No. R799, March, 2000
Hancock, GJ and Rasmussen, KJR
Compression Tests of DuraGal Angles Loaded Parallel With a Leg
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Abstract
This report presents the results of 11 compression tests performed on cold-Formed, inline galvanised, slender 50x50x2.5 DuraGal equal angles. The angles were tested between pinned ends and loaded axially with eccentric load which caused bending parallel with a leg at the ends. Tests were performed over a range of lengths to produce column strength curves. The sensitivity to load eccentricity was investigated by applying the load at the centroid, at a leg and at a point outside the section. Detailed measurements of material properties, residual stresses and geometric imperfections
were conducted.
The test data are compared with the design rules of the Australian Standards for ColdFormed (AS/NZS 4600-1996) and Hot-Rolled (AS 4100-1998) Steel Structures as well as the American Iron and Steel Institute (AISI-1997) Specification for the Design of Cold-formed Steel Structural Members, the American Society of Civil Engineers Standard (ASCE-1991) for the Design of Latticed Steel Transmission Structures and the American Institute of Steel Construction (AISC-1993) Specification for Load and Resistance Factor Design of Single-Angle Members. Recommendations on the application of these design rules to cold-formed angles are included in the paper.
The test results show that the design rules of both Australian standards and the AISI and AISC specifications are conservative. The conservatism is most pronounced at short lengths. Improved design rules for AS/NZS 4600 and the AISI Specification are suggested. The design rules of the ASCE Standard are in fairly good agreement with the tests.
No. R800, April, 2000
Trahair, NS and Teh, LH
Second Order Moments in Torsion Members
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Abstract
This paper is concerned with the elastic flexural buckling of structural members under torsion, and with second-order moments in torsion members. Previous research is reviewed, and the energy method of predicting elastic buckling is presented. This is used to develop the differential equilibrium equations for a buckled member.
Approximate solutions based on the energy method are obtained for a range of conservative applied torque distributions and flexural boundary conditions. A comparison with the limited range of independent solutions available and with independent finite element solutions suggests that the errors in the approximate solutions may be as small as 1%.
The predicted linear elastic buckling torques may be used to approximate the second-order bending moments caused by torsion in members under more general loading. A method is developed for approximating these second-order moments. This is used as the basis of a method of estimating when these second-order moments may be significant by comparing the actual member slenderness with a reference value.
Reference values of slenderness are calculated for two examples involving an equal angle member and a circular hollow section member (both simply supported), and the importance of second-order torsion effects in an I-section member is estimated. The reference values of slenderness are found to be very high, and it is concluded that second-order moments caused by torsion in typical structural steel members with slenderness ratios L/ry less than 300 are very small and may be neglected.
Keywords
Bending, buckling, elasticity, flexure, moments, second-order effects, steel structures, torsion.
No. R801, May, 2000
Liu, MD, Hull, TS and Carter, JP
Compression Behaviour of Sand
Abstract
The compression behaviour of sands has been investigated, and it is proposed that a linear relationship between voids ratio, e, and mean effective stress, p¢, instead of the more widely employed e-lnp¢ relationship, can best describe this behaviour. A general equation is presented describing the compression behaviour of sands under first loading. The proposed compression equation has been applied to ten different types of sand and one crushed rock with the compression pressures reaching 850 MPa. It is seen that the proposed equation can describe very satisfactorily the behaviour of all these materials.
A simplified model for virgin compression loading, unloading and reloading of sands is then formulated. It contains only four material parameters and describes a linear variation between the voids ratio and the compression stress for both virgin yielding and purely elastic behaviour. Based on the comparison between predictions of the model and experimental data, it is seen that the proposed model captures important features of sand behaviour, including the response to cycles of load, and provides a simple, yet realistic, material idealisation for constitutive modelling of sand behaviour.
Keywords
Sands, fabric/structure of soils, compressibility, constitutive relations.
No. R802, July, 2000
Teh, LH and Hancock, GJ
Strength of Fillet Welded Connections in G450 Sheet Steels
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Abstract
This paper investigates the reliability of the existing design equations specified in AS/NZS 4600:1996 for fillet welded connections in cold-reduced high-strength G450 sheet steels. The existing design equations are adapted from the AWS D1.3 Structural Welding Code, which is based on the testing results of double-lap connections in mainly mild sheet steels. Double-lap and single lap fillet welded connections in 1.5-mm and 3.0-mm sheet steels are manufactured using different GMAW procedures and tested to failure. The approximate tensile strengths of the heat-affected-zones (HAZs), which are significantly lower than the corresponding tensile strengths of the virgin sheet steels, are used to predict the failure loads of the specimens. The HAZ strengths are close to the nominal design tensile strength of 480 MPa specified in AS/NZS 4600:1996. Despite this fortuitous agreement, the lack of ductility of G450 sheet steels compared to mild steels leads to earlier failure of the fillet welded connections loaded in the longitudinal direction of the welds. Failure modes of different types of connections and of connections in different sheet thicknesses are described and discussed. Relaxation of the target safety index for longitudinal fillet welded connections is proposed. It is suggested that the existing design rules may be applied conservatively to transverse fillet welded connections which do not undergo inclination failure, and to longitudinal fillet welded connections.
Keywords
Cold-formed steel, design standards, fillet welds, load and resistance factor design, sheet metal, welded connections
No. R803, September, 2000
Denoon, RO, Roberts, RD, Letchford. CW and Kwok, KCS
Field Experiments to Investigate Occupant Perception and Tolerance of Wind-Induced Building Motion
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Abstract
Field measurements were conducted at three control towers to determine occupant reaction to wind-induced building motion. The towers used were Brisbane Airport Control Tower, Sydney Airport Control Tower and the Port Operations & Communications Centre in Sydney. Occupants at Brisbane and Sydney Airport Control Towers were provided with push-buttons on which they could register motion perception and/or tolerance. Surveys were conducted with occupants in Sydney Airport Control Tower and the Port Operations & Communications Centre.
Motion perception was found to be dependent on peak accelerations. It was found that the factors affecting motion tolerance are: magnitude of motion leading to fear and alarm; and the frequency of occurrence of perceptible motion. Education and habituation was found to increase tolerance of wind-induced motion.
No. R804, October, 2000
Denoon, RO, Roberts, RD, Letchford. CW and Kwok, KCS
Effects of Wind-Induced Building Motion on Cognitive Performance
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Abstract
Field and laboratory experiments were conducted to investigate the effects of wind-induced building motion on cognitive performance. This was done with particular reference to determining whether there was a decrement in the performance of air traffic controllers due to motion in air traffic control towers.
Field experiments were unsuccessful due to a lack of control of environmental factors. A laboratory motion simulator was designed and constructed. The laboratory experiments found no evidence of simulated wind-induced building motion affecting cognitive performance. Any effects which do exist are much smaller than inter- and intra-subject variability.