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Geometric imperfections have a significant effect on both buckling and strength capacities of structural members. It is essential to accurately measure the geometric imperfections for finite element simulation especially for thin-walled... more
Geometric imperfections have a significant effect on both buckling and strength capacities of structural members. It is essential to accurately measure the geometric imperfections for finite element simulation especially for thin-walled sections. This paper presents the procedure to measure and incorporate geometric imperfections into finite element models using ABAQUS software package with the focus of attention for cold-rolled aluminium sections. Laser scanners are firstly used to measure geometric imperfections along high-precision tracks while recording the distances to corresponding points on the surface of specimen. The measurement lines are located around the cross-section. Subsequently, a MATLAB code is developed to incorporate the measured imperfection magnitudes into a perfect mesh of the finite element model. The Fourier series approximation is used in the longitudinal direction along measurement lines while the linear interpolation is used for flanges, lips and web in the transverse direction.
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© 2017 Elsevier Ltd <br>This paper explores the use of an explicit solver available in ABAQUS/Explicit to simulate the behaviour of blind bolted endplate connections between composite beams and concrete-filled steel tubular (CFST)... more
© 2017 Elsevier Ltd <br>This paper explores the use of an explicit solver available in ABAQUS/Explicit to simulate the behaviour of blind bolted endplate connections between composite beams and concrete-filled steel tubular (CFST) columns. Main aspects of the explicit analysis such as solution technique, blind bolt modelling, choice of element type and contact modelling are discussed and illustrated through the simulation of a large-scale test on the considered joint. The mass scaling option and smooth step amplitude are very effective tools to speed up the explicit simulation. Shell elements can be used in modelling the I-beam due to their computational efficiency and accuracy in capturing local buckling effects. With a proper control of the loading rate, the explicit analysis can provide accurate and efficient predictions of the quasi-static behaviour of the bolted endplate composite connections.
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Self-drilling screws have been used extensively in cold-formed steel structures. The American Specification and Australian Standard both provide design checks for different limit states of screwed connections. However, in a connection... more
Self-drilling screws have been used extensively in cold-formed steel structures. The American Specification and Australian Standard both provide design checks for different limit states of screwed connections. However, in a connection undergoing bending, while a screw may fail, other screws may be still in the elastic state. Therefore, investigation in the load-deflection response of screw connectors before failure is required for further understanding of complex screwed connections. This paper describes a shear test using 3 screws connecting in G450 steel sheets. A 3D finite element (FE) model was developed and validated using ABAQUS software. The simulation is able to reproduce the experiment’s results in term of shear strength, stiffness and ductility of the connections. The simplicity of this model allows it to be adapted into full scale connection modeling.
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This paper presents the numerical investigation of cold-rolled channel columns made of 5052 aluminium alloy subjected to member buckling. A detailed Finite Element (FE) model using software ABAQUS v 6.14 was developed to simulate an... more
This paper presents the numerical investigation of cold-rolled channel columns made of 5052 aluminium alloy subjected to member buckling. A detailed Finite Element (FE) model using software ABAQUS v 6.14 was developed to simulate an experimental program recently performed at the University of Sydney. In the FE simulations, actual measured properties and geometric imperfections were incorporated into the FE models. The FE results are compared and validated against the experimental results. These accurate and reliable FE models will be used for the future parametric study to extend the data range for the development of the design guidelines for the cold-rolled aluminium alloy channel columns subjected to member buckling.
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Thin-walled channel members subjected to shear are commonly perforated with web openings to provide access for building service systems. The changes in the stress distribution due to the presence of holes can cause the changes in the... more
Thin-walled channel members subjected to shear are commonly perforated with web openings to provide access for building service systems. The changes in the stress distribution due to the presence of holes can cause the changes in the critical buckling load and the overall strength of the perforated members in shear. Recent research by S.H. Pham has provided buckling solutions based on Finite Element Method for determining the shear buckling loads of channel sections with web holes with shear aspect ratio up to 2.0. However, the research only focused on square and circular holes. With the same methodology, this paper provides a buckling solution for perforated channel members with elongated web holes in shear. FE models were constructed to generate the elastic buckling loads with a very wide range of hole dimensions. The assumptions about the stress distribution from the previous studies were also utilized in this study. A dimensional transformation is also proposed in this paper.
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This research was funded by the Australian Research Council Discovery Project through the Grant ID DP160104640. The first author’s research degree was supported by the Dean’s Faculty of Engineering and Information Technologies PhD... more
This research was funded by the Australian Research Council Discovery Project through the Grant ID DP160104640. The first author’s research degree was supported by the Dean’s Faculty of Engineering and Information Technologies PhD Scholarship for Vietnam, the University of Sydney. The steel sheets were provided by BlueScope Steel. The HILTI power-actuator tool, fasteners and charges were provided by Hilti Pty Ltd.
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Funding provided by the Australian Research Council Discovery Project Grant DP160104640 has been used to carry out this project. The first author gratefully acknowledges the support provided by a Dean's Faculty of Engineering PhD... more
Funding provided by the Australian Research Council Discovery Project Grant DP160104640 has been used to carry out this project. The first author gratefully acknowledges the support provided by a Dean's Faculty of Engineering PhD Scholarship for Vietnam.
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The use of cold-formed steel structures in the construction industry has become widely popular over the past decade. This has led to the necessary understanding of the effects of cold-working process on cold-formed steel members. The... more
The use of cold-formed steel structures in the construction industry has become widely popular over the past decade. This has led to the necessary understanding of the effects of cold-working process on cold-formed steel members. The manufacturing process of cold-formed steels starts with cold-rolling the hot-rolled steel sheet under a series of rollers until a thickness is achieved. The process is followed by cold-bending to create cold-formed sections with desired shapes at ambient temperature. The plastic deformation associated with the rolling and bending processes results in strain hardening of the material and this in turn affects the properties. This paper presents both microstructural and micromechanical investigations on the blank and bent areas of 3.0 mm thick C-shaped cold-formed sections. Vickers hardness tests show a hardness increase at the bent areas. The observation of the bent region using scanning electron microscopy (SEM) reveals changes in the grain structures. A...
The Semi-Analytical Finite Strip Method (SAFSM) of buckling analysis for thin-walled sections has been recently extended from bending and compression to shear and localised loading. A new computer program called THIN-WALL-2 has been... more
The Semi-Analytical Finite Strip Method (SAFSM) of buckling analysis for thin-walled sections has been recently extended from bending and compression to shear and localised loading. A new computer program called THIN-WALL-2 has been recently developed at the University of Sydney using a MATLAB graphical interface and Visual Studio C++ computational engines. This paper describes the development of the MATLAB graphical interfaces including localised loading and shear. For localised loading, a linear pre-buckling analysis is required to determine the membrane stresses for use in the buckling analysis. The program includes output of these membrane stresses and deformed shapes as well as buckling modes determined from these stresses.
The paper will describe finite element analyses using the program ABAQUS of SupaCee ® Sections in Shear. These high strength (450 MPa) C-profile steel sections contain additional return lips and web stiffeners which enhance the bending... more
The paper will describe finite element analyses using the program ABAQUS of SupaCee ® Sections in Shear. These high strength (450 MPa) C-profile steel sections contain additional return lips and web stiffeners which enhance the bending and shear capacity of the sections. They are used widely in Australia as purlins in roof and wall systems. The results of nonlinear analyses by the finite element method (FEM) depend heavily on the imperfections assumed for the analysis of the thin-walled members. Different buckling modes (Mode 1 Anti-Symmetric and Mode 2 Symmetric) are assumed with different magnitude levels of imperfection as proposed by Camotim in Portugal and Schafer in the USA. The paper summarises the results of the finite element nonlinear simulations of the shear tests on SupaCee ® sections performed at the University of Sydney and described in a separate paper. The FEM results are compared with the tests to calibrate the imperfection magnitudes and modes against the tests. Co...
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Abstract A range of new and innovative cold-formed shapes using high-strength steels has been introduced into the Australian and New Zealand marketplace over the last 20 years. The high-strength steels are normally cold-reduced steel to... more
Abstract A range of new and innovative cold-formed shapes using high-strength steels has been introduced into the Australian and New Zealand marketplace over the last 20 years. The high-strength steels are normally cold-reduced steel to Australian Standard AS1397 and have typical yield stress values in the range 450–550 MPa (65–80 ksi) depending upon the thickness and the degree of cold reduction. They are normally galvanized with zinc. A recent development is to include additional flange, web, and lip stiffeners in the sections to increase the buckling capacity in line with the increased yield strength. A further development is to decrease the gauge of the sections once additional stiffeners are included. This chapter describes the behavior of these sections, demonstrating their structural advantages using testing and finite element method modeling. Signature curves of buckling stress versus half-wavelength in both flexure and shear for the innovative sections are shown for use in the direct strength method of design in the American Iron and Steel Institute specification NAS S100:2012 and the Australian/New Zealand standard AS/NZS 4600:2005.
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The behaviour and strength of cold-formed columns are mainly influenced by local, distortional and global buckling or coupled instability phenomena. Distortional buckling may govern the column strengths of open cold-formed sections with... more
The behaviour and strength of cold-formed columns are mainly influenced by local, distortional and global buckling or coupled instability phenomena. Distortional buckling may govern the column strengths of open cold-formed sections with intermediate lengths. The objective of this paper is to investigate the distortional mode and ultimate capacity of cold-rolled aluminium channel sections in compression. A total of nine columns with three different cross-sectional geometries were performed at the University of Sydney. These commercially available cross-sections were fabricated by using the cold-rolling process instead of extrusion. The geometric imperfections of channel specimens were measured using a specially designed measuring rig. Tensile coupon tests were also conducted from the flat portions and the corner regions of the cross-sections to determine the material properties. The specimens were tested in axial compression between two fixed ends. The ultimate loads and observed failure modes in the column tests are reported.
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The Finite Strip Method (FSM) has been developed for pre-buckling and buckling analyses of thin-walled sections under localised loading for general end boundary conditions. The theory is included in the THIN-WALL-2 V2.0 program which has... more
The Finite Strip Method (FSM) has been developed for pre-buckling and buckling analyses of thin-walled sections under localised loading for general end boundary conditions. The theory is included in the THIN-WALL-2 V2.0 program which has been developed at the University of Sydney using a MATLAB graphical interface, Visual Studio C++ computational engines and a FSM module. The paper describes the application of the THIN-WALL-2 V2.0 program in analysis of thin-walled sections under the four localised loading cases namely IOF (Interior one-flange loading), EOF (End one-flange loading), ITF (Interior two-flange loading) and ETF (End two-flange loading). A linear analysis is required for pre-buckling analysis to determine the pre-buckling modes and the membrane stresses of structural members subjected to localised loading. These stresses are then used in the buckling analysis to get the buckling load and the buckling modes of the structural members.
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Abstract Screws are commonly used as connectors in cold-formed steel structures as they can be drilled easily through thin sheet steels, allowing on-site assembly. However, in a connection undergoing shear and bending, while a screw may... more
Abstract Screws are commonly used as connectors in cold-formed steel structures as they can be drilled easily through thin sheet steels, allowing on-site assembly. However, in a connection undergoing shear and bending, while a screw may fail, other screws may be still in the elastic state. Therefore, investigation in the load-deflection response of screw connectors before failure is required for further understanding of complex screwed connections. Experiments and simulation are being carried out at the University of Sydney in order to investigate the behaviour of cold-formed steel connections with screw fasteners in shear. The screw model is built with solid deformable elements containing the screw threads. A plasticity model is applied to the steel sheets to represent different stress states of steel during failure. The model successfully simulates the different behaviour occurring simultaneously in the screwed connection tests: tearing and piling up of the steel sheets, end plate failure, tilting and fracture of the screws.
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ABSTRACT The plain Z-section is one of the most common cold-formed steel purlins in use for roof systems. Its lapping ability provides continuity, and double thickness material at the support regions results in greater performance and... more
ABSTRACT The plain Z-section is one of the most common cold-formed steel purlins in use for roof systems. Its lapping ability provides continuity, and double thickness material at the support regions results in greater performance and more economical designs. Design methods for this section are normally specified in the Australian/New Zealand Standard for Cold-Formed Steel Structures or the North American Specification for Cold-Formed Steel Structural Members. The newly developed Direct Strength Method (DSM) presented (Chapter 7 of AS/NZS 4600:2005, Appendix 1 of NAS S100-2007) is limited to pure compression and pure bending. Recently, design proposals for shear, and combined bending and shear for DSM have been added to the 2012 Edition of the North American Specification. The situation of combined bending and shear as occurs in a continuous purlin system is not considered in detail. Hence, this paper presents numerical simulations using the Finite Element Method (FEM) to determine the ultimate strength. The simulations are compared with and calibrated against tests at two lap lengths. For each lap length, tests were also conducted with and without straps screwed on top flanges. These straps provide torsion/distortion restraints which may enhance the capacity of the purlins. The accurate results from FEM allowed extension of test data by varying the lap lengths and section thicknesses. The results of both the experimental tests and FEM were used and plotted on the recently proposed DSM design interaction curves. Proposals for an extension to the DSM in combined bending and shear are given in the paper.
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Abstract This paper explores the use of the finite element software package ABAQUS/Explicit to simulate the behaviour and strength of power-actuated fastener (PAF) connections joining cold-formed steel sheet to hot-rolled steel plate... more
Abstract This paper explores the use of the finite element software package ABAQUS/Explicit to simulate the behaviour and strength of power-actuated fastener (PAF) connections joining cold-formed steel sheet to hot-rolled steel plate subjected to monotonic shear loading. The finite element (FE) models are developed for the simulation of the entire process including both installation and loading stages. The fastener is firstly driven into the steel materials to consider the initial plastic deformations around the contacts between steel plates and fastener caused by dynamic impact. Subsequently, monotonic shear loading is applied to the PAF connections until failure by a displacement control at a low speed. Various aspects of the FE models such as fracture model of the materials, loading rate, mesh sensitivity are calibrated to optimise the computing time and improve the accuracy of the FE models. The simulations are validated against experiments conducted in a separate study by the authors, and good agreement between the test and numerical results is achieved. The accurate and reliable FE models in this study are able to simulate and provide insights into the shear behaviour of the power-actuated fastener connections in terms of initial stiffness, maximum shear capacity, failure modes as observed in the experiments (i.e., bearing, shear fracture, and pull-out of the fastener), ductility, and damage patterns of the connectors. It is demonstrated that FE analysis can therefore be used to extend experimental data in a parametric study and to optimise the design of PAF connections in shear.