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Research paper thumbnail of Bayesian updated correlation length of spatial concrete properties using limited data

Bayesian updated correlation length of spatial concrete properties using limited data

Computers and Concrete, 2014

ABSTRACT A Bayesian response surface updating procedure is applied in order to update the paramet... more ABSTRACT A Bayesian response surface updating procedure is applied in order to update the parameters of the covariance function of a random field for concrete properties based on a limited number of available measurements. Formulas as well as a numerical algorithm are presented in order to update the parameters of response surfaces using Markov Chain Monte Carlo simulations. The parameters of the covariance function are often based on some kind of expert judgment due the lack of sufficient measurement data. However, a Bayesian updating technique enables to estimate the parameters of the covariance function more rigorously and with less ambiguity. Prior information can be incorporated in the form of vague or informative priors. The proposed estimation procedure is evaluated through numerical simulations and compared to the commonly used least square method.

Research paper thumbnail of Using Bayesian response surface updating for estimating the covariance function of random fields based on limited measurements

Using Bayesian response surface updating for estimating the covariance function of random fields based on limited measurements

ABSTRACT Bayesian statistics can be used to update previously obtained information regarding para... more ABSTRACT Bayesian statistics can be used to update previously obtained information regarding parameters of prediction models. Observed data is often modelled by a nonlinear function of multiple model parameters. Markov Chain Monte Carlo (MCMC) simulations can be used to incorporate these phenomena in the response surface estimation. Formulas as well as an numerical algorithm are presented in order to update the parameters of such response surfaces. Furthermore, the Bayesian response surface updating procedure is applied in order to update the parameters of covariance functions for random fields based on a limited number of available measurements. When there is a lack of sufficient data to effectively apply traditional methods such as the least-squares method (e.g. in case of destructive testing), the parameters of the covariance function are often based on expert judgment. However, a Bayesian updating methodology enables to estimate these parameters more rigorously and with less ambiguity. More specifically, the above mentioned Bayesian response surface updating approach using MCMC simulations is used for this. Prior information can be incorporated in the form of vague or informative priors, which may be based on previous results or expert judgment. The proposed estimation procedure is evaluated trough numerical simulations and compared to the least square (LSQ) method.

Research paper thumbnail of Creep experiments and analysis of T-shaped beams subjected to loading and unloading at young age

Creep and shrinkage are important time-dependent phenomena to consider when designing reinforced ... more Creep and shrinkage are important time-dependent phenomena to consider when designing reinforced concrete structures. Depending on the concrete age, the loading history (sequence and timing), the dimensions of the structural elements and environmental factors, the creep deflection can be more than two times larger than the elastic deflection. This, off course, can lead to unacceptable deflections of the structure or instability problems leading to failure. Creep under a sustained load is a well-studied phenomenon. However, many structures are subjected to changes in the loading due to construction activities. Typically the quasi-permanent load combination is used to predict the long-term deformation in a creep analysis without taking the load history into account. This approach has been proven useful, however, it does not allow for the prediction of the deformations considering the rather important early age creep of the structure. Creep rate decreases with an increase of the hydration degree, meaning that concrete is more susceptible to creep at young age. Furthermore, the expected loading history of a structural element should be considered in the design, since this strongly influences the point at which cracking of the element will occur, leading to a reduced stiffness of the element. In order to investigate creep deformation caused by load changes at young age and its effect on the long-term deformation a series of T-shaped beams has been subjected to different load scenarios. An overview of the measurement results is given as well a cross-sectional numerical procedure to estimate the creep deformation due to the loading history during construction.

Research paper thumbnail of Stress redistribution of concrete prisms due to creep and shrinkage: long-term observations and analysis

Stress redistribution of concrete prisms due to creep and shrinkage: long-term observations and analysis

Research paper thumbnail of Using Bayesian response surface updating for estimating the covariance function of random fields based on limited measurements

Using Bayesian response surface updating for estimating the covariance function of random fields based on limited measurements

Safety, Reliability, Risk and Life-Cycle Performance of Structures and Infrastructures, 2014

ABSTRACT Bayesian statistics can be used to update previously obtained information regarding para... more ABSTRACT Bayesian statistics can be used to update previously obtained information regarding parameters of prediction models. Observed data is often modelled by a nonlinear function of multiple model parameters. Markov Chain Monte Carlo (MCMC) simulations can be used to incorporate these phenomena in the response surface estimation. Formulas as well as an numerical algorithm are presented in order to update the parameters of such response surfaces. Furthermore, the Bayesian response surface updating procedure is applied in order to update the parameters of covariance functions for random fields based on a limited number of available measurements. When there is a lack of sufficient data to effectively apply traditional methods such as the least-squares method (e.g. in case of destructive testing), the parameters of the covariance function are often based on expert judgment. However, a Bayesian updating methodology enables to estimate these parameters more rigorously and with less ambiguity. More specifically, the above mentioned Bayesian response surface updating approach using MCMC simulations is used for this. Prior information can be incorporated in the form of vague or informative priors, which may be based on previous results or expert judgment. The proposed estimation procedure is evaluated trough numerical simulations and compared to the least square (LSQ) method.

Research paper thumbnail of Creep experiments and analysis of T-shaped beams subjected to loading and unloading at young age

Life-Cycle of Civil Engineering Systems, 2014

Creep and shrinkage are important time-dependent phenomena to consider when designing reinforced ... more Creep and shrinkage are important time-dependent phenomena to consider when designing reinforced concrete structures. Depending on the concrete age, the loading history (sequence and timing), the dimensions of the structural elements and environmental factors, the creep deflection can be more than two times larger than the elastic deflection. This, off course, can lead to unacceptable deflections of the structure or instability problems leading to failure. Creep under a sustained load is a well-studied phenomenon. However, many structures are subjected to changes in the loading due to construction activities. Typically the quasi-permanent load combination is used to predict the long-term deformation in a creep analysis without taking the load history into account. This approach has been proven useful, however, it does not allow for the prediction of the deformations considering the rather important early age creep of the structure. Creep rate decreases with an increase of the hydration degree, meaning that concrete is more susceptible to creep at young age. Furthermore, the expected loading history of a structural element should be considered in the design, since this strongly influences the point at which cracking of the element will occur, leading to a reduced stiffness of the element. In order to investigate creep deformation caused by load changes at young age and its effect on the long-term deformation a series of T-shaped beams has been subjected to different load scenarios. An overview of the measurement results is given as well a cross-sectional numerical procedure to estimate the creep deformation due to the loading history during construction.

Research paper thumbnail of Bayesian estimation of the covariance function of random fields based on a limited number of measurements

Bayesian estimation of the covariance function of random fields based on a limited number of measurements

A Bayesian response surface updating procedure is applied in order to update covariance functions... more A Bayesian response surface updating procedure is applied in order to update covariance functions for random fields based on a limited number of measurements. Formulas as well as a numerical algorithm are presented in order to update the parameters of complex response surfaces using Markov Chain Monte Carlo simulations. In case of random fields, the parameters of the covar-iance function are often based on some kind of expert judgment. However, a Bayesian updating technique enables to estimate the parameters of the covari-ance function more rigorously and with less ambiguity. Prior information can be incorporated in the form of vague or informative priors, and the latter can be based on e.g. expert judgment. The proposed estimation procedure is evaluated through numerical simulations and the influence of the position of measurement points is investigated.

Research paper thumbnail of Modeling the effect of random environmental influences on stochastic creep in concrete members

Modeling the effect of random environmental influences on stochastic creep in concrete members

abstractThe most significant contribution to the variability of long-term creep for in-situ struc... more abstractThe most significant contribution to the variability of long-term creep for in-situ structural concrete members stems from the effect of environmental influences. Many of these external processes are both seasonal and random. Specifically, ambient temperature, relative humidity, and wind are key factors with regard to creep response. But the influencing factors also include the time of casting/construction, the severity and the extent of seasonality, the exposure characteristics of the concrete member, the geographic location of the structure together with its prevailing meteorological regime, and the correlation between temperature and humidity. In order to investigate the impact of these various factors on the net macroscopic creep coefficient used in analysis and design, a discretized 2D physical model is developed, formulated in term of combined heat transfer and moisture diffusion. The "local" strain response throughout the structural element in space/time is ...

Research paper thumbnail of Prediction of the spatial occurrence of fire induced spalling in concrete slabs using random fields

MATEC Web of Conferences, 2013

As the loss of concrete cover can significantly influence the reliability of concrete elements du... more As the loss of concrete cover can significantly influence the reliability of concrete elements during fire, spalling should be taken into account when performing reliability calculations. However, the occurrence and spatial variation of spalling are highly uncertain. A first step towards a probabilistic analysis of spalling is made by combining existing deterministic models with a stochastic representation of the concrete tensile strength and by using random fields to model the tensile strength spatial variation.

Research paper thumbnail of CONCRETE STRUCTURES UNDER IMPACT LOADING: GENERAL ASPECTS Călin MIRCEA Nele De BELIE

Dynamic loading conditions distress the structural integrity of a structure differently than the ... more Dynamic loading conditions distress the structural integrity of a structure differently than the static ones. Such actions transfer high rate strains and instant energy waves to the structure, inducing the possibility of imminent collapse and casualties as a direct consequence. In the latest years, considering the dramatic increase of terrorist threats and global warming, the structural safety criteria imply more than ever the need to withstand this kind of loading (e.g., missiles and blast, projectiles, strong winds, tornados and earthquakes) in addition to the static ones. The aim of this paper is to provide a general overview with regard to impact loading in terms of defining the phenomenon from physical and mechanical perspective, its complex local or global effect on the targeted structure, relevant material characteristics, main research approaches, namely theoretical studies and experimental procedures developed for improving the predictability of the dynamic loads and their effects. New directions in developing superior cementitious composites, with better characteristics in terms of dynamic loading performance are also emphasized.

Research paper thumbnail of Bayesian updated correlation length of spatial concrete properties using limited data

Bayesian updated correlation length of spatial concrete properties using limited data

Computers and Concrete, 2014

ABSTRACT A Bayesian response surface updating procedure is applied in order to update the paramet... more ABSTRACT A Bayesian response surface updating procedure is applied in order to update the parameters of the covariance function of a random field for concrete properties based on a limited number of available measurements. Formulas as well as a numerical algorithm are presented in order to update the parameters of response surfaces using Markov Chain Monte Carlo simulations. The parameters of the covariance function are often based on some kind of expert judgment due the lack of sufficient measurement data. However, a Bayesian updating technique enables to estimate the parameters of the covariance function more rigorously and with less ambiguity. Prior information can be incorporated in the form of vague or informative priors. The proposed estimation procedure is evaluated through numerical simulations and compared to the commonly used least square method.

Research paper thumbnail of Using Bayesian response surface updating for estimating the covariance function of random fields based on limited measurements

Using Bayesian response surface updating for estimating the covariance function of random fields based on limited measurements

ABSTRACT Bayesian statistics can be used to update previously obtained information regarding para... more ABSTRACT Bayesian statistics can be used to update previously obtained information regarding parameters of prediction models. Observed data is often modelled by a nonlinear function of multiple model parameters. Markov Chain Monte Carlo (MCMC) simulations can be used to incorporate these phenomena in the response surface estimation. Formulas as well as an numerical algorithm are presented in order to update the parameters of such response surfaces. Furthermore, the Bayesian response surface updating procedure is applied in order to update the parameters of covariance functions for random fields based on a limited number of available measurements. When there is a lack of sufficient data to effectively apply traditional methods such as the least-squares method (e.g. in case of destructive testing), the parameters of the covariance function are often based on expert judgment. However, a Bayesian updating methodology enables to estimate these parameters more rigorously and with less ambiguity. More specifically, the above mentioned Bayesian response surface updating approach using MCMC simulations is used for this. Prior information can be incorporated in the form of vague or informative priors, which may be based on previous results or expert judgment. The proposed estimation procedure is evaluated trough numerical simulations and compared to the least square (LSQ) method.

Research paper thumbnail of Creep experiments and analysis of T-shaped beams subjected to loading and unloading at young age

Creep and shrinkage are important time-dependent phenomena to consider when designing reinforced ... more Creep and shrinkage are important time-dependent phenomena to consider when designing reinforced concrete structures. Depending on the concrete age, the loading history (sequence and timing), the dimensions of the structural elements and environmental factors, the creep deflection can be more than two times larger than the elastic deflection. This, off course, can lead to unacceptable deflections of the structure or instability problems leading to failure. Creep under a sustained load is a well-studied phenomenon. However, many structures are subjected to changes in the loading due to construction activities. Typically the quasi-permanent load combination is used to predict the long-term deformation in a creep analysis without taking the load history into account. This approach has been proven useful, however, it does not allow for the prediction of the deformations considering the rather important early age creep of the structure. Creep rate decreases with an increase of the hydration degree, meaning that concrete is more susceptible to creep at young age. Furthermore, the expected loading history of a structural element should be considered in the design, since this strongly influences the point at which cracking of the element will occur, leading to a reduced stiffness of the element. In order to investigate creep deformation caused by load changes at young age and its effect on the long-term deformation a series of T-shaped beams has been subjected to different load scenarios. An overview of the measurement results is given as well a cross-sectional numerical procedure to estimate the creep deformation due to the loading history during construction.

Research paper thumbnail of Stress redistribution of concrete prisms due to creep and shrinkage: long-term observations and analysis

Stress redistribution of concrete prisms due to creep and shrinkage: long-term observations and analysis

Research paper thumbnail of Using Bayesian response surface updating for estimating the covariance function of random fields based on limited measurements

Using Bayesian response surface updating for estimating the covariance function of random fields based on limited measurements

Safety, Reliability, Risk and Life-Cycle Performance of Structures and Infrastructures, 2014

ABSTRACT Bayesian statistics can be used to update previously obtained information regarding para... more ABSTRACT Bayesian statistics can be used to update previously obtained information regarding parameters of prediction models. Observed data is often modelled by a nonlinear function of multiple model parameters. Markov Chain Monte Carlo (MCMC) simulations can be used to incorporate these phenomena in the response surface estimation. Formulas as well as an numerical algorithm are presented in order to update the parameters of such response surfaces. Furthermore, the Bayesian response surface updating procedure is applied in order to update the parameters of covariance functions for random fields based on a limited number of available measurements. When there is a lack of sufficient data to effectively apply traditional methods such as the least-squares method (e.g. in case of destructive testing), the parameters of the covariance function are often based on expert judgment. However, a Bayesian updating methodology enables to estimate these parameters more rigorously and with less ambiguity. More specifically, the above mentioned Bayesian response surface updating approach using MCMC simulations is used for this. Prior information can be incorporated in the form of vague or informative priors, which may be based on previous results or expert judgment. The proposed estimation procedure is evaluated trough numerical simulations and compared to the least square (LSQ) method.

Research paper thumbnail of Creep experiments and analysis of T-shaped beams subjected to loading and unloading at young age

Life-Cycle of Civil Engineering Systems, 2014

Creep and shrinkage are important time-dependent phenomena to consider when designing reinforced ... more Creep and shrinkage are important time-dependent phenomena to consider when designing reinforced concrete structures. Depending on the concrete age, the loading history (sequence and timing), the dimensions of the structural elements and environmental factors, the creep deflection can be more than two times larger than the elastic deflection. This, off course, can lead to unacceptable deflections of the structure or instability problems leading to failure. Creep under a sustained load is a well-studied phenomenon. However, many structures are subjected to changes in the loading due to construction activities. Typically the quasi-permanent load combination is used to predict the long-term deformation in a creep analysis without taking the load history into account. This approach has been proven useful, however, it does not allow for the prediction of the deformations considering the rather important early age creep of the structure. Creep rate decreases with an increase of the hydration degree, meaning that concrete is more susceptible to creep at young age. Furthermore, the expected loading history of a structural element should be considered in the design, since this strongly influences the point at which cracking of the element will occur, leading to a reduced stiffness of the element. In order to investigate creep deformation caused by load changes at young age and its effect on the long-term deformation a series of T-shaped beams has been subjected to different load scenarios. An overview of the measurement results is given as well a cross-sectional numerical procedure to estimate the creep deformation due to the loading history during construction.

Research paper thumbnail of Bayesian estimation of the covariance function of random fields based on a limited number of measurements

Bayesian estimation of the covariance function of random fields based on a limited number of measurements

A Bayesian response surface updating procedure is applied in order to update covariance functions... more A Bayesian response surface updating procedure is applied in order to update covariance functions for random fields based on a limited number of measurements. Formulas as well as a numerical algorithm are presented in order to update the parameters of complex response surfaces using Markov Chain Monte Carlo simulations. In case of random fields, the parameters of the covar-iance function are often based on some kind of expert judgment. However, a Bayesian updating technique enables to estimate the parameters of the covari-ance function more rigorously and with less ambiguity. Prior information can be incorporated in the form of vague or informative priors, and the latter can be based on e.g. expert judgment. The proposed estimation procedure is evaluated through numerical simulations and the influence of the position of measurement points is investigated.

Research paper thumbnail of Modeling the effect of random environmental influences on stochastic creep in concrete members

Modeling the effect of random environmental influences on stochastic creep in concrete members

abstractThe most significant contribution to the variability of long-term creep for in-situ struc... more abstractThe most significant contribution to the variability of long-term creep for in-situ structural concrete members stems from the effect of environmental influences. Many of these external processes are both seasonal and random. Specifically, ambient temperature, relative humidity, and wind are key factors with regard to creep response. But the influencing factors also include the time of casting/construction, the severity and the extent of seasonality, the exposure characteristics of the concrete member, the geographic location of the structure together with its prevailing meteorological regime, and the correlation between temperature and humidity. In order to investigate the impact of these various factors on the net macroscopic creep coefficient used in analysis and design, a discretized 2D physical model is developed, formulated in term of combined heat transfer and moisture diffusion. The "local" strain response throughout the structural element in space/time is ...

Research paper thumbnail of Prediction of the spatial occurrence of fire induced spalling in concrete slabs using random fields

MATEC Web of Conferences, 2013

As the loss of concrete cover can significantly influence the reliability of concrete elements du... more As the loss of concrete cover can significantly influence the reliability of concrete elements during fire, spalling should be taken into account when performing reliability calculations. However, the occurrence and spatial variation of spalling are highly uncertain. A first step towards a probabilistic analysis of spalling is made by combining existing deterministic models with a stochastic representation of the concrete tensile strength and by using random fields to model the tensile strength spatial variation.

Research paper thumbnail of CONCRETE STRUCTURES UNDER IMPACT LOADING: GENERAL ASPECTS Călin MIRCEA Nele De BELIE

Dynamic loading conditions distress the structural integrity of a structure differently than the ... more Dynamic loading conditions distress the structural integrity of a structure differently than the static ones. Such actions transfer high rate strains and instant energy waves to the structure, inducing the possibility of imminent collapse and casualties as a direct consequence. In the latest years, considering the dramatic increase of terrorist threats and global warming, the structural safety criteria imply more than ever the need to withstand this kind of loading (e.g., missiles and blast, projectiles, strong winds, tornados and earthquakes) in addition to the static ones. The aim of this paper is to provide a general overview with regard to impact loading in terms of defining the phenomenon from physical and mechanical perspective, its complex local or global effect on the targeted structure, relevant material characteristics, main research approaches, namely theoretical studies and experimental procedures developed for improving the predictability of the dynamic loads and their effects. New directions in developing superior cementitious composites, with better characteristics in terms of dynamic loading performance are also emphasized.