Post-cracking tensile behaviour of steel-fibre-reinforced roller-compacted-concrete for FE modelling and design purposes

Abstract

ABSTRACT:Fracture of steel-fibre-reinforced-concrete occurs mostly in the form of a smeared crack band undergoing progressive microcracking. For FE modelling and design purposes, this crack band could be characterised by a stress-strain (σ-ε) relationship. For industrially-produced steel fibres, existing methodologies such as RILEM TC 162-TDF (2003) propose empirical equations to predict a trilinear σ-ε relationship directly from bending test results. This paper evaluates the accuracy of these methodologies and their applicability for rollercompacted-concrete and concrete incorporating steel fibres recycled from post-consumer tyres. It is shown that the energy absorption capacity is generally overestimated by these methodologies, sometimes up to 60%, for both conventional and roller-compacted concrete. Tensile behaviour of fibre-reinforced-concrete is estimated in this paper by inverse analysis of bending test results, examining a variety of concrete mixes and steel fibres. A multilinear relationship is proposed which largely eliminates the overestimation problem and can lead to safer designs. RESUMEN:Comportamiento a tracción posterior a la fisuración del hormigón reforzado con fibras de acero compactado con rodillo para el diseño y modelado EF. La rotura del hormigón reforzado con fibra de acero se produce principalmente en forma de una banda de fisuración que sufre progresiva microfracturación. Para el diseño y modelado EF, esta banda se puede caracterizar por una relación tensión-deformación (σ-ε). Para fibras de acero industriales, existen metodologías (RILEM TC 162-TDF 2003) que proponen ecuaciones empíricas para predecir una relación σ-ε trilinear a partir de resultados de pruebas de flexión. En este artículo se evalúa la precisión de estas metodologías y su aplicación para hormigón compactado con rodillo y hormigón reforzado con fibras de acero recicladas provenientes de neumáticos usados. Se demuestra que estas metodologías generalmente sobreestiman la capacidad de absorción de (hasta un 60%) tanto para el hormigón convencional como para el compactado con rodillo. En este artículo se calcula el comportamiento a tracción del hormigón reforzado con fibra mediante el análisis inverso de resultados de pruebas de flexión de varias composiciones de hormigón y fibras de acero. Se propone una relación multilinear que elimina en gran medida el problema de sobreestima, y puede conducir a diseños más seguros.

Postcracking tensile behavior of blended steel fiber‐reinforced concrete

“…As reported in several studies, for SFRC prisms (with steel fibers up to dosages of 140 kg/m 3 ) under flexural loading, the compressive strain remains in the linear elastic region, and the dominant failure mode is the tensile cracking of concrete. To simplify the analysis, the bilinear stress–strain relationship (see Figure ) for concrete in compression was used, but the compressive stress in concrete is not expected to exceed the first linear portion of the bilinear curve.…”

“…Furthermore, the CDP model was preferred to the BC model because the latter is only available for explicit dynamic or quasi‐dynamic problems. Hence, the CDP model, which has been successfully applied in various numerical studies for SFRC, was adopted in this study.…”

“…The dilation angle ψ and flow potential eccentricity ɛ are parameters used to define the flow rule. A dilation angle ψ =31 ° was adopted in this study as suggested in literature for SFRC reinforced with RTSF or MSF at a low total fiber dosage. An insignificant influence of steel fibers on this parameter was reported in the literature .…”

“…An insignificant influence of steel fibers on this parameter was reported in the literature . The eccentricity, ɛ =0.1, proposed by some researchers for SFRC, was also adopted in this research. A small value of 0.00025 for the viscosity parameter was chosen since a small value was reported to provide better convergence for cracked concrete .…”

“…Inverse analysis, or back calculation, is a useful tool extensively used to determine best‐fitting stress–strain (or stress‐crack) relations for SFRC from flexural tests . Kooiman et al, Barros et al, and Neocleous et al have suggested that the flexural behavior of SFRC prisms with up to 140 kg/m 3 of MSF can be simulated well using a trilinear relation.…”