Direction-dependent behaviour and size effect of steel fibre reinforced concrete based on the double punch test

The post-cracking behaviour of steel fibre reinforced concrete (SFRC) is typically determined following an inverse analysis of flexural prism tests. Although these tests have significant practical merit, it has been argued that the anisotropy of the material due to the dispersion and orientation of the fibres cannot be accounted for in these tests. Multidirectional double punch tests on cubes have been proposed to overcome these issues. These tests are also well-suited to study size effects. However, no generally accepted inverse analysis method for these tests presently exists. This paper presents a simple and mechanically consistent inverse analysis procedure to estimate the residual post-cracking strength of SFRC from the results of double punch tests conducted on cubes. To explore the potential and limitations of this methodology, an experimental investigation was conducted on 30 double punch tests on cubes of varying sizes, varying fibre dosage and loading direction with respect to the concrete casting direction. The results demonstrate that the approach provides useful comparative information on the anisotropy of the material, however further investigation on the input parameters is required to prove its reliability in quantifying the residual tensile stress offered by the fibres.

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