1996 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)
Rasmussen, KJR and Hasham, AS, Flexural and flexural-torsional bifurcation of locally buckled beam-columns, Research Report No. R721, January 1996
Rousch, CJ and Hancock, GJ, Determination of purlin R-factors using a non-linear analysis, Research Report No. R722, February 1996
Poulos, HG, Chen, LT, Hull, TS, Model tests on single piles subjected to lateral soil movement, Research Report No. R723, February 1996
Rousch, CJ and Hancock, GJ, Purlin-sheeting connection tests, Research Report No. R724, February 1996
Poulos, HG, A comparison of some methods for the design of piles through embankments, Research Report No. R725, June 1996
Teh, LH and Clarke, MJ, Eight definitions for spatial rotations and their implications in the second-order analysis of space frames, Research Report No. R726, June 1996
Teh, LH and Clarke, MJ, An updated Lagrangian formulation for second-order elastic analysis of space frames using beam elements, Research Report No. R727, September 1996
Chen, LT and Poulos, HG, The behaviour of piles adjacent to tunnelling operations, Research Report No. R728, September 1996
Chen, LT, Poulos, HG and Hull, TS, Model tests on pile groups subjected to lateral soil movement, Research Report No. R729, September 1996
Popovic, D, Hancock, GJ and Rasmussen, KJR, Axial compression tests of Duragal angles, Research Report No. R730, September 1996
Chen, LT and Poulos, HG, The behaviour of piles subjected to lateral soil movements, Research Report No. R731, September 1996
Valentino, J, Pi, YL and Trahair NS, Inelastic buckling of steel beams with central torsional restraints, Research Report No. R732, November 1996
Teh, LH and Clarke, MJ, The implications of linearisations, approximations and computation algorithms in the second-order analysis of frames, Research Report No. R733, November 1996
Pi, YL and Trahair, NS, Nonlinear elastic behaviour of I-beams curved in plan, Research Report No. R734, December 1996
Rogers, CA and Hancock, GJ, Ductility of G550 sheet steels in tension-elongation measurements and perforated tests, Research Report No. R735, December 1996
Pi, YL and Trahair, NS
Effects of curvature on the nonlinear behaviour of elastic arches
Research Report No. R720, January 1996
Arches are structures which combine the bending member function of transmitting transverse forces with the compression member function of transmitting axial forces. The axial deformations of an arch affect its deformed curvatures, giving rise to some high order curvature terms. These terms are not usually considered in the conventional nonlinear analysis of elastic arches, and their effects have not been investigated adequately.
This paper develops a new curved finite element model for the nonlinear analysis of elastic arches which includes the effects of the high order terms in the deformed curvatures, and investigates the effects of these terms on the in-plane nonlinear behaviour of elastic arches. The use of deformed curvatures with these high order terms can describe the deformations of arches more accurately. Numerical examples demonstrate that the model is efficient, effective and accurate and that the effects of the high order curvature terms on the in-plane nonlinear behaviour of arches are significant in some cases. The nonlinear buckling and postbuckling behaviours of elastic pin-ended arches subjected to uniformly distributed radial loads are investigated numerically using the model. It is found that the existence of a linear bifurcation buckling load is not a sufficient condition for linear bifurcation buckling to occur; that the effects of prebuckling deformations on the buckling of shallow arches are significant; and that the nonlinear buckling loads may be much lower than the linear buckling loads.
Rasmussen, KJR and Hasham,
AS
Flexural and flexural-torsional bifurcation of locally buckled
beam-columns
Research Report No. R721, January 1996
The report describes the overall bifurcation behaviour of locally buckled I-sections in combined compression and major axis bending. The overall bifurcation loads are calculated using the tangent rigidities of the locally buckled cross-section for minor axis flexure and warping torsion. The expression for the overall bifurcation load is analytic while the tangent rigidities are calculated numerically using an elastic nonlinear finite strip local buckling analysis.
It is shown that while the interaction curves for local buckling and overall flexural-torsional buckling of the undistorted cross-section are convex, the interaction curves for the flexural-torsional bifurcation of locally buckled beam-columns maybe convex, linear or concave depending on the cross-geometry and the extent of local buckling. It is demonstrated that the overall bifurcation load depends primarily on the local buckling of the flanges. The overall bifurcation load of sections that are locally buckled in the web only is virtually unaffected by local buckling for any combination of bending and compression.
Rousch, CJ and Hancock, GJ
Determination of purlin R-factors using a non-linear analysis
Research Report No. R722, February 1996
In both Australia and the USA, the design procedure for purlins under wind uplift loading is based on the use of reduction factors (R-factors), which allow for the flexural-torsional or non-linear twisting behaviour of purlins with screw-fastened sheeting. To date, all R-factors have been determined by testing. However, in the future it may be more efficient to obtain R-factors from numerical models to minimise testing.
This report shows how a numerical model of the twisting behaviour of channel and Z-section purlins can be used to generate R-factors. Comparisons between experimentally determined and numerically based R-factors are made.
Poulos, HG, Chen, LT, Hull, TS
Model tests on single piles subjected to lateral soil movement
Research Report No. R723, February 1996
This paper describes a series of laboratory tests on single instrumented model piles embedded in calcareous sand undergoing lateral movement. Key parameters influencing the maximum being moment in the pile for a constant soil density have been identified to be pile head fixity condition, the ratio of the depth of moving soil to the pile embedded length, and pile diameter and stiffness. Normalised expressions for maximum bending moment are also presented. The agreement between the experimental results and the theoretical predictions by an existing boundary element program is shown to be reasonably good.
Rousch, CJ and Hancock, GJ
Purlin-sheeting connection tests
Research Report No. R724, February 1996
Purlin-sheeting connection tests have been performed in an effort to quantify the magnitude of the torsional restraint provided by sheeting when screw-fastened to one flange of a cold-formed steel channel or Z-section purlin. The purlin and sheeting types tested were the same as those used in full-scale purlin-sheeting vacuum rig tests conducted at the University of Sydney.
In this report, two series of purlin-sheeting connection tests are described. The torsional restraints determined from tests by Ings and Trahair and with those determined from equations in Eurocode 3 Part 1.3.
Poulos, HG
A comparison of some methods for the design of piles through embankments
Research Report No. R725, June 1996
This paper reviews some available methods for the design of piles through embankments, including:
-
the method of Tscheborarioff (1973)
-
the method of De Beer and Wallays (1972)
-
the method of Stewart et al (1992)
-
an approach used by a road authority in Australia
-
a simplified analysis of pile downdrag
-
design charts developed from boundary element analyses of pile-soil interaction
Comparisons between these methods are presented for the following aspects of design interest:
maximum bending moment in the piles
-
lateral pile head deflection
-
maximum axial force in pile
-
axial pile head settlement
Four cases are considered, an idealised case involving an embankment on a homogeneous clay layer, and three actual cases of bridge piles in the state of New South Wales in Australia.
It is found that there are significant differences among the methods considered, especially for predicting the lateral response of the piles.
Teh, LH and Clarke, MJ
Eight definitions for spatial rotations and their implications in the
second-order analysis of space frames
Research Report No. R726, June 1996
Although it is widely recognised by structural researchers that sequential rotations about axes fixed in space are not commutative, there prevails confusion in the literature about different definitions of rotations and different rotational parameters employed in handling compound spatial rotations. Different definitions of rotations or different parameters have been referred to by the same name and vice versa, and computation algorithms that are valid for certain types of rotation have been applied indiscriminately. Some researchers misunderstand the relationships between rotations and moments in space, and others fail to grasp the implications of certain types of rotation in the second-order analysis of space frames subjected to conservative loads. A redefinition of semi-tangential rotations as vectorial rotations is also proposed.
Teh, LH and Clarke, MJ
An updated Lagrangian formulation for second-order elastic analysis of
space frames using beam elements
Research Report No. R727, September 1996
It has been demonstrated previously by the authors that conservative internal moments of a spatial beam are of the so-called fourth kind, and that the rotation variables which are work-conjugate with such moments are vectoral rotations. If the vectoral rotations of a spatial beam element are approximated by the corresponding transverse displacement derivatives to the first order in formulating the governing equilibrium equation, incorrect element stiffness matrices will result unless a measure is taken to account for the distinction between the two displacement parameters. The required correction naturally depends on the "assumed" rotational behaviour of internal moments in the system. The present work derives the stiffness matrices of a spatial beam element based on the definitive knowledge of the rotational behaviour of conservative internal moments established previously by the authors. It is shown through numerical experiments that the resulting computational algorithms are robust and accurate.
Chen, LT and Poulos, HG
The behaviour of piles adjacent to tunnelling operations
Research Report No. R728, September 1996
In this paper, a two-stage approach is used to analyze the lateral and axial responses of piles due to tunneling. Firstly, free-field soil movements are estimated based on empirical and analytical methods, and secondly, these estimated soil movements are imposed on the pile in simplified boundary element analyses to compute the pile responses. Results of analyses of simple cases show that tunnelling may have appreciable impact on, and cause serious damage to, adjacent piled foundations. Through parametric studies, it is shown that the influence of tunneling on pile response depends on a number of factors, including tunnel geometry, ground loss ratio, soil strength, pile diameter and ratio of pile length and tunnel cover depth. Simple design charts are presented for estimating maximum pile responses and may be used in practice to assess the behaviour of existing piles adjacent to tunnelling operations. A published case history has been studied in which the measured lateral pile deflections are compared with those computed using the present method and fair agreement is found.
Chen, LT, Poulos, HG and Hull, TS
Model tests on pile groups subjected to lateral soil movement
Research Report No. R729, September 1996
This paper describes a series of model tests on instrumented pile groups embedded in calcareous sand undergoing lateral movement. The extent of the group effect on the lateral response of a pile in a group was found to be dependent on a number of factors, including the position of the pile in the group, pile spacing, the number of piles, and the head fixity condition. The agreement between the experimental results and the theoretical predictions by an existing boundary element program is shown to be reasonably good, provided that appropriate parameters are adopted.
Popovic, D, Hancock, GJ and
Rasmussen, KJR
Axial compression tests of Duragal angles
Research Report No. R730, September 1996
Cold-formed steel structural members are playing a greater role in modern steel structures due to their higher strength and lighter weight which is leading to cost reductions in the construction industry. The cold-formed projects manufactured by BHP Structural and Pipeline Products, which include tubular sections, angles and channels, are in-line galvanised during the forming process. The in-line galvanising process taken in conjunction with cold-forming has been found to enhance the strength properties of the sections up to 30%. The traditional thicknesses of cold-formed open sections in Australia are up to 3.5mm. With recent developments in cold-forming technology, it is now possible to produce cold-formed open sections up to 8mm thick. The BHP Structural and Pipeline Products sections fit between the current hot-rolled sections which usually have a stress grade of 250-300 MPa, and the thin-walled cold-formed sections such as purlin shapes with the stress grades of 450, 500 and 550 MPa.
This research report presents the results of a series of compression tests performed on cold-formed DuraGal angles manufactured by BHP Structural and Pipeline Products. The tests presented in this report are the first stage of a wider ARC Collaborative Research Project entitled "Behaviour and Design of Galvanised Cold-Formed Steel Structural Members". The objective of this project is to provide more test data to determine design rules for cold-formed angles and channels which can be used for design to the Australian Limit States Steel Structures Standard AS4100-1990. Since the current AS 4100-1990 does not recognise yield enhancement of cold-formed angles and channels, the benefits from the cold-forming process cannot be used in the design of this type of section at present. However, the draft Australian/New Zealand Standard for Cold-Formed Steel Structures does allow for yield enhancement from cold-forming.
The specific objectives of this program are to test slender and non-slender equal angle columns, to compare the test results with the multiple column curves in AS4100-1990 and to recommend appropriate curves for use in design. The test results are also compared with the design rules in the draft Australian/New Zealand Standard for Cold-Formed Steel Structures AS1538-1996. Recommendations on the applicability of these design rules to cold-formed angles are included in the report.
Chen, LT and Poulos, HG
The behaviour of piles subjected to lateral soil movements
Research Report No. R731, September 1996
This paper presents a theoretical procedure for analyzing the lateral response of piles subjected to lateral soil movements. The lateral pile response is computed via a simplified boundary element analysis, using the specified free-field soil movement profile. For pile groups, the group effect may need to be pre-assessed via a finite element analysis. Based on an appropriate assessment of the lateral soil movement, soil Young's modulus and limiting pile-soil contact pressure, the present method can generally give a satisfactory prediction of the pile response, as demonstrated via a study of some model tests and published case histories. For practical convenience, some elastic solutions have been generated using the present boundary element program and are presented in chart form. These design charts tend to give an upper bound estimation of the maximum pile bending moment and pile head deflection, although a close estimation may be obtained for small soil movements.
Valentino, J, Pi, YL and Trahair
NS
Inelastic buckling of steel beams with central torsional restraints
Research Report No. R732, November 1996
It is well known that a central elastic torsional restraint restricts the lateral buckling shape of an elastic I-beam, induces actions which resist the buckling deformations, and increases the elastic flexural-torsional buckling resistance. The elastic buckling resistance increases with the stiffness of the central torsional restraint until a limiting value of the stiffness is reached at which the elastic buckling resistance is equal to that of a rigidly restrained beam. However, the effect of torsional restraints on inelastic buckling has not been studied, and it is not known whether the limiting stiffness for elastic buckling can be applied to beams which buckle inelastically.
This paper develops a finite element model for the inelastic nonlinear flexural-torsional analysis of steel I-beams, and uses it to investigate the effects of central elastic torsional restraints on the inelastic flexural-torsional buckling of steel I-beams.
It is found that a central elastic torsional restraint generally increases the inelastic strength of the beam, but that the increase in the inelastic strength decreases as the beam's modified slenderness decreases. The limiting value of the stiffness of a central elastic torsional restraint at which the inelastic strength of the beam is equal to that of the corresponding beam with a rigid restraint is related to the modified slenderness of the beam. For a beam with a low modified slenderness which buckles inelastically, the limiting restraint stiffness is much smaller than that for a beam which buckles elastically. For slender beams, the moment transferred by a central torsional restraint of the limiting stiffness exceeds the strength design requirements for the restraint implied by AS4100 as a result of excessive central twist rotation.
Teh, LH and Clarke, MJ
The implications of linearisations, approximations and computation
algorithms in the second-order analysis of frames
Research Report No. R733, November 1996
This paper discusses the implications of linearisations, approximations, and computation algorithms involved in the elastic second-order finite element analysis of frames. While most of the linearisations and approximations are well recognised in the literature, their implications on the nonlinear solution prove to be subtle and frequently elude the understanding of researchers in the field. Indeed, a careful reading of the relevant published literature reveals that the formulated equilibrium equations, the computation algorithms used or the statements made by some researchers often lack consistency and rigour. In this paper, algorithms that are consistent with the assumptions applied to nonlinear problems are elucidated and compared with each other. Numerical examples are presented in order to compare differing algorithms to verify the propositions made in the paper.
Pi, YL and Trahair, NS
Nonlinear elastic behaviour of I-beams curved in plan
Research Report No. R734, December 1996
The vertical deflections perpendicular to the plane of a horizontal beam curved in plan are coupled with its twist rotations, and its axial deflections are coupled with its horizontal radial deflections. Because of the first of these couplings, a horizontally curved beam subjected to vertical loading has both primary bending and torsion actions. In the nonlinear range, second-order couplings between the vertical and horizontal deflections and the twist rotations are developed, and the nonlinear behaviour of the curved beam becomes more complicated. This paper studies the linear, neutral, and nonlinear equilibrium of elastic horizontally curved I-beams under vertical loading, and develops a curved finite element model for their analysis.
It is found that when the initial curvature of a curved beam is small, the primary coupling is also small and bending is the major action. In this case, the nonlinear behaviour is similar to the elastic flexural-torsional buckling of a straight beam. However, if the initial curvature of the curved beam is not small, the primary coupling becomes significant and both torsion and bending are major actions. In this case, nonlinear behaviour develops very early and is quite different from the flexural-torsional buckling behaviour of a straight beam.
Rogers, CA and Hancock, GJ
Ductility of G550 sheet steels in tension-elongation measurements and
perforated tests
Research Report No. R735, December 1996
Cold formed structural members are fabricated from sheet steels which must meet various material requirements prescribed in applicable national design standards. The Australian/New Zealand Design Standard allows for the use of thing (t<0.9mm), high strength (fy = 550MPa) sheet steels in all structural sections. However, in design the engineer must use a yield stress and ultimate strength reduced to 75% of the minimum specified values, due to the lack of ductility exhibited by sheet steels which are cold reduced to thickness. The American Iron and Steel Institute (AISI) Design 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 high strength G550 sheet steels currently used in construction.
This report details the findings of the first phase of a research project into the tensile behaviour of G550 sheet steels which range in base metal thickness from 0.40 to 0.60mm. Tensile coupons were milled from the longitudinal, transverse and diagonal directions of the sheet to determine the degree of anisotropy and its effect on material properties, including ductility. Measurements of overall, local and uniform elongation were completed using a fine gauge length grid (2.5mm c/c) marked on the surface of the tensile coupons. Perforated specimens were tested to determine the ability of the G550 sheet steels to redistribute stress concentrations throughout the cross-section, and to calculate resistance (capacity) and partial safety factors for use in limit states tensile design.
Test results indicate 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. The G550 sheet steels included in this report do not meet the Dhalla and Winter elongation and ultimate strength to yield stress ratio requirements regardless of direction, except for uniform elongation of longitudinal test specimens. However, perforated specimens are able to develop the full net section capacity under tensile load. The current resistance (capacity) and safety factors specified by the Australian/New Zealand, North American and European Design Standards are adequate for use in the prediction of tensile loads for concentrically loaded coupon specimens. The second and third phases of this project will consist of the testing of concentric and eccentric bolted and screwed single lap connections, as well as additional finite element analysis.