Comparison of classical and higher order continuum models for shear failure of concrete

Classical and higher order continuum formulations of the widely used Concrete Damage Plasticity model by Grassl & Jirásek (2006) are assessed with regard to their ability to represent shear failure of plain concrete in an objective manner. To this end, a transverse shear test for anchor channels serves as benchmark. The experimental results are compared with the results of complex 3D numerical simulations, performed on the basis of (i) a classical local formulation with mesh-adjusted softening modulus, (ii) a higher order gradient-enhanced formulation by Poh & Swaddiwudhipong (2009) and (iii) a recently proposed gradient-enhanced micropolar formulation by Neuner et al. (2020). The comparison highlights the limitations of the classical local formulation, whereas the higher order continuum approaches show great potential, in particular for modeling the structural post-peak response of the anchoring system. Moreover, the load-displacement behavior, which is associated with different failure modes observed for varying values of the edge distance of the anchor channel is accurately predicted by means of the higher order continuum formulations, further highlighting their predictive capabilities.