This study develops a validated finite element (FE) model for T-stub connections with Howick Rivet Connectors (HRCs) and carries out a systematic parametric analysis considering variations in rivet diameter, plate thickness, and steel grade. Using numerical simulations together with previously published experimental data, the accuracy of existing bearing and shear strength formulas is evaluated, revealing substantial discrepancies when these formulas are applied to a wider dataset. To address these limitations, new strength formulas are proposed and validated through reliability analysis, achieving an average test/FEA-to-predicted ratio of 1.04 and correctly identifying failure modes in 91% of cases. Compared with existing design formulas, the proposed equations reduce prediction bias by approximately 18% and decrease strength dispersion by about 5%, demonstrating notable improvements in both accuracy and reliability. Based on the combined numerical and experimental findings, design recommendations are provided to support the practical use of HRC connections in cold-formed steel structures.

New Zealand’s housing crisis, caused by poor insulation, high energy consumption, and lacking thermal comfort, highlights the urgent need for energy-efficient building systems. This study investigates a Fiber-Reinforced Polymer (FRP) wall panel system, which includes phenolic foam rigid insulation in the panel cavities that create 26 mm air gaps for thermal regulation and thermal transmittance. This research primarily focuses on examining the gap between the designed and the actual performance of the system through field monitoring of external walls, using K-type thermocouples, picologgers, and heat flux plates to measure thermal transmittance (U-value), heat flux, and temperature profiles. The results showed a U-value of 0.206 W/m2·K during the observation period, outperforming conventional wall requirement (0.500 W/m2·K) set by H1 energy efficiency New Zealand building code 2022. Furthermore, the findings indicated that the combination of insulation-filled cavities and air gaps worked effectively together: the insulation reduced heat transfer, while the air gaps and insulation collectively contributed to thermal regulation by slowing heat flow and temporarily storing heat, which was gradually released as temperatures dropped, helping to maintain indoor temperatures between 18–25 ℃ for 83.9

Cold-formed steel (CFS) bolted joints formed with back-to-back channel sections are widely used in portal frame construction due to their efficiency and ease of fabrication. However, the discrete force transfer between individual channels produces non-uniform stress distributions within the joint region, leading to localised stress concentrations, shear lag effects, bimoment-induced stresses due to restrained warping, and premature web buckling. These effects can reduce the moment capacity of typical joints by up to 40% compared with the nominal capacity of the connected members; however, this reduction is not explicitly addressed in current CFS design standards, including AISI S100, AS/NZS 4600, and EN 1993–1–3, which treat member and joint capacities independently. To address this gap, this paper presents a comprehensive experimental and parametric investigation to quantify the capacity reduction in CFS bolted joints and provide a reliable design method for practical applications. A detailed finite element (FE) model was first developed and validated against experimental results from CFS portal frame joint tests. Subsequently, an extensive parametric study comprising over 3400 FE simulations was performed to capture the influence of cross-sectional non-dimensional slenderness, as well as a wide range of geometric, material, and joint parameters. Based on these findings, a simplified design equation is proposed to enable reliable prediction of the reduced moment capacity of back-to-back channel bolted joints. The application of the proposed design equation is then verified against both numerical and experimental results of CFS frames, demonstrating excellent accuracy, with predictions within 1–3% of the actual capacities on average and coefficients of variation ranging from 0.06 to 0.09.

Cold-formed steel (CFS) structural members are widely used in residential construction due to their favourable properties and advances in manufacturing. To improve thermal performance, slits are often introduced into the webs of these members. However, this alteration can compromise their axial strength. Although this has important structural implications, few studies have quantified the effect of slits on axial capacity, particularly under eccentric loading conditions. The authors previously examined slitted CFS sections under concentric axial compression and through this research address that gap by conducting a comprehensive parametric study on CFS studs with slits, subjected to combined axial compression and minor axis bending through eccentric loading. A total of 1134 finite element analysis (FEA) models were created, varying parameters such as member length, thickness, cross-sectional dimensions, and six different load eccentricities. These models evaluated how slits influence axial capacity when minor-axis bending occurs due to eccentric loads. The FEA results were compared with predictions from the general interaction equation provided in the Australian/New Zealand Standard AS/ NZS 4600. On average, the design equations underestimated the strengths by approximately 13% for eccentricities ranging from 10 mm to 25 mm, while they overestimated the strengths by about 20% for 50 mm eccentricities. Based on these findings, a new design interaction equation was developed, incorporating element and web slenderness ratios. A reliability analysis within the AISI-S100 framework confirmed that the proposed design modifications satisfy required safety standards.

The use of aluminium for roof claddings provides a durable alternative to cold-formed steel (CFS). However, these claddings can experience localised pull-through failure at the connections under wind uplift. Currently, no design guidelines exist for predicting the pull-through capacity of trapezoidal aluminium roof claddings. This study investigates the pull-through failure behaviour of trapezoidal aluminium roof claddings with wide pans and closely spaced ribs under static wind uplift. A finite element (FE) model was developed and validated against existing CFS trapezoidal cladding experimental tests under static wind uplift, with additional validation for representing the behaviour of aluminium as a material. Further, a comprehensive parametric study involving 698 FE models was conducted by varying material properties, thickness, geometry, cladding span, and screw head/washer diameter. The comparison of the parametric study results with predictions from existing aluminium design guidelines (Aluminium Design Manual (ADM 2020), Australia and New Zealand Standard (AS/NZS 1664), and Eurocode (EN 1999-1-4)) revealed that the design equations in these guidelines were inaccurate for predicting the pull-through capacity of trapezoidal aluminium claddings. Therefore, simplified design equations were developed to determine the pull-through capacity of trapezoidal aluminium claddings. Finally, a reliability analysis confirmed the high reliability of these proposed design equations.

The use of cold-formed aluminium (CFA) channel sections in harsh environments could be a feasible alternative to cold-formed steel (CFS), where web holes are often provided in the beam member to accommodate electrical and plumbing services. When web depth is limited, elongated holes are preferred over circular ones, though they can considerably reduce flexural capacity. To mitigate this effect, stiffeners are often added around the hole edges. Currently there is very limited research available on the flexural behaviour of CFA channel sections with different types of web holes. This study investigates the moment capacity of CFA channels with various types of web openings, using experimentally validated finite element (FE) models. A comprehensive parametric study is conducted using 1168 FE models to investigate the effects of cross-section size, web hole shape and size, and stiffener length for four different cases: (i) elongated unstiffened, (ii) elongated stiffened, (iii) circular unstiffened, and (iv) circular stiffened CFA channel web holes. It is shown that the moment capacity of the sections considerably decreases as the web hole length-to-depth ratio (b/d) increases, with greater impact at higher hole diameter-to-depth ratios (a/d), on average by 14.3 % and 9.3 % for channels with unstiffened and stiffened web holes, respectively. The results also indicate that the current Direct Strength Method (DSM) design equations are conservative by 11 %, 9 %, 19 %, and 13 % for unstiffened elongated, stiffened elongated, unstiffened circular, and stiffened circular web holes, respectively. As a result, two sets of new DSM-based design equations are proposed for each scenario to predict local buckling and distortional/local-distortional buckling of CFA channel with web holes. Finally, the robustness of these equations is confirmed through reliability analysis, with a reliability index greater than 2.5 for all cases.

Cold-formed steel (CFS) built-up box sections often exhibit axial strengths greater than the sum of their individual components. Since truss members primarily carry axial forces, they are well-suited for replacement with such sections. Incorporating high-performance Howick Rivet Connectors (HRCs) enables these built-up members to substantially improve the load-bearing performance of truss systems. However, related studies remain limited. This study addresses this gap by investigating the structural performance and design methodology of such trusses for potential applications in modular construction. A comparative experimental program, involving 64 specimens, was conducted to evaluate the axial capacity and failure behavior of built-up columns with HRCs versus conventional screw fasteners. Finite element models were developed and validated against experimental results, enabling a parametric study of trusses with built-up chord and diagonal members. Among the truss configurations investigated, replacing only the chord members with built-up sections achieved the highest ratio of serviceability limit strength to self-weight and demonstrated the most structurally efficient performance. A practical design method was subsequently proposed to enhance the accuracy of truss strength predictions by accounting for the effects of eccentric compressive loading in the chord members.

Cold-formed steel (CFS) portal frames, typically consisting of back-to-back channel sections with bolted eaves and apex joints formed through brackets, are commonly used in industrial, agricultural, and commercial buildings in New Zealand and Australasia. In design practice, their design is often simplified by assuming rigid joints, which can underestimate frame deflections by a factor of two (or more), and underestimate the bending moment at the apex by as much as 40 %. Furthermore, particularly for column design, shear lag effects at the eaves are ignored, overestimating strength by around 20 % to 40 %. A combination of these simplifications by practicing engineers can lead to premature failures in the connection zones and potentially result in unsafe design outcomes. This paper presents, for the first time, a simple beam idealization method that engineers can use to predict frame capacity. A detailed non-linear finite element (FE) model of a CFS portal frame is developed and validated against experimental results. Using the validated FE model, the ultimate failure load of a frame can be predicted (assuming that the brackets do not fail first). The validated FE model is then used to assess the influence of joint flexibility, moment capacities of the eaves and apex brackets, and the reduced moment capacity of the channel section due to the shear lag effect in the eaves joints. Based on these findings, the accuracy of the simplified design method is assessed. The simplified approach predicts the load capacity of CFS portal frames within 1 % of detailed FE models.

This paper presents an experimental and numerical investigation into the behaviour of cold-formed steel (CFS) lipped channel sections with plain webs, unstiffened circular web openings, and edge-stiffened circular web openings subjected to combined bending and shear. A total of 24 laboratory tests and 378 validated nonlinear finite element (FE) models were used to quantify the effects of shear-span ratio, opening ratio, web slenderness, and stiffener geometry on strength and failure modes. The results show that the shear-span ratio governs the global response, controlling the transition from shear-dominated behaviour to bending-shear interaction, while web openings significantly reduce capacity under shear-dominated conditions by disrupting the diagonal load path and promoting local buckling. Edge stiffeners enhance local stability and partially restore strength, particularly for large openings and short shear spans, although their influence diminishes as global behaviour becomes dominant. Comparisons with AISI S100 indicate that the current interaction equation is conservative for plain-web sections, underestimating capacity by approximately 16%, and that it does not account for web openings. New design equations based on reduction factors are proposed for sections with unstiffened and edge-stiffened openings, with the functional form reflecting the interaction between opening-induced local instability and global bending-shear behaviour. The proposed equations are shown to satisfy target reliability requirements and provide a practical basis for the design of perforated CFS members under combined bending and shear.

The use of sustainable composite building materials is essential for developing infrastructure that benefits the environment while reducing energy consumption [...]

Globally, sustainability indicators have become increasingly important in the building construction sector. While contractors play a critical role in advancing sustainability during the construction phase, there is limited guidance on the specific practices they should adopt. This study aims to address that gap by identifying sustainable practices relevant to building construction and developing an initial set of practical guidelines to support contractors in enhancing their sustainability performance. Based on a literature review and the author’s experiences in New Zealand, a list of 49 sustainable practices for building construction has been developed, addressing the three pillars of sustainability: environmental, economic, and social. The research focuses on the building construction phase and emphasises contractor-level key implementation challenges, such as regulatory barriers and the need for enhanced waste management during construction. The proposed list of practices can serve as a valuable tool to guide contractors’ commitment to sustainability and may inform contractor selection for future tender projects.

Self-drilling wing screws are commonly used in hardwood and composite board applications and offer a promising alternative to traditional bolts for connecting thick hot-rolled high-strength steel to timber in Australia and New Zealand because timber cracking is avoided during installation. Despite this potential, the shear behaviour of self-drilling wing screw connections in structural steel-timber systems has not yet been investigated. This study investigates the shear performance and load-carrying capacity of self-drilling wing screw connections between radiata pine timber and hot-rolled steel plates through an extensive experimental programme. Material characterisation included tensile coupon tests, screw bending tests, moisture content measurements, screw pull-out tests, and screw embedment tests to determine the mechanical properties of the steel, timber, and screws. A total of 70 connection tests were conducted with varying steel thickness (8-20 mm), timber thickness (15-45 mm), number of screws (1-3), and screw axis angle (45 degrees-90 degrees). The effects on load capacity, initial stiffness, and ductility were evaluated. Increasing the steel plate thickness from 8 mm to 15 mm increased the average shear capacity by approximately 25%, whereas increasing the timber thickness from 15 mm to 45 mm increased the capacity by 17% for single-screw and 32% for double-screw configurations. Comparisons with Eurocode 5 (2024) show significant inconsistencies: in some cases the design predictions are up to 30% conservative, while in others they overestimate the capacity by as much as 50%. To address these discrepancies, modified design equations based on Johansen yield theory are proposed to predict the shear capacity of self-drilling wing screw steel-timber connections.

This study investigates the buckling performance of built-up cold-formed steel (CFS) columns, with a focus on how different thermal exposures and cooling strategies influence their susceptibility to various failure mechanisms. Addressing the gap in the literature on the fire behavior of mild steel (MS)-based CFS columns, the research aims to provide new insights. Compression tests were conducted on MS-based CFS column specimens after they were exposed to fire, to assess their post-fire buckling strength. The columns were subjected to controlled fire conditions following standardized protocols and then allowed to cool to room temperature. The study examined axial load-bearing capacity and deformation characteristics under elevated temperatures. To improve fire resistance, protective coatings—gypsum, perlite, and vermiculite—were applied to certain specimens before testing, and their performance was compared to that of uncoated specimens. A comprehensive finite element analysis (FEA) was also performed to model the structural response under different thermal and cooling scenarios, providing a detailed comparison of the coating effectiveness, which was validated against experimental results. The findings revealed significant variations in axial strength and failure mechanisms based on the type of fire-resistant coating used, as well as the heating and cooling durations. Among the coated specimens, those treated with perlite showed the best performance. For example, the air-cooled perlite-coated column (MBC2AC) retained a load capacity of 277.9 kN after 60 min of heating, a reduction of only 6.0% compared to the unheated reference section (MBREF). This performance was superior to that of the gypsum-coated (MBC1AC) and vermiculite-coated (MBC3AC) specimens, which showed reductions of 3.6% and 7.9% more, respectively. These results highlight the potential of perlite coatings to enhance the fire resistance of CFS columns, offering valuable insights for structural fire design.

Technological advancements such as digitalisation and automation are propelling significant changes in the construction sector, known as Construction 4.0. While research on Construction 4.0 is on the rise, there is limited exploration of integrating Indigenous knowledge (IK) into its adoption. This study aims to uncover the potential ways to integrate IK, specifically mātauranga Māori, into the strategy for applying Construction 4.0. A systematic review approach was employed to identify the current state of integration between IK and Western science. The review found some integration of IK in Western science and engineering spaces, but noted a scarcity of studies on its intersection with Construction 4.0. Intersecting IK was found to potentially enhance the success of engineering projects and initiatives, including those related to the Construction 4.0 transformation and sustainable development. Nonetheless, this intersection still needs to be explored, and a comprehensive intersection protocol is required to fully leverage the potential benefits.

Cold-formed steel (CFS) built-up sections have attracted attention for their enhanced strength and stability over single channels. While previous research has focused on the axial behaviour of CFS built-up sections under monotonic compression, studies on their cyclic performance are limited. Cyclic actions can affect the material properties and potentially cause early failure, making it crucial to understand the cyclic behaviours of CFS builtup sections. This research examined the cyclic responses of G550 high-strength CFS built-up compression members through experimental and numerical investigations. Different built-up sections, such as open-lipped built-up sections (OL series) and closed-unlipped built-up sections (CU series), composed of various section sizes and screw spacings, were studied. These proposed parameters assessed the influence of the member slenderness and section slenderness on the CFS built-up sections with thin-walled profiles. The results demonstrated that the cyclic actions have little influence on the structural performance of the CFS built-up sections at the prepeak stage. At the post-peak stage, a faster degradation in strength and stiffness was observed for specimens with greater member slenderness and section slenderness. Moreover, the increase in section slenderness leads to higher axial ductility for the CU series but minimal influence on the OL series. Furthermore, a greater member slenderness leads to smaller energy dissipation capacity, especially for the specimens with smaller section slenderness. The OL series is recommended to be designed as a strength-control element that provides structural stability and integrity, such as primary columns. In contrast, the CU series can be used as the sacrificial element to dissipate energy, such as lateral bracing in the framing system, to minimise the risk of catastrophic collapse subject to extreme loadings such as typhoons or earthquakes.

Cold-formed steel (CFS) channel sections are regularly used as floor joists, and such sections are vulnerable to web crippling, especially as span lengths increase, leading to potential failure under combined web crippling and bending. Over the past decade, the industry in New Zealand has developed CFS channel sections with circular edge-stiffened web holes. However, no experimental tests or numerical studies for these channel sections when subject to combined web-crippling and bending have been reported in the literature. This paper presents a numerical investigation using non-linear finite element analysis (FEA) to study the combined web crippling and bending behaviour of these CFS channel sections that have not only edge-stiffened web holes but also unstiffened holes. Validated FEA models enabled a parametric study on CFS channel sections, encompassing 2268 FEA results. Those FEA results were compared with the interaction equations in three CFS design standards. Moreover, the effectiveness of design equations presented in the literature was also evaluated. New design equations with the form of combined web crippling-bending strength reduction factors (R-p) are proposed. Finally, a reliability analysis was conducted to ensure the proposed equations are accurate in predicting the combined web crippling-bending strength of CFS channel sections with unstiffened and edged-stiffened circular web holes.

Various steel section forms, such as I, T, C-angle, and Z sections, are commonly used in construction. Among these, the angle section is particularly popular because of its flexibility in connecting with other structural members, especially in infrastructure expansion projects. This study focuses on a newly designed cold-formed steel (CFS) with an inward opening-slipped angle section, which is selected for its potential advantages in structural applications. The primary failure mode in the intermediate columns of this section is distortional buckling. To address this issue, a novel angle bracket plate is introduced to enhance both distortional and flexural buckling behavior in CFS angle columns. A total of 85 finite element models (FEMs) are analyzed. Initially, an accurate FEM was developed, validated against existing experimental data, and the strength and buckling behavior of an open CFS section under varying slenderness ratios were systematically explored. The study first evaluated the strength and buckling behavior of an open CFS section under varying slenderness ratios. It then focuses on optimizing the shape of the bracket plate, followed by an assessment of its size, location, and depth to determine the most effective configuration. Additionally, the effects of variations in the thickness, depth, and yield stress on the strength and buckling behavior are examined. Finally, this study compares the performance of open CFS inward-lipped angle sections with and without brackets across different slenderness ratios to provide a comprehensive understanding of their structural benefits.

Roof cladding, a vital component of any structure, is fabricated from material that is durable, affordable, and weatherproof. Metal roof claddings, known for their lightweight nature, durability, cost-effectiveness in construction and maintenance, and impressive strength-to-weight ratio, have been widely adopted worldwide. However, despite these advantages, metal roof claddings are particularly prone to failure during extreme wind events, such as storms, cyclones, and hurricanes. The two primary categories of metal roof claddings are long-run profiles and tray profiles. This study conducts a comprehensive review of research focused on standards used for quantifying wind loadings on roof structures, as well as the wind resistance capacity of various profiles of metal roof claddings under wind uplift loading. The review encompasses both experimental and numerical studies, exploring test methods, numerical modeling techniques, and modes of failures associated with different roof cladding profiles under wind uplift loading conditions. Additionally, the paper examines studies related to fragility and vulnerability analysis, along with risk assessment, pertaining to metal roof claddings. In conclusion, the paper offers critical remarks and provides recommendations for future work based on identified research gaps. The aim is to guide future studies in addressing challenges related to the wind performance of metal roof claddings and contribute to the development of more resilient and secure roofing systems.

Cold-formed steel (CFS) channel sections with web openings are widely used to accommodate services in light-frame construction. However, their structural performance under combined axial compression and bending, particularly when openings are either unstiffened or edge-stiffened, remains poorly understood. This study develops a validated nonlinear finite element model that accounts for material nonlinearity and initial imperfections to assess the behaviour of such sections under eccentric loading. A comprehensive parametric study involving 3078 simulations was conducted to quantify the effects of slenderness, width-to-thickness ratio, hole configuration (number, size, location), stiffener ratio, and eccentricity about both principal axes. Results show that unstiffened web holes can increase the axial-bending interaction ratio by up to 60 % beyond the limits of AISI S100 and AS/NZS 4600, while edge stiffeners effectively limit this increase and improve capacity by 15 % on average. The detrimental effects of unstiffened holes diminish with increasing eccentricity and become negligible beyond specific eccentricity thresholds. Based on the simulation results, new design equations are proposed to account for geometric and loading parameters explicitly. These equations reduce prediction error by 20 % and address key conservatism and non-conservatism issues in current design standards, offering a pathway toward safer and more economical CFS member design.