Statistical modeling of cracking in large concrete structures under Thermo-Hydro-Mechanical loads: Application to Nuclear Containment Buildings. Part 1: Random field effects (reference analysis)

In the case of homogeneously distributed stress loads, the intrinsically random distribution of voids and defaults in the concrete volume is one of the driving factors of strain localization, crack initiation and propagation. In this contribution, a macroscopic approach based on a stochastic and continuous damage model is suggested to describe concrete's cracking under simultaneous Thermo-Hydro-Mechanical (THM) loads. Statistical and energetic size effects at the structural scale are taken into account by (a) reducing the mean tensile strength of the considered concrete's effective volume according to a probabilistic-based Size Effect Law (SEL) adapted to local models, (b) performing an energy-based regularization for mesh independency and (c) describing the spatial distribution of the Young's modulus property using autocorrelated lognormal Random Fields (RF). The proposed strategy is applied to the first lift of the VeRCoRs Nuclear Containment Building mock-up (the gusset) which undergoes, at early age, restrained endogenous and thermal shrinkages and, during the Operational Phase (OP), several pressurization tests leading to possible concrete cracking and damage increase. Different cracking patterns are predicted and their evolution in time due to the concrete's ageing phenomena is analyzed. The predicted numerical results (i.e. temperature, strains and cracking patterns) are in line with in situ observations and support the need for statistical description of concrete cracking rather than classical deterministic analyses.