Web crippling tests of cold-formed steel channels under two flange load cases

Cold-formed steel members have many advantages over hot-rolled steel members. However, they are susceptible to various buckling modes at stresses below the yield stress of the member because of their relatively high width-to-thickness ratio. Web crippling is a form of localized failure mode that can occur when the members are subjected to transverse high concentrated loadings and/or reactions. The four common loading conditions are the end-one-flange (EOF), interior-one-flange (IOF), end-two-flange (ETF) and interior-two-flange (ITF) loadings. Recently a test method has been proposed by AISI to obtain the web crippling capacities under these four loading conditions. Using this test method 42 tests were conducted in this research to investigate the web crippling behaviour and strengths of unlipped channels with stocky webs under ETF and ITF cases. DuraGal sections having a nominal yield stress of 450 MPa were tested with different web slenderness and bearing lengths. The flanges of these channel sections were not fastened to the supports. In this research the suitability of the currently available design rules for unlipped channels subject to web crippling was investigated, and suitable modifications were proposed where necessary. In addition to this, a new design rule was proposed based on the direct strength method to predict the web crippling capacities of tested beams. This paper presents the details of this experimental study and the results.

Pull-through failure tests of thin steel roof battens under wind uplift load

Thin profiled steel roof sheeting and battens are increasingly used in the construction of roofing systems of residential, commercial, industrial and farm buildings in Australia. The critical load combination of external wind suction and internal wind pressures that occur during high wind events such as thunderstorms and tropical cylcones often dislocate the roofing systems partially or even completely due to premature roof connection failures. Past wind damage investigations have shown that roof sheeting failures occured at their screw connections to battens. In most of these cases, the screw fastener head pulled through the thin roof sheeting whilst the screw fasteners also pulled out from the battens. Research studis undertaken on the roof sheeting to batten connection failures have improved this situation. However, the batten to rafter or truss connections have not been investigated adequately. Failure of these connections can cause the failure of the entire roof structure as observed during the recent high wind events. Therefore a detailed experimental study consisting of both small scale and full scale tests has been undertaken to investigate the steel roof batten pull-through failures in relation to many critical parameters such as steel batten geometry, thickness and grade, screw fastener head sizes and screw tightening. This paper presents the details of this experimental study and the pull-through failure load results obtained from them. Finally it discusses the development of suitable design rules that can be used to determine the pull-through connection capacities of thin steel roof battens under wind uplift loads.

Web crippling tests of rivet fastened rectangular hollow flange channel beams under two flange load cases

Recent research on hollow flange beams has led to the development of an innovative rectangular hollow flange channel beam (RHFCB) for use in floor systems. The new RHFCB is a mono-symmetric structural section made by intermittently rivet fastening two torsionally rigid closed rectangular hollow flanges to a web plate element, which allows section optimisation by selecting appropriate combinations of web and flange widths and thicknesses. However, the current design rules for cold-formed steel sections are not directly applicable to rivet fastened RHFCBs. To date, no investigation has been conducted on their web crippling behaviour and strengths. Hence an experimental study was conducted to investigate the web crippling behaviour and capacities of rivet fastened RHFCBs under End Two Flange (ETF) and Interior Two Flange (ITF) load cases. It showed that RHFCBs failed by web crippling, flange crushing and their combinations. Comparison of ultimate web crippling capacities with the predictions from the design equations in AS/NZS 4600 and AISI S100 showed that the current design equations are unconservative for rivet fastened RHFCB sections under ETF and ITF load cases. Hence new equations were proposed to determine the web crippling capacities of rivet fastened RHFCBs. These equations can also be used to predict the capacities of RHFCBs subject to combined web crippling and flange crushing conservatively. However, new capacity equations were proposed in the case of flange crushing failures that occurred in thinner flanges with smaller bearing lengths. This paper presents the details of this web crippling experimental study of RHFCB sections and the results.

Experimental studies of lipped channel beams subject to web crippling under ETF and ITF load cases

Lipped channel beams (LCBs) are commonly used as floor joists and bearers in buildings. However, they are subjected to specific failure modes such as web crippling. Despite considerable web crippling research, recent studies [1-6] have shown that the current web crippling design rules are unable to predict the test capacities under ETF and ITF load cases. In many instances, the predictions by the available design standards such as AISI S100, AS/NZS 4600 and Eurocode 3 Part 1-3 [7-9] are inconsistent. Hence thirty-six tests were conducted to assess the web crippling behaviour and strengths of LCBs under two flange load cases. Experimental web crippling capacities were then compared with the predictions from the current design rules. These comparisons showed that AS/NZS 4600 and AISI S100 design equations are very unconservative for LCB sections under ETF load case and are conservative for ITF load case. Hence improved equations were proposed to determine the web crippling capacities of LCBs. Suitable design rules were also developed using the direct strength method. This paper presents the details of this study and the results including improved design rules.

Bearing capacity of cold-formed unlipped channels with restrained flanges under EOF and IOF load cases

Bearing failure is a form of localized failure that occurs when thin-walled cold-formed steel sections are subjected to concentrated loads or support reactions. To determine the bearing capacity of cold-formed channel sections, a unified design equation with different bearing coefficients is given in the current North American specification AISI S100 and the Australian/New Zealand standard AS/NZS 4600. However, coefficients are not available for unlipped channel sections that are normally fastened to supports through their flanges. Eurocode 3 Part 1.3 includes bearing capacity equations for different load cases, but does not distinguish between fastened and unfastened support conditions. Therefore, an experimental study was conducted to determine the bearing capacities of these sections as used in floor systems. Twenty-eight web bearing tests on unlipped channel sections with restrained flanges were conducted under End One Flange (EOF) and Interior One Flange (IOF) load cases. Using the results from this study, a new equation was proposed within the AISI S100 and AS/NZS 4600 guidelines to determine the bearing capacities of cold-formed unlipped channels with flanges fastened to supports. A new design rule was also proposed based on the direct strength method.

Cyclic plastic deformation characteristics of subgrade under moving train wheel load

Cyclic plastic deformation of subgrade and other engineered layers is generally not taken into account in the design of railway bridge transition zones, although the plastic deformation is the governing factor of frequent track deterioration. Actual stress behavior of fine grained subgrade/embankment layers under train traffic is, however, difficult to replicate using the conventional laboratory test apparatus and techniques. A new type of torsional simple shear apparatus, known as multi-ring shear apparatus, was therefore developed to evaluate the actual stress state and the corresponding cyclic plastic deformation characteristics of subgrade materials under moving wheel load conditions. Multi-ring shear test results has been validated using a theoretical model test results; the capability of the multi-ring shear apparatus for replicating the cyclic plastic deformation characteristics of subgrade under moving train wheel load conditions is thus established. This paper describes the effects of principal stress rotation (PSR) of the subgrade materials to the cyclic plastic deformation in a railroad and impacts of testing methods in evaluating the influence of principal stress rotation to the track deterioration of rail track.

Simulation of parthenium weed canopy under changing climate using L-systems

Parthenium weed (Parthenium hysterophorus L.) is an erect, branched, annual plant of the family Asteraceae. It is native to the tropical Americas, while now widely distributed throughout Africa, Asia, Oceania, and Australasia. Due to its allelopathic and toxic characteristics, parthenium weed has been considered to be a weed of global significance. These effects occur across agriculture (crops and pastures), within natural ecosystems, and has impacts upon health (human and animals). Although integrated weed management (IWM) for parthenium weed has had some success, due to its tolerance and good adaptability to temperature, precipitation, and CO2, this weed has been predicted to become more vigorous under a changing climate resulting in an altered canopy architecture. From the viewpoint of IWM, the altered canopy architecture may be associated with not only improved competitive ability and replacement but also may alter the effectiveness of biocontrol agents and other management strategies. This paper reports on a preliminary study on parthenium weed canopy architecture at three temperature regimes (day/night 22/15 °C, 27/20 °C, and 32/25 °C in thermal time 12/12 hours) and establishes a threedimensional (3D) canopy model using Lindenmayer-systems (L-systems). This experiment was conducted in a series of controlled environment rooms with parthenium weed plants being grown in a heavy clay soil. A sonic digitizer system was used to record the morphology, topology, and geometry of the plants for model construction. The main findings include the determination of the phyllochron which enables the prediction of parthenium weed growth under different temperature regimes and that increased temperature enhances growth and enlarges the plants canopy size and structure. The developed 3D canopy model provides a tool to simulate and predict the weed growth in response to temperature, and can be adjusted for studies of other climatic variables such as precipitation and CO2. Further studies are planned to investigate the effects of other climatic variables, and the predicted changes in the pathogenic biocontrol agent effectiveness.

Agronomic benefits and risks associated with the irrigated peanut–maize production system under a changing climate in northern Australia

With the aim of increasing peanut production in Australia, the Australian peanut industry has recently considered growing peanuts in rotation with maize at Katherine in the Northern Territory—a location with a semi-arid tropical climate and surplus irrigation capacity. We used the well-validated APSIM model to examine potential agronomic benefits and long-term risks of this strategy under the current and warmer climates of the new region. Yield of the two crops, irrigation requirement, total soil organic carbon (SOC), nitrogen (N) losses and greenhouse gas (GHG) emissions were simulated. Sixteen climate stressors were used; these were generated by using global climate models ECHAM5, GFDL2.1, GFDL2.0 and MRIGCM232 with a median sensitivity under two Special Report of Emissions Scenarios over the 2030 and 2050 timeframes plus current climate (baseline) for Katherine. Effects were compared at three levels of irrigation and three levels of N fertiliser applied to maize grown in rotations of wet-season peanut and dry-season maize (WPDM), and wet-season maize and dry-season peanut (WMDP). The climate stressors projected average temperature increases of 1°C to 2.8°C in the dry (baseline 24.4°C) and wet (baseline 29.5°C) seasons for the 2030 and 2050 timeframes, respectively. Increased temperature caused a reduction in yield of both crops in both rotations. However, the overall yield advantage of WPDM increased from 41% to up to 53% compared with the industry-preferred sequence of WMDP under the worst climate projection. Increased temperature increased the irrigation requirement by up to 11% in WPDM, but caused a smaller reduction in total SOC accumulation and smaller increases in N losses and GHG emission compared with WMDP. We conclude that although increased temperature will reduce productivity and total SOC accumulation, and increase N losses and GHG emissions in Katherine or similar northern Australian environments, the WPDM sequence should be preferable over the industry-preferred sequence because of its overall yield and sustainability advantages in warmer climates. Any limitations of irrigation resulting from climate change could, however, limit these advantages.

Stress analysis of a thick plate having a circular hole under axisymmetric radial load

In this paper a solution for the determination of stresses and displacements in a thick plate having a cylindrical hole subjected to localised hydrostatic loading has been given. Detail numerical results have been presented and compared with the results of an infinite hole subjected to localised hydrostatic load and a semiinfinite hole subjected to localised end load. It has been shown that for certain ratio of thickness of the pate to the radius of the hole and loading, the results could be obtained by using the solution of infinite or semiinfinite hole subjected to the same hydrostatic loading.

Experimental studies of lipped channel beams subject to web crippling under two-flange load cases

Lipped channel beams (LCBs) are commonly used as flexural members such as floor joists and bearers in the construction 6 industry. These thin-walled LCBs are subjected to specific buckling and failure modes, one of them being web crippling. Despite considerable 7 research in this area, some recent studies have shown that the current web crippling design rules are unable to predict the test capacities under 8 end-two-flange (ETF) and interior-two-flange (ITF) load conditions. In many instances, web crippling predictions by the available design 9 standards such as AISI S100, AS/NZS 4600 and Eurocode 3 Part 1-3 are inconsistent, i.e., unconservative in some cases, although they 10 are conservative in other cases. Hence, experimental studies consisting of 36 tests were conducted in this research to assess the web crippling 11 behavior and capacities of high-strength LCBs under two-flange load cases (ETF and ITF). Experimental results were then compared with the 12 predictions from current design rules. Comparison of the ultimate web crippling capacities from tests showed that the design equations are 13 very unconservative for LCB sections under the ETF load case and are conservative for the ITF load case. Hence, improved equations were 14 proposed to determine the web crippling capacities of LCBs based on the experimental results from this study. Current design equations do 15 not provide the direct strength method (DSM) provisions for web crippling. Hence, suitable design rules were also developed under the DSM 16 format using the test results and buckling analyses using finite-element analyses.

Experimental studies on web crippling strength of hollow flange channels under EOF and IOF load cases

LiteSteel beam (LSB) is a hollow flange channel made from cold-formed steel using a patented manufacturing process involving simultaneous cold-forming and dual electric resistance welding. LSBs are currently used as floor joists and bearers in buildings. However, there are no appropriate design standards available due to its 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 LSBs under pure bending, predominant shear and combined actions. However, web crippling behaviour and strengths of LSBs still need to be examined. Therefore, an experimental study was undertaken to investigate the web crippling behaviour and strengths of LSBs under EOF (End One Flange) and IOF (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 LSB sections very conservatively under EOF and IOF load cases. Therefore, suitably improved design equations were proposed to determine the web crippling capacity of LSBs based on experimental results. In addition, new design equations were also developed under the Direct Strength Method format. This paper presents the details of this experimental study on the web crippling behaviour and strengths of LiteSteel beams under EOF and IOF load cases and the results.

Web crippling tests of hollow flange channel beams with flanges fastened to supports under two flange load cases

Thin-walled steel hollow flange channel beams known as LiteSteel beam (LSB) sections were developed for use as joists and bearers in various flooring systems. However, they are subjected to specific buckling and failure modes, one of them being web crippling. Despite considerable research in this area, much of the current design predictions for cold-formed steel sections are not directly applicable to LSBs. This is due to the geometry of the LSB, which consists of two closed rectangular hollow flanges, and its unique residual stress characteristics and initial geometric imperfections. Hence an experimental study was conducted to investigate the web crippling behaviour and capacities of LSBs with their flanges fastened to supports. Thirty nine web crippling tests were conducted under two flange load cases (End Two Flange (ETF) and Interior Two Flange (ITF)). Test results showed that for ETF load case the web crippling capacities increased by 50% on average while they increased by 97% for ITF load case when flanges were fastened to supports. Comparison of the ultimate web crippling capacities from tests showed that AS/NZS 4600 and AISI S100 web crippling design equations are conservative for LSB sections with flanges fastened to supports under ETF and ITF load cases. Hence new equations were proposed to determine the web crippling capacities of LSBs with flanges fastened to supports. This paper presents the details of the experimental study into the web crippling behaviour of LSB sections with their flanges fastened under ETF and ITF load cases, and the results.

Experimental and numerical studies of hollow flange channel beams subject to web crippling under ETF and ITF load cases

This paper presents the details of experimental and numerical studies on the web crippling behaviour of hollow flange channel beams, known as LiteSteel beams (LSB). The LSB has a unique shape of a channel beam with two rectangular hollow flanges, made using a unique manufacturing process. Experimental and numerical studies have been carried out to evaluate the behaviour and design of LSBs subject to pure bending actions, predominant shear actions and combined actions. To date, however, no investigation has been conducted into the web crippling behaviour and strength of LSB sections under ETF and ITF load conditions. Hence experimental studies consisting of 28 tests were first conducted in this research to assess the web crippling behaviour and strengths of LSBs under two flange load cases (ETF and ITF). Experimental web crippling capacity results were then compared with the predictions from AS/NZS 4600 and AISI S100 design rules, which showed that AS/NZS 4600 and AISI S100 design equations are very unconservative for LSBs under ETF and ITF load cases. Hence improved equations were proposed to determine the web crippling capacities of LSBs. Finite element models of the tested LSBs were then developed, and used to determine the elastic buckling loads of LSBs under ETF and ITF load cases. New equations were proposed to determine the corresponding elastic buckling coefficients of LSBs. Finally suitable design rules were also developed under the Direct Strength Method format using the test results and buckling analysis results from finite element analyses.

Web crippling tests of rivet fastened rectangular hollow flange channel beams under two-flange load cases

The rivet-fastened rectangular hollow flange channel beam (RHFCB) is a new cold-formed hollow section proposed as an alternative to welded hollow flange steel beams. To date, no investigation has been conducted on their web crippling behaviour and strengths. Hence an experimental study was conducted to investigate the web crippling behaviour and capacities of rivet fastened RHFCBs under End Two Flange (ETF) and Interior Two Flange (ITF) load cases. Experimental results showed that the current design rules are unconservative for rivet fastened RHFCB sections under ETF and ITF load cases. Hence new equations were proposed to determine the web crippling capacities of rivet fastened RHFCBs.

Optimisation techniques for planning automatic under frequency load shedding in New Zealand’s power system

Electricity generation is vital in developed countries to power the many mechanical and electrical devices that people require. Unfortunately electricity generation is costly. Though electricity can be generated it cannot be stored efficiently. Electricity generation is also difficult to manage because exact demand is unknown from one instant to the next. A number of services are required to manage fluctuations in electricity demand, and to protect the system when frequency falls too low. A current approach is called automatic under frequency load shedding (AUFLS). This article proposes new methods for optimising AUFLS in New Zealand’s power system. The core ideas were developed during the 2015 Maths and Industry Study Group (MISG) in Brisbane, Australia. The problem has been motivated by Transpower Limited, a company that manages New Zealand’s power system and transports bulk electricity from where it is generated to where it is needed. The approaches developed in this article can be used in electrical power systems anywhere in the world.