References of "Franssen, Jean-Marc"
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See detailA performance indicator for structures under natural fire
Gernay, Thomas ULg; Franssen, Jean-Marc ULg

in Engineering Structures (2015), 100

Fires in buildings are characterized by a heating phase followed by a cooling phase, yet the effects of the latter on structures are not well covered in the current approaches to structural fire ... [more ▼]

Fires in buildings are characterized by a heating phase followed by a cooling phase, yet the effects of the latter on structures are not well covered in the current approaches to structural fire engineering. Indeed the actual requirement of non-occurrence of structural failure at peak temperature does not guarantee against a delayed failure during or after the cooling phase of a fire, which puts at risk the fire brigades and people proceeding to a building inspection after a fire. Therefore there is an urgent need to better comprehend and characterize the materials and structures behavior under decreasing temperatures. Sensitivity to delayed failure of a structural component depends on its typology and constituting materials. In particular, two structural components with the same Fire Resistance rating (R) under standardized fire may exhibit very distinct behavior under natural fire, one of them being more prone to delayed failure than the other. With the aim of quantifying this effect, a new indicator is proposed that characterizes the performance of structures under natural fire conditions. The paper presents the methodology to derive this new indicator as well as results for different typologies of structural components. Parametric analyses highlight the prime influence of constitutive material and thermal inertia of the element on the post-peak behavior. Used in conjunction with the Fire Resistance rating, it is shown how the new indicator carries additional and significant information for classifying structural systems in terms of their fire performance and propensity to delayed failure. [less ▲]

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See detailSAFIR: Capabilities and examples of applications
Gernay, Thomas ULg; Scifo, Anthony ULg; Franssen, Jean-Marc ULg

Report (2015)

This document presents the capabilities of the software SAFIR, as well as examples of applications. SAFIR is a computer program that models the behavior of building structures subjected to fire. The ... [more ▼]

This document presents the capabilities of the software SAFIR, as well as examples of applications. SAFIR is a computer program that models the behavior of building structures subjected to fire. The structure can be made of a 3D skeleton of linear elements such as beams and columns, in conjunction with planar elements such as slabs and walls. Volumetric elements can be used for analysis of details in the structure such as connections. Different materials such as steel, concrete, timber, aluminum, gypsum or thermally insulating products can be used separately or in combination in the model. [less ▲]

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See detailCharacteristics and implementation of Hybrid Fire Testing (HFT)
Sauca, Ana ULg; Gernay, Thomas ULg; Robert, Fabienne et al

Conference (2015, June 18)

This presentation is dedicated to real time hybrid testing of building members subjected to the action of fire. It will be shown why, whereas pseudo-dynamic testing is possible in other fields, real time ... [more ▼]

This presentation is dedicated to real time hybrid testing of building members subjected to the action of fire. It will be shown why, whereas pseudo-dynamic testing is possible in other fields, real time hybrid testing is the only possible option for the evaluation of fire performance (except, perhaps, for pure metallic unprotected structures). For some structures subjected to fire, the load bearing mechanism in the physical component is completely modified during the test and this modification can take place within a very short period of time. Because of that, the computational demand can be very challenging if the simulated element is simulated in a fully nonlinear computer model, especially if the thermal problem (temperature distribution in the structure) and the mechanical problem have both to be solved within each time step. In order to avoid these difficulties, a possible solution may be to calculate the stiffness matrix that dictates the reaction of the simulated element on the tested element before the test. This matrix can be constant or vary as a function of the displacements measured at the interface during the test. This procedure is very robust but it also has some shortcomings and limitations. The main topic of this paper is the discussion of the advantages and limitations of this procedure applied to hybrid fire testing. A series of three tests which is now under preparation to be performed in the furnace PROMETHEE of CERIB, in France, will also be described in this respect. Preliminary results will be presented if some or all of the tests have been performed at the date of the conference. [less ▲]

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See detailResearch Self-Evaluation Report of the Department ArGEnCo
Collin, Frédéric ULg; Dewals, Benjamin ULg; Elsen, Catherine ULg et al

Report (2015)

Evaluation is nowadays a general trend in the European Universities. At the University of Liège, the evaluation process is threefold: fist there is the evaluation of the bachelor and master degrees, then ... [more ▼]

Evaluation is nowadays a general trend in the European Universities. At the University of Liège, the evaluation process is threefold: fist there is the evaluation of the bachelor and master degrees, then the second evaluation concerns the internal administrations and finally Research activities are being evaluated. This quality policy at the different levels of the Institution is organized by the Vice-Rector for Quality, Pr. Freddy Coignoul and the SMAQ service (Service de Management et d’Accompagnement à la Qualité), which aims to promote, coordinate and disseminate within the University of Liège a culture of the Quality, founded on the values of the Institution. The Research assessment is a procedure undertaken by the University in order to promote the quality of the research in the Departments or research centres. Within the Faculty of Applied Sciences, the evaluation of the Bachelor and Master degrees in Engineering was carried out in 2013 by the AEQES (Agence pour l’Evaluation de la Qualité de l’Enseignement) and CTI (Commission des Titres d’Ingénieur - France). The present report is dedicated to the evaluation of research led in the Education and Research Department (DER) ArGEnCo. The present evaluation report proposes a global presentation of all our research activities. At the Department level, one of the elected members of the Executive Bureau is in charge of the Research, covering both evaluation and quality policy. In October 2013, the Executive bureau appointed a research steering committee, whose fist task was to coordinate the present evaluation report, following the guidelines of the SMAQ service. The draft of such a document arises from the work of the steering committee but also from the contributions of all Department members, who were asked to contribute to the report or to complete databases. The progress of this evaluation report was presented by the Steering committee to the Department Council and during the General Assembly of the Department. Moreover, two Focus groups were organized by the SMAQ service, in order to get the feedback of technician and administrative members on one hand and scientific members on the other hand, on the general organization of the research in the ArGEnCo Department. The reports of these two Focus groups (Appendix 4 in French) underpinned our thinking about our research management. This report is therefore the fist evaluation of the research led in the Department, the present effort should be pursued, and deepened, within the coming years. Some of the databases necessary for the evaluation have been developed in the frame of this procedure. This has resulted in a huge amount of work for every Department members to collect all the data. New procedures in the management of the Department will help establishing the next research evaluation reports systematically, in particular for the collection of the complete dataset. Following the guidelines of the SMAQ service, this evaluation report is divided into two main parts: the fist one focuses on a self-evaluation report of the research activities and the second part presents the Action Plan of the Department for the next five years to come. The self-evaluation report is composed of four Sections: Section one presents the Research organization and topics of the Department, Section two focuses on the Research activities, Section three gives an overview of the mobility (in and out), the attractiveness and the scientific recognition of the Department and finally Section four is dedicated to the resources available in ArGEnCo Department. Each Section ends up with a SWOT analysis. The Action Plan proposed by the Steering Committee results from the analysis of the self-evaluation report, insofar as it synthesizes and prioritizes the actions of the Department for the next fie years. These priorities are formulated as proposals following a contractual approach between research entities and Institution authorities, to whom the report will be presented. [less ▲]

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See detailA plastic-damage model for concrete in fire: Applications in structural fire engineering
Gernay, Thomas ULg; Franssen, Jean-Marc ULg

in Fire Safety Journal (2015), 71

The research aims at developing a new multiaxial constitutive model for concrete in the fire situation. In addition to validity at the material level, a crucial feature of a constitutive model is the ... [more ▼]

The research aims at developing a new multiaxial constitutive model for concrete in the fire situation. In addition to validity at the material level, a crucial feature of a constitutive model is the applicability at the structural level; yet for concrete in fire there remains a serious lack of models combining reliability and robustness. The theoretical aspects and validation of the new model, which rely on a plastic-damage formulation, have been the subject of a former publication; they are briefly summarized here. This paper explores the capabilities of the concrete model for being used in a performance-based structural fire engineering framework. Several examples of numerical simulations by non-linear finite element method are discussed, with emphasis on practical applications that are demanding for the material model. In particular, it is shown that the simulations using the new concrete model succeed in capturing, at ambient temperature, the crack pattern in a plain concrete specimen and the influence of the loading path on reinforced concrete (RC) slabs. At high temperature, the presented applications include a RC slab subjected to furnace fire and a large-scale composite steel–concrete structure subjected to natural fire. In the numerical analyses, no parameter calibration was required on the particular concrete type, except for the uniaxial strengths and tensile crack energy which are to be defined case-by-case. The results illustrate the reliability and numerical robustness of the model. Also, they suggest that satisfactory prediction of structural behavior in fire can be obtained when no additional data is available on the specific properties of the particular concrete mix that is used in the project, as is often the case in practice, by using standard values of parameters. [less ▲]

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See detailSimulation of 5 fire tests on reinforced concrete columns using SAFIR
Gernay, Thomas ULg; Franssen, Jean-Marc ULg

Report (2015)

This report presents the results of numerical simulations on five tests conducted on reinforced concrete columns in fire. The data for the studied RC columns have been provided by the CERIB in the ... [more ▼]

This report presents the results of numerical simulations on five tests conducted on reinforced concrete columns in fire. The data for the studied RC columns have been provided by the CERIB in the document “CEN-TC250-SC2-WG1-TG5_N0043_Annex_C_examples_Jesper_Jensen”. This study is part of the research project CEN-TC250-SC2-WG1-TG5 on the revision of EN1992-1-2, which focuses on the columns. 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 detailLoadbearing capacity criteria in fire resistance testing
Dumont, Fabien ULg; Wellens, Eric ULg; Franssen, Jean-Marc ULg

Report (2015)

Experimental testing may be used to demonstrate the fire resistance of building construction elements. In order to allow comparing the results of tests made in different laboratories on various types of ... [more ▼]

Experimental testing may be used to demonstrate the fire resistance of building construction elements. In order to allow comparing the results of tests made in different laboratories on various types of elements, the tests have to be performed under well-defined standardised conditions. Such standards define the heating and loading conditions, but also the performance criteria that have to be applied to measure the fire resistance duration. In Europe, the procedure that leads to the classification of building construction elements with regards to fire resistance involves a two level process. In the first stage, one or several tests are performed by a laboratory that must have accreditation according to ISO 17025, and one test report is issued for each test. Thereafter, a competent body will compile the necessary test reports and issue a classification report, the results of which can be used by the different stakeholders of the construction process, e.g. by authorities having jurisdiction. For the loadbearing performance, it appears that different logical combinations of the criteria are considered in the test standard and in the classification standard, leading to a inextricable situation. This situation has to be fixed in order to lead to a complete credible and applicable system. In order to provide scientific evidence about the consequences of adopting one or the other of both loadbearing definitions, the results of 46 tests performed in the fire resistance lab of the University of Liege in the recent years are analysed in this paper. [less ▲]

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See detailNumerical analysis of hydrocarbon pool fire tests
Tondini, Nicola; Hanus, François; Nadjai, Ali et al

in Proceedings of the XXV Giornate Italiane della Costruzione in Acciaio (2015)

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See detailNumerical analysis of hydrocarbon pool fire tests
Tondini, Nicola; Hanus, François; Nadjai, Ali et al

in Proceeding of the 1st International Conference on Structural Safety under Fire & Blast (2015)

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See detailStabilité des Constructions
Denoël, Vincent ULg; Franssen, Jean-Marc ULg

Learning material (2015)

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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 CERIB 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 CERIB 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 Fire Safety Science 11 (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 detailFIRE TESTING OF HIGH-STRENGTH STEEL CIRCULAR COLUMNS
Tondini, Nicola; Van Long, Hoang; Demonceau, Jean-François ULg et al

Conference (2013, September 30)

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 load. The evolution of temperature and defor-mation patterns were measured by means of a comprehensive instrumentation made of ther-mocouples 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 EN1993-1-2 associated with two different sets of reduction factors: i) those provided by EN1993-1-2 valid up to S460 steel grades; and ii) those proposed in the literature and based on tests on HSS. [less ▲]

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