Publications

Attard, MM & Stewart, MG 1998, 'A two parameter stress block for high-strength concrete', ACI Structural Journal, vol. 95, no. 3, pp. 305-317.
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The rectangular stress block parameters in the current ACI Code are limited to concrete strengths in the range 20 to 50 MPa (2900 to 7250 psi). This paper looks at the applicability of the ACI rectangular stress block parameters to high-strength concretes. New rectangular stress block parameters are proposed that are based on a probabilistic analysis using a stress-strain relationship for high-strength concrete and that include estimates of variability and distribution of the input properties. A sensitivity analysis is also carried out to ascertain the effect of parameter uncertainty. The probabilistic models proposed can be used in a code calibration of design formula for high-strength concrete. It is shown that for a ductile singly-reinforced rectangular section, the ultimate moment capacity is relatively insensitive to the stress block model. Estimates of the ductility level at both ultimate and column capacity in primary compression failure, however, are significantly affected by the choice of the stress block model.

Ball, JE & Luk, KC 1998, 'Modeling Spatial Variability of Rainfall over a Catchment', Journal of Hydrologic Engineering, vol. 3, no. 2, pp. 122-130.
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Ball, JE, Jenks, R & Aubourg, D 1998, 'An assessment of the availability of pollutant constituents on road surfaces', SCIENCE OF THE TOTAL ENVIRONMENT, vol. 209, no. 2-3, pp. 243-254.
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Baweja, D, Roper, H & Sirivivatnanon, V 1998, 'Chloride-induced steel corrosion in concrete: Part 1 - Corrosion rates, corrosion activity, and attack areas', ACI MATERIALS JOURNAL, vol. 95, no. 3, pp. 207-217.

Bishop, DW, Thomas, PS & Ray, AS 1998, 'Raman spectra of nickel(II) sulfide', MATERIALS RESEARCH BULLETIN, vol. 33, no. 9, pp. 1303-1306.
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The phase morphology of nickel sulfide (NiS) has received attention because of the possible correlation between fracture of toughened window glass panels and the alpha-beta phase transition. The detection of NiS in situ in glass, however, has proven diff

Indraratna, B & Redana, IW 1998, 'Development of the smear zone around vertical band drains', Proceedings of the Institution of Civil Engineers - Ground Improvement, vol. 2, no. 4, pp. 165-178.
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This study describes the effect of smear on the settlements of soft clay foundations which have been improved by installation of vertical drains. The smear zone propagation around a band-shaped drain was monitored using a large, radial drainage consolidometer. The test results reveal that a significant reduction in the horizontal permeability takes place towards the central drain, whereas the vertical permeability remains relatively unchanged. The estimated smear zone was about 3–4 times the cross-section area of the band-shaped drain (mandrel). In the analysis, the classical axisymmetric solution for consolidation by vertical drain has been converted into an equivalent 2D plane strain analysis. The plain strain model is subsequently applied to a number of embankments stabilized with vertical drains. It is revealed that the inclusion of smear effects improves the settlement prediction significantly.

Indraratna, B & Redana, IW 1998, 'Laboratory Determination of Smear Zone due to Vertical Drain Installation', Journal of Geotechnical and Geoenvironmental Engineering, vol. 124, no. 2, pp. 180-184.
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INDRARATNA, B, HAQUE, A & AZIZ, N 1998, 'Laboratory modelling of shear behaviour of soft joints under constant normal stiffness conditions', Geotechnical and Geological Engineering, vol. 16, no. 1, pp. 17-44.
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Shear behaviour of regular sawtooth rock joints produced from casting plaster are investigated under constant normal stiffness (CNS) conditions. Test results obtained in this investigation are also compared with the constant normal load (CNL) tests. It is observed that the peak shear stress obtained under CNL conditions always underestimates the peak shear stress corresponding to the CNS condition. Plots of shear stress against normal stress show that a nonlinear (curved) strength envelope is acceptable for soft rock joints subjected to a CNS condition, in comparison with the linear or bilinear envelopes often proposed for a CNL condition. Models proposed by Patton (1966) and Barton (1973) have also been considered for the predictions of peak shear stress of soft joints under CNS conditions. Although Patton's model is appropriate for low asperity angles, it overestimates the shear strength in the low to medium normal stress range at higher asperity angles. In contrast, while Barton's model is realistic for the CNL condition, it seems to be inappropriate for modelling the shear behaviour of soft joints under CNS conditions. The effect of infill material on the shear behaviour of the model joints is also investigated, and it is found that a small thickness of bentonite infill reduces the peak stress significantly. The peak shear stress almost approached that of the shear strength of infill when the infill thickness to asperity height ratio (t/a) reached 1.40. This paper also introduces an original, empirical shear strength envelope to account for the change in normal stress and surface degradation during CNS shearing.

Indraratna, B, Ionescu, D & Christie, HD 1998, 'Shear Behavior of Railway Ballast Based on Large-Scale Triaxial Tests', Journal of Geotechnical and Geoenvironmental Engineering, vol. 124, no. 5, pp. 439-449.
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Kenney, TC, Reddi, LN & Indraratna, B 1998, 'Discussions and Closure: Analytical Model for Particle Migration within Base Soil-Filter System', Journal of Geotechnical and Geoenvironmental Engineering, vol. 124, no. 10, pp. 1044-1047.
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Khalili, N & Khabbaz, MH 1998, 'A unique relationship for χ for the determination of the shear strength of unsaturated soils', Géotechnique, vol. 48, no. 5, pp. 681-687.
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Sriwongsitanon, N, Ball, JE & Cordery, I 1998, 'An investigation of the relationship between the flood wave speed and parameters in runoff-routing models', HYDROLOGICAL SCIENCES JOURNAL-JOURNAL DES SCIENCES HYDROLOGIQUES, vol. 43, no. 2, pp. 197-213.
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Stewart, M 1998, 'Accident and design—Contemporary debates in risk management', Structural Safety, vol. 20, no. 1, pp. 111-112.
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Stewart, MG 1998, 'Reliability‐based bridge design and assessment', Progress in Structural Engineering and Materials, vol. 1, no. 2, pp. 214-222.
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AbstractInformation about present and anticipated bridge reliabilities, in conjunction with decision models, provides a rational and powerful decision‐making tool for the design and assessment of bridges. This review describes the concepts, methodology, immediate applications and the potential of reliability‐based bridge design and assessment. Present applications include reliability‐based design specifications and bridge assessment for present conditions. The practical implementation of lifecycle reliabilities promises optimum expenditure when making decisions related to design, construction, inspection, maintenance and repair.

Stewart, MG & Rosowsky, DV 1998, 'Time-dependent reliability of deteriorating reinforced concrete bridge decks', Structural Safety, vol. 20, no. 1, pp. 91-109.
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A structural deterioration reliability model is developed to calculate probabilities of structural failure (flexure) for a typical reinforced concrete continuous slab bridge. Corrosion may be initiated from the application of de-icing salts or atmospheric exposure in a marine environment. It is assumed that corrosion will lead to a reduction in the cross-sectional area of the reinforcing steel. Monte Carlo simulation is used to calculate probabilities of failure for annual increments over the lifetime of the structure (75 years). The application of de-icing salts or atmospheric marine exposure is shown to cause significant long-term deterioration and reduction in structural safety. Reducing the cover from that currently specified for design results in a significant increase in failure probabilities. © 1998 Elsevier Science Ltd. All rights reserved.

Val, DV, Stewart, MG & Melchers, RE 1998, 'Effect of reinforcement corrosion on reliability of highway bridges', Engineering Structures, vol. 20, no. 11, pp. 1010-1019.
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This paper presents several aspects of a method for reliability assessment of reinforced concrete (RC) slab bridges with corroded reinforcement. It is assumed that corrosion will lead to a reduction in cross-sectional area of the reinforcing steel and/or a reduction in bond strength. Two types of corrosion are considered: general and localized corrosion. The method includes a non-linear finite element structural model and probabilistic models for traffic loads, corrosion propagation, bond characteristics, material properties, element dimensions and reinforcement placement. Reliability is estimated in terms of the reliability index using the first-order reliability method (FORM). For illustrative purposes, bridge reliabilities are calculated for a deteriorating, simple-span RC slab bridge, for ultimate strength and serviceability limit states.

Zhou, JL, Fileman, TW, Evans, S, Donkin, P, Llewellyn, C, Readman, JW, Mantoura, RFC & Rowland, SJ 1998, 'Fluoranthene and pyrene in the suspended particulate matter and surface sediments of the Humber Estuary, UK', Marine Pollution Bulletin, vol. 36, no. 8, pp. 587-597.
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Zhou, JL, Huang, PL & Lin, RG 1998, 'Sorption and desorption of Cu and Cd by macroalgae and microalgae', Environmental Pollution, vol. 101, no. 1, pp. 67-75.
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Zoysa, AKN, Loganathan, P & Hedley, MJ 1998, 'Effect of forms of nitrogen supply on mobilisation of phosphorus from a phosphate rock and acidification in the rhizosphere of tea', AUSTRALIAN JOURNAL OF SOIL RESEARCH, vol. 36, no. 3, pp. 373-387.
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Nitrogen (N) is the main fertiliser input to tea plantations because of the large removal of this element with regular harvests of young shoots in the field. The form of N supply is known to influence the uptake of other plant nutrients, notably phosphorus (P), through its effect on soil pH in the rhizosphere. A glasshouse study was conducted to test the effect of N form (NH4/+, NO3/-, or both) on the transformation of soil P in the rhizosphere and its availability to tea (Camellia sinensis L.) plants fertilised with sparingly soluble Eppawala phosphate rock (EPR). Four-month-old tea (TRI 2025) plants were grown in rhizosphere study containers containing an Ultisol from Sri Lanka (pH 4.5 in water) amended with EPR and KCl at 200 μg P or K/g soil, and mixed with (NH4)2SO4 (100% NH4/+-N), NH4NO3 (50% NH4/+-N and 50% NO3/--N), and Ca(NO3)2 (100% NO3/--N) at the rate of 200 μg N/g soil, with a control (no N fertiliser), as treatments. Rhizosphere pH decreased compared with the bulk soil when N was supplied as NH4/+ or NH4/+-NO3/- forms, and increased when N was supplied as NO3/-. The cation-anion balance estimations in the plants showed that the plants had taken up more NO3/- than NH4/+ even in (NH4)2SO4 treated soil, suggesting high nitrification rates, especially in the rhizosphere, in spite of using a nitrification inhibitor. More EPR dissolved in the rhizosphere compared with that in the bulk soil, regardless of the N form applied. The (NH4)2SO4 treatment had the highest dissolution rate of EPR in the rhizosphere, whereas Ca(NO3)2 treatment had the lowest, reflecting the degree of acidification in the rhizosphere. Resin-P and NaOH-P(i) (inorganic P) concentrations were lower and NaOH-P(o) (organic P) concentration was higher in the rhizosphere than in the bulk soil. Plant and possible microbial uptake of P is the main reason for the decrease in resin-P and NaOH-P(i). The increase in NaOH-P(o) concentration in the rhizosphere is believed to be due to transformatio...

Zoysa, AKN, Loganathan, P & Hedley, MJ 1998, 'Phosphate rock dissolution and transformation in the rhizosphere of tea (Camellia sinensis L.) compared with other plant species', EUROPEAN JOURNAL OF SOIL SCIENCE, vol. 49, no. 3, pp. 477-486.
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Tea (Camellia sinensis L.) is generally grown in highly weathered acidic Ultisols of the humid tropics. The low pH, large P fixing capacity and moisture content of these soils favour the dissolution of phosphate rock. Plant species differ widely in their ability to take up P from phosphate rock, and we have compared phosphate mobilization in the rhizosphere of tea with that under calliandra (Calliandra calothyrsus L.), Guinea grass (Panicum maximum L.) and bean (Phaseolus vulgaris L.) by studying the changes in the concentration of P fractions at known distances from the root surface in an acidic (pH in water 4.5) Ultisol from Sri Lanka treated with a phosphate rock. Plants were grown in the top compartment of a two-compartment device, comprising two PVC cylinders physically separated by a 24-μm pore-diameter polyester mesh. A planar mat of roots was formed on the mesh in the top compartment, and the soil on the other side of the mesh in the lower compartment was cut into thin slices parallel to the rhizosphere and analysed for pH and P fractions. All plant species acidified the rhizosphere (pH [water] difference between bulk and rhizosphere soils was 0.17-0.26) and caused more rock to dissolve in the rhizosphere (10-18%) than in the bulk soil (8-11%). Guinea grass was most effective, though the rate of acidification per unit root surface area was least (0.02 μmol H+ cm-2) among the four species. Tea produced the largest rate of acidification per unit root surface area (0.08 μmol H+ cm-2). All species depleted P extracted by a cation-anion exchange resin and inorganic P extracted by 0.1 m NaOH. All except tea depleted organic P extracted by 0.1 m NaOH in the rhizosphere. The external P efficiencies (mg total P uptake) of Guinea grass, bean, tea and calliandra in soil fertilized with phosphate rock were 4.82 ± 0.42, 4.02 ± 0.32, 1.06 ± 0.02 and 0.62 ± 0.02, respectively, and the corresponding internal P efficiencies (mg shoot dry matter production per mg plant P) ...

Crews, KI & Walter, G 1970, 'Innovation and Efficiency for Timber Bridge Construction in Australia Utilising Stress Laminated 'Tee' and 'Cellular' Beam Decks', Proceedings of the Structural Engineering World Wide Congress 1998, Structural Engineering World Wide Congress 1998, Elsevier Science Ltd., San Francisco, California, USA, pp. 1-8.
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The research work in Australia is funded collaboratively by the Australian Research Council and industry, and has involved both full scale serviceability and ultimate load testing (up to 12.2m) as well as an examination and analytical investigation into fundamental behaviour of cellular and âT❠beam structural forms constructed from timber elements. Several prototype bridge decks spanning up to 12.2m have been constructed and research is currently being undertaken to extend this technology to applications with clear spans of 25 to 30m. This paper presents a general overview of the R & D programs and applications of stress laminated timber technology in Australia, with an emphasis on the implications of âbuiltâup❠technology for timber bridges. A unique case study is presented in detail for the Hopkins River Bridge at Warrnambool, Australia, reviewing the research, design and construction aspects for a âbuiltâup❠deck superstructure based on both âTee / cellular❠forms and using incremental launching techniques. The paper concludes with discussion on the economic benefit of this new construction method.

Greenland, AG, Crews, KI & Bakoss, SL 1970, 'Enhancing timber structures with advanced fibre reinforced plastic composite reinforcements', 5TH WORLD CONFERENCE ON TIMBER ENGINEERING, VOL 2, PROCEEDINGS, 5th World Conference on Timber Engineering, PRESSES POLYTECHNIQUES ET UNIVERSITAIRES ROMANDES, MONTREUX, SWITZERLAND, pp. 608-615.

Luk, KC, Ball, JE & Sharma, A 1970, 'Rainfall forecasting through artificial neural networks', HYDROINFORMATICS '98, VOLS 1 AND 2, 3rd International Conference on Hydroinformatics, A A BALKEMA PUBLISHERS, COPENHAGEN, DENMARK, pp. 797-804.

Sirivivatnanon, V & Khatri, RP 1970, 'Selective use of Fly Ash concrete', American Concrete Institute, ACI Special Publication, pp. 37-57.
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Structural grade fly ash (FA) concrete and concrete with high volume of fly ash (HVFA) are well accepted and utilized in the Australian construction industry. These are concretes with fly ash (ASTM C 618 type F) making up between 10 and 50 %by weight of the total cementitious material. This paper is intended to demonstrate the importance of the selection of the appropriate amount of FA content for a range of applications. The durability performance of the FA concretes was compared with portland cement concretes of equivalent 28-day compressive strength, in terms of the resistance to carbonation, chloride penetration and sulfate attack. Some mixture design data for both FA and HVFA concretes and their mechanical properties are given. The likely optimum fly ash percentages for a range of applications are highlighted with respect to their properties and construction demands. It was found that a lower fly ash dosage would be more suitable for above-ground structures where a carbonation-related deterioration mechanism applied. However, for structures in aggressive sulfate ground condition or in marine environments, HVFA concrete was found to be much more suitable. Available field performance data have confirmed laboratory evaluated performance.