Optimum design of cold-formed steel beams subject to bending, shear and web crippling

Recently, cold-formed steel (CFS) members have become more prevalent within the construction industry. CFS beams can be optimised to increase their load carrying capacity. In this research, shape optimisation method is developed to obtain high structural resistance of cold-formed steel beams by taking into account the bending, shear and web crippling actions. First, the flexural strengths of the sections are determined based on the effective width method adopted in EC3, while the optimisation process is performed using the Particle Swarm Optimisation (PSO). Five different CFS channel cross-section are considered in the optimisation process. The flexural strengths of the optimised sections are then verified using detailed nonlinear finite element analysis. The results indicated that the optimised CFS beams provide a bending capacity which is up to 50% higher than the conventional CFS channel sections with the same amount of material. Shear, web crippling behaviours of five optimisedCFS beams were then investigated. Finally, innovative optimised CFS beam was proposed for lightweight forms of buildings and modular building systems to obtain high structural resistance

Numerical studies of steel channels with staggered slotted perforations subject to combined bending and shear actions

Cold-formed steel studs and purlins with staggered slotted perforations in webs are used in construction to improve thermal performance of the profiles and energy efficiency of structures. On the other hand, the web perforations adversely affect structural performance of the members, especially their shear, bending and combined bending and shear strengths. Relatively little research has been reported on this subject despite its importance. Many research studies have been carried out to evaluate the combined bending and shear behaviour of conventional cold-formed channel beams. To date, however, no investigation has been conducted into the strength of cold-formed steel channels with staggered slotted perforations under combined bending and shear actions. Finite element models of cold-formed steel channels with staggered slotted perforations were developed to simulate their combined bending and shear behaviour and strength. They were then validated by comparing the results with available experimental test results and used in a detailed parametric study. This paper presents the details of the numerical studies of cold-formed steel channels with staggered slotted perforations and the results

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

Shear Capacity of Cold-Formed Stainless Steel Beam with Elliptical Web Openings: Numerical Analyses

Cold-formed stainless-steel sections are increasingly being used in the construction industry, for both architectural and structural applications. The excellent combination of mechan-ical properties and corrosion resistance makes stainless steel a very good material for structural applications. Due to the lack of design rules for stainless steel, the design rules for carbon steel have been generally adopted in the stainless-steel design. However, the prominent non-linear be-haviour of stainless steel, which is the main difference with carbon steel, makes the standards for carbon steel not always accurate in the stainless-steel design. The provision of web openings at appropriate locations in such sections is also important to avoid cutting holes at an inappropriate location during the implementation stage. The type of section and the shape of opening were primarily chosen based on the application. The scope of this study is however limited to stainless steel Lipped Channel Beams (LCB) with elliptical web openings. The provision of openings in web affects the shear behaviour and shear capacity of LCB sections, but only very limited re-searches have been conducted so far. Hence, a numerical analysis was undertaken to investigate the shear behaviour and strength of cold-formed stainless steel LCB section with elliptical web openings. Finite element models of cold-formed ferritic stainless steel LCB with centered web openings were developed under the simply supported loading condition. They were validated with currently available shear test results and a detailed parametric study was undertaken to develop an extensive shear strength database. Numerical results showed that the currently available reduc-tion factor equations of circular web opening are either conservative or unsafe to use for the non-circular openings. Hence, numerical results were then used to develop a reduction factor to the shear capacities of cold-formed stainless steel LCBs with elliptical web opening

Fire performance of innovative 3D printed concrete composite wall panels – A Numerical Study

The 3-Dimensional (3D) printing technology in the construction sector has seen an accelerating growth owing to its potential advantages. For this layer-based construction, a detailed investigation on fire performance is necessary. However, there are limited research studies for 3D Printed Concrete (3DPC) walls exposed to fire. Therefore, this paper investigates the fire performance of different types of 3D printed concrete walls using validated Finite Element Models (FEMs). Validated heat transfer FEMs were extended to investigate the fire performance of a range of 3DPC wall configurations (solid, cavity, and composite) under standard fire conditions. The results show that 3DPC non-load bearing cavity walls underperform when subjected to standard fire compared to solid 3DPC walls. The novel composite 3DPC walls with the use of Rockwool as cavity insulation offers superior fire resistance

Flexural Behaviour of optimised cold-formed steel beams with sleeve stiffened web openings

CFS beams are often provided with web openings to accommodate building services. However, the area reduction in the web affects their load-bearing capacities. The reduction of bending capacity can be regained through providing suitable stiffeners in the vicinity of the web openings and through providing the web openings to the optimised CFS beams. Many research studies have been conducted for the former but no research studies have been reported for the latter. This paper presents an investigation on providing reinforced web openings to optimised CFS beams to restore the original flexural capacity. A computational analysis was carried out. The Finite Element (FE) elements were validated against experimental data from the literature and then used in conducting detailed parametric studies (80 FE models). The influence of the rectangular openings with four different sizes (hole height-to-web depth ratios: 0.2, 0.4, 0.6 and 0.8) and four different sleeve stiffening lengths (5, 10, 15 and 20 mm) on the bending capacity subject to distortional buckling was investigated in the parametric study. The results indicated that introducing web openings to the optmised CFS along with sleeve stiffening arrangement is a satisfactory approach to restore the original bending capacity. In addition, the optimum sleeve length was found and updated direct strength-based design equations are proposed to predict the bending capacity of the CFS beams with sleeve stiffened rectangular web openings subject to distortional buckling