B.I.G. Barr

Bio: B.I.G. Barr is an academic researcher from Cardiff University. The author has contributed to research in topics: Round robin test & Test method. The author has an hindex of 14, co-authored 18 publications receiving 1444 citations.

RILEM TC 162-TDF: Test and design methods for steel fibre reinforced concrete' - sigma-epsilon-design method - Final Recommendation

Abstract: General information Publication status: Published Organisations: Section for Structural Engineering, Department of Civil Engineering Contributors: Vandewalle, L., Nemegeer, D., Balazs, L., Barr, B., Barros, J., Bartos, P., Banthia, N., Criswell, M., Denarie, E., Di Prisco, M., Falkner, H., Gettu, R., Gopalaratnam, V., Groth, P., Hausler, V., Kooiman, A., Kovler, K., Massicotte, B., Mindess, S., Reinhardt, H., Rossi, P., Schaerlaekens, S., Schumacher, P., Schnutgen, B., Shah, S., Skarendahl, A., Stang, H., Stroeven, P., Swamy, R., Tatnall, P., Teutsch, M., Walraven, J. Pages: 560-567 Publication date: 2003 Peer-reviewed: Yes

An overview of the fatigue behaviour of plain and fibre reinforced concrete

Abstract: The paper provides a general overview of recent developments in the study of the fatigue behaviour of plain and fibre reinforced concrete (FRC). The fatigue performance of plain concrete and FRC, as reported in the literature, is compared in order to quantify the influence of fibre inclusion on fatigue behaviour. Despite the conflicting information regarding the fatigue behaviour of concrete reported in the literature, the majority of researchers show that the inclusion of fibres can benefit the fatigue performance of concrete.

Evaluation of strains at peak stresses in concrete: A three-phase composite model approach

Abstract: A wide range of concretes was evaluated to explain the reasons for large strain values of high strength concretes (HSCs) at peak stresses under different loading conditions, such as uniaxial compression, uniaxial tension, bending and torsion. To determine the influences of constituents on the stress distributions at the matrix-aggregate interface, around the aggregate and in the matrix close to the aggregate, concrete was considered as a three-phase composite material consisting of a continuous mortar matrix, model aggregate and the interfacial zone between cement and aggregate. The results obtained show that in normal strength concretes (NSCs) i.e. the hard inclusion case, the elastic mismatch of aggregate and matrix is significant and large tangential, radial and shear stresses occur at the interface. However, in both HSCs and lightweight concretes (LCs), the elastic modulus of the aggregate is closer to that of the matrix, and lower tangential, radial and shear stress distributions occur at the aggregate-matrix interface, resulting in these concretes having a much more uniform stress distribution at the interfaces than NSCs. In both HSCs and LCs, tensile stresses occur at the tips of the aggregate (at the poles in the model) perpendicular to the applied stress, and tangential stresses in the matrix close to the interface or at the aggregate surface are larger than those in NSC ones. These imply that the crack will be forced to go through the aggregate and lower strains will develop in ascending branches of these concretes. Based on the model proposed and on additional microstructural studies, it can be concluded that the levels of strains observed at peak stresses under the different loading conditions are as expected.

Toughness measurement — the need to think again

Abstract: The first part of the paper reviews a number of concurrent developments which have taken place in recent years in the concrete research area. The developments include the commercial development of FRC materials, the proposals for evaluating the enhanced performance of FRC materials, the development of high performance (high strength/brittle) concretes, the application of fracture mechanics to concrete together with the revolution in testing machines with the introduction of closed-loop testing. The limitations of current standards and guidelines for evaluating the toughness of FRC materials are also reviewed and proposals for overcoming these limitations are advanced. It is proposed that notched beams, subjected to three-point loading, rather than unnotched beams subjected to four-point loading should be used for toughness measurement and that the deformation of the beams should be measured directly from the specimen rather than through the testing machine.

Properties of strain hardening ultra high performance fiber reinforced concrete (UHP-FRC) under direct tensile loading

Abstract: Enhanced matrix packing density and tailored fiber-to-matrix interface bond properties have led to the recent development of ultra-high performance fiber reinforced concrete (UHP-FRC) with improved material tensile performance in terms of strength, ductility and energy absorption capacity. The objective of this research is to experimentally investigate and analyze the uniaxial tensile behavior of the new material. The paper reviews and categorizes a variety of tensile test setups used by other researchers and presents a revised tensile set up tailored to obtain reliable results with minimal preparation effort. The experimental investigation considers three types of steel fibers, each in three different volume fractions. Elastic, strain hardening and softening tensile parameters, such as first cracking stress and strain, elastic and strain hardening modulus, composite strength and energy dissipation capacity, of the UHP-FRCs are characterized, analyzed and linked to the crack pattern observed by microscopic analysis. Models are proposed for representing the tensile stress–strain response of the material.

Effect of silica fume on mechanical properties of high-strength concrete

Abstract: This paper presents the results of experimental work on short- and long-term mechanical properties of high-strength concrete containing different levels of silica fume. The aim of the study was to investigate the effects of binder systems containing different levels of silica fume on fresh and mechanical properties of concrete. The work focused on concrete mixes having a fixed water/binder ratio of 0.35 and a constant total binder content of 500 kg/m3. The percentages of silica fume that replaced cement in this research were: 0%, 6%, 10% and 15%. Apart from measuring the workability of fresh concrete, the mechanical properties evaluated were: development of compressive strength; secant modulus of elasticity; strain due to creep, shrinkage, swelling and moisture movement. The results of this research indicate that as the proportion of silica fume increased, the workability of concrete decreased but its short-term mechanical properties such as 28-day compressive strength and secant modulus improved. Also the percentages of silica fume replacement did not have a significant influence on total shrinkage; however, the autogenous shrinkage of concrete increased as the amount of silica fume increased. Moreover, the basic creep of concrete decreased at higher silica fume replacement levels. Drying creep (total creep − basic creep) of specimens was negligible in this investigation. The results of swelling tests after shrinkage and creep indicate that increasing the proportion of silica fume lowered the amount of expansion. Because the existing models for predicting creep and shrinkage were inaccurate for high-strength concrete containing silica fume, alternative prediction models are presented here.