The role of crack rate dependence in the long-term behaviour of cementitious materials

摘要

The main purpose of this paper is to bring forth new evidence that the introduction of cracking rate terms in the analysis of quasi-static localisation in cementitious materials is not merely a numerical artefact. It has been introduced in the past to regularise the continuum description of localisation. In this paper it is demonstrated that the rate terms also have a physical role. They introduce the correct time scale in quasi-static cracking. Crack rate models are presented in a finite element setting, which combines linear visco-elasticity and anisotropic Rankine plasticity. The introduction of a cracking viscosity is shown to regularise the cracking in a shrinking masonry wall, which is externally restrained by the foundation. Subsequently, the physical role of the rate terms is brought out by the analysis of three-point bending creep failure experiments on concrete. If the crack rate dependence is ignored, the global load-deformation response can be represented, but the time to failure under the sustained load is overestimated by several orders of magnitude. Upon introduction of crack rate dependence, which is characterised by the inverse analysis of separate, material characterisation experiments, the correct, i.e. the experimentally observed time to failure is calculated. (C) 2001 Elsevier Science Ltd. All rights reserved. [References: 18]