Practical applications of a combined finite/discrete element method to estimate crack openings

Abstract : In the context of sustainable development, the study of cracking of large concrete structures – which means crack features such as openings, rugosity and tortuosity – has become of primary importance. Indeed, cracks determine the principal functions during the life cycle of a structure (deformability, tightness, durability and safety). Two levels of analysis appear: the member scale and the crack scale. At the structural level, non-linear finite element analyses based on continuum damage mechanics can be carried out. Nevertheless, the use of such models requires the introduction of a characteristic length (Hillerborg based approach, enhanced second order gradient or non local technique), to prevent the occurrence of spurious mesh dependency in case of strain softening. This characteristic length tends to smooth the discontinuity and thus makes the study of the cracks harder. More recent advances have promoted the enhancement of finite element discretization by directly introducing material discontinuities in the finite element formulations through the displacement field. In the case of large-scale reinforced concrete structures, for which hundreds of cracks may initiate and propagate, such numerical procedures would lead to an excessive and prohibitive CPU time consumption. The cyclic loadings including crack closing are also difficult to handle. At the crack level, an explicit description of the crack can be achieved using discrete element methods. This way, the main failure mechanisms of quasi-brittle materials are recovered, such as spatial correlation, crack tortuosity or scale effects. But the mesh density required for such modelling is nevertheless prohibitive to treat a whole industrial structure. A non intrusive technique has been proposed, allowing the use of finite element models at a structural scale and a decoupled local analysis of some interesting areas, i.e. around cracks, for which a discrete element model is used. This presentation aims at comparing the numerical results obtained from the proposed strategy with experimental results, and at exploring the applicability of the approach. Physical mechanisms such as crack propagation, openings and scale effects are under the scope of investigation. The confrontation with experimental results will benefit from digital image correlation analysis in order to obtain the full displacement field over the studied sample, and to quantify the crack opening values all along the crack path. An extensive analysis of the choice of the area of interest and the number of reanalyses will also be addressed, thanks to the use of a gap estimator.
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https://hal.archives-ouvertes.fr/hal-01692546
Contributor : Cécile Oliver-Leblond <>
Submitted on : Friday, January 26, 2018 - 1:26:40 PM
Last modification on : Saturday, May 25, 2019 - 1:44:19 AM

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  • HAL Id : hal-01692546, version 1

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Cécile Oliver-Leblond, B. Richard, A. Delaplace, F. Ragueneau. Practical applications of a combined finite/discrete element method to estimate crack openings. Computational Modeling of Fracture and Failure of Materials and Structures (CFRAC2011), 2011, Barcelone, Spain. ⟨hal-01692546⟩

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