References of "Franssen, Jean-Marc"
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See detailExperimental assement of the effect of the real flame emissivity for steel elements engulfed into fire
Tondini, Nicola; Vassart, Olivier; Franssen, Jean-Marc ULg

in xxx (in press)

This paper presents the results of an experimental campaign performed to assess the effect of the flame emissivity for steel members engulfed into fire. In detail, two sizes of circular steel tubes were ... [more ▼]

This paper presents the results of an experimental campaign performed to assess the effect of the flame emissivity for steel members engulfed into fire. In detail, two sizes of circular steel tubes were engulfed into pool fires of two different diameters. Two fuels were used and for both fuels tests without column (used as comparison with existing localised fire models) and with column were performed. The temperature of the column and of the flames were measured at different heights. The width of the flame was also measured and used to calculate the emissivity of the flame the value of which was employed in numerical simulations in order to predict the evolution of the temperature of the steel column. Comparison with numerical analyses where the recommended values of the Eurocode were used is also shown. [less ▲]

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See detailRevision of the tabulated methods of EN1992-1-2 for concrete columns in fire - Part 2
Gernay, Thomas ULg; Franssen, Jean-Marc ULg

Report (2014)

This report presents the results of numerical simulations conducted on reinforced concrete columns in fire for comparison of the computed fire resistance with the fire resistance obtained by the tabulated ... [more ▼]

This report presents the results of numerical simulations conducted on reinforced concrete columns in fire for comparison of the computed fire resistance with the fire resistance obtained by the tabulated methods of EN1992-1-2. The data for the studied RC columns have been provided by the CTICM in the document “CENTC250-SC2-WG1-TG5_N0038_Column_Calculation”. This study is part of the research project CEN-TC250-SC2-WG1-TG5. The objective is to assess the validity of and possibly to revise the tabulated methods of EN1992-1-2. The numerical software that is used for the simulations is the non-linear finite element software SAFIR, version 2013a0. [less ▲]

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See detailRevision of the tabulated methods of EN1992-1-2 for concrete columns in fire - Part 1
Gernay, Thomas ULg; Franssen, Jean-Marc ULg

Report (2014)

This report presents the results of numerical simulations conducted on reinforced concrete columns in fire for comparison of the computed fire resistance with the fire resistance obtained by the tabulated ... [more ▼]

This report presents the results of numerical simulations conducted on reinforced concrete columns in fire for comparison of the computed fire resistance with the fire resistance obtained by the tabulated methods of EN1992-1-2. The data for the studied RC columns have been provided by the CTICM in the document “CENTC250-SC2-WG1-TG5_N0037_Annex_C_studies_Jesper_Jensen”. This study is part of the research project CEN-TC250-SC2-WG1-TG5. The objective is to assess the validity of and possibly to revise the tabulated methods of EN1992-1-2. The numerical software that is used for the simulations is the non-linear finite element software SAFIR, version 2013a0. [less ▲]

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See detailExperimental tests and numerical modelling on eight slender steel columns under increasing temperatures
Franssen, Jean-Marc ULg; Zhao, Bin; Gernay, Thomas ULg

in Li, G.Q.; Jiang, S.C.; Chen, Suwen (Eds.) et al Progress on Safety of Structures in Fire (2014, June 11)

In order to fill the lack of knowledge about slender elements behavior at elevated temperatures,, a European research project called FIDESC4 has been funded by the RFCS. This project involves experimental ... [more ▼]

In order to fill the lack of knowledge about slender elements behavior at elevated temperatures,, a European research project called FIDESC4 has been funded by the RFCS. This project involves experimental testing, parametric numerical analyses and development of simple design rules. The present paper reports the characteristics and the results of the FIDESC4 experimental test campaign performed at the University of Liege on slender steel columns at elevated temperatures. A total of eight columns have been tested, all of them with I shape section. Six columns were made of welded sections (some prismatic and some tapered members) and two columns were with hot rolled sections. The nominal length of the columns was 3 meters with the whole length being heated. The strength of the material (webs and flanges) was measured on sample before the tests. The order of magnitude of the initial geometrical imperfections was recorded. The columns were not restrained against longitudinal thermal elongation. The supports at the ends were cylindrical thus inducing a restrain against rotation in one plane while allowing rotation in the other plane. The allowed direction of rotation was chosen in each test to induce buckling around the strong or the weak axis. The load was applied at ambient temperature and maintained for a period of 15 minutes after which the temperature was increased under constant load. The load was applied concentrically on some tests and with an eccentricity in other tests. The load eccentricity was either applied at both ends, leading to constant bending moment distribution along the length, or at one end only, leading to a triangular bending moment distribution. Heating was applied by electrical resistances enclosed in ceramic pads. The columns and the ceramic pads were wrapped in ceramic wool insulating material. This technique was preferred to gas heating in a standard test furnace because it allows applying a slower and better controlled heating rate and thus obtaining a more uniform temperature distribution in the member. It is also easier to measured lateral displacements of the column. Preliminary blank tests were performed on unloaded specimen in order to determine the heating range to be used later on the loaded columns. The paper will also report on a modification of the heating technique that was applied and improved significantly the uniformity in the temperature distribution. Numerical simulations were performed before the tests using shell elements of the software SAFIR and assumed values of the material properties in order to predict the failure modes. It was essentially crucial to determine whether lateral supports at intermediate levels should be provided in order to ensure failure in the desired direction. Experience showed that the failure modes developed as predicted by the numerical simulations. Besides a thorough description of the experiments, the paper will also present the obtained results in terms of failure mode, ultimate temperature and evolution of longitudinal and transverse displacement. Some information will also be given about the level of detail that has to be used in the numerical model in order to get accurate results at a reasonable price. [less ▲]

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See detailEffective stress method to be used in beam finite elements to take local instabilities into account
Franssen, Jean-Marc ULg; Cowez, Baptiste; Gernay, Thomas ULg

in Proceedings of the 11th IAFSS Symposium (2014, February)

In the fire situation, Bernoulli beam finite elements are the workhorse used in numerical calculation model for simulating the behaviour of the structure. Such finite elements treat all sections as class ... [more ▼]

In the fire situation, Bernoulli beam finite elements are the workhorse used in numerical calculation model for simulating the behaviour of the structure. Such finite elements treat all sections as class 1 (stocky) sections whatever the slenderness of the plates that make the section, allowing the development of a full plastic stress distribution in the section which leads to complete plastic redistribution along the members in the structure. This type of element is thus not adapted for modeling structures that contain slender sections of class 2, 3 or 4. This document presents a new approach to take into account local instabilities in slender sections using beam finite elements. The new approach is based on an effective constitutive law of steel. The effective law is not symmetrical with respect to tension and compression because, in tension, the stress-strain relationship is not modified whereas, in compression, the stress-strain relationship is modified. [less ▲]

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See detailAre Simple Calculation Models always on the Safe Side?
Franssen, Jean-Marc ULg

in Schaumann, Peter (Ed.) Festschrift Peter Schaumann (2014)

This paper examines the question whether simple calculation models are always on the safe side compared to advanced calculation models. This question is examined for the shadow effect, for the contact ... [more ▼]

This paper examines the question whether simple calculation models are always on the safe side compared to advanced calculation models. This question is examined for the shadow effect, for the contact between steel and concrete in composite steel-concrete floors, for the buckling curves of steel sections and, finally, for the factors κ1 and κ2 applied to the bending resistance of steel beams. [less ▲]

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See detailA multiaxial constitutive model for concrete in the fire situation: Theoretical formulation.
Gernay, Thomas ULg; Millard, Alain; Franssen, Jean-Marc ULg

in International Journal of Solids and Structures (2013), 50(22-23), 3659-3673

This paper aims to develop a multiaxial concrete model for implementation in finite element softwares dedicated to the analysis of structures in fire. The need for proper concrete model remains a ... [more ▼]

This paper aims to develop a multiaxial concrete model for implementation in finite element softwares dedicated to the analysis of structures in fire. The need for proper concrete model remains a challenging task in structural fire engineering because of the complexity of the concrete mechanical behavior characterization and the severe requirements for the material models raised by the development of performance-based design. A fully threedimensional model is developed based on the combination of elastoplasticity and damage theories. The state of damage in concrete, assumed isotropic, is modeled by means of a fourth order damage tensor to capture the unilateral effect. The concrete model comprises a limited number of parameters that can be identified by three simple tests at ambient temperature. At high temperatures, a generic transient creep model is included to take into account explicitly the effect of transient creep strain. The numerical implementation of the concrete model in a finite element software is presented and a series of numerical simulations are conducted for validation. The concrete behavior is accurately captured in a large range of temperature and stress states. A limitation appears when modeling the concrete post-peak behavior in highly confined stress states, due to the coupling assumption between damage and plasticity, but the considered levels of triaxial confinement are unusual stress states in structural concrete. [less ▲]

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See detailResistencia al fuego de armaduras de acero inoxidable
Franssen, Jean-Marc ULg; Gernay, Thomas ULg

in Bastidas, David M; Medina Sanchez, Eduardo (Eds.) Armaduras de Acero Inoxidable (2013)

Un incendio constituye un riesgo por dos razones, la toxicidad del aire y las altas temperaturas. Dependiendo de si se produce al aire libre o en un recinto cerrado la magnitud del peligro varía ... [more ▼]

Un incendio constituye un riesgo por dos razones, la toxicidad del aire y las altas temperaturas. Dependiendo de si se produce al aire libre o en un recinto cerrado la magnitud del peligro varía notablemente. En el exterior, es poco probable superar los 700ºC, sin embargo, en el interior la temperatura puede llegar a ser mucho más elevada. Infraestructuras críticas son los túneles, además de por ser recintos cerrados, por la naturaleza de los materiales inflamables que albergan. El diseño y la resistencia de los materiales son aspectos claves para garantizar un tiempo suficiente hasta el colapso. Los efectos en las estructuras de hormigón armado empiezan en el propio comportamiento de los materiales. El hormigón pierde menos capacidad a altas temperaturas que el acero, por lo tanto, utilizar aceros con mejores propiedades a altas temperaturas como los inoxidables aumentan las prestaciones del conjunto de la estructura. En este capítulo se describen las características térmicas del acero inoxidable y cómo varían sus características mecánicas en función de la temperatura. Por medio de simulaciones informáticas (software SAFIR de la Universidad de Lieja) se ha realizado un análisis térmico de armaduras de acero inoxidable de diferentes tipos y al carbono, embebidas en hormigón con distintos recubrimientos, en sección de columna y de viga. Finalmente, se ha realizado un análisis estructural de dichos elementos sometidos a diferentes cargas en puntos temporales distintos en condiciones de fuego. [less ▲]

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See detailNumerical simulations in support of fire resistance tests
Franssen, Jean-Marc ULg

Conference given outside the academic context (2013)

This paper presesnts how non linear numerical simulations can be used as a tool to support experimental tests made to determine the fire resistance of building structures. Numerical simulations have been ... [more ▼]

This paper presesnts how non linear numerical simulations can be used as a tool to support experimental tests made to determine the fire resistance of building structures. Numerical simulations have been made to calculate precisely the flexibility of the loading frame, to verify that no undesirable failure mode can develop in a test to be performed, to choose the load to be applied in order to obtain a desired failure temperature and to estimate the influence of observed non uniform temperature distribution. [less ▲]

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See detailRecherches sur le comportement au feu des structures en bois menées à l’Université de Liège
Franssen, Jean-Marc ULg

Conference given outside the academic context (2013)

This Powerpoint presents the main experimental research works performed in the laboratory of the University of Liege on the fire resistance of timber structures. The presented topics are: timber fire ... [more ▼]

This Powerpoint presents the main experimental research works performed in the laboratory of the University of Liege on the fire resistance of timber structures. The presented topics are: timber fire resistant doors, charing rates on tropical hardwood species, fire resistance of a massive timber wall, fire resistance of timber stairway with 2 different species and 3 different stair thicknesses, fire resistance of a massive timber slab, fire resistance of 4 diffrent joints between a timber floor and a timber exterior wall and fire resistance of a box girder timber floor. [less ▲]

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See detailA multiaxial constitutive model for concrete in the fire situation
Gernay, Thomas ULg; Franssen, Jean-Marc ULg

in Proceedings of the 13th Fire and Materials Conference (2013, January 28)

Performance-based design in fire engineering leads to increasing demand for advanced temperature-dependent material models for the load bearing materials used in building structures. These models must be ... [more ▼]

Performance-based design in fire engineering leads to increasing demand for advanced temperature-dependent material models for the load bearing materials used in building structures. These models must be valid in natural fire situations including cooling down phase and must be sufficiently robust for complex numerical calculations such as, for example, the analysis of tensile membrane action in composite slabs. 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 material and because of the necessity to ensure the numerical robustness of the models. This paper presents a new multiaxial concrete model based on a plastic-damage formulation and developed to meet the specific requirements of structural fire engineers and researchers. The model, which incorporates an explicit term for transient creep strain and encompasses a limited number of material parameters, has been implemented in a finite element software dedicated to the nonlinear analysis of structures in fire. The paper presents a series of numerical simulations conducted to highlight the model ability to capture the main phenomena that develop in concrete under fire (permanent strains, degradation of the elastic properties, unilateral effect) as well as its ability to be used for the fire analysis of large-scale structural elements. As an example, the new concrete model is used in the numerical analysis of a full scale fire test on a composite steel-concrete slab and it is shown that the computed and measured results agree. [less ▲]

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See detailNumerical analysis of partially fire protected composite slabs
Zaharia, Raul; Vulcu, Christian; Vassart, Olivier et al

in Steel and Composite Structures (2013), 14(1), 21-39

The paper presents a numerical investigation, done with the computer program SAFIR, in order to obtain simpler finite element models for representing the behaviour of the partially protected composite ... [more ▼]

The paper presents a numerical investigation, done with the computer program SAFIR, in order to obtain simpler finite element models for representing the behaviour of the partially protected composite steel concrete slabs in fire situation, considering the membrane action. Appropriate understanding and modelling of the particular behaviour of composite slabs allows a safe approach, but also substantial savings on the thermal insulation that has to be applied on the underlying steel structure. The influence of some critical parameters on the behaviour and fire resistance of composite slabs such as the amount of reinforcing steel, the thickness of the slab and the edge conditions is also highlighted. The numerical models are calibrated using the results of three full scale fire tests on composite slabs that have been performed in recent years. [less ▲]

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See detailExperimental investigation on ferritic stainless steel columns in fire
Tondini, Nicola; Rossi, Barbara; Franssen, Jean-Marc ULg

in Fire Safety Journal (2013)

This paper presents the performance of EN 1.4003 ferritic stainless steel hollow section columns when exposed to fire loading. Experimental analysis of the behaviour of ferritic stainless steel structural ... [more ▼]

This paper presents the performance of EN 1.4003 ferritic stainless steel hollow section columns when exposed to fire loading. Experimental analysis of the behaviour of ferritic stainless steel structural members in fire represents a novelty. In detail, three column tests were carried out in the framework of the RFCS project named Structural Applications of Ferritic Stainless Steels (SAFSS, RFSR-CT-2010-00026). Tubular thin-walled members were considered in this study because structural applications of ferritic stainless steels generally incorporate such profiles. Three columns were tested: two square hollow sections (SHS) and a rectangular hollow section (RHS) of different length. Fire loading was applied under a constant concentrically compressive load. Identical column tests at room temperature are also reported. [less ▲]

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See detailExperimental and numerical investigation of high-strength steel circular columns subjected to fire
Tondini, Nicola; Hoang, Van Long ULg; Demonceau, Jean-François ULg et al

in Journal of Constructional Steel Research (2013), 80

This paper presents an experimental–numerical study on the behaviour of High Strength Steel (HSS) columns at elevated temperature, both on Circular Hollow Sections (CHS) and on a Concrete Filled Tube (CFT ... [more ▼]

This paper presents an experimental–numerical study on the behaviour of High Strength Steel (HSS) columns at elevated temperature, both on Circular Hollow Sections (CHS) and on a Concrete Filled Tube (CFT). The measured yield strength of the circular sections was in the order of 820 MPa. In detail, three HSS CHS and a HSS CFT were tested under the standard ISO fire with constant eccentric compression applied load. The evolution of temperature and deformation patterns were measured by means of a comprehensive instrumentation made of thermocouples and displacement transducers. Numerical analyses were performed and compared with experimental data by employing stress–strain relationships of carbon steel at elevated temperatures provided by the Eurocodes associated to two different sets of reduction factors: i) those provided by the Eurocodes valid up to S460 steel grades; and ii) those proposed in the literature and based on tests on HSS. [less ▲]

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See detailStructural fire design and optimisation of a building
Tonicello, Eric; Vassart, Olivier; Zanon, Riccardo et al

in Structural Engineering International (2012), 22(4), 541-544

The "Maison de la Paix" building will be built for the Graduate Institute of International and Development Studies in Geneva (IHEID). At its heart will be a library, numerous auditoriums and seminar rooms ... [more ▼]

The "Maison de la Paix" building will be built for the Graduate Institute of International and Development Studies in Geneva (IHEID). At its heart will be a library, numerous auditoriums and seminar rooms, and a cafeteria. A complete fire analysis has been performed to optimise the steel structures. [less ▲]

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See detailSimplified design method for slim floor beams exposed to fire
Cajot, Louis-Guy; Gallois, Louis; Debruyckere, Rik et al

in Proceedings of NSCC2012 (2012, September 07)

One of the most important advantages of using the slim or integrated floor beams (SFB and IFB supporting full concrete slab, precast units or steel deck composite slab) is a significant fire resistance ... [more ▼]

One of the most important advantages of using the slim or integrated floor beams (SFB and IFB supporting full concrete slab, precast units or steel deck composite slab) is a significant fire resistance. However, despite of its common use in construction, no specific simplified calculation methods for the fire resistance of IFB and SFB exist in the Eurocode. This study, based on existing calculation rules of Eurocode 4, a parametrical study using soft-ware SAFIR and fire tests results, define a set of formulas to determine the thermal field and to deduce the mechanical resistance from classical plastic design. [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 detailConsideration of local instabilities in beam finite elements by means of effective constitutive laws
Franssen, Jean-Marc ULg; Cowez, Baptiste ULg

in Fontana, A; Frangi, A; Knobloch, M (Eds.) Proceedings of the 7th International Conference on Structures in Fire (2012, June 06)

In the fire situation, Bernoulli beam finite elements are the workhorse used in the general calculation model for simulating the behaviour of the structure. Such finite elements treat all sections as ... [more ▼]

In the fire situation, Bernoulli beam finite elements are the workhorse used in the general calculation model for simulating the behaviour of the structure. Such finite elements treat all sections as class 1 (stocky) sections whatever the slenderness of the plates that make the section, allowing the development of a full plastic stress distribution in the section which leads to complete plastic redistribution in the structure. This type of element is thus not adapted for modelling structures that contain slender sections of class 2, 3 or 4. This document presents a new approach to take into account local instabilities using beam finite elements. The new approach is based on an effective constitutive law of steel. The effective law is not symmetrical with respect to tension and compression because, in tension, the stress-strain relationship is not modified whereas, in compression, the stress-strain relationship is modified. [less ▲]

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See detailFire analysis of a new steel bridge
Tonicello, Eric; Desanghere, Sylvain; Vassart, Olivier et al

in Fontana, Mario; Frangi, Andrea; Knobloch, Markus (Eds.) Proceedings of the 7th International Conference on Structures in Fire (2012, June 06)

The new steel bridge “Hans-Wilsdorf” in Geneva is an exceptional steel structure that will drive general traffic through a main transportation axis. As the investment cost of the project is important, a ... [more ▼]

The new steel bridge “Hans-Wilsdorf” in Geneva is an exceptional steel structure that will drive general traffic through a main transportation axis. As the investment cost of the project is important, a structural fire analysis has been performed to study the sensitivity of the structure to a high temperature exposure, such as a truck in fire on the deck. This analysis will allow deciding whether a severe fire could be an unacceptable economical risk for the bridge. [less ▲]

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