Discrete modeling of mixed-mode crack growth in concrete

článek ve sborníku mimo WoS a Scopus

angličtina

In the framework of cohesive crack models and FEA, simulations of the mixed-mode crack propagation in concrete presents a challenging task both from the numerical point of view and in the view of material laws definition. In contrary to mode I propagation, mixed-mode crack patterns are much more complex and can not be predicted a priory. Therefore, remeshing techniques or XFEM implementation need to be employed, resulting in increased computational demands, especially in 3D. Beyond mode I traction separation law, mode II traction separation law referring shear opening to a bridging shear stress needs to be defined. Moreover, a law projecting mode I and II laws into a general direction of the crack opening has to be defined. A description of the shear dilatancy caused by the roughness of the real crack is a further material law required. Determination of the material parameters presents a complicated process since most of them can not be measured directly. On the other hand, discrete models leaving the assumption of homogeneity of the material and moving to simpler material laws on a lower material scale, can be an attractive choice with at least comparative results to the traditional aforementioned approach. In the presented contribution, two discrete models based on different assumptions are applied to simulate mixed-mode fracture tests of laboratory scale specimens under varying loading. The first model belongs to lattice models discretizing the material into three types of lattice elements - aggregate, matrix and ITZ. The elements behave elasto-brittle and with the elastic limit dependent on the direction of straining. The other model belongs to the group of particle models. Contacts between particles are defined and discretized by nonlinear struts. The models are used to simulate a non-proportional mixed-mode test. The specimen is loaded in mode I opening up to the peak load and then sheared/opened under 45_. Despite the different assumptions, both models are capable of predicting correctly trends observed in the experiments and have proven to be convenient alternatives to the traditional approaches, especially when computational demands and identification of material parameters are considered.

Discrete modeling of mixed-mode crack growth in concrete

SKOČEK, J.; ELIÁŠ, J.

2009

11. 5. 2009

Jeju, Korea

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