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• 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]

Behaviour of low rise cold-formed steel-framed residential structures when subject to lateral loading (e.g. wind and earthquake loads) is significantly influenced by both structural and non-structural elements. The ceiling is normally considered as a horizontal diaphragm for the distribution of such lateral loads to the bracing walls. In Australia, the ceiling diaphragm, in single and two storey cold-formed steel-framed houses, is made of plasterboard lining fixed to ceiling battens which in turn are screwed to the roof trusses. Determination of the stiffness and strength of the ceiling diaphragm is crucial for accurate distribution of the lateral load to the lateral resisting elements (e.g. bracing walls). This paper presents experimental results from tests of typical ceiling diaphragms. Further, a detailed finite element model is described which was validated against the experimental results. The model is capable of reproducing the initial stiffness, non-linear deformation and ultimate strength. The finding from this work would assist engineers in designing the lateral load resisting system for houses. • Performance of steel-framed ceiling diaphragms is mainly governed by the behavior of the sheathing-to-framing connections. • Ceiling diaphragm test showed a failure of the plasterboard connections at the corners of the specimen. • Presence of end-wall top plate increased the load carrying capacity and displacement capacity of ceiling diaphragm. • Finite element model results showed good agreement with the experimental results. • Design engineer can prepare design charts to provide maximum spacing of bracing walls for houses constructed in Australia. [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]

This paper presents an experimental investigation of the flexural buckling behaviour and resistance of innovative self-compacting lightweight concrete (LWSCC)-filled cold-formed built-up box section (CFBBS) columns. A series of sixteen LWSCC-filled CFBBS columns and four reference hollow columns formed by two nested asymmetric lipped channel sections using breakstem rivets at flanges with various member relative slendernesses ratios, concrete strengths and section sizes were tested under pin-ended boundary conditions. Material tests and initial global geometry imperfection measurements were carried out and reported in present study. The failure modes and deformation developments, lateral deflection distribution along the column specimens, flexural buckling resistance and load-end shortening relationship of the specimens were scrutinised and discussed concerning the effect of parameters and the associated coupling effects. Furthermore, a comprehensive strain analysis was conducted and reported based on the longitudinal and lateral strain developments at both compression and tension zones under flexure; it was found that the composite action abated as the member length increased. Finally, as there is no existing design codes for LWSCC-filled CFBBS columns, the experimental results were used to evaluate the applicability of relevant international codified provisions, including Eurocode (EC4), Australia/New Zealand Standard (AS/NZS 2327) and America Specification (AISC 360-16). It was found that AS/NZS 2327 yielded the most accurate and moderately scattered predictions while the predictions from EC4 were found to be the most scattered but with reasonable accuracy and those from AISC 360-16 were overly conservative, albeit the least scattered among these design codes. • Pin-ended tests were performed on the LWSCC-filled CFBBS columns. • The flexural buckling behaviour and resistance of LWSCC-filled CFBBS columns were studied. • Influences of concrete strength, member slenderness, section sizes and their coupling effects were discussed. • Comprehensive strain analysis was conducted to scrutinise the composite action. • Existing design provisions were assessed for their applicability to LWSCC-filled CFBBS columns. [ABSTRACT FROM AUTHOR]

Cold-formed steel (CFS) roof and wall cladding systems are commonly used in Australia and around the world. The use of CFS claddings in bushfire prone areas is becoming more popular due to their non-combustibility and is recommended in the Australian standard AS 3959 for construction in bushfire areas. However, severe fire events occur more frequently and in recent bushfire events, strong winds and fire–wind interactions have been observed. Thus, the behaviour of CFS claddings exposed to a combined action of fire and wind needs to be considered for the safe design of buildings in bushfire prone areas. In this study, a small-scale test set-up was developed and used to simulate the wind suction loading on crest-fixed CFS roof and wall claddings while also being exposed to elevated temperatures. Experiments were conducted on three commonly used 0.42 mm high strength (G550) CFS cladding profiles at ambient and elevated temperatures and their critical localised pull-through failures of the crests under the screw heads were investigated at increasing temperatures. The results showed that the failure mode of trapezoidal cladding profiles changed from a transverse splitting type to a localised dimpling type pull-through failure. They also showed different rates of reduction in the pull-through capacity with increasing temperatures and the type of cladding profile. This paper has proposed a suitable equation for the pull-through capacity reduction with increasing temperatures and made suitable recommendations in relation to the use of CFS cladding systems in bushfire prone areas. • Investigated the safety of external building envelope made of thin steel claddings in bushfires. • Simulated the combined action of wind and fire (elevated temperature) using small-scale tests of three cladding systems. • Pull-through failures were due to localised splitting or dimpling depending on the type of profile and temperature. • Proposed an equation to predict the reduction in the pull-through failure capacity with increasing temperature. • Recommended cladding profiles failing by dimpling to eliminate any gaps in the building envelope during bushfires. [ABSTRACT FROM AUTHOR]

Lite Steel Beams (LSB) are innovative cold-formed formed steel sections, made of two rectangular hollow flanges with a web, and introduced in Australia claiming of flexural capacity enhancement. However, these sections are vulnerable to web crippling under concentrated loads and support reactions because of their slender webs when used as bearers and joists in floor systems. Limited research studies have been performed to investigate web crippling behaviour of these sections with fastened and unfastened supports under all four load cases, but without considering web hole effects. Recently few research studies indicated that the web crippling capacity of these sections reduced with the introduction of centred beneath and offset web holes under the End-Two-Flange load case, and hence it is critical. However, no investigations have been performed to explore the web hole effect of these sections under the Interior-Two-Flange load case. Therefore, this paper investigates the web crippling behaviour of LSB sections with three types of web holes: centred beneath, one offset, and two offset web holes, under Interior-Two-Flange (ITF) load case. The FE validations have been performed using four different experimental data sets from past research studies to generate accurate finite element models in ANSYS. In addition, a parametric study has been performed using validated FE models. A parametric study using 1126 FE models has proposed suitable capacity reduction equations for LSBs for centred beneath, one-side offset and both-side offset web holes. The results showed that the proposed equations provide accurate web crippling strength compared to design standards. • Investigated the web crippling of hollow flange channel beams with web holes under ITF load case. • Performed a parametric study using 1126 FE models of LSB sections without and with web holes. • FE validations were performed based on past experimental results. • FEA data was used to verify the accuracy of current design equations. • Revised design equations were proposed without and with web holes for LSB sections. [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]

In this paper, the structural stability and compressive capacity of pin-ended cold-formed stainless steel angle columns with different slenderness were experimentally investigated. The experimental programme was performed on press-braked lean duplex stainless steel equal-leg angle sections with nominal dimensions of 80 × 80 × 4 mm, and involved material testing, initial imperfection measurements and 11 column tests. The test setup and procedure, together with the key experimental results, axial load vs. lateral deflections, axial load vs. torsional rotations and characterised failure modes, were fully reported and analysed. The experimental observations reveal that the failure mode type, including local/torsional, flexural-torsional and flexural effects, is highly dependent on the column's slenderness and initial imperfections. The measured compressive strengths were compared with the resistance predictions determined according to European and Australia/New Zealand codified design procedures. It was found that experimentally obtained ultimate capacities are significantly higher than those calculated according to the specifications. However, the database of test results is still quite limited, and a further research is needed to amplify the data needed to enable a more precise assessment of the codified procedures. • Eleven pin-ended cold-formed stainless steel equal-leg angle columns were tested. • Different buckling failure modes were systematically investigated. • Failure loads conservatively predicted by European and Australian design procedures. [ABSTRACT FROM AUTHOR]