David Bouhjiti

Institut de Radioprotection et de Sûreté Nucléaire (IRSN) | IRSN · LMAPS - Structural Performance Modeling and Analysis Laboratory

This work estimates air leakage through concrete porosity for structures by using data obtained in field combined with stochastic finite element (SFE) modelling. For this purpose, a methodology is proposed to evaluate permeability under representative over-pressurization conditions based on in-field measurements under vacuum. This makes it possible...

The forecast of large concrete structures behavior such as Nuclear Containment Buildings (NCB) is a critical safety issue, whether for the structure itself or for its surrounding environment. Over the past few decades, complex finite element models have been developed for assessing the mechanical behavior and the leak tightness of large concrete st...

Electricit´e de France (EDF) operates a large fleet of nuclear reactors and is responsible for demonstrating the safety of facilities, including concrete containment buildings (CCB), which are non-replaceable components. The leak-tightness of CCBs is assessed every 10 years during integrated leak-rate tests (IRLT). For double-wall containments, whi...

The control of random cracking in reinforced concrete members is of crucial interest to assess their serviceability and durability. From a regulatory point of view, such control within the design phase is ensured using a set of guidelines (definition of the reinforcement ratio, limitation of the crack width, limitation of the deflection, etc.). One...

Strategic civil engineering structures, particularly those with a containment role, are mostly made up of reinforced and prestressed concrete. Several mechanisms take place in order to tend, over time, toward a stable and balanced state between the different phases that compose concrete. This chapter introduces stochastic finite element methods and...

This paper describes a set of theoretical and practical aspects related to the modelling of cracking in axially reinforced concrete members subjected to pure tension accounting for size effects. In particular, the paper describes a new methodology to achieve a probabilistic description of the crack’s spacing using a spatially correlated Weibull ran...

Considérer le contexte incertain en ingénierie mécanique dans le but d’améliorer les performances des futurs produits ou systèmes apparaît désormais comme un avantage compétitif, voire une nécessité pour garantir une exigence de sûreté de plus en plus élevée. Ingénierie mécanique en contexte incertain traite de la modélisation, de la quantification...

This work proposes a global Stochastic Finite Element Method (SFEM) to model the effects of concrete ageing uncertainties on the serviceability and durability of large reinforced and prestressed structures with a containment role. As their modelling requires strongly non-linear, coupled and expensive calculations with a large number of parameters,...

In the case of quasi-homogeneously applied tensile loads, the intrinsic scattering of concrete properties leads to spatially random strain localization, crack initiation and propagation. The modelling of such spatial randomness, in the case of Equivalent-Homogeneous-Material Finite Elements based approaches, can be achieved thanks to the use of Ran...

La modélisation du comportement Thermo-Hydro-Mécanique (THM) des grands ouvrages en béton, en particulier ceux avec un rôle de confinement (barrages, réservoirs, etc.), doit tenir compte des hétérogénéités du matériau béton, des incertitudes associées à son comportement multiphasique complexe et de la variation spatio-temporelle intrinsèque de ses...

The restrained ring test under constant temperature is used for estimating cracking tendency of pastes, mortar or concrete. This test induces hygro-mechanical interactions, with intricate interplay of several phenomena such as autogenous shrinkage, drying shrinkage, basic and drying creep, as well as evolution of tensile strength and fracture energ...

Concrete is a heterogeneous, multiphasic and ageing material. Consequently, its properties show intrinsically spatiotemporal variations. For large reinforced and prestressed concrete structures such as Nuclear Containment Buildings (NCB), these variations directly affect the kinetic of their ageing process in terms of cracking, drying, creep and ti...

In this contribution, an explicit and analytical-based probabilistic strategy is suggested to assess the cracking risk at early age of large concrete structures such as Nuclear Containment Buildings (NCB). A staggered Thermo-Mechanical (TM) strategy is retained to describe concrete's behavior during hydration. To allow analytical developments, seve...

This contribution aims at defining a Stochastic Finite Elements Method to deal with concrete ageing in large concrete structures; particularly Nuclear Containment Buildings. The behaviour of concrete is described using a staggered Thermo-Hydro-Mechanical+Leakage approach within a viscoelastic framework. The existence of early cracks is accounted fo...

As demonstrated in Part I of this contribution, the precise and full prediction of the cracking patterns and concrete's global behaviour in ageing structures is a complex task. Though the suggested modelling strategy allows the prediction of the main cracking patterns, its drawbacks are mainly related to (a) the use of the so-called Statistical Siz...

This contribution aims at the probabilistic modelling of the Thermo-Hydro-Mechanical (THM) behaviour of concrete in large reinforced and prestressed structures. The work particularly focuses on cracking and air tightness issues of containment buildings; nuclear containment walls for instance. The suggested strategy consists of performing the variou...

This article presents analyses and the design of a post-tensioned anchorage zone made of ultra-high-performance concretes with three-dimensional finite element analyses. The structural behavior was investigated through the failure modes and cracking patterns to show the anchorage zone resistance enhancement with an increase of the strength in concr...

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 conc...

This contribution aims at improving the finite element modelling of concrete's damage‐permeability coupling using continuous and elastic‐based damage approaches. With this aim in view, a review of existing local and nonlocal damage formulations is performed showing how they differ in terms of damage estimation, crack propagation, and spatial discre...

This contribution aims at the probabilistic modelling of the Thermo-Hydro-Mechanical (THM) behaviour of concrete in large reinforced and prestressed structures. The work particularly focuses on cracking and air tightness issues of containment buildings; nuclear containment walls for instance. The suggested strategy consists of performing the variou...

The prediction of large concrete structures behavior such as bridges, dams and Nuclear Containment Buildings (NCB) is a key issue with regards to the evaluation of their durability, safety and the safety of their surrounding environment. In this work, a weakly coupled Thermo-Hydro-Mechanical (THM) modeling strategy is presented within the serviceab...

Les travaux de recherche menés portent sur la modélisation probabiliste du vieillissement du béton des enceintes de confinement des réacteurs nucléaires (Figure 1a) afin d’anticiper l’évolution de leur comportement pendant les épreuves décennales. Au sens large, le vieillissement réfère aux différents processus Thermo-Hydro-Mécaniques THM (thermo-h...

In this contribution, a global random FE modeling strategy is proposed to account for the observed cracking state during the pre-operational phase of nuclear containment buildings whilst computing the long-term ageing effect on the concrete’s air tightness evolution. The global behavior of concrete (drying and creep) is computed using a weakly coup...

The aim of this paper is to propose a weakly coupled Thermo-Mechanical approach in order to assess the risk of early age cracking for large concrete structures accounting for statistical and energetic size effects. The strategy is applied to the first lift of the VeRCoRs containment wall mock-up (scale 1:3) and the obtained results are compared to...

This paper aims at studying and defining the influence of the spatial distribution of concrete’s mechanical properties on its cracking patterns. The modeling of concrete’s cracking is based on a continuous energy-regularized and strain-based local damage model. Statistical and energetic size effects at the structural scale are taken into account (a...

The purpose of this article is to identify the most influent parameters of a given thermo-hydro-mechanical (THM) finite elements (FE) model with regards to nuclear power plants (NPP) ageing. The term ageing here refers to the continuous drying and also crack evolution in time within massive concrete volumes. These two aspects are actually one of th...

This paper proposes a reliability analysis strategy based on thermo-hydro-mechanical-leakage (THM-L) finite elements (FE) modeling of large reinforced concrete structures with a containment role. Applied to massive structures such as dams or nuclear containment buildings, the coupled THM-L models require a considerable computational time and the id...

The evolution in time of concrete thermal, hydric and mechanical properties may affect the strength and, more significantly, the tightness of large concrete structures such as nuclear containment buildings. During the first hours and days after concrete casting, the thermo-hydration and drying kinetics induce volumetric shrinkages (autogenous, desi...