References of "Gernay, Thomas"
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See detailValidation of the Advanced Calculation Model SAFIR Through DIN EN 1991-1-2 Procedure
Zaharia, Raul; Gernay, Thomas ULg

in Proceedings of the 10th International Conference ASCCS 2012 (2012, July 03)

The validation of advanced calculation models for the fire design is an important issue for computer code developers, designers and authorities. One approach consists in the comparison with experimental ... [more ▼]

The validation of advanced calculation models for the fire design is an important issue for computer code developers, designers and authorities. One approach consists in the comparison with experimental results, which are not always available or are not always useful, due to the lack of details about the input data or the results, or uncertainties about the boundary conditions. This paper presents the validation of the special purpose computer program SAFIR (2005) for structural fire analysis, through DIN EN1991-1-2 procedure (2010), which represents an alternative to the validation through fire tests. [less ▲]

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See detailLarge-scale fire test of unprotected cellular beam acting in membrane action
Vassart, Olivier; Bailey, C.G.; Hawes, M. et al

in Proceedings of the Institution of Civil Engineers: Structures and Buildings (2012), 165(7), 327334

This paper describes a full scale fire test performed recently on a composite floor for analysing the possibility of tensile membrane action to develop when the unprotected steel beams in the central part ... [more ▼]

This paper describes a full scale fire test performed recently on a composite floor for analysing the possibility of tensile membrane action to develop when the unprotected steel beams in the central part of the floor are made of cellular beams. The natural fire was created by a wood crib fire load of 700 MJ/m² and the 9 x 15 m floor survived the fire that peaked at 1000°C and lasted for about 90 minutes. Blind predictions of the air temperature development by the software OZone and of the structural behaviour by the software SAFIR which proved quite satisfactory are also described. [less ▲]

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See detailA formulation of the Eurocode 2 concrete model at elevated temperature that includes an explicit term for transient creep
Gernay, Thomas ULg; Franssen, Jean-Marc ULg

in Fire Safety Journal (2012), 51

The first objective of this paper is to highlight the capabilities and limitations of concrete uniaxial constitutive models at elevated temperatures for thermo-mechanical behavior modeling, depending on ... [more ▼]

The first objective of this paper is to highlight the capabilities and limitations of concrete uniaxial constitutive models at elevated temperatures for thermo-mechanical behavior modeling, depending on the implicit or explicit consideration of transient creep strain in the model. The characteristics inherent to the two types of models are described and compared. It appears that one of the major limitations of implicit models concerns the unloading stiffness. Based on numerical analysis performed on loaded concrete columns subjected to natural fire, it is shown that the stress–temperature paths experienced by structural concrete are varied and complicated and that concrete material models cannot handle properly these complex situations of unsteady temperatures and stresses without explicit consideration of transient creep. The second objective of the paper is to propose a new formulation of the Eurocode 2 concrete material model that contains an explicit term for transient creep. The new model is implemented in the software SAFIR and validated against experimental data of the mechanical strain developed by concrete cylinders under different unsteady temperatures and loads. It is shown that the actual material behavior is better matched with the new explicit model than with the current implicit Eurocode 2 model. Finally, a comparison is given between experimental and computed results on a centrally loaded concrete column submitted to heating–cooling sequence. [less ▲]

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See detailA multiaxial concrete model for applications in structural fire engineering
Gernay, Thomas ULg; Millard, Alain

in Fontana, M.; Frangi, A.; Knobloch, M. (Eds.) Proceedings of the 7th International Conference on Structures in Fire (2012, June 07)

Temperature-dependent material models are required in numerical softwares dedicated to the nonlinear analysis of structures in fire. Although structural concrete is widely used in civil engineering ... [more ▼]

Temperature-dependent material models are required in numerical softwares dedicated to the nonlinear analysis of structures in fire. Although structural concrete is widely used in civil engineering, proper modelling of its thermo-mechanical behaviour remains a challenging issue for engineers mainly because of the complexity of the phenomena that result from the microcracking process in this composite material and because of the lack of numerical robustness of the models. This paper presents a new multiaxial concrete model developed for the analysis of concrete structures in fire. The multiaxial model is based on a plastic-damage formulation and incorporates an explicit term for transient creep strain. After implementation in a finite element software for structural fire engineering calculations, numerical simulations have been performed to highlight the ability of the model to capture some of the main phenomena that develop in concrete (permanent strains, degradation of the elastic properties, unilateral effect) as well as the ability to be used for the fire analysis of large-scale structural elements. [less ▲]

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See detailModeling the mechanical behavior of concrete in the fire situation
Gernay, Thomas ULg

Scientific conference (2012, April 26)

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See detailEffect of Transient Creep Strain Model on the Behavior of Concrete Columns Subjected to Heating and Cooling
Gernay, Thomas ULg

in Fire Technology (2012), 48(2), 313-329

In the numerical analysis of structures in fire, the material models that are used have important implications on the global behavior of the structure. In concrete, a particular phenomenon appears when ... [more ▼]

In the numerical analysis of structures in fire, the material models that are used have important implications on the global behavior of the structure. In concrete, a particular phenomenon appears when subjected to high temperatures: the transient creep strain. Models integrating explicitly a term for transient creep strain have been proposed in the literature but, in the current Eurocode 2 model, there is no explicit term for transient creep strain. This phenomenon is included in the Eurocode 2 model, but it is implicitly considered in the mechanical strain term. A series of experimental fire tests on axially restrained concrete columns subjected to heating and cooling has been recently performed at South China University of Technology and described by Wu et al. (Fire Technol 46:231–249). In the original paper, it was shown that using the implicit model of Eurocode 2, the behavior of the columns cannot be simulated properly, especially during the cooling phase. The objective of the present paper is to perform again the fire tests simulations using a new formulation of the Eurocode 2 model that contains an explicit term for transient creep. In the first part of the paper, the explicit formulation of the Eurocode 2 model is presented. In the second part, the fire tests are modeled with the software SAFIR using, on the one hand, the implicit Eurocode model and, on the other hand, the new explicit model. It is shown that the transient creep model has significant implications on the global behavior of structural concrete members, as the residual axial load sustained by the columns at the end of the fire can differ by up to 25% of the initial applied load depending on the transient creep strain model that is used for the calculation. The experimental behavior is better matched with the new explicit model than with the current Eurocode model. Particularly, the results given by the Eurocode model during the cooling phase are unconservative as the residual axial load is overestimated. Finally, it is explained why, on the basis of an example, in a performance-based approach, these results can have important implications on the global fire resistance of a structure. [less ▲]

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See detailLarge-Scale Fire Test of Unprotected Cellular Beam Acting in Membrane Action
Vassart, Olivier; Bailey, C. G.; Hawes, M. et al

in Journal of Structural Fire Engineering (2011), 2(4), 259-268

This paper describes a full scale fire test performed the 27th of February 2010 on a composite floor for analysing the possibility of tensile membrane action to develop when the unprotected steel beams in ... [more ▼]

This paper describes a full scale fire test performed the 27th of February 2010 on a composite floor for analysing the possibility of tensile membrane action to develop when the unprotected steel beams in the central part of the floor are made of cellular beams. The natural fire was created by a wood crib fire load of 700 MJ/m2 and the 9 × 15 m floor survived the fire that peaked at 1000°C and lasted for 90 minutes. Blind predictions of the air temperature development by the software OZone and of the structural behaviour by the software SAFIR which proved quite satisfactory are also described. [less ▲]

Detailed reference viewed: 76 (32 ULg)
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See detailNew features in SAFIR: Structural Fire Analysis of a Shell Roof Structure
Gernay, Thomas ULg; Franssen, Jean-Marc ULg

Scientific conference (2011, November 15)

The structural fire analysis of a roof structure made of two concrete shells has been performed with the software SAFIR.

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See detailNew features in SAFIR: Damage-Plastic Multiaxial Model for Concrete
Gernay, Thomas ULg; Franssen, Jean-Marc ULg

Scientific conference (2011, November 15)

The need for robust, reliable multiaxial constitutive relationships for concrete is a challenging issue in structural fire engineering. A new damage-plastic model has been developed to capture the ... [more ▼]

The need for robust, reliable multiaxial constitutive relationships for concrete is a challenging issue in structural fire engineering. A new damage-plastic model has been developed to capture the development of permanent strains and the degradation of elastic properties in concrete subjected to thermo-mechanical loading. This model has been implemented in the software SAFIR for using with SOLID finite elements (multiaxial model) and with SHELL finite elements (plane stress model). [less ▲]

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See detailNew features in SAFIR: Transient Creep in Eurocode Concrete Model
Gernay, Thomas ULg; Franssen, Jean-Marc ULg

Scientific conference (2011, November 15)

A new formulation of the Eurocode 2 concrete model at elevated temperature has been implemented in which the transient creep strain is treated by an explicit term in the strain decomposition. This new ... [more ▼]

A new formulation of the Eurocode 2 concrete model at elevated temperature has been implemented in which the transient creep strain is treated by an explicit term in the strain decomposition. This new model gives the same answer as the Eurocode model when the load and the temperature increase, but the new model is better than the Eurocode model at capturing the concrete behavior when the load or the temperature decrease owing to the explicit transient creep term. This new concrete model, called Explicit Transient Creep Eurocode model (ETC), has been implemented in the software SAFIR. [less ▲]

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See detailStructural Behavior of Concrete Columns under Natural Fires including Cooling Down Phase
Gernay, Thomas ULg; Dimia, M. S.

in Barros, Helena; Faria, Rui; Pina, Carlos (Eds.) et al Proceedings of The International Conference on Recent Advances in Nonlinear Models - Structural Concrete Applications (2011, November)

This study deals with the structural behavior of concrete columns subjected to natural fire, with special focus on the cooling down phase. As the reliability of the numerical simulations largely depends ... [more ▼]

This study deals with the structural behavior of concrete columns subjected to natural fire, with special focus on the cooling down phase. As the reliability of the numerical simulations largely depends on the validity of the constitutive models that are used, this issue is addressed in details in the first part of the paper. It is found that the current concrete model of Eurocode may not be adapted for representing the behavior of concrete during a cooling phase because the effects of transient creep are incorporated implicitly in the mechanical strain term. A formulation of the Eurocode concrete model that contains an explicit term for transient creep strain has been developed and, after implementation in the software SAFIR, it was used for the numerical simulations presented in this paper. In its second part, the study gives an insight into the possibility of collapse of reinforced concrete columns during and after the cooling phase of the natural fire. It is found that failure during the cooling phase of a fire is a possible event and, more dangerous, that a failure of the concrete columns is still possible when the fire has been completely extinguished. The main mechanisms that lead to this type of failure are found to be the delayed increase of temperature in the central zones of the element and the additional loss of concrete strength during the cooling phase of the fire. A parametric study shows that the most critical situations with respect to delayed failure arise for short fires and for columns with low slenderness or massive sections. The numerical analyses have been performed also with the concrete model of Eurocode and the results also show a risk of delayed collapse. Yet, the occurrence of collapse during or after the cooling phase is predicted more often with the explicit creep model than with the implicit model of Eurocode, which suggests that the way the transient creep effects are handled in the Eurocode model may lead to unsafe results when considering the cooling phase of a fire. [less ▲]

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See detailCollapse of concrete columns during and after the cooling phase of a fire
Dimia, Mohamed Salah; Guenfoud, Mohamed; Gernay, Thomas ULg et al

in Journal of Fire Protection Engineering (2011), 21(4), 245263

This paper presents a study performed on the collapse of reinforced concrete columns subjected to natural fire conditions during and after the cooling phase of the fire. The aim is, first, to highlight ... [more ▼]

This paper presents a study performed on the collapse of reinforced concrete columns subjected to natural fire conditions during and after the cooling phase of the fire. The aim is, first, to highlight the phenomenon of collapse of concrete columns during and after the cooling phase of a fire and then, to analyze the influence of some determinant parameters. The main mechanisms that lead to this type of failure are found to be the delayed increase of the temperature in the central zones of the element and the additional loss of concrete strength during the cooling phase of the fire. A parametric study is performed considering different fires and geometric properties of the column. This shows that the most critical situations with respect to delayed failure arise for short fires and for columns with low slenderness or massive sections. [less ▲]

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See detailSimplified Fire Design for Slim Floor Beams
Zaharia, Raul; Duma, Diana Maria ULg; Vassart, Olivier et al

in Dunai, Laszlo (Ed.) Proceedings of the 6th European Conference on Steel and Composite Structures (2011, September 02)

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See detailSAFIR Materials Manual - SILCON_ETC, CALCON_ETC
Gernay, Thomas ULg; Franssen, Jean-Marc ULg

Report (2011)

This document describes the material constitutive models SILCON_ETC and CALCON_ETC, which are uniaxial material models implemented in the software SAFIR (from version 2011.b.0). The material models SILCON ... [more ▼]

This document describes the material constitutive models SILCON_ETC and CALCON_ETC, which are uniaxial material models implemented in the software SAFIR (from version 2011.b.0). The material models SILCON_ETC and CALCON_ETC are based on the Explicit Transient Creep Eurocode constitutive model (ETC model) for concrete at elevated temperature, which has been developed at University of Liege by the authors of this document. [less ▲]

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See detailSimplified method for the temperature distribution in slim floor beams
Zaharia, Raul; Duma, Diana Maria ULg; Vassart, Olivier et al

in Wald, F.; Horova, K.; Jirku, J. (Eds.) Proceedings of International Conference Applications of Structural Fire Engineering (2011, April 29)

From extensive numerical thermal simulations made with SAFIR, simple design equations have been derived that allow calculating the temperature in slim floor sections subjected to an ISO 834 fire.

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See detailEconomic analysis of Stainless Steel- Reinforced Concrete members designed for a Fire Resistance of 2 hours
Gernay, Thomas ULg; Franssen, Jean-Marc ULg

Report (2011)

While Stainless steel is used primarily for its corrosion resistance, there is a growing interest in other properties, such as mechanical, high temperature resistance, aesthetics and others. The ... [more ▼]

While Stainless steel is used primarily for its corrosion resistance, there is a growing interest in other properties, such as mechanical, high temperature resistance, aesthetics and others. The properties at high temperatures (400 – 650°C ) of stainless steels are known and put to use in a number of applications such as steam turbines and equipment for the chemical industry. Some research on the fire resistance of stainless steels has been carried out for welded I beams and for concrete-filled tubes, with positive results. However, there are no published results on the behavior of concrete reinforced with stainless steel rebar. In a preliminary research program conducted by the University of Liege for ISSF, a preliminary assessment of the performance of stainless steel reinforced concrete has been carried out, using computer simulation methods. This preliminary study has shown that stainless steel reinforced concrete members can behave better than carbon steel reinforced concrete members in fire situation. However, an economic analysis is still needed to determine whether stainless steel reinforcement can be interesting for practical applications. This report is divided in two parts. The first part presents the assumptions and the results of the numerical simulations performed by University of Liege. The numerical simulations aim to design stainless and carbon steel -reinforced concrete members satisfying to a fire resistance of 2 hours (Standard fire conditions). The two structural members considered in this study are a reinforced concrete beam and a composite slab (with the so-called « membrane » behavior). The numerical simulations are performed with the SAFIR 20011.a.3 software developed in University of Liege. The second part presents the assumptions and the results of the economic analysis of the structural members designed in the first part. The stainless and carbon steel –reinforced solutions for a fire resistance of 2 hours are compared on an economic basis. [less ▲]

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See detailNonlinear numerical analysis of ship impact on lock gates
Gernay, Thomas ULg

in Van Schel, L (Ed.) PIANC Yearbook 2010 (2011)

This paper focuses on ship impact analysis on lock gate. First, the lock gate structure is determined by an elastic design and optimization process. Then, a nonlinear numerical analysis by finite elements ... [more ▼]

This paper focuses on ship impact analysis on lock gate. First, the lock gate structure is determined by an elastic design and optimization process. Then, a nonlinear numerical analysis by finite elements is conducted to study the response of the lock gate in case of ship impact. It is shown that the elastically optimized structure is not able to resist significant impacts, because of the buckling of its reinforcement elements; the gate is thus reinforced. Finally, several ship impact analyses are conducted on the reinforced gate and they highlight the influence of the stiffener dimensions and the impact zone on the structural behavior of the gate. The results of the numerical analyses underline the importance of the development of a global plastic mechanism with the purpose of dissipating a large amount of energy. [less ▲]

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See detailDevelopment of Multiaxial Constitutive Relationships for Concrete
Gernay, Thomas ULg

Scientific conference (2011, March 18)

Recent research in structural fire engineering has shown that concrete or composite building structures can develop unexpected modes of strength when subjected to fire. Under certain conditions, a ... [more ▼]

Recent research in structural fire engineering has shown that concrete or composite building structures can develop unexpected modes of strength when subjected to fire. Under certain conditions, a structure will present a robust behavior that can dramatically increase its fire resistance compared to the fire resistance calculated by a predictive approach. An example of such robust behavior is the membrane action that can be developed by a structural slab in fire. However, the numerical simulation of such behaviors requires the development of reliable and accurate multiaxial constitutive relationships for modelling the behavior of concrete. This presentation is based on the work performed by the author during a six month research stay at CEA Saclay, in the team of Alain Millard. The aim of the research stay was to develop a concrete multiaxial model that can be used for the numerical analysis by the finite elements method of concrete structures in fire. To be able to accurately simulate the structural behavior during every phases of a natural fire, the concrete model includes plasticity and damage phenomena. The main features and parameters of the model are presented and its implementation in the softwares SAFIR and CAST3M is briefly discussed. Then, a few applications are given and the presentation ends with a comment on the remaining issues and perspectives. [less ▲]

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See detailDéveloppement d'un modèle constitutif multiaxial de béton
Gernay, Thomas ULg; Millard, Alain; Franssen, Jean-Marc ULg

Scientific conference (2011, March 03)

Detailed reference viewed: 52 (24 ULg)