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Papers by Francesco Pesavento
International Journal of Solids and Structures, 2011
The paper deals with modelling of hygro-thermal performance and thermo-chemical degradation of co... more The paper deals with modelling of hygro-thermal performance and thermo-chemical degradation of concrete exposed to high temperature. Several possible simplifications in modelling of heat and mass transport phenomena in heated concrete are considered and their effect on the results of numerical simulations is analyzed.
... 1 Department of Structural and Transportation Engineering, University of Padova, via F. Marzo... more ... 1 Department of Structural and Transportation Engineering, University of Padova, via F. Marzolo 9 ... reaction through an Arrhenius-type relationship, as usual for thermally activated chemical reactions: ... to a growth of the volume fraction of load-bearing hydrated cement, which itself ...
A new numerical model for the simulation of ASR in cement-based materials considering both the ef... more A new numerical model for the simulation of ASR in cement-based materials considering both the effect of temperature and moisture content is presented. A mechanistic approach, based on the mechanics of porous media, was used to obtain the governing equations by means of a hybrid mixture theory. The model equations, mass (water species and dry air), energy and momentum balances are written in terms of the chosen primary variables: gas pressure, capillary pressure, temperature and displacement vector, while the ASR evolution is described by the reaction extent being the internal variable. The model takes into account full coupling between hygral, thermal and chemical phenomena, as well as changes of concrete properties caused by chemical reaction, i.e. porosity, density, permeability. Phase changes and chemical processes, as well as the related heat and mass sources are considered. Material chemical and mechanical degradation is considered with the isotropic damage theory. The model equations are numerically solved using finite element method for discretization in space and finite differences for time integration. The model results are validated by comparison with some published experimental data concerning ASR expansion in constant and variable hygro-thermal conditions.
Lecture Notes in Computer Science, 2002
Solving fully-coupled non-linear hygro-thermo-mechanical problems relative to the behavior of con... more Solving fully-coupled non-linear hygro-thermo-mechanical problems relative to the behavior of concrete at high temperatures is nowadays a very interesting and challenging computational problem. These models require an extensive use of computational resources, such as main memory and computational time, due to the great number of variables and the numerical characteristics of the coefficients of the linear systems involved. In this
Proceedings of the Ninth International Conference on Computational Structures Technology, 2008
Journal of the Mechanics and Physics of Solids, 2010
The work input for unsaturated elastic porous media is investigated based on averaged conservatio... more The work input for unsaturated elastic porous media is investigated based on averaged conservation equations for phases, interfaces, and common curves. In this analysis, the interfaces between the air-water interfaces are allowed to move and the surface tension appears explicitly in the analysis. Expressions for the work of the solid alone and for the medium are obtained. Conditions under which the result obtained here for the medium reduces to a more traditional expression are indicated. In this analysis, a form of the solid phase stress tensor, recently derived within the framework of thermodynamically constrained averaging theory for phase and interface properties, is used.
Frontiers of Architecture and Civil Engineering in China, 2011
Many problems are linked with the long term behaviour of dams, both earth-dams and concrete dams.... more Many problems are linked with the long term behaviour of dams, both earth-dams and concrete dams. They range from hydraulic fracturing to alkali-silica reaction and to repair work in concrete dams, from seismic behaviour to secondary consolidation in earth-dams. A common framework for simulation of such systems is shown, based on the mechanics of multiphase porous media. The general model is particularized to specific situations and several examples are shown.
Fire Safety Journal, 2008
Fire loading of concrete tunnel linings is characterized by various physical, chemical, and mecha... more Fire loading of concrete tunnel linings is characterized by various physical, chemical, and mechanical processes, resulting in spalling of nearsurface concrete layers and degradation of strength and stiffness of the remaining tunnel lining. In this paper, the governing transport processes taking place in concrete at elevated temperatures are considered within a recently published fire-safety assessment tool [Savov K, Lackner R, Mang HA. Stability assessment of shallow tunnels subjected to fire load. Fire Safety J 2005; 40: 745-763] for underground structures. In contrast to consideration of heat transport only [Savov et al.], a coupled thermo-hydro-chemical analysis, simulating the heat and mass transport in concrete under fire loading, is performed, giving access to more realistic temperature distributions as well as gas-pressure distributions within the tunnel lining. These data serve as input for the structural safety assessment tool considering, in addition to the temperature dependence of mechanical properties, the effect of the gas pressure on the strength properties of the heated lining concrete. The combination of the two analysis tools (coupled analysis of governing transport processes and structural safety assessment) is illustrated by the fire-safety assessment of a cross-section of the Lainzer tunnel (Austria) characterized by low overburden (shallow tunnel).
Progress in Industrial Mathematics …, 2006
A mathematical and numerical model to predict the non-linear behaviour of concrete as multiphase ... more A mathematical and numerical model to predict the non-linear behaviour of concrete as multiphase porous material is proposed. The model can be usefully applied to several practical cases: evaluation of concrete performance in the high temperature range, e.g. during fire, to early stages of maturing of massive concrete structures, to shotcrete in tunnelling, and to durability. All the important phase changes of water and chemical reactions, i.e. adsorption-desorption, condensation-evaporation, and hydration-dehydration, as well as the related heat and mass sources or sinks are considered. Changes of the material properties caused by temperature and pressure changes, concrete damage or carbonation, fresh concrete hardening, as well as coupling between thermal, hygral and mechanical phenomena are taken into account. This model further allows to incorporate sorption hysteresis. Some relevant applications of the model will be shown in this work.
Computers and Geotechnics, 2004
Models for thermo-hydro-mechanical behaviour of saturated-unsaturated porous media are reviewed. ... more Models for thermo-hydro-mechanical behaviour of saturated-unsaturated porous media are reviewed. The necessary balance equations are derived using averaging theories. Constitutive equations are obtained using the Coleman-Noll procedure and thermodynamic equations for the model closure are introduced. A simplified form of the governing equations is then solved numerically and the numerical properties are discussed. An example dealing with behaviour of concrete structures during tunnel fires concludes the paper. The heat and mass transfer calculations in the tunnel needed as the input for the multiphase concrete model are also shown. The behaviour of concrete under such situations, where very high temperatures are reached, can be satisfactorily simulated only with an approach of the type presented here.
Computational Mechanics, 2006
A mathematical model of hygro-thermo-mechanical phenomena in heated concrete, treated as multipha... more A mathematical model of hygro-thermo-mechanical phenomena in heated concrete, treated as multiphase porous material is briefly presented. Some modifications necessary to analyse high-temperature performance of a concrete containing the PP-fibres have been introduced, experimentally validated and applied for analysis of performance of a concrete tunnel lining during a 10-MW fire and the ISO standard fire. Three methods for protecting concrete structures against excessive degradation in fire conditions have been numerically analysed by means of the computer model. The analysed protection methods are based either upon application on a structure surface of a reflective layer, or covering it with a protective layer made of a very porous concrete or an addition of the PP fibres to the concrete mix. Efficiency of these methods has been numerically analysed in thermal conditions corresponding to the ISO-834 standard fire. The results obtained show that even relatively simple methods, like application a protective layer or increasing the surface reflectance, can retard to some extent concrete degradation during a fire.
International Journal of Solids and Structures, 2011
The paper deals with modelling of hygro-thermal performance and thermo-chemical degradation of co... more The paper deals with modelling of hygro-thermal performance and thermo-chemical degradation of concrete exposed to high temperature. Several possible simplifications in modelling of heat and mass transport phenomena in heated concrete are considered and their effect on the results of numerical simulations is analyzed.
... 1 Department of Structural and Transportation Engineering, University of Padova, via F. Marzo... more ... 1 Department of Structural and Transportation Engineering, University of Padova, via F. Marzolo 9 ... reaction through an Arrhenius-type relationship, as usual for thermally activated chemical reactions: ... to a growth of the volume fraction of load-bearing hydrated cement, which itself ...
A new numerical model for the simulation of ASR in cement-based materials considering both the ef... more A new numerical model for the simulation of ASR in cement-based materials considering both the effect of temperature and moisture content is presented. A mechanistic approach, based on the mechanics of porous media, was used to obtain the governing equations by means of a hybrid mixture theory. The model equations, mass (water species and dry air), energy and momentum balances are written in terms of the chosen primary variables: gas pressure, capillary pressure, temperature and displacement vector, while the ASR evolution is described by the reaction extent being the internal variable. The model takes into account full coupling between hygral, thermal and chemical phenomena, as well as changes of concrete properties caused by chemical reaction, i.e. porosity, density, permeability. Phase changes and chemical processes, as well as the related heat and mass sources are considered. Material chemical and mechanical degradation is considered with the isotropic damage theory. The model equations are numerically solved using finite element method for discretization in space and finite differences for time integration. The model results are validated by comparison with some published experimental data concerning ASR expansion in constant and variable hygro-thermal conditions.
Lecture Notes in Computer Science, 2002
Solving fully-coupled non-linear hygro-thermo-mechanical problems relative to the behavior of con... more Solving fully-coupled non-linear hygro-thermo-mechanical problems relative to the behavior of concrete at high temperatures is nowadays a very interesting and challenging computational problem. These models require an extensive use of computational resources, such as main memory and computational time, due to the great number of variables and the numerical characteristics of the coefficients of the linear systems involved. In this
Proceedings of the Ninth International Conference on Computational Structures Technology, 2008
Journal of the Mechanics and Physics of Solids, 2010
The work input for unsaturated elastic porous media is investigated based on averaged conservatio... more The work input for unsaturated elastic porous media is investigated based on averaged conservation equations for phases, interfaces, and common curves. In this analysis, the interfaces between the air-water interfaces are allowed to move and the surface tension appears explicitly in the analysis. Expressions for the work of the solid alone and for the medium are obtained. Conditions under which the result obtained here for the medium reduces to a more traditional expression are indicated. In this analysis, a form of the solid phase stress tensor, recently derived within the framework of thermodynamically constrained averaging theory for phase and interface properties, is used.
Frontiers of Architecture and Civil Engineering in China, 2011
Many problems are linked with the long term behaviour of dams, both earth-dams and concrete dams.... more Many problems are linked with the long term behaviour of dams, both earth-dams and concrete dams. They range from hydraulic fracturing to alkali-silica reaction and to repair work in concrete dams, from seismic behaviour to secondary consolidation in earth-dams. A common framework for simulation of such systems is shown, based on the mechanics of multiphase porous media. The general model is particularized to specific situations and several examples are shown.
Fire Safety Journal, 2008
Fire loading of concrete tunnel linings is characterized by various physical, chemical, and mecha... more Fire loading of concrete tunnel linings is characterized by various physical, chemical, and mechanical processes, resulting in spalling of nearsurface concrete layers and degradation of strength and stiffness of the remaining tunnel lining. In this paper, the governing transport processes taking place in concrete at elevated temperatures are considered within a recently published fire-safety assessment tool [Savov K, Lackner R, Mang HA. Stability assessment of shallow tunnels subjected to fire load. Fire Safety J 2005; 40: 745-763] for underground structures. In contrast to consideration of heat transport only [Savov et al.], a coupled thermo-hydro-chemical analysis, simulating the heat and mass transport in concrete under fire loading, is performed, giving access to more realistic temperature distributions as well as gas-pressure distributions within the tunnel lining. These data serve as input for the structural safety assessment tool considering, in addition to the temperature dependence of mechanical properties, the effect of the gas pressure on the strength properties of the heated lining concrete. The combination of the two analysis tools (coupled analysis of governing transport processes and structural safety assessment) is illustrated by the fire-safety assessment of a cross-section of the Lainzer tunnel (Austria) characterized by low overburden (shallow tunnel).
Progress in Industrial Mathematics …, 2006
A mathematical and numerical model to predict the non-linear behaviour of concrete as multiphase ... more A mathematical and numerical model to predict the non-linear behaviour of concrete as multiphase porous material is proposed. The model can be usefully applied to several practical cases: evaluation of concrete performance in the high temperature range, e.g. during fire, to early stages of maturing of massive concrete structures, to shotcrete in tunnelling, and to durability. All the important phase changes of water and chemical reactions, i.e. adsorption-desorption, condensation-evaporation, and hydration-dehydration, as well as the related heat and mass sources or sinks are considered. Changes of the material properties caused by temperature and pressure changes, concrete damage or carbonation, fresh concrete hardening, as well as coupling between thermal, hygral and mechanical phenomena are taken into account. This model further allows to incorporate sorption hysteresis. Some relevant applications of the model will be shown in this work.
Computers and Geotechnics, 2004
Models for thermo-hydro-mechanical behaviour of saturated-unsaturated porous media are reviewed. ... more Models for thermo-hydro-mechanical behaviour of saturated-unsaturated porous media are reviewed. The necessary balance equations are derived using averaging theories. Constitutive equations are obtained using the Coleman-Noll procedure and thermodynamic equations for the model closure are introduced. A simplified form of the governing equations is then solved numerically and the numerical properties are discussed. An example dealing with behaviour of concrete structures during tunnel fires concludes the paper. The heat and mass transfer calculations in the tunnel needed as the input for the multiphase concrete model are also shown. The behaviour of concrete under such situations, where very high temperatures are reached, can be satisfactorily simulated only with an approach of the type presented here.
Computational Mechanics, 2006
A mathematical model of hygro-thermo-mechanical phenomena in heated concrete, treated as multipha... more A mathematical model of hygro-thermo-mechanical phenomena in heated concrete, treated as multiphase porous material is briefly presented. Some modifications necessary to analyse high-temperature performance of a concrete containing the PP-fibres have been introduced, experimentally validated and applied for analysis of performance of a concrete tunnel lining during a 10-MW fire and the ISO standard fire. Three methods for protecting concrete structures against excessive degradation in fire conditions have been numerically analysed by means of the computer model. The analysed protection methods are based either upon application on a structure surface of a reflective layer, or covering it with a protective layer made of a very porous concrete or an addition of the PP fibres to the concrete mix. Efficiency of these methods has been numerically analysed in thermal conditions corresponding to the ISO-834 standard fire. The results obtained show that even relatively simple methods, like application a protective layer or increasing the surface reflectance, can retard to some extent concrete degradation during a fire.