Web Crippling Behaviour of Cold-Formed Carbon Steel, Stainless Steel, and Aluminium Lipped Channel Sections with Web Openings

This paper reviews the research advancements and design practices related to the structural web crippling response of lipped Cold-Formed (CF) carbon steel, stainless steel, and aluminium channels with web perforations. The web crippling response differs among each material based on the non-linear stress-strain characteristics and degree of strain hardening. Therefore, the reduction in the web crippling strength of web-perforated CF channel sections made of different materials may not be equivalent. The research activities surrounding the web crippling response of CF channels with and without web openings were reviewed initially. Despite the limited design provisions given in the international specifications for the web crippling design of lipped CF channels with web openings, web crippling studies conducted across the world have developed suitable design equations in the form of reduction factors. Past research studies have substantially captured the web crippling response of carbon steel channels with web openings while that of stainless steel and aluminium are limited, as identified in this paper. Lastly, numerical models were developed for simulating the web crippling behaviour of lipped CF carbon steel, stainless steel, and aluminium channels with web opening and validated with past experimental data, with a view for developing unified design guidelines

Numerical Investigation on Fire Performance of LSF and Steel Modular Floor Panels

The steel Modular Building Systems (MBSs) that have been influenced by the Light-gauge Steel Frame (LSF) techniques have become a prominent culture in the industry. However, the detrimental behaviour of steel structural components at high temperatures has elevated the risk of fatal accidents in the event of a fire. Although several research investigations have addressed the fire performance of steel modular wall systems, the behaviour of modular floor systems has not been adequately addressed in the state of the art. Hence, to promote the fire safety and optimum design techniques in the modular construction industry by addressing the aforementioned research gap, this study investigated 48 conventional LSF and MBS floors for their structural and insulation Fire Resistance Levels using Finite Element Modelling (FEM) and Heat Transfer Analyses (HTA) techniques. Initially, full-scale experimental fire tests were modelled using FEM methods, and the validity of the techniques was verified prior to the analyses of parametric floor systems. Furthermore, the structural behaviour of the channel section joists in the elevated temperatures was studied, and hence a correlation was established to determine the critical steel temperature at the structural fire failure with respect to the applied Load Ratio (LR). An additional 12.5 mm thick plasterboard sheathing on single plasterboard sheathed floors resulted a 30 min improvement in structural and insulation FRLs. In addition, the modular floor systems demonstrated enhanced structural and insulation Fire Resistance Levels (FRLs) against the corresponding conventional LSF floor designs due to double LSF skin build-up. The incorporation of rockwool insulation and the increase in the insulation volume implied increased structural and fire performances. However, insulation material in the modular designs was more effective. The fire-rated conventional and modular LSF floor systems are expected to be practised in the construction industry to achieve required fire resistances with optimum material usage

Web crippling behaviour of cold-formed high-strength steel unlipped channel beams under End-One-Flange load case

High-strength Cold-Formed Steel (CFS) members are widely adopted as structural members in building structures due to its higher ultimate capacity. The flexural members are often subjected to concentrated transverse loads which may leads to buckling instabilities including web crippling. However, there is no appropriate design rules and studies are available to estimate the web crippling strength of high-strength CFS members. Hence, this paper presents a detailed numerical investigation on high-strength CFS unlipped channel sections subjected to End-One-Flange (EOF) loading condition with nominal yield strengths of 700 MPa, 900 MPa and 1000 MPa. For numerical simulation study, non-linear Finite Element (FE) models were developed and validated with the experimental results followed by an extensive parametric study using ABAQUS. In total, 243 FE models were developed with different geometric and material parameters including section thickness, material strength, web slenderness ratio, inside bent radius to thickness ratio and bearing length to thickness ratio. The ultimate web crippling strength results were compared with the available design guidelines to check their suitability and accuracy in terms of strength prediction. Then, new design rules to predict the web crippling capacity of high-strength CFS unlipped channel section under EOF condition based on unified and Direct Strength Method (DSM) approaches were proposed

Integration of origami and deployable concept in volumetric modular units

Modular building systems (MBS) and Origami are two emerging methods used in current construction practice. Origami is directly associated with the principles of the ancient Japanese art of paper folding, characterised by high morphological possibilities and ultimately creates foldable structures with tuneable mechanical properties. However, there is a lack of knowledge on the structural behaviour of origami for architectural engineering applications. MBS is a volumetric prefabricated construction technique enhancing productivity in construction. In this paper, a modular unit is designed which employs origami techniques. The roof and floor panels of the modular units formed with steel joists were substituted with origami sandwich panels, while corner posts were substituted with origami columns. The origami-like foldable system demonstrated superior efficiency in constructability, being highly compact during transportation and requiring few operations for the in-situ installation. The structural performances of the developed and foldable modular units were assessed through finite element analysis. It was found that, without increasing the self-weight of the system, the design of origami-like modular units can be tuned for high structural performances and various structural sizes, which can impact the usability of space and the aesthetics of architecture. While this is a preliminary study and physical testing is needed, the positive results open the possibility of exploring highly deployable modular structures of novel shapes that can be employed during post-disaster and emergencies (Covid-19)

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

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