Flexural Behaviour of Built-up Beams Made of Optimised Sections

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

Web Crippling Behaviour of Cold-Formed High Strength Steel Unlipped Channel Beams

Cold-formed sections (CFS) fabricated using high strength steel have recently been utilised in construction due to their numerous advantages, such as higher load-to-weight ratio, flexibility of shape, and availability in relatively long spans. High strength CFS channel sections can be used as purlins and joists in structural systems; thus, they are vulnerable to different buckling instabilities, including web crippling. Predicting their web crippling capacity using the current design guidelines may be insufficient due to their empirical nature. This study, therefore, aims to investigate the web crippling capacity of high strength unlipped CFS sections under End-Two-Flange (ETF) loading conditions. Numerical simulations were carried out using nonlinear finite element (FE) analysis. The developed models were first validated against available experimental data and then used as a base for conducting an extensive parametric study. The ultimate web crippling capacity obtained from the parametric study was used to assess the accuracy of the available design equations in the standards and those proposed in the relevant studies. The assessment revealed that the existing design equations are not suitable for predicting the ultimate web crippling capacity for high strength CFS channel sections under the ETF loading condition. Thus, a modified design equation was proposed, following the same technique of current design standards, and a new Direct Strength Method (DSM) approach was developed

Sustainable Performance of a Modular Building System Made of Built-Up Cold-Formed Steel Beams

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

Web crippling behaviour of sigma sections under end two flange loading – Numerical investigation

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.</p

Web crippling design of modular construction optimised beams under ETF loading

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.</p

Shear behaviour of doubly symmetric rectangular hollow flange beam with circular edge-stiffened openings

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.</p