The uniaxial compression of an initially isotropic concrete specimen induces a damage pattern tha... more The uniaxial compression of an initially isotropic concrete specimen induces a damage pattern that is anisotropic: in the direction of loading the concrete undergoes compaction, while in the directions orthogonal to the loading direction concrete cracking can be observed. In order to quantify such damage patterns, one possibility is to observe the changes in the stiffness tensor of a compressed specimen with respect to the stiffness tensor of the corresponding virgin state specimen. The eigensolutions of the Kelvin-Christoffel matrix for anisotropic media provide the relation between ultrasound wave velocities in given wavefront and polarization directions and the stiffness matrix components. In this study, it is shown how using the pitch-catch method for the determination of first time arrival, one can evaluate the sound wave velocities in different directions and compute the stiffness tensor components for a damaged concrete specimen. Plots of stiffness tensor components as a func...
This paper presents a numerical analysis of reinforced concrete slabs under missile impact loadin... more This paper presents a numerical analysis of reinforced concrete slabs under missile impact loading. The specimen used for the numerical simulation was tested by the Technical Research Center of Finland. LS-DYNA, commercial available software, is used to analyze the model. The structural components of the reinforced concrete slab, missile, and their contacts are fully modeled. Included in the analysis is material nonlinearity considering damage and failure. The results of analysis are then verified with other research results. Parametric studies with different longitudinal rebar ratios, shear bar ratios, and concrete strengths are conducted to investigate their influences on the punching behavior of slabs under the impact of a missile. Finally, efficient designs are recommended.
The Nordic Seminar on Computational Mechanics, Oct 1, 2019
This article proposes a relaxed strategy for the calibration of the Abaqus Concrete Damaged Plast... more This article proposes a relaxed strategy for the calibration of the Abaqus Concrete Damaged Plasticity (CDP) model in order to avoid the use of computationally expensive optimization techniques.
This paper has been written to highlight the edition of an OECD/NEA/IAGE (2014) state of the art ... more This paper has been written to highlight the edition of an OECD/NEA/IAGE (2014) state of the art report for Nuclear Power Plant (NPP) containment tendons. This subject is a critical one due to the major role of containment, in particular, during accident scenarios and many other issues. This OECD/NEA document deals in detail with the three major aspects on this topic including: • Design (Design Basis and Beyond Design Basis) • Construction • In Service Inspection (ISI)
In structures with uniform material properties, time dependent creep damage will develop in locat... more In structures with uniform material properties, time dependent creep damage will develop in locations where the stress state is aggravated by triaxiality constraints. However, for non-uniform structures, such as welds, where several material zones (differing in microstructure and material properties) are present, the pinpointing of the "weakest link" is even more challenging. For girth-welded pipes, the unfavourable conditions are known to be found in the vicinity of the heat-affected zone on the outer diameter. To find out how the triaxiality constraints influence accumulated "creep exhaustion", three girth welds simulated for different steels have been studied using the-filtering technique. The-filtering has been developed for finite element modelling for visualising the combined effect of creep ductility, creep rate and triaxiality constraint evolution assuming rigid plastic deformation for the stress triaxiality-dependent part. In this work, the creep response of three-zone girth welds was studied. In the case of the P23 steel, data for a real (experimental) consumable was used and for the others, assumption on creep strength and creep curve shapes was made according to material property ratios. The creep strain rate formulation used for this work is the logistic creep strain prediction model and its multiaxial implementation has been run in the Comsol multiphysics software package. The results of the weld simulations predict similar behaviour for the P22 and P91 welds, with assumed weld metal behaviour closer to the base material, and differing behaviour for the P23 with an overmatching (experimental) weld metal.
Aircraft impact is considered as a relevant loading case in designing modern nuclear power plants... more Aircraft impact is considered as a relevant loading case in designing modern nuclear power plants. Numerical methods and models need to be verified against experimental data in order to guarantee the reliability of results when simulating full scale applications. The IMPACT test facility has been developed starting in 2003 and is has reached a mature phase where well repeatable tests can be conducted and broad range of dynamic data acquired reliably.
Electricite de France (EDF) operates a large fleet of nuclear reactors and is responsible for dem... more Electricite 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, which have no metallic liners, the leak-tightness is strongly influenced by the degree of cracking of concrete and opening of the cracks, which mostly depends on (a) the prestress decrease due to the delayed strains of concrete and to a lesser extent due to relaxation of tendons steel, and (b) the saturation degree of the Powered by Editorial Manager® and ProduXion Manager® from Aries Systems Corporation concrete wall. Therefore, to optimize the maintenance programs on CCBs, it is important to predict the evolution of drying, creep and shrinkage strains of concrete to be able to correctly assess the pre-stress losses, and finally the air leak-...
The uniaxial compression of an initially isotropic concrete specimen induces a damage pattern tha... more The uniaxial compression of an initially isotropic concrete specimen induces a damage pattern that is anisotropic: in the direction of loading the concrete undergoes compaction, while in the directions orthogonal to the loading direction concrete cracking can be observed. In order to quantify such damage patterns, one possibility is to observe the changes in the stiffness tensor of a compressed specimen with respect to the stiffness tensor of the corresponding virgin state specimen. The eigensolutions of the Kelvin-Christoffel matrix for anisotropic media provide the relation between ultrasound wave velocities in given wavefront and polarization directions and the stiffness matrix components. In this study, it is shown how using the pitch-catch method for the determination of first time arrival, one can evaluate the sound wave velocities in different directions and compute the stiffness tensor components for a damaged concrete specimen. Plots of stiffness tensor components as a func...
This paper presents a numerical analysis of reinforced concrete slabs under missile impact loadin... more This paper presents a numerical analysis of reinforced concrete slabs under missile impact loading. The specimen used for the numerical simulation was tested by the Technical Research Center of Finland. LS-DYNA, commercial available software, is used to analyze the model. The structural components of the reinforced concrete slab, missile, and their contacts are fully modeled. Included in the analysis is material nonlinearity considering damage and failure. The results of analysis are then verified with other research results. Parametric studies with different longitudinal rebar ratios, shear bar ratios, and concrete strengths are conducted to investigate their influences on the punching behavior of slabs under the impact of a missile. Finally, efficient designs are recommended.
The Nordic Seminar on Computational Mechanics, Oct 1, 2019
This article proposes a relaxed strategy for the calibration of the Abaqus Concrete Damaged Plast... more This article proposes a relaxed strategy for the calibration of the Abaqus Concrete Damaged Plasticity (CDP) model in order to avoid the use of computationally expensive optimization techniques.
This paper has been written to highlight the edition of an OECD/NEA/IAGE (2014) state of the art ... more This paper has been written to highlight the edition of an OECD/NEA/IAGE (2014) state of the art report for Nuclear Power Plant (NPP) containment tendons. This subject is a critical one due to the major role of containment, in particular, during accident scenarios and many other issues. This OECD/NEA document deals in detail with the three major aspects on this topic including: • Design (Design Basis and Beyond Design Basis) • Construction • In Service Inspection (ISI)
In structures with uniform material properties, time dependent creep damage will develop in locat... more In structures with uniform material properties, time dependent creep damage will develop in locations where the stress state is aggravated by triaxiality constraints. However, for non-uniform structures, such as welds, where several material zones (differing in microstructure and material properties) are present, the pinpointing of the "weakest link" is even more challenging. For girth-welded pipes, the unfavourable conditions are known to be found in the vicinity of the heat-affected zone on the outer diameter. To find out how the triaxiality constraints influence accumulated "creep exhaustion", three girth welds simulated for different steels have been studied using the-filtering technique. The-filtering has been developed for finite element modelling for visualising the combined effect of creep ductility, creep rate and triaxiality constraint evolution assuming rigid plastic deformation for the stress triaxiality-dependent part. In this work, the creep response of three-zone girth welds was studied. In the case of the P23 steel, data for a real (experimental) consumable was used and for the others, assumption on creep strength and creep curve shapes was made according to material property ratios. The creep strain rate formulation used for this work is the logistic creep strain prediction model and its multiaxial implementation has been run in the Comsol multiphysics software package. The results of the weld simulations predict similar behaviour for the P22 and P91 welds, with assumed weld metal behaviour closer to the base material, and differing behaviour for the P23 with an overmatching (experimental) weld metal.
Aircraft impact is considered as a relevant loading case in designing modern nuclear power plants... more Aircraft impact is considered as a relevant loading case in designing modern nuclear power plants. Numerical methods and models need to be verified against experimental data in order to guarantee the reliability of results when simulating full scale applications. The IMPACT test facility has been developed starting in 2003 and is has reached a mature phase where well repeatable tests can be conducted and broad range of dynamic data acquired reliably.
Electricite de France (EDF) operates a large fleet of nuclear reactors and is responsible for dem... more Electricite 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, which have no metallic liners, the leak-tightness is strongly influenced by the degree of cracking of concrete and opening of the cracks, which mostly depends on (a) the prestress decrease due to the delayed strains of concrete and to a lesser extent due to relaxation of tendons steel, and (b) the saturation degree of the Powered by Editorial Manager® and ProduXion Manager® from Aries Systems Corporation concrete wall. Therefore, to optimize the maintenance programs on CCBs, it is important to predict the evolution of drying, creep and shrinkage strains of concrete to be able to correctly assess the pre-stress losses, and finally the air leak-...
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Papers by Kim Calonius