Shear Strength of Strain-Hardening Cementitious Materials

Concrete and other semi-brittle materials are pressure sensitive. Their resistance to shear depends on the confining pressure acting normal to the shear plane. This behaviour is modelled using experimentally calibrated failure criteria, such as the Mohr–Coulomb failure surface. Pressure sensitivity is also strongly evident in fibre-reinforced, strain-hardening cementitious composites (SHCC), despite the internal confinement these materials possess on account of their fibre content. However, because of the great range and variety of mixes used in such materials, no general failure criteria have yet been proposed. In this paper, the pressure-sensitive shear strength of SHCC containing short discontinuous PVA fibres is modelled with a three-parameter failure criterion. The parameters of the criterion are calibrated to the experimental results obtained from several tests that combine shear and normal pressure. These include uniaxial tension and compression, split tests, triaxial compression, and a series of push-off tests with and without reinforcement crossing the shear sliding plane. The calibration of the failure criterion explicitly accounted for the magnitude of internal confinement which is generated in the cementitious matrix in response to fibre tension. The criterion is appropriate for general purpose analysis of the stress state of SHCC, but most importantly it is used to assess the SHCC contribution to the shear strength of structural elements.