Poologanathan Keerthan

The rivet-fastened rectangular hollow flange channel beam (RHFCB) is a new cold-formed steel section and is considered to be a substitute for welded hollow flange channel beams. This monosymmetric channel section is made from two torsionally rigid rectangular hollow flanges connected to a web plate using rivets at intermittent spacing. This fabrication process allows great flexibility in selecting different combinations of web and flange element sizes to attain optimum design capacities. Although the shear behavior of the commonly used lipped channel beam (LCB) and welded hollow flange beam (HFB) sections, with and without web openings, has been investigated previously, the shear strength and behavior of rivet-fastened RHFCBs with web openings have not been investigated yet. Therefore a series of shear tests was conducted to investigate the shear behavior and strength of rivet-fastened RHFCBs with circular web openings. Simply supported test specimens with aspect ratios of 1.0 and 1.5 were loaded at midspan until failure. The shear capacities determined from the tests were compared with those predicted by current cold-formed steel design standards. The results revealed that the existing design equations were not able to accurately predict the shear capacities of rivet-fastened RHFCBs with circular web openings. This is mainly due to the shear buckling capacity improvements provided by the rectangular hollow flanges and associated postbuckling strength. Hence the shear strength capacity results were used to propose improved design equations for rivet-fastened RHFCBs with circular web openings. This paper presents the details of the shear tests, observations, design capacity comparison, and proposed design equations.

Fire performance of light gauge steel framed (LSF) walls sheathed with gypsum plasterboards has been investigated using experimental and numerical studies by many researchers in the past. Provision of cavity or external insulation, improving the thermal‐mechanical properties of plasterboard, and changing the stud geometry are several options previously employed to enhance the Fire Resistance Level (FRL) of such wall systems. Past studies of steel sheathed cold‐formed steel (CFS) framed walls have shown that the use of steel sheathing improves the shear strength of LSF walls. However, such studies have not investigated the possible improvements to the fire performance of LSF walls due to the use of steel sheathing in addition to plasterboards. This numerical study investigates the thermal performance of three common LSF wall configurations sheathed with steel sheets on both sides under fire conditions. Three steel sheathing configurations (internal and/or external sheathing) were considered for each LSF wall. Thermal Finite Element (FE) models were developed and used to simulate the heat progression across the walls, following validation using previous experimental studies. The walls were exposed to ISO 834‐1 standard fire curve on one side. Results were then compared with those from LSF walls sheathed only with plasterboards. Internal steel sheathing was found to be capable of reducing the ambient side temperatures compared to plasterboard only walls due to the lower emissivity of steel, whereas external steel sheathing increased them further. Although the stud hot flange (HF) temperatures are generally increased with the addition of steel sheets, provision of back‐blocking was able to eliminate this deficiency. A novel arrangement is proposed for back‐blocking which is found to significantly delay the stud temperature rise and improve the FRL. The use of corrugated steel sheet profiles is found to reduce both the stud and ambient side plasterboard temperatures. The results from this study give useful information to develop load bearing and non‐load bearing LSF walls with superior fire performance. This paper presents the details of this numerical study and the results.

The advantage of having no unstiffened elements coupled with material located away from the neutral axis makes hollow flange channel (HFC) beam sections structurally efficient in bending when compared with other commonly used open cold‐formed steel sections. This concept is similar to hot‐rolled steel sections such as the universal beam and channel beam sections, which are very efficient in bending. However, the hot‐rolled sections are heavier, torsionally weak, and have low resistance to flexural‐torsional buckling. The two hollow flanges in HFC beams make them torsionally strong and also eliminate the occurrence of distortional and local flange buckling modes in most cases. However, HFC beams have slender webs, making them vulnerable to web crippling failure modes. To understand the web crippling behaviour of HFC beams and develop accurate design rules, finite element models of HFC beams were developed and validated using available experimental results under End One Flange (EOF) and Interior One Flange (IOF) load cases. Using the validated finite element models, a detailed parametric study was conducted for many HFC sections. Finite element analyses provided the required elastic buckling and ultimate loads of HFC beams in web crippling (EOF and IOF load cases). New predictive equations were proposed to determine the elastic buckling coefficients of HFC beams, followed by Direct Strength Method (DSM) based design rules using the test, elastic buckling and nonlinear analysis results from finite element analyses. This paper presents the details of the web crippling design rules developed based on the detailed numerical study on the web crippling behaviour of hollow flange channel beams under one flange load cases.

Purpose: This research was aimed at investigating the fire performance of LSF wall systems by using 3-D heat transfer FE models of existing LSF wall system configurations.Design/methodology/approach: This research was focused on investigating the fire performance of LSF wall systems by using 3-D heat transfer finite element models of existing LSF wall system configurations. The analysis results were validated by using the available fire test results of five different LSF wall configurations.Findings: The validated finite element models were used to conduct a parametric study on a range of non-load bearing and load bearing LSF wall configurations to predict their fire resistance levels (FRLs) for varying load ratios.Originality/value: Fire performance of LSF wall systems with different configurations can be understood by performing full-scale fire tests. However, these full-scale fire tests are time consuming, labour intensive and expensive. On the other hand, finite element analysis (FEA) provides a simple method of investigating the fire performance of LSF wall systems to understand their thermal-mechanical behaviour. Recent numerical research studies have focused on investigating the fire performances of LSF wall systems by using finite element (FE) models. Most of these FE models were developed based on 2-D FE platform capable of performing either heat transfer or structural analysis separately. Therefore, this paper presents the details of a 3-D FEA methodology to develop the capabilities to perform fully-coupled thermal-mechanical analyses of LSF walls exposed to fire in future.

Lipped channel beams (LCBs) are commonly used as flexural members such as floor joists and bearers in the construction industry. These thin-walled LCBs are subjected to specific buckling and failure modes, one of them being web crippling. Despite considerable research in this area, some recent studies have shown that the current web crippling design rules are unable to predict the test capacities under end-two-flange (ETF) and interior-two-flange (ITF) load conditions. In many instances, web crippling predictions by the available design standards such as AISI S100, AS/NZS 4600 and Eurocode 3 Part 1-3 are inconsistent, i.e., unconservative in some cases, although they are conservative in other cases. Hence, experimental studies consisting of 36 tests were conducted in this research to assess the web crippling behavior and capacities of high-strength LCBs under two-flange load cases (ETF and ITF). Experimental results were then compared with the predictions from current design rules. Comparison of t...

A new rivet fastened rectangular hollow flange channel beam (RHFCB) was proposed using an intermittently rivet fastening process as an alternative to welded beams. The rivet fastened RHFCB allows greater section optimisation and flexibility in designing suitable combinations of web and flange widths and thicknesses for many industrial applications. In the industrial applications of rivet fastened RHFCBs as flooring, roofing or modular building systems, their flanges will be fastened to supports, which will provide increased capacities. However no research has been conducted to investigate the web crippling capacities of RHFCBs with flanges unfastened and fastened to supports under one‐flange load cases. Similarly the applicability of current design rules for cold‐formed steel sections are not suitable for rivet fastened RHFCBs. Hence to address these issues, an experimental study was conducted to investigate the web crippling behaviour and capacities of RHFCBs based on the new AISI S909 standard test method. This study included rivet fastened RHFCBs with flanges unfastened and fastened to supports under End One Flange (EOF) and Interior One Flange (IOF) load cases. Tests with flanges fastened to supports showed that web crippling capacities increased by 39 and 5 % for EOF and IOF load cases. Comparisons of experimental web crippling capacity results with predictions using the current AS/NZS 4600 and AISI S100 design standards showed that web crippling design equations are conservative for rivet fastened RHFCBs with flanges unfastened and fastened to supports under EOF and IOF load cases. Hence new equations are proposed to determine the web crippling capacities of rivet fastened RHFCBs. This paper presents the details of this web crippling experimental study of rivet fastened RHFCB sections and the results.

LiteSteel beam is a hollow flange channel made from cold-formed steel using a patented manufacturing process involving simultaneous cold-forming and dual electric resistance welding. LiteSteel beams are currently used as floor joists and bearers in buildings. However, there are no appropriate design standards available due to their unique hollow flange geometry, residual stress characteristics and initial geometric imperfections arising from manufacturing processes. Recent research studies have focused on investigating the structural behaviour of LiteSteel beams under pure bending, predominant shear and combined actions. However, web crippling behaviour and strengths of LiteSteel beams still need to be examined. Therefore, an experimental study was undertaken to investigate the web crippling behaviour and strengths of LiteSteel beams under end-one-flange and interior-one-flange load cases. A total of 23 web crippling tests were performed and the results were compared with the current AS/NZS 4600 and AISI S100 design standards, which showed that the cold-formed steel design rules predicted the web crippling capacity of LiteSteel beam sections very conservatively under end-one-flange and interior-one-flange load cases. Therefore, suitably improved design equations were proposed to determine the web crippling capacity of LiteSteel beams based on experimental results. In addition, new design equations were also developed under the direct strength method format. This article presents the details of this experimental study on the web crippling behaviour and strengths of LiteSteel beams under end-one-flange and interior-one-flange load cases and the results.