engleski

Dynamic fracture of concrete: Experimental and numerical studies on compact tension and L- specimen

Recent numerical simulations performed on plain concrete specimens showed very interesting and complex fracture behavior of concrete under high loading rates. The simulations performed on compact tension (CT) specimen (Ožbolt et al., 2011) highlighted the phenomenon of crack branching at high loading speeds, while the simulations on L-specimen (Ožbolt and Sharma, 2012) brought out the influence of loading rate on direction of crack propagation. In order to confirm the findings of numerical study and to obtain the experimental evidence on dynamic fracture of concrete, experiments were performed on both CT-specimen and L- specimen. The phenomenon of crack branching, as predicted by numerical studies, was reproduced experimentally for CT-specimen. The evaluation of test and numerical results show that for strain rates of approximately above 50/s, crack branching occurs. This phenomenon is related directly to the sudden and progressive increase of resistance and is controlled primarily by inertia. For L-specimen, the experiments confirm the influence of loading rate on the direction of crack propagation as numerically predicted. For quasi- static load, the crack tends to propagate horizontally, perpendicular to the loading direction. However, with increase of the loading rate the crack propagation tends to get vertical, parallel to the loading direction. The comparison between numerical and experimental results proves that relatively simple modeling approach based on continuum mechanics, rate dependent microplane model and standard finite elements is capable to realistically predict complex phenomena related to dynamic fracture of concrete and no special criterion is required to capture crack branching, change in crack propagation or progressive increase of apparent strength.

Dynamic fracture; Concrete; Experiments; Finite element analysis; Rate sensitivity; Structural inertia; Crack propagation; Crack branching

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