Development of a computational multi-physical framework for the use of nonlinear explicit approach in the assessment of concrete structures affected by alkali-aggregate reaction

Abstract

This paper proposes an innovative methodology for the use of the explicit approach in the assessment of concrete structures affected by alkali-aggregate reaction (AAR). Efficiency of the explicit approach has been proven in previous works for the case of large concrete structural models with high degree of nonlinearity. In the proposed methodology, the strain is decomposed into mechanical, thermal, creep, shrinkage and AAR strain components. The AAR component is computed according to Saouma and Perotti model [1] for the anisotropic distribution of the volumetric expansion and according to Larive model [2] for the AAR kinetics. One advantage of the approach is that it can be used with any existing concrete model that has undergone a rigorous verification and validation (V&V) process for the mechanical part. In this work the EPM3D concrete model [2] implemented as a user-subroutine in Abaqus-Explicit is used. The general methodology is based on three different finite element analyses: thermal implicit, hygral implicit and the final nonlinear multiphysical explicit analysis. An innovative formulation to address the problem of time scale difference between the implicit and explicit approaches is presented. A new incremental numerical formulation is presented to correctly handle the dependency of the AAR kinetics on the temperature field in case of cyclic temperature variation. A verification example is presented at the material level, along with qualitative assessment of the cracking pattern of an existing hydraulic structure affected by AAR. This last application at structural level demonstrates the efficiency of the suggested methodology and the feasibility within an industrial context.

Stability of cracked concrete hydraulic structures by nonlinear quasi-static explicit finite element and 3D limit equilibrium methods

“…The velocity field and the total kinetic energy were used as slope stability indicators. Lately, Abaqus/Explicit models have been applied in the field of concrete hydraulic structures using the quasi-static approach [13,14]. The nonlinear quasi-static explicit finite element method (QSE-FEM) is used in this work as an alternative to the classical implicit FEM.…”

“…QSE-FEM requires the definition and interpretation of criteria to detect the loss of static equilibrium leading to instability with respect to the initial position. In addition to the kinetic energy criterion used in the previous studies [8,12,13,14], one additional criterion is proposed herein: the absolute crack surface motions at particular degrees of freedom (DOF). In addition, simple tools, such as the classical limit equilibrium method, should be used for verification purposes to bound the sliding safety factors computed from QSE-FEM.…”