EXECUTIVE SUMMARY

“The Épernon Fire Tests Programme” is a multi-partner collaborative research project launched in 2017. The project seeks to understand the links between normative fire resistance ratings and real fire performance in buildings. The project has several objectives, such as quantification of the energy participation of combustible materials in standard furnace tests, the influence of combustible surfaces and ventilation factors on the dynamics of compartment fires (including external flaming), and the thermomechanical behaviour of structures under standard and natural fires.

The experimental campaign included fire testing of two different loaded structures, ceiling slabs made of cross-laminated timber (CLT) and ceiling slabs made of reinforced concrete. These two types of slabs were tested both in standard fire resistance (i.e. furnace) tests, and in compartment fire experiments with timber cribs as a fuel load. Different opening factors were tested. The campaign was conducted at the CERIB testing facility in Épernon, France (Figure 1 and Figure 2).

Figure 1. Test matrix of the Epernon Fire Tests Programme
Figure 2. Illustration of compartment configurations and corresponding opening factor.

The outer dimensions of the CLT elements were 5,900 x 3,900 x 165 mm3. These CLT panels were composed of five layers of wooden lamellae, with adjacent lamellae perpendicular to each other. The lamellae were bonded together over the entire surface. Each lamella was 33 mm thick. The adhesive used, manufactured by the company PURBOND, consisted of a single-component polyurethane resin, HB S709.
Outer dimensions of the concrete elements were 5,900 x 3,900 x 180 mm3. The strength class of the concrete was a C35/45. The elements were cast in situ with a steel welded mesh (ST50C, 5.03 cm²/m, Ø8 mm every 10 cm in both directions) with a clear concrete cover of 20 mm (axis distance 24 mm).

During the fire tests, the slabs were loaded with 2,950 kg of dead weights, according to the Eurocode accidental combination (G + 0.5 Q) (Figure 3). The fire load during the compartment tests was 891 MJ/m² related to the floor area (with the dimensions of the compartment being 6 x 4 m² in plan and a height of 2.52 m , Figure 4). This fire load was chosen to be representative of the characteristic fire load for dwellings according to EN 1991-1-2 (Annex E).

Figure 3. The loaded CLT element with steel beams as line loads on top of the fire compartment (left) and the furnace (right).
Figure 4.Fire test with natural fire according to scenario 2. The loaded test element was the ceiling of the fire compartment. Also note the simplified facade element on top of the fire compartment. This mock-up façade was used to characterize the external flaming out from the openings of the compartment.

Fire dynamics in the fire compartment

During the compartment fire experiments, the tested elements were used as the ceilings of the structure (Figure 5 and Figure 6). The ventilation conditions had an impact on the development of the fire inside of the compartment. Additionally, the materials in the two structures (i.e. concrete and CLT) influenced the fire in different ways. The main differences were that the wooden structure released additional pyrolysis gases (fuel) to the compartment and that the thermal properties were different between CLT and concrete. In the case of concrete more heat was absorbed and conducted away from the fire. The three scenarios are all more severe than the standard fire exposure. This was expected when comparing with the parametric fire model in the Eurocode EN 1991-1-2. More comparisons with the parametric fire can be found in (Jansson McNamee et al, 2020).

Figure 5. Fire dynamics in the fire compartments during the natural fires with CLT or concrete as ceilings. The standard fire curve is the fire exposure used when doing standardized testing in a fire resistance furnace.
Figure 6. A comparison of the temperature development inside the compartment for the three different scenarios.

External flaming

During the compartment experiments, the heat flux by radiation was measured at a distance of 3 m from the openings of the compartment and at a height 1.5 m . The radiation at that location is a combination of the radiation out from the fire compartment and from the external plume over the openings. These measurements show considerably higher values for the configurations with a CLT ceiling (Figure 7).

Figure 7. Heat flux by radiation to a point 3 m from the opening at the height 1.5 m.

Fire resistance

The three performed furnace fire tests led to a fire resistance rating REI 120 for both the CLT and the concrete slabs. The criteria that was broken and gave the fire resistance time in all cases was the deflection rate. In the concrete element test the collapse occurred at the same time as the breaking of the deflection rate criteria (Table 1).

During the furnace tests, the test on concrete was shown to have consumed nearly three times more natural gas than did the tests performed on CLT slabs, even though the thermal exposure was identical for the three standard tests.

Table 1. Results from standardized fire resistance tests in the furnace.

Broken criteria Concrete CLT (test 1) CLT (test 2)
Limiting deflection 125 minutes 141 minutes 131 minutes
Limiting deflection rate 125 minutes 125 minutes 121 minutes

During the compartment fire tests, the CLT slab in scenario 3 collapsed after 108 minutes of exposure, being earlier than the determined fire resistance in the furnace tests. Further on, the CLT slab in scenario 2 collapsed 29 hours after the start of the fire test. No collapse was observed for the other tested elements.

MORE INFORMATION

The test reports, the excel sheets and a summary report of the project including further analysis can be downloaded from the table below. A number of peer reviewed publications with further analysis from the project are listed below.
The outcomes of the project shed light on several issues which should be considered when assessing a building using a fire safety engineering approach to provide an adequate level of safety.

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Project Team

The tests are performed in the framework of a collaborative partnership involving the following authors.

Pr Luke BISBY Dr Alastair BARTLETT Dr Jean-Christophe MINDEGUIA Dr Robert JANSSON MCNAMEE Pr Jochen ZEHFUß Pr Jean-Marc FRANSSEN Dr Fabienne ROBERT Christophe TESSIER Dr Siyimane MOHAINE
                 

School of Engineering
University of Edinburgh
United Kingdom


The University of Bordeaux
I2M laboratory
France


Brandskyddslaget AB
Sweden


The Institute of Building Materials, Concrete Construction and Fire Safety of Technische Universität Braunschweig (IBMB-Braunschweig), Division of Fire Safety
Germany


Liège University
Belgium


CERIB
Fire Testing Centre
France

Project Team

The tests are performed in the framework of a collaborative partnership involving the following collaborating authors:

Pr Luke BISBY Dr Alastair BARTLETT
   

School of EngineeringUniversity of EdinburghUnited Kingdom

Dr Jean-Christophe MINDEGUIA
 

The University of BordeauxI2M laboratoryFrance

Dr Robert JANSSON MCNAMEE
 

Brandskyddslaget ABSweden

Pr Jochen ZEHFUß
 

The Institute of Building Materials, Concrete Construction and Fire Safety of Technische Universität Braunschweig (IBMB-Braunschweig), Division of Fire SafetyGermany

Pr Jean-Marc FRANSSEN
 

Liège UniversityBelgium

Dr Fabienne ROBERT Christophe TESSIER Dr Siyimane MOHAINE
     

CERIBFire Testing CentreFrance

Synthesis Report

Synthesis Report

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Synthesis Report.

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Test Reports

Test Report Data sheets Tested element Type of fire
010618

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Test Report 010618.

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Download 010618

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Test Report 010618 data sheets.

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Loadbearing CLT slab Standard fire (EN 1365-2)
010616

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Test Report 010616.

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Test Report 010616 data sheets.

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Loadbearing concrete slab
010615

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Test Report 010615.

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Download 010615

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Test Report 010615 data sheets.

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Loadbearing concrete slab Natural fire (Scenario 1)
010617

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Test Report 010617.

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Download 010617

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Test Report 010617 data sheets.

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Loadbearing CLT slab
013596

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Test Report 013596.

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Download 013596

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Test Report 013596 data sheets.

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Loadbearing CLT slab Standard fire (EN 1365-2)
013598

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Test Report 013598.

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Download 013598

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Test Report 013598 data sheets.

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Loadbearing concrete slab Natural fire (Scenario 2)
013597

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Test Report 013597.

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Download 013597

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Test Report 013597 data sheets.

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Loadbearing CLT slab
013599

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Test Report 013599.

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Download 013599

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Test Report 013599 data sheets.

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Loadbearing CLT slab Natural fire (Scenario 3)
013600

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Test Report 013600.

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Test Report 013600 data sheets.

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Loadbearing concrete slab

Publications

  • Comparative Energy Analysis of Fire Resistance Tests on Combustible versus Non-Combustible Slabs
    Alastair I. Bartlett, Robert McNamee, Fabienne Robert, and Luke Bisby, Fire and Materials, 2019
    https://onlinelibrary.wiley.com/doi/abs/10.1002/fam.2760
  • Structural Capacity of One-Way Spanning Large-Scale Cross-Laminated Timber Slabs in Standard and Natural Fires
    Felix Wiesner, Alastair Bartlett, Siyimane Mohaine, Fabienne Robert, Robert McNamee, Jean-Christophe Mindeguia & Luke Bisby, Fire Technology, 2020.
    https://link.springer.com/article/10.1007/s10694-020-01003-y
  • Enclosure fire dynamics with a combustible ceiling
    Robert McNamee, Jochen Zehfuss, Alastair I. Bartlett, Mohammad Heidari, Fabienne Robert and Luke Bisby, Fire and Materials, 2020
    https://onlinelibrary.wiley.com/doi/full/10.1002/fam.2904?af=R
  • Thermo-mechanical behaviour of cross-laminated timber slabs under standard and natural fires
    Jean-Christophe Mindeguia, Siyimane Mohaine, Luke Bisby, Fabienne Robert, Robert McNamee, Alastair Bartlett, Interflam, 1-3 July 2019, London
    http://www.intersciencecomms.co.uk/html/conferences/Interflam/if19/if19proceedings.htm
  • Heat fluxes to a façade resulting from compartment fires with combustible and non-combustible ceilings
    Alastair Bartlett, Angus Law, Robert Jansson McNamee, Jochen Zehfuss, Siyimane Mohaine, Christophe Tessier, Luke Bisby, 3rd international symposium for Fire Safety of Façades, 25-27 September 2019, Paris
  • Thermal and mechanical response of reinforced concrete slabs under natural and standard fires
    Siyimane Mohaine, Nataša Kalaba, Jean-Marc Franssen, Luke Bisby, Alastair Bartlett, Jean-Christophe Mindeguia, Robert McNamee, Jochen Zehfuss & Fabienne Robert, 6th International Workshop on Concrete Spalling due to Fire Exposure, 19-20 September 2019, Sheffield
    https://firespallingworkshop2019.group.shef.ac.uk/wp-content/uploads/2019/09/Fire-Spalling-Workshop_Proceedings.pdf

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