Hamid Sadouki

CHLORIDE PENETRATION MODEL CONSIDERING MICROCLIMATE

Two main factors govern the ingress of chloride ions into concrete reinforced with ordinary steel reinforcement, from de-icing salts: (1) the cover concrete (permeability, thickness), and (2) the microclimatic conditions (humidity, temperature, concentration of de-icing salts) at the concrete surface. A numerical model of chloride transport, taking into consideration environmental conditions (temperature, humidity, snow, rain and salt spreading), was used to predict the chloride profiles in concrete representative of that found in bridge element, for two types of exposure to water (splash, mist). This model was applied for two different regions in Switzerland: on the plateau in Lausanne, where there is a relatively mild winter climate and in the Alps where there is severe winter climate.

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

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.