Keywords: fibre reinforced concrete, experimental testing, computational modelling, plasticity, quassibrittle behaviour.

This paper discusses the numerical re-modelling of the experimental testing of fibre reinforced concrete specimens. The elastoplastic model with Chen-Chen plasticity criteria and a smeared crack model have been used. The works presented are limited to two-dimensional models. The paper also includes a brief information concerning related experimental testing and describes an approach which has been selected for postprocessing of the experimental tests results.

There are many ongoing research projects that are studying the properties of different types of fibre reinforced concrete. The experimental results should also be accompanied by computational simulations for verification of the usability of constitutive models for these materials.

The elasto-plastic model have utilised the Chen-Chen [1] condition as a plasticity and failure criteria. The Chen-Chen criterion respects the different material behaviour of concrete in different stress states.

A hardening of the material has been studied in several alternative ways. An ideally elasto-plastic material (without hardening) has been used as a basic approach but also linear hardening has been studied. The most sophisticated alternative has been an approach that was initially proposed by Ohtani and Chen [2]. This approach respects an influence of a stress state to the size of a hardening parameter. In this case the hardening function for all important stress states (tension-tension, tension-compression and compression-tension) were defined with the use of Ramberg-Osgood function. This method was proposed by Materna and Chvosta [3] and it has been verified in several other studies [4].

A smeared crack approach has been used as an alternative to the elasto-plastic constitutive modelling. The model used is based on an equivalent one-dimensional material law and on the use of Bazant's [5] crack band model. Because of the nature of remodelled experiments, concrete behaviour in compression has been assumed to be linear.

The discussed approaches have been illustrated on a numerical model of a four-point bending test. The material models have been compared. Acceptable results have been obtained for the discussed case.

1

A.C.T. Chen, W.F. Chen, "Constitutive Relations for Concrete", Journal of the Engineering Mechanics Division ASCE, 1975.

2

Y. Ohtani, W.F. Chen "Multiple Hardening Plasticity for Concrete Materials", Journal of the EDM ASCE, 1988. doi:10.1061/(ASCE)0733-9399(1988)114:11(1890)

3

P. Chvosta, A. Materna, "Nekteré modely chování betonu pri rovinné napjatosti" (in Czech: "Selected models for concrete under plane stress conditions"), Brno University of Technology, Brno, Czech Republic, 1980.

4

S.A.M. Hekal, "Solution of Plate Structures Respecting Real Material Properties", Brno University of Technology, Brno, Czech Republic 1992.

5

Z.P. Bazant, J. Planas, "Fracture and Size Effect in Concrete and Other Quasibrittle Materials", CRC Press, Boca Raton, USA, 1998.

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