Modular construction is gaining prominence for its sustainability, speed of assembly, reduced material waste, and cost-effectiveness. Cold-formed steel (CFS) beams, such as the Modular Construction Optimised (MCO) beam, play a vital role in these structures due to their lightweight characteristics, high strength-to-weight ratio, and ease of fabrication. However, the thin-walled geometry of CFS beams introduces challenges in structural design, particularly due to complex buckling and failure modes. The structural behaviour of the MCO beam remains insufficiently explored, with no prior research focusing on its web crippling performance under interior two-flange (ITF) loading. Existing design codes provide equations for estimating web crippling capacity. However, these provisions have been shown to underestimate the actual capacity of complex CFS sections, resulting in overly conservative designs and inefficient material use. To address these limitations, this study investigates the web crippling behaviour of the MCO beam using finite element analysis (FEA). Numerical models were developed and validated against experimental web crippling data from similar beam types. A parametric study involving 162 FE models was conducted to assess the influence of key geometric parameters displaying an average reduction of 27% due to corner radius effects. All models assumed unfastened flanges, reflecting common modular construction practices. Based on the results, new design equations were proposed to improve the accuracy of web crippling capacity predictions, providing a mean value of 1.00 and COV value of 0.08 and 0.07. These findings support the development of more efficient design practices, reduce material overuse, and contribute to the optimisation of lightweight modular steel structures.

This study presents a comprehensive numerical investigation into the web crippling behaviour of cold-formed sigma sections subjected to the End One Flange (EOF) load case, a configuration that has received limited attention in existing literature. A total of 756 finite element models were developed using ABAQUS/CAE 2020, covering a wide range of geometric parameters and material types, including carbon steel, aluminium, and stainless steel. The models were validated against experimental data, achieving strong correlation with mean test-to-FE ratios of 1.03, 1.00, and 1.01 for carbon steel, aluminium, and stainless steel, respectively. The results revealed that web crippling capacity decreases by up to 35% with increasing section depth and radius, while yield strength enhancements of up to 60% significantly improve capacity. Stainless steel sections consistently outperformed the other materials under identical geometric and loading conditions due to their superior strain-hardening characteristics. Existing design standards (AS/NZS 4600, AS/NZS 4673, and AS/NZS 1664) were found to inadequately predict the web crippling strength of sigma sections. Consequently, two unified design equations were proposed by modifying existing formulations, achieving mean prediction ratios of 1.00 with COVs below 0.11 across all materials. A reliability analysis confirmed the robustness of the proposed equations, recommending a resistance factor of 0.85. These findings provide a validated and practical design framework for predicting the web crippling capacity of sigma sections under EOF loading, supporting their broader application in structural engineering.

Cold-formed steel (CFS) has become increasingly prominent in modular construction owing to its high strength-to-weight ratio, formability and sustainability advantages. The recently developed Modular Construction Optimised (MCO) beam, featuring a hollow triangular-flange cross-section, may offer improved flexural efficiency and material savings compared with conventional CFS profiles. However, MCO beams remain vulnerable to localised failures such as web crippling, particularly under concentrated Interior-Two-Flange (ITF) loading typical of modular stacking, transportation and temporary support conditions. The inclusion of large circular web openings (40–80% of the clear web height, d wh /d 1 ) for service integration further complicates design, while current standards provide limited specific guidance for such configurations. This study presents a purely numerical investigation into the web crippling behaviour of MCO cold-formed steel beams with circular web openings under Interior-Two-Flange (ITF) loading. A comprehensive finite-element (FE) programme comprising 648 models (486 perforated and 162 plain-web beams) was developed and validated against existing experimental data for comparable cold-formed steel sections, achieving strong agreement (mean = 1.00, COV = 0.06). The parametric analyses examined the effects of hole size, web thickness, bearing length, corner radius and yield strength. Results indicated mean reductions of 11%, 19% and 26% in web-crippling capacity for 40%, 60% and 80% openings, respectively, with reductions most sensitive to web thickness, corner radius and bearing length. A modified reduction-factor equation, incorporating web-thickness and corner-radius parameters not considered in existing design provisions, is proposed, achieving excellent agreement with FE predictions (mean = 1.00, COV = 0.04) and a corresponding resistance factor of 0.92. The proposed formulation enables a preliminary design approach for MCO beams with service penetrations, addressing a major limitation of existing codes. Future experimental and independent validation is required before practical application. The study enhances understanding of web-crippling mechanisms in optimised CFS geometries and supports the safe and material-efficient use of MCO beams in modular construction.

Modular Construction Optimised (MCO) beams, cold-formed steel sections with rigid hollowflanges tailored for prefabricated floor systems, require clear guidance when incorporating large unstiffened circular web openings (>38 % of clear web height). This study fills that gap by: (1) developing and validating detailed nonlinear finite-element (FE) models against thirteen experimental tests (mean FE/exp = 1.01, COV = 0.02 for plain and web-perforated sections); (2) conducting a systematic parametric study of 288 FE models varying section dimensions, material yield (300-600 MPa), and opening ratios (0.4-0.8); (3) quantifying that openings up to 60 % reduce ultimate moment capacity (Mu) by < 5 %, while 80 % openings incur a 10 % average reduction; and (4) deriving simple reduction-factor equations that predict Mu with mean = 1.00 and COV = 0.03. Comparative analyses demonstrate that MCO beams with 80 % openings outperform equivalent unperforated Lipped Channel Beams by an average of 32 % in Mu, highlighting their strength-to-weight advantage despite large hole sizes. These findings provide engineers with validated design rules and practical equations for integrating large service openings into modular cold-formed steel floors.

Sigma sections are one of the innovative sections modified from the conventional section to improve its bending and shear capacity. However, web crippling behaviour of Cold-Formed (CF) sections is considered as crucial aspect considering its higher slender values. Hence, web crippling behaviour of CF sigma sections must be scrutinized. Limited studies have been conducted on sigma sections. Therefore, this research paper intends to numerically analyse the web crippling behaviour of sigma sections made of CF carbon steel, aluminium, and stainless steel under IOF load case. The numerical approach was opted based on the numerical verification study and comprehensive parametric plan consisting of 756 models was selected. The parametric plan accommodates the key parameters of CF sections based on the literature available. Accordingly, numerical models were developed, and numerical analysis was conducted with the aid of ABAQUS/CAE 2020. The results from the numerical analysis are presented for all three material sigma sections. Detailed analysis regarding the effect of parameters on the web crippling capacity is provided. In addition, the existing design equations were checked for their applicability to predict the web crippling capacity of sigma section under IOF load case. As they were found inapplicable, new modified design provisions were developed and presented to accurately predict the web crippling capacity of sigma sections.

Numerous section profiles have been introduced to the conventional steel industry. Such sections can be applicable to stainless steel as well and the merits of the section profiles can be amplified. Sigma section is one of the innovative section profiles which offers numerous benefits including higher torsional resistance and high cross‐sectional resistance. However, the existence of longitudinal stiffeners in sigma sections might cause web crippling failure under concentrated loads. Hence, this article intends to study the web crippling behaviour of stainless‐steel sigma sections under end‐two‐flange (ETF) load case. Comprehensive numerical investigation was conducted utilizing finite element analysis (FEA) software package, ABAQUS CAE. The numerical model was successfully validated against experimental results and a parametric plan was developed. The results were analysed with each critical parameter. Ultimately, web crippling capacity of stainless‐steel sigma sections was compared with similar carbon steel sections.

Cold-Formed (CF) sections have emerged in the construction industry due to their merits, including ease of fabrication for different section profiles, sustainability, and cost-effectiveness. As a result, various innovative section profiles have been introduced to the CF industry. Sigma sections are one such innovative profile that has been introduced in the CF industry. The inclusion of longitudinal stiffeners in Sigma sections improves their bending capacity. Additionally, Sigma sections offer high stiffness, increased torsional rigidity, and superior load-carrying capacity. However, the inclusion of web longitudinal stiffeners might induce localised failures under concentrated loads, known as web crippling failures. Therefore, it is necessary to explore the web crippling behaviour of Sigma sections to effectively employ them in the industry. However, limited research has been conducted on Sigma sections in terms of web crippling. Thus, this research intends to investigate the web crippling behaviour of Sigma sections under the ETF load case. A comprehensive numerical study consisting of 1512 numerical models was conducted on Sigma sections made of aluminium (432 numerical models), carbon steel (648 numerical models), and stainless steel (432 numerical models) after successfully validating the numerical approach. The results obtained from the numerical study were compared using parameters such as section depth, thickness, yield strength, bearing length, and radii. The numerical results were also compared with existing design equations and considering their inaccuracy in predicting the web crippling capacity of Sigma sections made of CF carbon steel, stainless steel, and aluminium under the ETF load case, modified design provisions were proposed. In addition, a numerical investigation was conducted to analyse the web crippling performance of Sigma section with conventional sections, and it was concluded that similar web crippling performance was observed for Sigma sections. Hence, the Sigma sections were highly recommended for extensive applications in the industry.

Aluminium sections have been emerged in the industry due to the advantages such as light weight, resistance to corrosion, recyclability, and flexibility. While the construction industry is moving towards to modular construction trend, aluminium sections are considered as a vital key to achieve the desirable outputs of modular industry. Modular industry needs high performing structural elements as well as light weight elements to reduce the overall weight of the modules which directly affects the transport cost, flexibility of the modular connections, construction duration, capacity of the equipment or machineries and required numbers of construction workers for assemble. Hence, the requirement of light weight elements is evident, and the aluminium sections have been considered to replace the conventional sections. However, the structural performance of aluminium sections has to be analysed to check the appropriateness of utilization though it is reasonable. Hence, aluminium sigma sections were selected in this study to check their performance in the web crippling scenario under Interior‐Two‐Flange (ITF) loading case. Sigma sections were opted based on the merits including high torsional rigidity and resistance towards local and distortional buckling. Appropriate numerical approach was selected, and the procedure was validated with experimental results. Accordingly, comprehensive numerical investigation was carried out by including different parameters such as depth, thickness, yield, and ultimate strength and bearing length. Subsequently, the results were compared with all critical parameters and the results were provided. Suggestions and recommendations were stated to utilise the aluminium sigma sections in the industry.

SupaCee sections are addressed as one of the innovative section profiles which was introduced to the Cold‐Formed Steel (CFS) industry in the past decade. Longitudinal stiffeners and return lips are the unique features which ensured the better structural performance in terms of bending and shear for CFS sections. However, web crippling performance of CFS SupaCee section was the critical aspect to employ them in the industry as the concentrated loads could induce web crippling failures. Hence, there is a necessity to address web crippling performance of any innovative profiles to utilize them in appropriate locations. On that note, aluminum sections are now emerging in the industry as load bearing profiles considering their lightweight nature, corrosion resistance, ease of fabrication and high specific strength. Aluminium sections are considered as a replacement for CFS sections for modular constructions where the necessity of light weight is higher considering the transport costs and fabrication costs. However, web crippling performance of aluminum sections has to be analyzed to ensure the utilization in modular constructions. Hence, a superior section among available sections in terms of structural performances, aluminium SupaCee section, was considered for this study. Accordingly, a comprehensive numerical study was conducted considering various parameters such as section depth, thickness, bearing length and yield strength, after the successful validation process of the numerical models with the experimental scenarios of End‐Two‐Flange (ETF) loading condition. Ultimately, the results were compared with key parameters and suggestions and recommendations were stated for the utilization aluminum SupaCee sections in the industry.

Timber structural members have been widely adopted and used in construction due to their inherent characteristics. The main objective of this work is to assess the performance of timber beams with GFRP pultruded beam reinforcement subjected to flexure. A finite element model (FEM) using ABAQUS FEM software is developed, aiming to provide a benchmark modelling procedure. The modelling method considers the fundamental role of the connections among timber beams, the reinforcing GFRP pultruded profile (adhesive and screw connections), and the grain direction in the timber. To understand the influence of the grain direction, different angles of deviations between the longitudinal direction (along the grain) and the beam axis are considered. The robustness of the developed FEM procedure is validated by the experimental results of timber beams with and without GFRP pultruded reinforcement under flexure. It is demonstrated that the angle of deviation (grain deviation) produces high reductions in the strength of unreinforced timber beams. However, this effect is minimal for GFRP-reinforced timber beams. The experimentally derived benchmark FEM procedure can be used as a computational tool for timber beams with GFRP pultruded reinforcement to capture the capacity, failure mode, and load–displacement response.

Recent trends in the construction industry have sought to use cold-formed (CF) carbon steel, CF aluminium and CF stainless-steel as flexural members and in some instances as primary load-carrying members. Flexural members when subjected to concentrated loads undergo various failure modes, a major failure mode being web crippling. The large width-to-thickness ratios of these thin-walled beams makes them vulnerable to local buckling failure. Although there are four loading conditions to consider, this paper focuses on Interior-OneFlange (IOF) loading condition. Currently, individual design equations are available for determining the web crippling capacity of CF carbon steel, CF aluminium and CF stainless-steel under IOF loading. However, to-date there has been no attempt to produce a unified web crippling design equation. An all-encompassing numerical study focussed on the key web crippling parameters, both cross-sectional dimensions and mechanical properties and a unified grade, fy = 220 MPa, was achieved across the three structural materials to allow for a unified design equation. A total of 378 Finite Element (FE) models were obtained. It was found that AS/NZS 4600, AISI S100 and Eurocode 3 provided good agreement, but with a higher coefficient of variation (COV) values than recommended. Additionally, AS/NZS 1664.1 was found to be unsafe. CF carbon steel parametric study results validated existing equations, which were accurate and able to predict the web crippling capacity under IOF loading. However, unified web crippling design equation was modified which can improve the accuracy when predicting the web crippling capacity of CF aluminium and CF stainless-steel lipped channel sections (LCBs) under IOF loading conditions. The unified equation was supplemented by web crippling coefficients specific to each of the structural materials.

Cold-Formed (CF) structural members have become important in conventional and emerging modular building constructions. However, point loads can result in web crippling failure of floor joists, purlins and decks. Due to their enhanced structural, aesthetic and resistive properties, CF aluminium and CF stainless-steel beams are used as an alternative solution to CF carbon steel beams. This paper ultimately investigates the web crippling behaviour of lipped channel beams under Interior Two-Flange (ITF) loading conditions. Since there is no unified approach is available for web crippling behaviour of various materials, this study focused on it. Three structural materials were considered as part of the study: carbon steel, aluminium and stainless-steel. Available experimental studies were used to validate Finite Element (FE) models, before an extensive parametric study (378 FE models) was carried out. Commercially available lipped channels with relatively lower web depth were considered to examine the web crippling behaviour under lower slenderness. Current design codes showed inaccurate prediction up to 15% against the results. This paper ultimately proposes new unified design guidelines for predicting the web crippling capacity of CF carbon steel, CF aluminium and CF stainless-steel lipped channel beams under ITF loading conditions.

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.

Cold-formed steel (CFS) and cross-laminated timber (CLT) structural components are widely employed in low- to mid-rise and modular building constructions. These two materials have individually shown to be lightweight, and possess relatively higher strength characteristics. Owing to these benefits, composite CLT-CFS sections can be used as structural elements and possibly be employed in modular buildings with enhanced structural performances. This paper presents the development of CLT-CFS composite beam for the floor system in modular buildings and investigates the structural performances through finite element (FE) analyses. Initially, the FE models of CFS beam and CLT panel were developed and validated with experimental results. Validated models were used to develop the FE model of CLT-CFS composite beam for the floor system. Results of FE analyses of the CLT-CFS composite floor systems showed that considerable benefits in terms of structural response can be achieved due to the mobilisation of composite action. For the CLT-CFS system investigated in this research, about 20% of enhancement in moment capacity was found. The presented study leads a path to highlight the gains in the structural performance of CLT-CFS composite beams floor system and it is a prospective option to be employed in sustainable modular building construction.