Comparative Energy Analysis from Fire Resistance Tests on Combustible versus Non-Combustible Slabs

Alastair Bartlett, R. McNamee, Fabienne Robert, Luke Bisby

Research output: Contribution to journalArticlepeer-review


Standard fire resistance tests have been used in the design of structural building elements for more than a century. Originally developed to provide comparative measures of the level of fire safety of non-combustible products and elements, the recent resurgence in engineered timber construction raises important questions regarding the suitability of standard fire resistance tests for combustible structural elements. Three standard fire resistance floor tests (5.9 m x 3.9 m in plan), one on a concrete slab and two on cross-laminated timber (CLT) slabs, were undertaken to explore some of the relevant issues. The fuel consumption rate within the furnace was recorded during these tests, and the energy supplied from this was determined. An external fuel supply (from natural gas supplied to the furnace) equating to approximately 3 MW was recorded throughout the concrete test, whereas this was about 1.25 MW throughout the CLT tests. The total heat release rate was calculated using Carbon Dioxide Generation calorimetry; this yielded values of approximately 1.75 MW during the CLT tests (i.e. an additional energy contribution of approximately 0.5 MW from the timber). This demonstrates that considerably more energy input (by about 1.25 MW) was needed to heat the system when the test sample was non-combustible. A further series of six large-scale compartment fire experiments (6 m x 4 m x 2.52 m) was undertaken to further explore comparative performance of combustible versus non-combustible construction when the external fuel load is kept constant and is governed by more realistic compartment fire dynamics. For a fuel-controlled case, the peak temperatures in the compartment with an unprotected CLT ceiling were approximately 200°C higher than in the compartments with a concrete ceiling, whereas for a ventilation-controlled case the compartment with a CLT slab ceiling displayed a burning duration that increased by approximately 15 min. Potential implications for standard fire resistance testing of combustible specimens are discussed.
Original languageEnglish
Article numberFAM190020R2
Number of pages15
JournalFire and Materials
Publication statusPublished - 28 Nov 2019


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