SIMULATIONS OF CONCRETE FRACTURE AT VARIOUS STRAIN RATES: PARAMETRIC STUDY

Abstract eng:
The contribution presents numerical simulations of a recently published experimental series on concrete specimens. The numerical model mimics the meso-structure of the concrete by representing material via system of interconnected rigid polyhedral particles. These particles correspond to mineral aggregates and surrounding matrix. The geometry of particles is based on Voronoi tessellation. The particles are rigid, but they may move and rotate. The displacement jump at their contacts gives rise interaction forces defined by the constitutive relation in a vectorial form. The constitutive equations are independent of the strain rate. Simulations are dynamical, the time dependent response is calculated using Newmark implicit scheme. Full inertia tensor of every particle is taken into account when assembling the mass matrix. To demonstrate the ability of the model to capture the strain rate dependence of the experimental results, series of specimens loaded under various displacement rates are simulated. For quasi-static loading, the initial microcracks usually localize into one highly damaged zone where main crack appears. With increasing strain rate, the amount of energy accumulated in the specimen body is not consumed by one crack only and crack branching occurs. The peak loading force increases with increasing rate as well. Both the strain rate dependence of the loading force and crack branching phenomena are captured by the presented numerical model. The obtained results are compared with the experimental response of the simulated specimens. Parametric study of the model is performed showing different effect of various parameters under different strain rates.

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