High aspect ratio interface elements for mesoscale modelling of concrete under dynamic fracture propagation

Concrete can show an increased material strength under dynamic loading conditions, which is related to the heterogeneity at the mesoscale, as well as the rate of loading. The ability to capture this phenomenon and predict behaviour under dynamic fracture propagation is of interest to different applications. High aspect ratio interface elements are developed here for mesoscale modelling of concrete under dynamic loading while attending to the dynamic strength enhancement. The high aspect ratio interface elements can be implemented in standard finite element codes, as they are based on the same integration rules and shape functions as bulk elements. A rate-dependent constitutive model based on two damage variables is proposed to simultaneously handle fracture propagation in modes I and II, including the contribution of friction. A strategy is also proposed to avoid material iterations due to the coupled modes. The framework is validated using several examples, including mixed mode tests with different loading rates. In general, both load versus displacement curves and crack patterns are found to be close to the experimental results. The importance of the sample heterogeneity and the rate-dependent constitutive model could be observed as critical components to predict the results of dynamic experiments. • High aspect ratio interfaces are proposed for dynamic load fracture propagation. • The interfaces can use the same constitutive model, shape functions, and integration as bulk elements. • A simplified rate-dependent constitutive law is proposed for modes I, II and mixed. • The framework captures the effect of concrete mesoscale structure in the dynamic response. • A good agreement is found with experiments under different loading rates.