1998 Research Reports
Books and Book Chapters - Journal Papers - Conference Papers
Higher Degree Theses
Click on the title of the research report to get the abstract and the download link for the PDF version of the report (if it is available)
J Valentino and NS Trahair, Torsional Restraint Against Elastic Lateral Buckling, Research Report No R763
Y-L Pi and NS Trahair, Inelastic Lateral Buckling Strength and Design of Steel Arches. Research Report No R764
M D Liu and J P Carter, On the Volumetric Deformation of Reconstituted Soils, Research Report No R765
NS Trahair, Plastic Torsion Analysis of Mono- and Point-Symmetric Beams, Research Report No R766
BM Put, Y-L Pi and NS Trahair, Lateral Buckling Tests on Cold-Formed Channel Beams, Research Report No R767
X Zheng, JR Booker and JP Carter, Limit Analysis of the Bearing Capacity of Fissured Materials, Research Report No R768
CA Rogers and GJ Hancock, New Bolted Connection Design Formulae for G550 and G300 Sheet Steels Less Than 1.0 mm Thick, Research Report No R769
MD Liu, JP Carter, CS Desai and KJ Xu, Analysis of the Compression of Structured Soils Using the Disturbed State Concept, Research Report No R770
KJR Rasmussen and J Rondal, Strength Curves for Aluminium Alloy Columns, Research Report No R771
CA Rogers and GJ Hancock, Failure Modes of Bolted Sheet Steel Connections Loaded in Shear, Research Report No R772
CA Rogers and GJ Hancock, Tensile Fracture Behaviour of Thin G550 Sheet Steels, Research Report No R773
BM Put, Y-L Pi and NS Trahair, Bending and Torsion of on Cold-Formed Channel Beams, Research Report No R774
BM Put, Y-L Pi and NS Trahair, Lateral Buckling Tests on Cold-Formed Z-Beams, Research Report No R775
JC Wang, JR Booker and JP Carter, Experimental Investigation of Contaminant Transport in Porous Media, Research Report No R776
JC Wang, JR Booker and JP Carter, Analysis of the Remediation of a Contaminated Aquifer by a Multi-Well System, Research Report No R777
Y-L Pi and NS Trahair, In-Plane Buckling and Design of Steel Arches, Research Report No R778
T Wilkinson and GJ Hancock, Tests of Knee Joints in Cold-Formed Rectangular Hollow Sections, Research Report No R779
BM Put, Y-L Pi and NS Trahair, Biaxial Bending of Cold-Formed Z-Beams, Research Report No R780
AS Hasham and KJR Rasmussen
Interaction Curves for Locally Buckled I-Section Beam-Columns
Research Report No R762
In a previous research report [1], a non-linear finite element analysis for predicting the ultimate load and behaviour of thin-walled I-section beam-columns subjected to compression and major axis bending was verified against tests. The tests were performed on welded I-sections with slender component plates. Local buckling was observed in the tests.
The tests were conducted to determine the section capacity of two different cross-sections, described fully in [2], and the member capacity of two different lengths of a slender I-section, described fully in [3]. In total, four series of tests were conducted in a purpose-built test rig capable of applying axial load and bending moment in a constant ratio. The tests were performed using different axial load to moment ratios, as well as pure axial load and pure bending moment, hence allowing the full moment-axial force interaction curves to be constructed for all series.
The tests were closely simulated using the commercially available finite element program “ABAQUS” [4]. The finite element analysis included the effects of material and geometric nonlinearities, residual stresses and geometric imperfections, as described in [1].
The theoretical and experimental results showed that the interaction curve for the flexural-torsional buckling of locally buckled I-section beam-columns may be linear or convex when subjected to combined compression and major axis bending, depending on the cross-section geometry and the extent of local buckling.
This report uses the finite element model developed in [1] to investigate the shape of the interaction curves of four different cross-sections at four different lengths subjected to compression and major axis bending. Furthermore, the results are compared with the design rules of the Australian Steel Structures Standard AS4100 [5, 6], the American Institute of Steel Construction Load and Resistance Factor Design Specification [7], and Eurocode 3: Part 1.1 [8].
J Valentino and NS Trahair
Torsional Restraint Against Elastic Lateral Buckling
Research Report No R763
It is well known that a central elastic torsional restraint restricts the lateral buckling shape of an elastic I-beam and increases its elastic flexural-torsional buckling resistance. However, available information on the effects of torsional restraints on elastic buckling are either incomplete, or in some cases inaccurate.
This paper makes computer analyses of the effects of moment distribution and load height on the elastic flexural-torsional buckling of beams with central torsional restraints. The effects of off-centre and continuous restraints are also studied. It is found that the results of these computer analyses can be approximated by a series of related equations, and that these can be used to estimate the effects of torsional restraints on a wide range of lateral buckling problems. A worked example is given of the application of the approximations to the design of steel beams.
Y-L Pi and NS Trahair
Inelastic Lateral Buckling Strength and Design of Steel Arches
Research Report No R764
Arches resist general loading by a combination of axial compression and bending actions. Under these actions, an arch loaded in-plane may suddenly deflect laterally and twist out of the plane of loading and fail in a flexural-torsional buckling mode. This paper investigates the inelastic flexural-torsional buckling strength and design of steel arches under general loading using an advanced nonlinear inelastic finite element method of analysis. It is found that the arch subtended angel significantly affects its flexural-torsional buckling strength. The effects of initial crookedness and twist and residual stresses on the strengths of arches are also investigated. Modifications of the design rules for steel beam-columns are developed for the design of steel arches under general loading, based on the finite element analysis results.
M D Liu and J P Carter
On the Volumetric Deformation of Reconstituted Soils
Research Report No R765
This paper reviews the phenomenon of volumetric hardening, which is a common feature of the mechanical behaviour of many geo-materials. Three different material idealisations have been proposed to describe this hardening, and the paper contains the corresponding mathematical formulation. These idealisations vary in their complexity and hence their ability to capture different aspects of real material behaviour. Any of the three postulates can be implemented into most constitutive models. As a demonstration of their capabilities, the postulates have been implemented into the well known Modified Cam Clay model, and computations are made with the resulting new constitutive models. It is seen that the new models can successfully represent important features of soil behaviour such as plastic yielding associated with loading inside the current virgin yield surface, the loosening or densifying of granular soils caused by shearing, and the accumulation of both volumetric and distortional deformation caused by repeated drained loading over a large number of cycles.
NS Trahair
Plastic Torsion Analysis of Mono- and Point-Symmetric Beams
Research Report No R766
This paper extends a simple method of analysing the plastic torsion collapse of compact equal flange I-section beams to mono- and point-symmetric beams. The method can be used manually, is much easier than elastic analysis, and is no more difficult than the plastic collapse analysis of beams in bending.
The use of plastic torsion analysis avoids the conservatism of first yield analysis and design, because it accounts for the spread of plasticity through the cross-section and the redistribution of torque which occurs in redundant members after the first hinge forms. Designs based on plastic analyses of torsion will lead to significant economies over first yield designs based on elastic analysis.
Equations are developed in this paper for the uniform torsion plastic torques and for the plastic bimoments of mono-symmetric I-sections, lipped and unlipped channels, and equal flange lipped angles, and of point-symmetric lipped and unlipped Z-sections. A worked example of the plastic torsion collapse and design of a lipped channel is presented.
BM Put, Y-L Pi and NS Trahair
Lateral Buckling Tests on Cold-Formed Channel Beams
Research Report No R767
This paper is concerned with the lateral buckling capacities of cold-formed lipped channel-section beams (CFCs). It is argued that design code formulations which are based on those for hot-rolled I-beams may be inappropriate for CFCs, because of the very different cross-sectional shapes and methods of manufacture, and that there is a need for test data on the lateral buckling capacities of CFCs.
The paper describes a series of ten lateral buckling tests on simply supported unbraced CFCs of two different cross-sections, and a series of subsidiary tests, including tension tests, a stub-column test, section moment capacity tests, torsion tests, residual stress measurements, and measurements of initial crookedness and twist.
The lateral buckling test results are compared with theoretical predictions and with capacities calculated using existing design codes. Improvements are suggested for future design code formulations of the lateral buckling capacities of CFCs.
X Zheng, JR Booker and JP Carter
Limit Analysis of the Bearing Capacity of Fissured Materials
Research Report No R768
Formulations for the upper and lower bound theorems of plasticity are presented for fissured soil and jointed rock. The methods ignore elastic deformations and are based on the assumption that the fissured soil or rock mass can be treated as an anisotropic, rigid-plastic continuum. In the upper bound formulation, velocity discontinuity multipliers are introduced to deal with the discontinuities in the velocity field. For both the upper and lower bound formulations, linearized failure surfaces for the fissured materials are developed. The illustrative examples indicate that the new procedures are very efficient even when a quite coarse mesh is used to represent the mass of failing material, and that the "exact" failure loads are always bracketed by the upper bound and lower bound calculations. Moreover, by increasing the number of planes in the failure surface or/and refining the meshes, the accuracy of the bounds is raised.
CA Rogers and GJ Hancock
New Bolted Connection Design Formulae for G550 and G300 Sheet Steels Less
Than 1.0 mm Thick
Research Report No R769
Cold formed structural members are fabricated from sheet steels which must meet the material requirements prescribed in applicable national design standards. The Australian / New Zealand standard for cold-formed steel structures (AS/NZS 4600) allows for the use of thin (t < 0.9 mm), high strength ( fy = 550 MPa) sheet steels in all structural sections. However, due to the low ductility exhibited by sheet steels which are cold reduced to thickness the engineer must use a yield stress and ultimate strength reduced to 75% of the minimum specified values. The American Iron and Steel Institute (AISI) Specification further limits the use of thin, high strength steels to roofing, siding and floor decking panels. Sheet steels are required to have a minimum elongation capability to ensure that members and connections can undergo small displacements without a loss in structural performance, and to reduce the harmful effects of stress concentrations. A previous research report entitled Ductility of G550 Sheet Steels in Tension - Elongation Measurements and Perforated Tests (No. R735) detailed the basic material behaviour of G550 sheet steels. It was concluded that the ability of G550 sheet steels to undergo deformation is dependent on the direction of load within the material, where transverse specimens exhibit the least amount of overall, local and uniform elongation.
A research project on the behaviour of bolted connections composed of 0.42 and 0.60 mm G550 and G300 sheet steels has been completed, and the results are contained in the following research report; Bolted Connection Tests of Thin G550 and G300 Sheet Steels (No. R749). The authors of this report concluded that the low ductility measured in coupon tests did not influence the net section fracture mode of failure, although a modification to the bearing coefficient provisions for thin G550 and G300 sheet steels is required to account for the reduced bearing resistance of the connected materials. This reduction in bearing resistance is related more to the steel thickness than to the steel grade (G550 vs. G300).
Additional bolted connection specimens composed of 0.80 and 1.00 mm G550 and G300 sheet steels have been tested and the results are incorporated into this report. They have been used to develop a gradated bearing coefficient method which is dependent on the thickness of the connected materials and the size of the bolt(s) used in the connection. The measured variation in bearing resistance between the thin 0.42 mm G550 sheet steels and the typical 1.0 mm and thicker sheet steels is incorporated into an all encompassing bearing formulation. The additional bolted connection specimens were dimensioned such that only bearing failure would occur, with test specimens milled from the longitudinal, transverse and diagonal directions of the sheet.
MD Liu, JP Carter, CS Desai and KJ Xu
Analysis of the Compression of Structured Soils Using the Disturbed State
Concept
Research Report No R770
The aim of this note is to quantify the influence of soil structure on the compression behaviour of natural soils using the disturbed state concept (DSC). The behaviour of the fully adjusted state is chosen to be that of the corresponding soil in a reconstituted condition so that the disturbance function is a direct measure of soil structure. A new DSC compression model is proposed. This model is able to describe the compression behaviour of structured soils under loading, swelling and reloading. Special versions of the proposed model are also described for situations (a) where the compression behaviour of the corresponding reconstituted soils is linear in the e-lnp? space and (b) where the compression is one-dimensional. The ability of the proposed model and its various versions to describe the compression behaviour of structured soils has been verified.
KJR Rasmussen and J Rondal
Strength Curves for Aluminium Alloy Columns
Research Report No R771
Abstract: The paper describes a column curve formulation capable of producing accurate strengths for extruded aluminium alloys failing by flexural buckling. The formulation uses a simple extension of the Perry-curve and is shown to be valid for the full range of alloys used in practice. The material properties are assumed to be expressed in terms of the Ramberg-Osgood parameters (E0, ?0.2, n), typically obtained from a stub column test of the finished product.
It is shown that firstly, the formulation is capable of reproducing closely the ECCS a-, b- and c-column curves for aluminium alloys. Secondly, by adopting the ECCS Recommendations of basing the column curve selection on the type of alloy (heat-treated or non-heat-treated), it is shown that better agreement with tests can be obtained by using the column curve formulation proposed in the paper compared with the column curves of the ISO Recommendations and the current pre-standard Eurocode9 for aluminium alloy structures.
Keywords: Columns, Flexural stability, material nonlinearity, structural design, aluminium, Eurocode9.
CA Rogers and GJ Hancock
Failure Modes of Bolted Sheet Steel Connections Loaded in Shear
Research Report No R772
Cold formed structural members may be joined with bolted connections, which are designed with the aid of applicable national design standards. The ultimate load carrying capacity of a connection will be governed by one of many failure modes including; bearing, end pull-out, net section fracture, bolt shear, block shear rupture, etc.. A research project in which the behaviour of bolted connections composed of 0.42 to 1.0 mm G550 and G300 sheet steels is investigated has been completed, and the results are contained in the following research reports; Bolted Connection Tests of Thin G550 and G300 Sheet Steels (No. R749) and New Bolted Connection Design Formulae for G550 and G300 Sheet Steels Less Than 1.0 mm Thick (No. R769). It was concluded in these reports that there are a number of problems with the existing load capacity formulations contained in the current cold formed steel design standards, based on observations made during the testing of thin bolted connection specimens. Both the Australian / New Zealand (AS/NZS 4600) and the American Iron and Steel Institute (AISI) design standards cannot be used to accurately predict the failure mode of thin sheet steel bolted connections loaded in shear. Typically, net section fracture is predicted when test results reveal that bearing distress in the sheet steel is the controlling mode of failure. A modification to the bearing coefficient provisions for thin G550 and G300 sheet steels is necessary to account for the reduced bearing resistance of the connected materials. This reduction in bearing resistance is related more to the steel thickness than to the steel grade (G550 vs. G300) and a proposed gradated bearing coefficient method is presented in research report No. R769. A revision of the net section fracture design method is also required. Furthermore, a detailed analysis of the procedure used to identify the cause of failure in bolted connections is needed to ensure that accurate failure mode assessments are made, and ultimately to ensure that accurate design equations are formulated. Misidentification of failure modes and the misuse of data can lead to serious errors in the accuracy and applicability of design equations.
This research report details the behaviour associated with bearing and net section failure of bolted connections loaded in shear. Bearing behaviour includes piling of the sheet material in front of the bolts, as well as the material tearing associated with out-of-plane sheet distortion. Recommendations concerning the procedure used to identify the net section fracture and bearing failure modes are made. In addition, a detailed discussion of the test data used in the development of the current AS/NZS 4600 and AISI design equations for net section fracture at connections is completed.
CA Rogers and GJ Hancock
Tensile Fracture Behaviour of Thin G550 Sheet Steels
Research Report No R773
Cold formed structural members are fabricated from sheet steels which must meet the material requirements prescribed in applicable national design standards. The Australian / New Zealand standard for cold-formed steel structures (AS/NZS 4600) allows for the use of thin (t < 0.9 mm), high strength (fy = 550 MPa) sheet steels in all structural sections. However, due to the low ductility exhibited by sheet steels which are cold reduced to thickness, the engineer must use a yield stress and ultimate strength reduced to 75% of the minimum specified values. The American Iron and Steel Institute (AISI) Specification further limits the use of thin, high strength steels to roofing, siding and floor decking panels. Sheet steels are required to have a minimum elongation capability to ensure that members and connections can undergo small displacements without a loss in structural performance, and to reduce the harmful effects of stress concentrations. The ductility criterion specified in the Australian / New Zealand and North American design standards is based on an investigation of sheet steels by Dhalla and Winter, which did not include the thin high strength G550 sheet steels available today.
A previous research report entitled Ductility of G550 Sheet Steels in Tension - Elongation Measurements and Perforated Tests (No. R735) details the basic material behaviour of G550 sheet steels. The authors concluded that the ability of G550 sheet steels to undergo deformation is dependent on the direction of load within the material, where transverse specimens exhibit the least amount of overall, local and uniform elongation. Furthermore, the G550 sheet steels that were tested for this project do not meet the Dhalla and Winter material requirements regardless of direction, except for the uniform elongation of longitudinal coupon specimens.
This document reports on the failure mechanisms, as well as the fracture properties of G550 sheet steels tested in tension. Descriptions of failure surfaces, which were observed through a scanning electron microscope are provided. The failure behaviour of perforated and solid coupon specimens is documented, the fracture resistance of G550 sheet steels is measured for a range of temperatures and a numerical study of the effect of cracks on structural performance in the elastic load range is completed using the FRANC2D finite element computer program.
BM Put, Y-L Pi and NS Trahair
Bending and Torsion of on Cold-Formed Channel Beams
Research Report No R774
This paper reports the results of 34 bending and torsion tests on unbraced simply supported cold-formed steel channel beams loaded eccentrically at mid-span. These results and those of 10 concentrically loaded beams are compared with analytical predictions and with simple design approximations.
The tests show that the beam strengths decrease as the load eccentricity increases, and that the strength is higher when the load acts on the centroid side of the shear centre than when the load acts on the side away from the shear centre.
Good agreement is demonstrated between the test results and analytical predictions of the strengths. An extended series of analytical predictions is used to develop simple interaction equations that can be used in the design of eccentrically loaded cold-formed channel beams.
BM Put, Y-L Pi and NS Trahair
Lateral Buckling Tests on Cold-Formed Z-Beams
Research Report No R775
This paper is concerned with the lateral buckling capacities of cold-formed lipped Z-beams (CFZs). It is argued that design code formulations which are based on those for hot-rolled I-beams may be inappropriate for CFZs, because of the very different cross-sectional shapes and methods of manufacture, and that there is a need for test data on the lateral buckling capacities of CFZs.
The paper describes a series of six lateral buckling tests on simply supported unbraced CFZs, and a series of subsidiary tests, including tension tests, a torsion test, and measurements of initial crookedness and twist.
The lateral buckling test results are compared with theoretical predictions and with capacities calculated using existing design codes. Improvements are suggested for future design code formulations of the lateral buckling capacities of CFZs.
JC Wang, JR Booker and JP Carter
Experimental Investigation of Contaminant Transport in Porous Media
Research Report No R776
When numerical methods are applied to simulate a real
contaminant transport problem, the values of a number of key parameters such
as porosity, hydrodynamic dispersion coefficient or dispersivity and Darcy
velocity or seepage velocity are needed. Unfortunately, it is usually
difficult to determine the hydrodynamic dispersion coefficient in the field
because of the complexity of the pore geometry and soil particle size and
the natural heterogeneities of the porous media. Experimental testing
is the only way to determine the values of these parameters reliably.
In this paper, two different experimental programs, involving two types of
column test and well simulation test, were designed to demonstrate that the
theory developed to explain contaminant transport in porous media is capable
of representing the actual phenomenon of contaminant migration in soil.
It is demonstrate that experiments can also be carried out to determine the
properties necessary to model a real case of contaminant migration in porous
media.
Keywords: Contaminant transport, Column test, Well simulation test,
Remediation.
JC Wang, JR Booker and JP Carter
Analysis of the Remediation of a Contaminated Aquifer by a Multi-Well
System
Research Report No R777
Various numerical techniques have been developed and used to design waste repositories such as landfills, in order to reduce the impact of contamination. However, even with good design, potential contamination such as groundwater contamination may still arise in the future due to unforseen circumstances or negligence. Thus there is a need to seek efficient, cost-effective and carefully designed remediation strategies for the cleanup of contaminated groundwater. This paper presents a study of the remediation of a contaminated aquifer of uniform thickness by multi-well systems, which include both discharge wells and recharge wells. These investigations show that an appropriately designed pump and treat system (PAT) can have a significant effect on the decontamination of a polluted aquifer and can preclude the further spreading of a contaminant plume. However, if the system is not designed appropriately, it may cause a further serious spreading of the contamination. This possibility is illustrated by the examples presented in the paper, which highlight the need for care in the design of remediation strategies.
Keywords: Remediation strategy, Multi-well system, Groundwater contamination.
Y-L Pi and NS Trahair
In-Plane Buckling and Design of Steel Arches
Research Report No R778
Many design codes do not give methods for designing steel arches against in-plane failure. The few that do provide methods that are essentially based on a linear interaction equation for the in-plane strengths of an equivalent beam-column which uses the maximum elastic bending moment and axial compression in the arch. However, the linear interaction equation for a beam-column may not be suitable for an arch for four reasons. Firstly, it is known that the in-plane member capacity of a beam-column is significantly affected by the bending moment distribution, and that a linear interaction equation is only appropriate for uniform bending. Secondly, the use of the maximum bending moment does not include the favourable moment redistribution that takes place in a redundant arch after the first plastic hinge forms. Thirdly, the use of the maximum axial compression does not allow for the non-uniform distribution of axial compression around the arch. Fourthly, the in-plane elastic buckling load and compression capacity of a shallow arch may be lower than expected.
This paper studies the in-plane buckling of arches in uniform compression and uses a nonlinear inelastic finite element model to develop a method for designing steel arches against uniform compression, and also to develop an interaction equation for the design of steel arches against non-uniform in-plane compression and bending.
Analytical solutions for the buckling loads of shallow
arches in uniform compression are obtained. The proposed design
approximations provide close predictions for the in-plane buckling loads of
both shallow and non-shallow arches in uniform compression. It is found that
design equations for steel columns cannot be used directly for steel arches
in uniform compression. The design equations proposed provide good
predictions for both shallow and non-shallow steel arches in uniform
compression. It is also found that design interaction equations for
steel beam-columns cannot be used directly for steel arches under
non-uniform compression and bending. The modified interaction equation
proposed provides good lower bounds for the in-plane strengths of both
shallow and non-shallow steel arches in bending and compression because it
considers the non-uniform distributions of the bending moment and axial
compression around the arch, the behaviour of shallow arches, and the
favourable moment redistribution after the first hinge forms.
T Wilkinson and GJ Hancock
Tests of Knee Joints in Cold-Formed Rectangular Hollow Sections
Research Report No R779
This report describes tests on various types of knee joints for portal frames constructed from cold-formed rectangular hollow sections (RHS). Welded stiffened and unstiffened knee joints, bolted knee joints with end plates, and connections with a fabricated internal sleeve, were included in the experimental investigation. Most connections tested under opening moment failed by fracture in the heat affected zone of the RHS near the weld. The connections tested under closing moment failed by web local buckling which occurred near the connection.
While the stiffened and unstiffened welded connections satisfied the strength interaction requirements in the available design guides, the connections did not maintain the plastic moment for sufficiently large rotation to be considered suitable for a plastic hinge location. The unstiffened welded joints were not able to reach the plastic moment.
The use of an internal sleeve moved the plastic hinge in the connection away from the connection centre-line and reduced the stress on the weld between the legs of the connection. It was found that sleeve connections were capable of sustaining the plastic moment for large rotations considered suitable for plastic design.
KEYWORDS: Cold-formed steel, hollow sections, RHS, welded connections, bolted connections, joints, plastic design, bending, rotation capacity, local buckling, fracture, heat affected zone, internal sleeve.
Full Report R779 in PDF (1356 kB) - Click here
BM Put, Y-L Pi and NS Trahair
Biaxial Bending of Cold-Formed Z-Beams
Research Report No R780
This paper reports the results of ten biaxial bending tests on unbraced simply supported cold-formed steel Z-beams loaded at mid-span in planes inclined to the major principal plane. These results and those of six beams loaded in the major principal plane are compared with analytical predictions and with simple design approximations.
The tests show that the beam strengths decrease as the load inclination to the major principal plane increases, and that the strength is higher when the load inclination is towards the web then when it is towards the flange lip.
Good agreement is demonstrated between the test results and analytical predictions of the strengths. An extended series of analytical predictions is used to develop simple interaction equations that can be used in the design of eccentrically loaded cold-formed Z-beams.