Abstract
This paper explores the computational modeling of nonlocal strain, damage, and fracture in concrete, considering the isolated contribution of two random, spatially variable properties related to the fracture process: Young’s modulus (E) and tensile strength (ft). Applying a continuum damage model, heterogeneous specimens of concrete with random and spatially varying E or ft were found to produce substantial differences when contrasted with traditional homogeneous (non-random) specimens. These differences include variable and uncertain strain and damage, wandering of the failure paths, and differing (sometimes lower) peak forces, i.e. increased probabilities of failure in the heterogeneous specimens. It is found that ft variability contributes more (from 1.7 to up to 4 times more, depending on the parameter) to the overall performance variability of the concrete than E variability, which has a comparatively lower contribution. Performance is evaluated using (1) force-displacement response, (2) individual, average, and standard deviation maps of non-local strain and damage, (3) fracture paths and strain and damage values along the fractures. The modeling methodology is illustrated for two specimen geometries: a square plate with a circular hole, and an L-shaped plate. The computational results correlate well with reported experimental data of fracture in concrete specimens.
Highlights
Many engineering and infrastructure materials result from mixing dissimilar components, and they exhibit a probable range of physical and mechanical properties, as well as a natural degree of randomness
We will assess the random behavior of fracture paths, through analyses of strain and damage occurring in several concrete specimens, and through the study of the force sustained by this material
Fracture: The fracture paths are calculated from the nodes in the mesh where non-local equivalent strain (NLE) and D are maximum
Summary
Many engineering and infrastructure materials result from mixing dissimilar components, and they exhibit a probable range of physical and mechanical properties, as well as a natural degree of randomness. Transfer, volume variations due to temperature changes, rates of chemical degradation, and susceptibility to specific environmental agents, among others The coexistence of such heterogeneity within the same material plays a vital role in explaining the variability of damage and failure/fracture processes in concrete. The computational modeling of damage and fracture in cement-based concrete, a quasi-brittle material, has been approached through discrete and phase-field methods. Discrete methods, such as the extended finite element method (X-FEM) (Moes and Belytschko, 2002; Moes et al, 1999), cohesive zone models (CZM) (Ferte et al, 2016; Park and Paulino, 2011), and the virtual crack closure technique (VCCT) (Irwin, 1957), are based on the theory of linear fracture mechanics to integrate the discontinuities into the primary field variables; they incorporate fracture through a tractionseparation law. It is important to remark that these methods require the phase variable to be coupled to the field of primary variables (e.g. displacements), resulting in higher number degrees of freedom, and increased computational effort
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