The primary objective of this research was to develop a new type of high-performance lightweight ... more The primary objective of this research was to develop a new type of high-performance lightweight beam providing better performance than conventional beams made of timber, steel or reinforced concrete (RC) by casting fibre-reinforced polymer (FRP) reinforcing bars (rebars) in ultra-high-performance concrete with short fibre reinforcement (UHPC-SFR). This new type of beam was developed to be lightweight, have high compressive and tensile strength, be able to sustain large bending moments and be resistant to shear. The main objective was to verify the mechanical behaviour of the beams and compare it with typical RC beam behaviour. For this purpose, an experimental program was designed to identify the failure modes and bending behaviour. The results indicate that the behaviour of such RC beams can be compared to typical RC beam behaviour to a certain extent. A model to validate this concept is presented in this paper; this analytical model is based on typical material law behaviour hypotheses of beam nonlinear mechanical behaviour. The load-displacement and moment-curvature relationships predicted with this model were compared to the experimental results obtained for four large-scale specimens. The comparisons revealed good correlation between the analytical and experimental results and illustrate the potential of these composite beam configurations in civil engineering structures.
The present paper presents a detailed description of a model elaborated to predict the behavior o... more The present paper presents a detailed description of a model elaborated to predict the behavior of hydrated cement systems subjected to sub-freezing temperatures. The model was developed within the framework of poromechanics and accounts for local thermodynamic equilibrium between various phases. Ice formation is described at the pore scale and its effects on the thermoporo-elastic behavior of the homogenized porous medium are considered. Basic numerical considerations are formulated. A comparison with experimental results illustrates the ability of the model to predict the volume instabilities of hydrated cement pastes upon freezing. RÉSUMÉ Les principaux aspects d'un modèle permettant de prédire le comportement au gel de matériaux cimentaires sont détaillés. Le modèle a été développé en se basant sur les concepts de la poromécanique et permet de prendre en considération l'équilibre thermodynamique local entre différentes phases. La formation de la glace est décrite à l'échelle du pore et ses effets sur le comportement thermo-poro-élastique du milieu poreux homogénéisé sont considérés. Des considérations numériques élémentaires sont formulées. Une comparaison avec des résultats expérimentaux illustre la capacité du modèle à prédire les instabilités volumiques de pâtes de ciment hydraté exposées à des conditions de gel.
DESIGN CREATIVITY The curse of creativity David Brown Enabling creativity through innovation chal... more DESIGN CREATIVITY The curse of creativity David Brown Enabling creativity through innovation challenges: The case of interactive lighting Stefania Bandini, Andrea Bonomi, Giuseppe Vizzari and Vito Acconci Facetwise study of modeling activities in the algorithm for inventive problem solving ARIZ and evolutionary algorithms Céline Conrardy, Roland De Guio and Bruno Zuber Exploring multiple solutions and multiple analogies to support innovative design Apeksha Gadwal and Julie Linsey Creative and inventive design support system: Systematic approach and ...
Propriétés mécaniques des matériaux cimentaires: effet de l’eau et de la microstructure, une ... more Propriétés mécaniques des matériaux cimentaires: effet de l’eau et de la microstructure, une approche par microindentation Soutenue publiquement a ̀ l’École des Ponts ParisTech le 13 Févier, 2014
Propriétés mécaniques des matériaux cimentaires: effet de l’eau et de la microstructure, une ... more Propriétés mécaniques des matériaux cimentaires: effet de l’eau et de la microstructure, une approche par microindentation Soutenue publiquement a ̀ l’École des Ponts ParisTech le 13 Févier, 2014
Mechanics and Physics of Creep, Shrinkage, and Durability of Concrete, 2013
ABSTRACT Concrete creeps, and this creep must be well characterized and modeled to properly desig... more ABSTRACT Concrete creeps, and this creep must be well characterized and modeled to properly design civil engineering infrastructures. Here, we present some results on the creep properties of cementitious materials obtained by using the indentation technique. Firstly, we show that minutes-long microindentations on cement paste yield a quantitative measurement of their long-term logarithmic creep kinetics, which can be used to predict the rate of long-term creep of concrete. Then, by performing microindentations, we study the effect of relative humidity on the long-term creep properties of hydrated C3S samples, compacted samples made of pure C-S-H, and compacted samples made of pure CH. The last part is dedicated to a study by nanoindentation of the creep properties of C-S-H phases directly within a hydrated cement paste. We identify scaling relations independent of mix proportion and heat treatment, which we can explain by drawing a thorough analogy between the mechanical behavior of C-S-H and that of clays.
This study is dedicated to comparing minutes-long microindentation creep experiments on cement pa... more This study is dedicated to comparing minutes-long microindentation creep experiments on cement paste with years-long macroscopic creep experiments on concrete and months-long macroscopic creep experiments on cement paste. For all experiments, after a transient period the creep function was well captured by a logarithmic function of time, the amplitude of which is governed by a so-called creep modulus. The non-logarithmic transient periods lasted for days at the macroscopic scale, but only for seconds at the scale of microindentation. The creep moduli (which thus govern the rate of the long-term logarithmic creep) of concrete samples were estimated from microindentations performed at the scale of cement pastes in combination with micromechanical models. Those estimates were proportional to the creep moduli measured on concrete samples by regular macroscopic uniaxial testing, thus proving that minutes-long microindentation can provide a measurement of the long-term creep properties of cementitious materials.
ABSTRACT This paper presents a critical analysis of the mechanisms of ice formation in high-perfo... more ABSTRACT This paper presents a critical analysis of the mechanisms of ice formation in high-performance materials. The process of ice formation in ordinary and high-performance concrete mixtures is first investigated by low-temperature calorimetry. Three concrete mixtures (with water-to-cement ratios of 0.25, 0.35, and 0.45) were prepared and tested. The mechanisms of ice formation were also studied from a theoretical point of view using a numerical model. In this analysis, special attention is placed on the phenomenon of solid/liquid interface propagation. Test results indicate that a reduction of the water-to-cement ratio contributes to refine the concrete pore structure and limit the amount of ice formed between 0 and -55 degrees C. However, low-temperature measurements and theoretical calculations show that it is hardly possible to totally impede ice formation in cement-based materials. According to both types of analysis, ice formation in high-performance concrete mixtures is most certainly initiated by the propagation of a solid/liquid interface.
... Evolutionary Algorithms Céline Conrardy, Roland de Guio, and Bruno Zuber INSA de Strasbourg, ... more ... Evolutionary Algorithms Céline Conrardy, Roland de Guio, and Bruno Zuber INSA de Strasbourg, France Lafarge Research Center, France The aim of this paper is to contribute to a better understanding of modelling activities required to solve inventive problems. ...
The objective of this work is to present an inverse method solving the transient heat-transfer pr... more The objective of this work is to present an inverse method solving the transient heat-transfer problem in walls aiming to estimate its thermal properties. Th e procedure uses a finite difference numerical scheme , simulated in the environment SIMSPARK that is non object oriented and allows solving highly non linea r problems. A method aiming to estimate building envelope thermal characteristics is elaborated knowing experimental in situ measurements. The results present a good agreement between the forward and the inverse method respectively on a high-weight concrete and then on a Phase Change Material wall. Extrapolation of the method on a building model is realized to find the required air ventilation rate for a summer and a winter climate. Finally, the procedure is applied on a multilayered wall to estimate the U-value using real experimenta l data. The study shows clearly the possibility to identify a modification occurred on the wall composition and the moment at which this mod...
This shuttering kit comprises a plurality of panels (10) of mineral material, these panels being ... more This shuttering kit comprises a plurality of panels (10) of mineral material, these panels being separable from each other and being adapted to be arranged, by juxtaposition of their edge, in the same plane so as to form a wall (P1; P2; P3) from the wall; and a plurality of struts (20), each strut being separable panels and including first (21) and second (22) connecting portions which are rigidly connected to each other by a connecting portion ( 23) of the spacer. The first connecting portion of each spacer is adapted to cooperate by complementarity of shapes with a portion of the edge of one or more of the panels forming a first wall of the wall while the second connecting portion of each spacer is adapted for cooperating with a second face of the wall, so as to fixedly hold in place the first and second walls, with the interposition therebetween of a shuttering space with a filling material.
The aim of the present work is to improve night ventilation control strategies, specially for the... more The aim of the present work is to improve night ventilation control strategies, specially for the mid-season periods where an unadapted control scheme can result in undesirable heat loads. We present a method based on developing an adaptive algorithm suitable for different types of buildings having different thermal masses. The algorithm, mainly based on the history of outside and inside temperatures, is characterized by a set of parameters that we attempt to identify: a coefficient related to building time constant and a couple of fixed set-point temperatures. Results show that the adaptive algorithm was able toadapt to the mid-season period, thus preventing unwanted heat loads while preserving remarkable thermal comfort conditions.
Concrete creeps, and this creep must be well characterized and modeled to properly design civil e... more Concrete creeps, and this creep must be well characterized and modeled to properly design civil engineering infrastructures. Here, we present some results on the creep properties of cementitious materials obtained by using the indentation technique. Firstly, we show that minutes-long microindentations on cement paste yield a quantitative measurement of their long-term logarithmic creep kinetics, which can be used to predict the rate of long-term creep of concrete. Then, by performing microindentations, we study the effect of relative humidity on the long-term creep properties of hydrated C3S samples, compacted samples made of pure C-S-H, and compacted samples made of pure CH. The last part is dedicated to a study by nanoindentation of the creep properties of C-S-H phases directly within a hydrated cement paste. We identify scaling relations independent of mix proportion and heat treatment, which we can explain by drawing a thorough analogy between the mechanical behavior of C-S-H an...
Hydrated cement systems are quasi-brittle porous materials which can be saturated (fully or par ... more Hydrated cement systems are quasi-brittle porous materials which can be saturated (fully or par tially). In service, these materials are often exposed to freezing temperatures. The formation of ice in these systems is known to generate significant internal pressures that may damage the material. Pressures are induced either directly by the formation of an ice crystal or by mass transfers in the weakly permeable medium. In this contribution, a numerical model which predicts the internal micro-cracking of hydrated cement systems sub jected to frost action, ice formation and the induced fluid flow motion is presented. Temperature-induced phase transitions of the interstitial fluid are followed using a thermodynamic analysis. The classical Biot's analysis of saturated porous media is used to model the hydro-mechanical behavior of the freezing saturated porous solid and the induced stress state in the solid skeleton. Damage due to microcracking is introduced in the mechanical model...
The aim of the present work is to improve night venti-lation control strategies, specially for th... more The aim of the present work is to improve night venti-lation control strategies, specially for the mid-season periods where an unadapted control scheme can re-sult in undesirable heat loads. We present a method based on developing an adaptive algorithm suitable for different types of buildings having different thermal masses. The algorithm, mainly based on the history of outside and inside temperatures, is characterized by a set of parameters that we attempt to identify: a coef-ficient related to building time constant and a couple of fixed set-point temperatures. Results show that the adaptive algorithm was able to adapt to the mid-season period, thus preventing unwanted heat loads while pre-serving remarkable thermal comfort conditions.
The primary objective of this research was to develop a new type of high-performance lightweight ... more The primary objective of this research was to develop a new type of high-performance lightweight beam providing better performance than conventional beams made of timber, steel or reinforced concrete (RC) by casting fibre-reinforced polymer (FRP) reinforcing bars (rebars) in ultra-high-performance concrete with short fibre reinforcement (UHPC-SFR). This new type of beam was developed to be lightweight, have high compressive and tensile strength, be able to sustain large bending moments and be resistant to shear. The main objective was to verify the mechanical behaviour of the beams and compare it with typical RC beam behaviour. For this purpose, an experimental program was designed to identify the failure modes and bending behaviour. The results indicate that the behaviour of such RC beams can be compared to typical RC beam behaviour to a certain extent. A model to validate this concept is presented in this paper; this analytical model is based on typical material law behaviour hypotheses of beam nonlinear mechanical behaviour. The load-displacement and moment-curvature relationships predicted with this model were compared to the experimental results obtained for four large-scale specimens. The comparisons revealed good correlation between the analytical and experimental results and illustrate the potential of these composite beam configurations in civil engineering structures.
The present paper presents a detailed description of a model elaborated to predict the behavior o... more The present paper presents a detailed description of a model elaborated to predict the behavior of hydrated cement systems subjected to sub-freezing temperatures. The model was developed within the framework of poromechanics and accounts for local thermodynamic equilibrium between various phases. Ice formation is described at the pore scale and its effects on the thermoporo-elastic behavior of the homogenized porous medium are considered. Basic numerical considerations are formulated. A comparison with experimental results illustrates the ability of the model to predict the volume instabilities of hydrated cement pastes upon freezing. RÉSUMÉ Les principaux aspects d'un modèle permettant de prédire le comportement au gel de matériaux cimentaires sont détaillés. Le modèle a été développé en se basant sur les concepts de la poromécanique et permet de prendre en considération l'équilibre thermodynamique local entre différentes phases. La formation de la glace est décrite à l'échelle du pore et ses effets sur le comportement thermo-poro-élastique du milieu poreux homogénéisé sont considérés. Des considérations numériques élémentaires sont formulées. Une comparaison avec des résultats expérimentaux illustre la capacité du modèle à prédire les instabilités volumiques de pâtes de ciment hydraté exposées à des conditions de gel.
DESIGN CREATIVITY The curse of creativity David Brown Enabling creativity through innovation chal... more DESIGN CREATIVITY The curse of creativity David Brown Enabling creativity through innovation challenges: The case of interactive lighting Stefania Bandini, Andrea Bonomi, Giuseppe Vizzari and Vito Acconci Facetwise study of modeling activities in the algorithm for inventive problem solving ARIZ and evolutionary algorithms Céline Conrardy, Roland De Guio and Bruno Zuber Exploring multiple solutions and multiple analogies to support innovative design Apeksha Gadwal and Julie Linsey Creative and inventive design support system: Systematic approach and ...
Propriétés mécaniques des matériaux cimentaires: effet de l’eau et de la microstructure, une ... more Propriétés mécaniques des matériaux cimentaires: effet de l’eau et de la microstructure, une approche par microindentation Soutenue publiquement a ̀ l’École des Ponts ParisTech le 13 Févier, 2014
Propriétés mécaniques des matériaux cimentaires: effet de l’eau et de la microstructure, une ... more Propriétés mécaniques des matériaux cimentaires: effet de l’eau et de la microstructure, une approche par microindentation Soutenue publiquement a ̀ l’École des Ponts ParisTech le 13 Févier, 2014
Mechanics and Physics of Creep, Shrinkage, and Durability of Concrete, 2013
ABSTRACT Concrete creeps, and this creep must be well characterized and modeled to properly desig... more ABSTRACT Concrete creeps, and this creep must be well characterized and modeled to properly design civil engineering infrastructures. Here, we present some results on the creep properties of cementitious materials obtained by using the indentation technique. Firstly, we show that minutes-long microindentations on cement paste yield a quantitative measurement of their long-term logarithmic creep kinetics, which can be used to predict the rate of long-term creep of concrete. Then, by performing microindentations, we study the effect of relative humidity on the long-term creep properties of hydrated C3S samples, compacted samples made of pure C-S-H, and compacted samples made of pure CH. The last part is dedicated to a study by nanoindentation of the creep properties of C-S-H phases directly within a hydrated cement paste. We identify scaling relations independent of mix proportion and heat treatment, which we can explain by drawing a thorough analogy between the mechanical behavior of C-S-H and that of clays.
This study is dedicated to comparing minutes-long microindentation creep experiments on cement pa... more This study is dedicated to comparing minutes-long microindentation creep experiments on cement paste with years-long macroscopic creep experiments on concrete and months-long macroscopic creep experiments on cement paste. For all experiments, after a transient period the creep function was well captured by a logarithmic function of time, the amplitude of which is governed by a so-called creep modulus. The non-logarithmic transient periods lasted for days at the macroscopic scale, but only for seconds at the scale of microindentation. The creep moduli (which thus govern the rate of the long-term logarithmic creep) of concrete samples were estimated from microindentations performed at the scale of cement pastes in combination with micromechanical models. Those estimates were proportional to the creep moduli measured on concrete samples by regular macroscopic uniaxial testing, thus proving that minutes-long microindentation can provide a measurement of the long-term creep properties of cementitious materials.
ABSTRACT This paper presents a critical analysis of the mechanisms of ice formation in high-perfo... more ABSTRACT This paper presents a critical analysis of the mechanisms of ice formation in high-performance materials. The process of ice formation in ordinary and high-performance concrete mixtures is first investigated by low-temperature calorimetry. Three concrete mixtures (with water-to-cement ratios of 0.25, 0.35, and 0.45) were prepared and tested. The mechanisms of ice formation were also studied from a theoretical point of view using a numerical model. In this analysis, special attention is placed on the phenomenon of solid/liquid interface propagation. Test results indicate that a reduction of the water-to-cement ratio contributes to refine the concrete pore structure and limit the amount of ice formed between 0 and -55 degrees C. However, low-temperature measurements and theoretical calculations show that it is hardly possible to totally impede ice formation in cement-based materials. According to both types of analysis, ice formation in high-performance concrete mixtures is most certainly initiated by the propagation of a solid/liquid interface.
... Evolutionary Algorithms Céline Conrardy, Roland de Guio, and Bruno Zuber INSA de Strasbourg, ... more ... Evolutionary Algorithms Céline Conrardy, Roland de Guio, and Bruno Zuber INSA de Strasbourg, France Lafarge Research Center, France The aim of this paper is to contribute to a better understanding of modelling activities required to solve inventive problems. ...
The objective of this work is to present an inverse method solving the transient heat-transfer pr... more The objective of this work is to present an inverse method solving the transient heat-transfer problem in walls aiming to estimate its thermal properties. Th e procedure uses a finite difference numerical scheme , simulated in the environment SIMSPARK that is non object oriented and allows solving highly non linea r problems. A method aiming to estimate building envelope thermal characteristics is elaborated knowing experimental in situ measurements. The results present a good agreement between the forward and the inverse method respectively on a high-weight concrete and then on a Phase Change Material wall. Extrapolation of the method on a building model is realized to find the required air ventilation rate for a summer and a winter climate. Finally, the procedure is applied on a multilayered wall to estimate the U-value using real experimenta l data. The study shows clearly the possibility to identify a modification occurred on the wall composition and the moment at which this mod...
This shuttering kit comprises a plurality of panels (10) of mineral material, these panels being ... more This shuttering kit comprises a plurality of panels (10) of mineral material, these panels being separable from each other and being adapted to be arranged, by juxtaposition of their edge, in the same plane so as to form a wall (P1; P2; P3) from the wall; and a plurality of struts (20), each strut being separable panels and including first (21) and second (22) connecting portions which are rigidly connected to each other by a connecting portion ( 23) of the spacer. The first connecting portion of each spacer is adapted to cooperate by complementarity of shapes with a portion of the edge of one or more of the panels forming a first wall of the wall while the second connecting portion of each spacer is adapted for cooperating with a second face of the wall, so as to fixedly hold in place the first and second walls, with the interposition therebetween of a shuttering space with a filling material.
The aim of the present work is to improve night ventilation control strategies, specially for the... more The aim of the present work is to improve night ventilation control strategies, specially for the mid-season periods where an unadapted control scheme can result in undesirable heat loads. We present a method based on developing an adaptive algorithm suitable for different types of buildings having different thermal masses. The algorithm, mainly based on the history of outside and inside temperatures, is characterized by a set of parameters that we attempt to identify: a coefficient related to building time constant and a couple of fixed set-point temperatures. Results show that the adaptive algorithm was able toadapt to the mid-season period, thus preventing unwanted heat loads while preserving remarkable thermal comfort conditions.
Concrete creeps, and this creep must be well characterized and modeled to properly design civil e... more Concrete creeps, and this creep must be well characterized and modeled to properly design civil engineering infrastructures. Here, we present some results on the creep properties of cementitious materials obtained by using the indentation technique. Firstly, we show that minutes-long microindentations on cement paste yield a quantitative measurement of their long-term logarithmic creep kinetics, which can be used to predict the rate of long-term creep of concrete. Then, by performing microindentations, we study the effect of relative humidity on the long-term creep properties of hydrated C3S samples, compacted samples made of pure C-S-H, and compacted samples made of pure CH. The last part is dedicated to a study by nanoindentation of the creep properties of C-S-H phases directly within a hydrated cement paste. We identify scaling relations independent of mix proportion and heat treatment, which we can explain by drawing a thorough analogy between the mechanical behavior of C-S-H an...
Hydrated cement systems are quasi-brittle porous materials which can be saturated (fully or par ... more Hydrated cement systems are quasi-brittle porous materials which can be saturated (fully or par tially). In service, these materials are often exposed to freezing temperatures. The formation of ice in these systems is known to generate significant internal pressures that may damage the material. Pressures are induced either directly by the formation of an ice crystal or by mass transfers in the weakly permeable medium. In this contribution, a numerical model which predicts the internal micro-cracking of hydrated cement systems sub jected to frost action, ice formation and the induced fluid flow motion is presented. Temperature-induced phase transitions of the interstitial fluid are followed using a thermodynamic analysis. The classical Biot's analysis of saturated porous media is used to model the hydro-mechanical behavior of the freezing saturated porous solid and the induced stress state in the solid skeleton. Damage due to microcracking is introduced in the mechanical model...
The aim of the present work is to improve night venti-lation control strategies, specially for th... more The aim of the present work is to improve night venti-lation control strategies, specially for the mid-season periods where an unadapted control scheme can re-sult in undesirable heat loads. We present a method based on developing an adaptive algorithm suitable for different types of buildings having different thermal masses. The algorithm, mainly based on the history of outside and inside temperatures, is characterized by a set of parameters that we attempt to identify: a coef-ficient related to building time constant and a couple of fixed set-point temperatures. Results show that the adaptive algorithm was able to adapt to the mid-season period, thus preventing unwanted heat loads while pre-serving remarkable thermal comfort conditions.
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