (LSF) wall systems made of 1.15 mm G500 steel studs and varying plasterboard and insulation configurations (cavity and external insulation) using full scale fire tests. Suitable finite element models of LSF walls were then developed and validated by comparing with test results. In this study, the validated finite element models of LSF wall panels subject to standard fire conditions were used in a detailed parametric study to investigate the effects of important parameters such as steel grade and thickness, plasterboard screw spacing, plasterboard lateral restraint, insulation materials and load ratio on their performance under standard fire conditions. Suitable equations were proposed to predict the time–temperature profiles of LSF wall studs with eight different plasterboard-insulation configurations, and used in the finite element analyses. Finite element parametric studies produced extensive fire performance data for the LSF wall panels in the form of load ratio versus time and critical hot flange (failure) temperature curves for eight wall configurations. This data demonstrated the superior fire performance of externally insulated LSF wall panels made of different steel grades and thicknesses. It also led to the development of a set of equations to predict the important relationship between the load ratio and the critical hot flange temperature of LSF wall studs. Finally this paper proposes a simplified method to predict the fire resistance rating of LSF walls based on the two proposed set of equations for the load ratio–hot flange temperature and the time–temperature relationships.

Aluminium alloys have recently drawn significant attention in structural applications due to its outstanding mechanical characteristics. Thin-walled members fabricated by aluminium alloys can be more competitive in construction industries than the conventional cold-formed steel sections, particularly in areas with high humidity and severe environmental conditions. Nevertheless, they are more vulnerable to various types of instability due to their relatively low elastic modulus compared to steel. Applying high concentrated load transversely on thin-walled members can cause critical damage to the web of the cross section called web crippling. Although a large number of studies has been performed to investigate the web crippling mechanisms on different types of sections, the existing studies are primarily of the empirical nature and thus merits further investigations. To fill the research gap, this study was thus performed based on our previously conducted experimental work to further comprehend the web crippling phenomenon of the roll-formed aluminium lipped channel (ALC) sections under the loading conditions of end-two-flange (ETF) and interior-two-flange (ITF). This was done through numerical investigations followed by a parametric study which are reported herein in details. A wide range of roll-formed ALC sections covering web slenderness ratios ranged from 28 to 130, inside bent radii ranging between 2 mm and 8 mm, bearing lengths ranged from 50 mm to 150 mm, and three sheeting aluminium alloy grades (5052-H32, 5052-H36 and 5052-H38) were considered in the parametric study. The acquired web crippling database was then used to assess the consistency and accuracy of the current design rules used in practice. It was found that the web crippling capacity determined by the current international specifications are unsafe and unreliable, whereas the predictions of the recently proposed equations agree very well. Furthermore, a Direct Strength Method (DSM)-based capacity prediction approach was proposed and then validated against the web crippling database acquired here as well as the experimental and numerical data for cold-formed steel lipped channel sections used in the literature.

This paper has presented the details of an investigation into the flexural and flexural–fl buckling behaviour of cold-formed structural steel columns with pinned and fixed ends. Current design rules for the member capacities of cold-formed steel columns are based on the same non-dimensional strength curve for both fixed and pinned-ended columns. This research has reviewed the accuracy of the current design rules in AS/NZS 4600 and the North American Specification in determining the member capacities of cold-formed steel columns using the results from detailed finite element analyses and an experimental study of lipped channel columns. It was found that the current Australian and American design rules accurately predicted the member capacities of pin ended lipped channel columns undergoing flexural and flexural torsional buckling. However, for fixed ended columns with warping fixity undergoing flexural–torsional buckling, it was found that the current design rules significantly underestimated the column capacities as they disregard the beneficial effect of warping fixity. This paper has therefore proposed improved design rules and verified their accuracy using finite element analysis and test results of cold-formed lipped channel columns made of three cross-sections and five different steel grades and thicknesses.

Light Gauge Steel Framing (LSF) walls made of cold-formed and thin-walled steel lipped channel studs with plasterboard linings on both sides are commonly used in commercial, industrial and residential buildings. However, there is limited data about their structural and thermal performance under fire conditions while past research showed contradicting results about the benefits of using cavity insulation. A new composite wall panel was recently proposed to improve the fire resistance rating of LSF walls, where an insulation layer was used externally between the plasterboards on both sides of the wall frame instead of using it in the cavity. In this research 11 full scale tests were conducted on conventional load bearing steel stud walls with and without cavity insulation, and the new composite panel system to study their thermal and structural performance under standard fire conditions. These tests showed that the use of cavity insulation led to inferior fire performance of walls, and provided supporting research data. They demonstrated that the use of insulation externally in a composite panel enhanced the thermal and structural performance of LSF walls and increased their fire resistance rating. This paper presents the details of the LSF wall tests and the thermal and structural performance data and fire resistance rating of load-bearing wall assemblies lined with varying plasterboard-insulation configurations under two different load ratios. Fire test results including the time–temperature and deflection profiles are presented along with the failure times and modes.

Current design rules for determining the member strength of cold-formed steel columns are based on the effective length of the member and a single column capacity curve for both pin-ended and fixed-ended columns. This research has reviewed the use of AS/NZS 4600 design rules for their accuracy in determining the member compression capacities of slender cold-formed steel columns using detailed numerical studies. It has shown that AS/NZS 4600 design rules accurately predicted the capacities of pinned and fixed ended columns undergoing flexural buckling. However, for fixed ended columns undergoing flexural-torsional buckling, it was found that current AS/NZS 4600 design rules did not include the beneficial effect of warping fixity. Therefore AS/NZS 4600 design rules were found to be excessively conservative and hence uneconomical in predicting the failure loads obtained from tests and finite element analyses of fixed-ended lipped channel columns. Based on this finding, suitable recommendations have been made to modify the current AS/NZS 4600 design rules to more accurately reflect the results obtained from the numerical and experimental studies conducted in this research. This paper presents the details of this research on cold-formed steel columns and the results.