Estimating static/dynamic strength of notched unreinforced concrete under mixed-mode I/II loading

The Theory of Critical Distances (TCD) is a powerful design tool capable of estimating the strength of notched/cracked materials, with this being done by directly post-processing the linear-elastic stress fields ahead of the stress raisers being assessed. In the present study, an advanced formulation of the TCD is devised to specifically predict static and dynamic strength of notched unreinforced concrete subjected to Mixed-Mode I/II loading. The reliability and accuracy of the design approach being proposed was checked against a large number of experimental results generated by testing plain concrete containing notches of different sharpness, with these experiments being run not only under various degrees of Mode mixity, but also under different values of the nominal displacement rate (i.e., in the range 0.002-35 mm/s). The predictions made by this advanced version of the TCD were seen to fall mainly within an error interval of ±30%, that is, within an error band as wide as the band characterizing the intrinsic scattering of the calibration data. This suggests that that the TCD philosophy can effectively be extended also to the assessment of notched plain concrete subjected to in-service static/dynamic Mixed-Mode loading, with the relevant stress fields being determined by modelling concrete as a linear-elastic, homogeneous and isotropic material.