An anisotropic elastoplastic-damage model for plain concrete

Abstract

A material model for plain concrete formulated within the framework of multisurface elastoplasticity-damage theory is proposed in this paper. Anisotropic sti ness degradation as well as inelastic deformations are taken into account. The applicability of the model encompasses cracking as well as the non-linear response of concrete in compression. The e ect of di erent softening laws on the stress-strain relationship and on the dissipation is investigated in the context of a 1D model problem. The integration of the evolution laws is based on the standard return map scheme. Further computational issues include the stability of the local iteration procedure and the treatment of the apex region of the damage surface. The model is employed for re-analyses of a cylinder splitting test and of a notched concrete beam. Results from the composite elastoplastic-damage model are compared with test results and results from other material models for concrete, respectively. ? 1998 John Wiley & Sons, Ltd.KEY WORDS: damage; plasticity; concrete; cracking; Rankine criterion; ÿnite element analysis INTRODUCTORY REMARKSBrittle materials such as geomaterials and concrete exhibit distributed as well as localized degradation of the mechanical properties with increasing loading. The phenomenological response of plain concrete subjected to predominantly tensile stresses is characterized by a more or less linear ascending branch of the stress-displacement curve followed by a progressively decreasing residual strength resulting in the formation of macrodefects in the form of discrete cracks. When unloaded in the post-peak regime, non-recoverable deformations as well as a degradation of the sti ness of the unloading branch is observed. From a microstructural point of view, the progressive degradation of the elastic moduli, commonly referred to as damage, is the result of growth and coalescence of existing microcracks and microvoids along the interfaces of the cement paste and the aggregates. This deterioration process prevents a complete closure of microcracks in unloading processes. As a consequence, permanent strains develop. On the phenomenological level, this e ect is often modelled by means of classical plasticity theory. Depending on the level of hydrostatic

On the equivalence between traction- and stress-based approaches for the modeling of localized failure in solids

“…To analyze strain localization in general inelastic softening solids, a unified elastoplastic damage framework [30,67] is presented in this section. Both stress-and traction-based elastoplastic damage models can be developed within this framework.…”

“…To differentiate the damage and plastic contributions to the dissipative strain rate P dis , a material parameter 2 OE0; 1 is introduced so that [30,44,67]…”

“…A particular evolution law for the compliance C (or the damage one C d ) satisfying Eq. (4.14b) is given by [30,67] …”

“…In this way, plasticity and damage mechanics or their combination [15,25] can be employed to develop appropriate inelastic constitutive laws. Induced anisotropy can be considered either theoretically [19,30,67] or in the computational context [12,13]. Furthermore, to guarantee objectivity of the energy dissipated during the fracture process, the softening regime has to be regularized with respect to the length scale of localization band.…”

Thermal Insulation and Strength Characteristics of Refractory Incorporating Natural Silica

“…At 7, 14 and 28 days, CSS values are 20.50, 22.70, and 28.25 Kg.cm -2 , respectively. Therefore, an internal stress field can modify the microstructural state of the material and thus can also strongly affect its mechanical behaviour [8,9]. As presented in several recent works dealing with the mechanical behaviour of such material [10,11,12,13].…”