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.

Cold-Formed Steel (CFS) sections are vulnerable to certain local and global failures, especially web crippling failures. CFS beams are generally employed in construction practices mainly as floor joists or bearers. The design standards, AISI S100, AS/NZS 4600 and Eurocode 3 Part 1–3 predict the web crippling capacity of CFS sections according to the experimental studies conducted in previous years. In most of the cases, the predictions of the equations were unsafe and hence innovative concepts of CFS should be examined undergoing web crippling. Therefore, the web crippling behaviour of the unlipped channel sections with high-strength material under Interior-Two-Flange (ITF) loading condition was investigated in this study by following the AISI S909 standard test method defined for web crippling. Numerical simulations using Finite Element Analysis (FEA) software (ABAQUS) were conducted on 243 parametric studies to replicate the loading conditions of ITF following a proper validation. Parametric study data were then taken into account to determine the accuracy of existing equations for web crippling capacity in the design standards and existing literature. Since the available design equations were conservative or unsafe and considering the empirical nature of CFS sections in terms of web crippling capacity, new modified equations were proposed to predict the ultimate web crippling capacity of high-strength unlipped channel sections and a new design approach based on the Direct Strength Method (DSM) was also developed.

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.

Cold-Formed Steel (CFS) has been used to a great extent due to the industry uptake given its merits with the key being its high strength-to-weight ratio. Besides, innovative section profiles are constantly introduced to uplift the structural applicability of CFS sections. SupaCee section is a novel section with enhanced structural performance due to its sectional attributes such as longitudinal web stiffeners and return lips. However, the necessity of web openings (holes) to provide service integrations is not considered adequately so far in previous studies with SupaCee sections. Hence, this study reports a comprehensive assessment on flexural performance of SupaCee sections with web openings. Accordingly, numerical analysis was carried out which followed by the validation of the elaborated Finite Element (FE) model and the development of parametric studies considering key parameters such as depth, thickness, yield strength, web opening ratio and hole spacing. Results from the numerical studies are discussed and compared with existing design standards. New design provisions are proposed to predict the flexural capacity of SupaCee sections with web openings. Moreover, FE model of Lipped Channel Beam (LCB) was developed and analysed with similar parameters of SupaCee sections. The comparison of LCB and SupaCee sections with and without web openings are reported and based on the flexural capacity comparisons; recommendations are stated to replace conventional CFS sections by SupaCee sections.

Cold-Formed Steel (CFS) sections are evolved through the last two decades compromising various aspects of construction needs. Doubly symmetric Rectangular Hollow Flange Beam (RHFB) is one of the innovative CFS sections, which was introduced to eliminate the drawbacks of conventional open CFS sections such as prone to complex buckling and torsional effects. Edge-stiffened web holes are recently recommended and available for extensive usage in the floor beams. Even though previous studies conducted researches on various kinds of stiffeners, there is no definite design equation or findings that were presented on shear behaviour. Therefore, this study focuses on the effect of edge-stiffened circular web openings on the shear capacity of doubly symmetric RHFB. Non-linear numerical models were developed using the ABAQUS software package for validation purposes and then comprehensive parametric studies were carried out for doubly symmetric RHFB with edge-stiffened openings. A total of 558 models consisting of edge-stiffeners, un-stiffened openings and plain webs were analysed in this study. Parametric results of with edge stiffeners exhibited shear capacity increment (1-90%) compared to unstiffened web openings. Hence, new design equations were proposed in the form of reduction factor and based on Direct Strength Method (DSM). Finally, optimum edge-stiffener length of 15 mm was recommended regardless of web opening size.

Cold-Formed Steel (CFS) sections provide many design and construction sophistications including lightweight and high strength-to-weight ratio. The SupaCee section was introduced to CFS industry due to its cost effectiveness, enhanced strength, better structural performance and high stiffness. Introduction of SupaCee sections lead to investigations of web crippling, flexural and shear behaviour of the sections. However, structural behaviour of SupaCee sections with web openings has not been addressed to date. Hence, this study intends to analyse the shear behaviour of SupaCee sections with web openings. Previous shear test results of SupaCee sections and Lipped Channel Beam (LCB) sections with openings were validated with developed FE models. An extensive parametric study was accomplished considering various geometric parameters such as depth, yield strength, thickness and web opening ratios. Since the results of the detailed study determined that existing design equations were over conservative, new design equations with reduction factor were proposed to predict the ultimate shear capacity of SupaCee sections with web openings. Moreover, the shear capacities of SupaCee sections were compared with shear capacities of similar dimensioned LCB sections. A web opening ratio of 0.2 is recommended, considering the ability to regain the shear capacity of plain LCB sections, as well as the availability of web openings in order to accommodate the services.

The modular construction industry often seeks cost-effective, high-performing, and longer-span members in buildings to ensure efficiency and quality. Accordingly, the idea of built-up sections was brought into gain numerous benefits including higher structural capacity, improved torsional rigidity, and increased stiffness. While limited research studies have been carried out to study the structural performances of built-up sections, few innovative section profiles have been developed in the industry considering the structural benefits, including improved stiffness. Hence, the application of newly developed built-up sections could enhance the employment of built-up sections in the industry. On that note, this research is focused on the flexural behaviour of optimised section profiles named the LCB-benchmark (Lipped Channel Beam), the optimised-LCB, folded-flange and the super-sigma sections. In addition, different materials, namely cold-formed carbon steel (CFS), cold-formed (CF) aluminium and CF stainless steel, were considered for built-up sections, in order to provide recommendations based on their flexural performances. Numerical analysis was carried out on single sections as well as on built-up sections to the developed parametric plan after the successful validation of experimental studies. The results were compared for single and built-up sections. Finally, based on the comparisons, the folded-flange built-up section is recommended for all three materials as it displayed the highest bending capacity, and the capacity enhancement compared to the corresponding single section was a minimum of 131%.

Cold-Formed Steel (CFS) sections are extensively used in structural engineering applications replacing the conventional hot-rolled sections due to their inherent advantages. Web openings are generally placed in CFS floor joists and bearers to accommodate the building services, which leads the reduction of floor height. The web openings significantly influence the shear behaviour and reduce the shear capacity. However, very limited research studies have been conducted on hollow flange CFS beams with web openings under shear load. Therefore, this study presents a detailed Finite Element (FE) investigation of the shear behaviour of CFS doubly symmetric Rectangular Hollow Flange Beams (RHFBs) with unreinforced circular web openings. Non-linear FE models were created and validated using the laboratory shear test results. A detailed parametric study was then carried out by extending the validated FE models for doubly symmetric RHFBs with circular web openings. In total,126 FE models were investigated with different geometric parameters including section depth, thickness, material strength and web opening sizes to observe their behaviour on shear strength. The results showed that the existing shear strength design equations are either unsafe or conservative for doubly symmetric RHFBs with unreinforced circular web openings. Therefore, new Direct Strength Method (DSM) based shear design rules are proposed to estimate the shear strength of doubly symmetric RHFBs with unreinforced circular web openings in conjunction with proposed shear reduction factor (qs).

Modular Building Systems (MBS) offer numerous benefits in terms of productivity, sustainability and safety. Therefore, MBSs are considered as a viable option to sort out the housing crisis in Britain as well as to drive Britain towards sustainable construction. Development in materials, manufacturing techniques, connection types and structural designs with respect to offsite construction is essential to achieve sustainable goals. Recent advancements in steel manufacturing, including Cold-Formed Steel (CFS), have showed potential benefits in structural performance compared to concrete and timber. Meanwhile, research was conducted to enhance the structural capacities of CFS sections by introducing different cross-sections, composite sections and techniques including optimization. Built-up sections were developed by connecting more than one channel section, and various research studies were conducted to assess their structural performances. However, sustainable performance of built-up sections in modular constructions is still unknown. Hence, this paper intends to develop an MBS using built-up sections for better sustainable performance. Literature review was carried out on the sustainability benefits of MBSs in terms of economic, environmental and social aspects. In addition to that, numerical analysis was performed to investigate the flexural capacity of built-up sections with different screw arrangements to address the sustainable aspects of modular construction by introducing novel sections. The numerical description, results and validations are also stated. Numerical results revealed that flexural capacities of built-up sections are improved up to 156% than those of single sections. Finally, the utilization of built-up sections in modular construction with sustainability enhancement is addressed and illustrated in a conceptual diagram.

In recent times, modular construction is considered as one of the most effective construction methods. It is necessary to understand the structural behaviour of modular construction elements for possible improvements. Modular Construction Optimised (MCO) beam is one of the innovative profiles and can be categorised into hollow flange Cold-Formed Steel (CFS) sections. The hollow flanges encourage bending stiffness and flexural performance, in contrast, slender web causes web crippling failure as these members are often subjected to concentrated loads and reactions. Even though research studies regarding MCO beams are very limited, the structural performance of other types of hollow flange beams has been covered in previous studies. However, to date, web crippling behaviour of MCO beams is still unknown and should be investigated to enhance the commercial aspects of MCO beams as this is an innovative section in the modular construction area. To address this research gap, this paper investigates the web crippling capacity of MCO beams under End-Two-Flange (ETF) load case with flanges unfastened to support condition using numerical analysis. Numerical models were developed and validated against the web crippling test results of hollow flange beams available in the literature. Subsequently, parametric numerical analysis (162 models) was conducted for MCO beams with varying key controlling parameters on web crippling capacity. The web crippling capacities of MCO beams were compared with existing codified (AISI S100, AS/NZ 4600) predictive equations and new design equations were developed to accurately predict the web crippling capacity of MCO beam under ETF load case with flanges unfastened condition.