The concrete strength assessment process is influenced by uncertainties at many levels, including... more The concrete strength assessment process is influenced by uncertainties at many levels, including random measurement errors, sampling uncertainty and identification of the conversion model parameters. Therefore, instead of estimating the true value of the concrete strength, it is preferable to say that the objective of the assessment process is to predict a strength value ranging at a tolerable distance from the true strength value. This implies a deep revision of the assessment paradigm, in which both the acceptable tolerance interval and the risk of a wrong assessment must be given at the very beginning of the investigation. A large series of simulations has been carried out in order to understand and quantify how, for a given tolerance on the strength estimation, the risk value varies as a function of the precision of measurements, the number of cores and the strength distribution. Empirical models have been identified from the simulation results. These models have been finally used to calculate how many cores are required in various situations, to achieve the accuracy corresponding to three different estimation quality levels. This chapter describes the principles of the simulation, and how their results were used in order to build a series of tables where the recommended number of cores is made available in a variety of situations
Non-Destructive In Situ Strength Assessment of Concrete, 2021
This benchmark aims to assess mean compressive strength at several scales and to identify the loc... more This benchmark aims to assess mean compressive strength at several scales and to identify the location and characteristics of possible weak areas in the structure. It concerns synthetic data simulated on a group of four concrete cylindrical structures of identical dimensions with different kinds of strength distribution, based on a real case study. After having received the test results corresponding to their request (non-destructive or destructive), all the experts have to analyze these data and assess the concrete properties and to localize possible weak areas. In addition, they have to define their assessment methodology, i.e. level of investigation, number, type and location of measurements. This study provides information about how the accuracy of the final estimates depend on choices done at the various steps of the assessment process, from the definition of the testing program to the final delivery of strength estimates
Les projets de construction sont soumis à de nombreux risques et leur maitrise est un enjeu impor... more Les projets de construction sont soumis à de nombreux risques et leur maitrise est un enjeu important. Pour y répondre, nous avons développé SMACC (Stochastic Multi-agent simulAtion for Construction projeCt), un outil de simulation de projet de construction considérant les risques, basé sur l'approche 'Agent'. Mais la simulation d'un projet de construction par SMACC nécessite de renseigner de nombreuses informations quant au projet et aux risques susceptibles de l'affecter. Or, nos précédents travaux ne se sont pas intéressés au processus d'instanciation du modèle à partir d'un projet réel. Cet article présente donc une approche se plaçant en amont de SMACC permettant d'instancier les agents du modèle et de les évaluer avec un focus particulier sur les agents 'risques'. Cette approche est basée sur la combinaison entre approches de gestion de projet et la méthode de sûreté de fonctionnement MADS MOSAR (Méthode Organisée Systémique d'Analys...
Non-Destructive In Situ Strength Assessment of Concrete, 2021
A benchmark is carried out in order to compare how 13 experts define and can carry out an NDT inv... more A benchmark is carried out in order to compare how 13 experts define and can carry out an NDT investigation program and derive strength values from NDT measurements. The benchmark is based on simulations, which reproduces a synthetic data set corresponding to a grid of twenty 3m-high columns defining the structure of a building made up of beams and columns. The experts must assess the mean and the standard deviation of compressive strength. Three levels of assessment are considered corresponding to different quantities of test results (destructive or non destructive) available for the experts. The comparison of the various strategies used by the experts and the analysis of results enables the identification of the most influential parameters that define an investigation approach and influence its efficiency and accuracy. A special emphasis is placed on the magnitude of the measurement error. A model of the investigation strategy is also proposed
The size of aggregates in concrete has an influence on the behavior of the material. The width of... more The size of aggregates in concrete has an influence on the behavior of the material. The width of the localized band can be related to this characteristic. Different experimental techniques are used and their results are compared. The validity of the hypothethis used in the calculations are discussed through the acoustic experiments. The characteristic length of microconcrete is found to be between four and six times the maximum aggregate size.
ASCE-ASME Journal of Risk and Uncertainty in Engineering Systems, Part A: Civil Engineering, 2019
AbstractAlthough variability in material properties and loading conditions is commonly accounted ... more AbstractAlthough variability in material properties and loading conditions is commonly accounted for in safety and reliability studies, this is not the case for model assumptions. In addition, many...
Le comportement a l’endommagement d’un composite a matrice metallique renforce de particules depe... more Le comportement a l’endommagement d’un composite a matrice metallique renforce de particules depend fortement de la repartition des particules en taille, nombre ou position dans la matrice. Une simulation de ce materiau en vue d’une utilisation dans un code de calcul, doit donc verifier un certain nombre de ces caracteristiques, avant et apres endommagement. Dans ce but, des images issues d’une coupe seriee realisee sur une eprouvette de traction apres essai sont analysees. Dans une premiere partie, la densite areale de particules est etudiee de facon a deduire la taille d’une image representative du materiau vis-a-vis de ce caractere. Puis un algorithme permettant l’identification des fissures est mis au point et permet ainsi l’analyse de la fissuration du materiau. Apres cette etape, il est possible de separer les particules en classes de taille, definies en fonction de l’aptitude des particules d’une taille donnee a se fissurer. Une taille d’image representative du materiau pour ce caractere est alors definie.
The concrete strength assessment process is influenced by uncertainties at many levels, including... more The concrete strength assessment process is influenced by uncertainties at many levels, including random measurement errors, sampling uncertainty and identification of the conversion model parameters. Therefore, instead of estimating the true value of the concrete strength, it is preferable to say that the objective of the assessment process is to predict a strength value ranging at a tolerable distance from the true strength value. This implies a deep revision of the assessment paradigm, in which both the acceptable tolerance interval and the risk of a wrong assessment must be given at the very beginning of the investigation. A large series of simulations has been carried out in order to understand and quantify how, for a given tolerance on the strength estimation, the risk value varies as a function of the precision of measurements, the number of cores and the strength distribution. Empirical models have been identified from the simulation results. These models have been finally used to calculate how many cores are required in various situations, to achieve the accuracy corresponding to three different estimation quality levels. This chapter describes the principles of the simulation, and how their results were used in order to build a series of tables where the recommended number of cores is made available in a variety of situations
Non-Destructive In Situ Strength Assessment of Concrete, 2021
This benchmark aims to assess mean compressive strength at several scales and to identify the loc... more This benchmark aims to assess mean compressive strength at several scales and to identify the location and characteristics of possible weak areas in the structure. It concerns synthetic data simulated on a group of four concrete cylindrical structures of identical dimensions with different kinds of strength distribution, based on a real case study. After having received the test results corresponding to their request (non-destructive or destructive), all the experts have to analyze these data and assess the concrete properties and to localize possible weak areas. In addition, they have to define their assessment methodology, i.e. level of investigation, number, type and location of measurements. This study provides information about how the accuracy of the final estimates depend on choices done at the various steps of the assessment process, from the definition of the testing program to the final delivery of strength estimates
Les projets de construction sont soumis à de nombreux risques et leur maitrise est un enjeu impor... more Les projets de construction sont soumis à de nombreux risques et leur maitrise est un enjeu important. Pour y répondre, nous avons développé SMACC (Stochastic Multi-agent simulAtion for Construction projeCt), un outil de simulation de projet de construction considérant les risques, basé sur l'approche 'Agent'. Mais la simulation d'un projet de construction par SMACC nécessite de renseigner de nombreuses informations quant au projet et aux risques susceptibles de l'affecter. Or, nos précédents travaux ne se sont pas intéressés au processus d'instanciation du modèle à partir d'un projet réel. Cet article présente donc une approche se plaçant en amont de SMACC permettant d'instancier les agents du modèle et de les évaluer avec un focus particulier sur les agents 'risques'. Cette approche est basée sur la combinaison entre approches de gestion de projet et la méthode de sûreté de fonctionnement MADS MOSAR (Méthode Organisée Systémique d'Analys...
Non-Destructive In Situ Strength Assessment of Concrete, 2021
A benchmark is carried out in order to compare how 13 experts define and can carry out an NDT inv... more A benchmark is carried out in order to compare how 13 experts define and can carry out an NDT investigation program and derive strength values from NDT measurements. The benchmark is based on simulations, which reproduces a synthetic data set corresponding to a grid of twenty 3m-high columns defining the structure of a building made up of beams and columns. The experts must assess the mean and the standard deviation of compressive strength. Three levels of assessment are considered corresponding to different quantities of test results (destructive or non destructive) available for the experts. The comparison of the various strategies used by the experts and the analysis of results enables the identification of the most influential parameters that define an investigation approach and influence its efficiency and accuracy. A special emphasis is placed on the magnitude of the measurement error. A model of the investigation strategy is also proposed
The size of aggregates in concrete has an influence on the behavior of the material. The width of... more The size of aggregates in concrete has an influence on the behavior of the material. The width of the localized band can be related to this characteristic. Different experimental techniques are used and their results are compared. The validity of the hypothethis used in the calculations are discussed through the acoustic experiments. The characteristic length of microconcrete is found to be between four and six times the maximum aggregate size.
ASCE-ASME Journal of Risk and Uncertainty in Engineering Systems, Part A: Civil Engineering, 2019
AbstractAlthough variability in material properties and loading conditions is commonly accounted ... more AbstractAlthough variability in material properties and loading conditions is commonly accounted for in safety and reliability studies, this is not the case for model assumptions. In addition, many...
Le comportement a l’endommagement d’un composite a matrice metallique renforce de particules depe... more Le comportement a l’endommagement d’un composite a matrice metallique renforce de particules depend fortement de la repartition des particules en taille, nombre ou position dans la matrice. Une simulation de ce materiau en vue d’une utilisation dans un code de calcul, doit donc verifier un certain nombre de ces caracteristiques, avant et apres endommagement. Dans ce but, des images issues d’une coupe seriee realisee sur une eprouvette de traction apres essai sont analysees. Dans une premiere partie, la densite areale de particules est etudiee de facon a deduire la taille d’une image representative du materiau vis-a-vis de ce caractere. Puis un algorithme permettant l’identification des fissures est mis au point et permet ainsi l’analyse de la fissuration du materiau. Apres cette etape, il est possible de separer les particules en classes de taille, definies en fonction de l’aptitude des particules d’une taille donnee a se fissurer. Une taille d’image representative du materiau pour ce caractere est alors definie.
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