References of "Gernay, Thomas"
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See detailSteel hollow columns with an internal profile filled with self-compacting concrete under fire conditions
Chu, Thi Binh; Gernay, Thomas ULg; Dotreppe, Jean-Claude ULg et al

in Proceeding of the Romanian Academy. Series A, Mathematics, Physics, Technical Sciences, Information Science (in press)

A detailed experimental and numerical investigation has been performed on the behavior under fire conditions of concrete filled steel hollow section (CFSHS) columns. In this study the internal ... [more ▼]

A detailed experimental and numerical investigation has been performed on the behavior under fire conditions of concrete filled steel hollow section (CFSHS) columns. In this study the internal reinforcement consists of another profile (tube or H section) being embedded with the concrete, and filling is realized by self-compacting concrete (SCC). Ten columns filled with self-compacting concrete embedding another steel profile have been tested in the Fire Testing Laboratory of the University of Liege, Belgium. Numerical simulations on the thermal and structural behavior of these elements have been made using the non linear finite element software SAFIR developed at the University of Liege. There is a rather good agreement between numerical and experimental results, which can be slightly improved by using the ETC (Explicit Transient Creep) model incorporated in SAFIR. This shows that numerical analyses can predict well the behavior of CFSHS columns under fire conditions. The properties at high temperatures of self-compacting concrete are considered the same as those of ordinary concrete. [less ▲]

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See detailExperimental Tests and Numerical Modelling on Slender Steel Columns at High Temperatures
Franssen, Jean-Marc ULg; Zhao, Bin; Gernay, Thomas ULg

in Journal of Structural Fire Engineering (in press)

This paper is about a series of experimental fire tests on eight full scale steel columns made of slender I shaped class 4 sections. Six columns were made of welded sections (some prismatic and some ... [more ▼]

This paper is about a series of experimental fire tests on eight full scale steel columns made of slender I shaped class 4 sections. Six columns were made of welded sections (some prismatic and some tapered members) and two columns were made of hot rolled sections. The nominal length of the columns was 2.7 meters with the whole length being heated. The load was applied at ambient temperature after which the temperature was increased under constant load. The load was applied concentrically on some tests and with an eccentricity in other tests. Heating was applied by electrical resistances enclosed in ceramic pads. Numerical simulations were performed with the software SAFIR® using shell elements. The paper presents the results obtained in terms of failure mode and ultimate temperature, in the experimental tests and in the numerical simulations. [less ▲]

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See detailLoadbearing capacity criteria in fire resistance testing
Dumont, Fabien ULg; Wellens, Eric ULg; Gernay, Thomas ULg et al

in Materials and Structures (2016)

The European system for fire testing and classification of loadbearing building elements lacks consistency because the two standards that have to be applied prescribe different criteria for assessing the ... [more ▼]

The European system for fire testing and classification of loadbearing building elements lacks consistency because the two standards that have to be applied prescribe different criteria for assessing the loadbearing performance. This article analyzes the implications of the present conflict between the standard for testing and the standard for classification. The prescribed criteria for loadbearing performance are related to the exceedance of deflection and rate of deflection thresholds. A database of 46 fire resistance tests performed at the University of Liege is collected that contains the time at which these thresholds are reached in fire tests with different typologies of elements (walls, floors, columns and beams). Then, the loadbearing performance (and hence the fire resistance rating) can be derived according to the two standards. The evolutions of deflection and rate of deflection during the tests are also analyzed to gain a better understanding of the adequacy of the standards. The selection of one or the other standard affects the time at which “failure” is deemed to occur in fire tests. Statistically speaking, the difference in terms of failure time that results from using one or the other standard has a 25% probability to exceed 10%. In certain cases, this results in a difference in fire resistance rating; this was observed for 3 of the analyzed tests. The apparent contradiction in two codes in application has potential practical implications and therefore needs to be solved. The article suggests some guidelines for defining homogenized and consistent criteria. [less ▲]

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See detailFire Fragility Curves for Steel Buildings in a Community Context: A Methodology
Gernay, Thomas ULg; Elhami Khorasani, Negar; Garlock, Maria

in Engineering Structures (2016)

This paper proposes a novel methodology for developing fire fragility functions for an entire steel building - meaning that the function is not specific to a location within the building. The aim is to ... [more ▼]

This paper proposes a novel methodology for developing fire fragility functions for an entire steel building - meaning that the function is not specific to a location within the building. The aim is to characterize the probabilistic vulnerability of steel buildings to fire in the context of community resilience assessment. In developing the fragility functions, uncertainties in the fire model, the heat transfer model and the thermo-mechanical response are considered. In addition several fire scenarios at different locations in the building are studied. Monte Carlo Simulations and Latin Hypercube Sampling are used to generate the probability distributions of demand placed on the members and structural capacity relative to selected damage thresholds. By assessing demand and capacity in the temperature domain, the thermal and the structural problems can be treated separately to improve the efficiency of the probabilistic analysis. After the probability distributions are obtained for demand and capacity, the fragility functions can be obtained by convolution of the distributions. Finally, event tree analysis is used to combine the functions associated with fire scenarios in different building locations. The developed fire fragility functions yield the probability of exceedance of predefined damage states as a function of the fire load in the building. The methodology is illustrated on an example consisting in a prototype nine-story steel building based on the SAC project. [less ▲]

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See detailNew features in SAFIR® 2016
Franssen, Jean-Marc ULg; Gernay, Thomas ULg

Scientific conference (2015, November 05)

This presentation gives an overview of the new features implemented in the version 2016 of SAFIR, the finite element software dedicated to the analysis of buildings in fire.

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See detailEvaluating a city’s vulnerability to fire following earthquake
Gernay, Thomas ULg

Scientific conference (2015, October 23)

Recent extreme events such as major earthquakes have emphasized the need for disaster-resilient communities. In a resilience framework, the built environment is designed to respond adequately to low ... [more ▼]

Recent extreme events such as major earthquakes have emphasized the need for disaster-resilient communities. In a resilience framework, the built environment is designed to respond adequately to low probability-high consequence events. The latter include cascading multi-hazard events such as fires following an earthquake, which can cause major social and economic losses in a community as observed for instance in the 1989 Loma Prieta and 1994 Northridge events in the United States. This presentation provides a methodology to evaluate the response of buildings in a community subject to fire following earthquake. First, a model is developed to determine the probability of ignition in buildings of a community due to an earthquake. Second, fragility functions are developed for buildings subject to fire, to quantify the structural damage and the expected losses. In the future, the ignition model, combined with the fragility functions, can be implemented in a GIS based risk management platform to evaluate economical losses in a region from fire following an earthquake. [less ▲]

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See detailSensitivity of structures to fire decay phases: quantitative comparison of structural components made of different materials
Gernay, Thomas ULg

in Wald, F.; Burgess, I.; Jelcic Rukavina, M. (Eds.) et al Proceedings of the Int. Conf. ASFE in Dubrovnik, 15-16 October 2015 (2015, October 16)

This work presents an analysis of the behaviour of different structural members under natural fires, with the aim to characterize their sensitivity to the fire decay phase. Thermo-mechanical numerical ... [more ▼]

This work presents an analysis of the behaviour of different structural members under natural fires, with the aim to characterize their sensitivity to the fire decay phase. Thermo-mechanical numerical simulations based on the non-linear finite element method are conducted using the parametric fire model of Eurocode to represent the natural fires. Results show that, for all the studied members (column, beam) and materials (reinforced concrete, steel, timber), structural failure during or after the cooling phase of a fire is a possible event. The major factors that promote delayed structural failure are the thermal inertia and the constituting material of the member. An indicator is proposed to quantify the propensity to delayed failure for structural members under natural fire. This work enhances the understanding of the structural behaviour under natural fires and has implications for the safety of the fire brigades and people proceeding to a building inspection after a fire. [less ▲]

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See detailAnalysis of a concrete building exposed to natural fire
Sauca, Ana ULg; Gernay, Thomas ULg; Robert, Fabienne et al

in Wald, F.; Burgess, I.; Jelcic Rukavina, M. (Eds.) et al Proceedings of the Int. Conf. ASFE in Dubrovnik, 15-16 October 2015 (2015, October 16)

In this paper is presented the analysis of a concrete building exposed to OZone fire. The temperature development in the elements and the structural behaviour were calculated in SAFIR using beam elements ... [more ▼]

In this paper is presented the analysis of a concrete building exposed to OZone fire. The temperature development in the elements and the structural behaviour were calculated in SAFIR using beam elements for the columns and beams and shell elements for the floor slabs. The first floor was modelled and the effects of action from the upper storeys are applied as external loads. It is shown how the numerical analysis allows understanding the behaviour of the structure when exposed to a natural fire until complete cooling by analysing the evolution of displacements, the distributions of bending moments in the beams, the membrane forces in the slab, and the stresses in the elements. All this detailed information would not be available from an experimental test. [less ▲]

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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 detailTools for Measuring a City’s Resilience in a Fire Following Earthquake Scenario
Elhami Khorasani, Negar; Gernay, Thomas ULg; Garlock, Maria

in Proceedings of IABSE Conference - Structural Engineering: Providing Solutions to Global Challenges (2015, September 25)

The paper provides a framework to evaluate the response of buildings in a community subject to fire following earthquake. First, a model is developed to determine the probability of ignition in buildings ... [more ▼]

The paper provides a framework to evaluate the response of buildings in a community subject to fire following earthquake. First, a model is developed to determine the probability of ignition in buildings of a community due to an earthquake. Second, fragility functions are developed for buildings subject to fire, to quantify the structural damage and the expected losses. The ignition model, combined with the fragility functions, can be implemented in a GIS based risk management platform to evaluate economical losses in a region from fire following an earthquake. [less ▲]

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See detailFragility Analysis of a Steel Building in Fire
Gernay, Thomas ULg; Elhami Khorasani, Negar; Garlock, Maria

in Usmani, Asif; Lu, Yong; Das, Purnendu (Eds.) Proceedings of the First International Conference on Structural Safety under Fire & Blast - CONFAB 2015 (2015, September 03)

Community resilience to extreme events is an issue of increasing concern in our interconnected and urbanized societies. This work provides a framework to evaluate the response of a community of buildings ... [more ▼]

Community resilience to extreme events is an issue of increasing concern in our interconnected and urbanized societies. This work provides a framework to evaluate the response of a community of buildings to fire following earthquake, a potentially highly destructive cascading multi-hazard event. In a previous part of the work, a model has been developed to predict the probability of ignition in a building due to an earthquake. Given an ignition in a building, the probability of the structure exceeding certain limit states must be evaluated in order to quantify the expected damage loss. Adopting an approach similar to that used in seismic engineering, fragility functions can be developed for structures subjected to fire. The methodology is described here for a prototype nine-story steel frame building. In developing the fragility functions, uncertainties in the fire model, the heat transfer model and the thermo-mechanical response are considered. In addition several fire scenarios at different locations in the building are studied. The demand on and capacity of the system are assessed probabilistically in terms of critical temperature. The developed fire fragility functions yield the probability of exceedance of predefined damage states as a function of the fire load in the building. Future works will aim to implement fire fragility functions into a GIS based risk assessment software platform for assessment of the expected risk and cost associated with fire following earthquake for a community of buildings. [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 detailResiliency of a Community of Buildings to Fire Following Earthquake
Gernay, Thomas ULg; Elhami Khorasani, Negar; Garlock, Maria

Conference (2015, June 19)

Cascading multi-hazard events, such as fires following an earthquake, can trigger progressive collapse of structures. In cascading earthquake and fire events, buildings that may have already experienced ... [more ▼]

Cascading multi-hazard events, such as fires following an earthquake, can trigger progressive collapse of structures. In cascading earthquake and fire events, buildings that may have already experienced damage due to a primary earthquake hazard, should cope with a secondary extreme event. This work provides a methodology to evaluate the risk of fire ignitions after an earthquake and building responses in a community. The work has two components: In the first part, a model is developed for predicting the probability of ignition in a building due to an earthquake. This probabilistic model relies on the data from seven significant earthquakes that took place in the U.S. between 1983 and 2014. The main parameters influencing the probability of ignition are found to be the peak ground acceleration, the type of building material, and the main features of the environment in which the buildings are located (i.e. the total square footage and the population density). In the second part of this work, fragility curves are developed for performance of structures under fire, to quantify the probability of exceeding a damage state given a fire scenario. The probabilistic ignition model is implemented in Ergo/Maeviz, a GIS based risk assessment software platform developed at the Mid-America Earthquake Center at UIUC. Ergo/Maeviz provides the probability of ignition after an earthquake for each building in a region of study, and the overall risk for the community. The developed package in Ergo/Maeviz is validated against number of historical fire following earthquake events. For the future work, the developed fragility curves for buildings under fire will be implemented in Ergo/Maeviz to integrate the probability of ignition and possible damage states of the buildings. This research integrates multi-hazard analysis and risk management to plan mitigation and recovery strategies, and to obtain resilient communities. [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 detailBuilding Structures in Fire: Insights from Numerical Models
Gernay, Thomas ULg

Scientific conference (2015, March 06)

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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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