The use of engineered timber products such as cross-laminated timber (CLT) is of increasing interest to architects and designers due to their desirable aesthetic, environmental, and structural properties. A key factor preventing widespread uptake of these materials is the uncertainty regarding their performance in fire. Currently, the predominant approach to quantifying the structural fire resistance of timber elements is the charring rate, which allows estimation of residual cross-section and hence strength. The charring rate is usually determined by testing timber specimens in a furnace by exposure to a ‘standard fire’. However, it is recognized that the resulting charring rates are not necessarily appropriate for non-standard fire exposures or for characterizing the structural response in a real timber building. The effect of heating rate on the charring rate of CLT samples is investigated. The charring rate resulting from three heating scenarios (constant, simulated ‘standard fire’ and quadratically increasing) was calculated using interpolation of in-depth temperature measurements during exposure to heating from a mobile array of radiant panels, or in a Fire Propagation Apparatus (FPA). Charring rate is shown to vary both spatially and temporally, and as a function of heating rate within the range 0.36–0.79 mm/min. The charring rate for tests carried out under simulated ‘standard fire’ exposures were shown to agree with the available literature, thus partially verifying the new testing approach; however under other heating scenarios the Eurocode charring rate guidance was found to be unconservative for some of the heat flux exposures in this study. A novel charring rate model is presented based on the experimental results. The potential implications of this study for structural fire resistance analysis and design of timber structures are discussed. The analysis demonstrates that heating rate, sample size and orientation, and test setup have significant effects on charring rate and the overall pyrolysis, and thus need to be further evaluated to further facilitate the use of structural timber in design.
A series of compartment fire experiments has been undertaken to evaluate the impact of combustible cross laminated timber linings on the compartment fire behaviour. Compartment heat release rates and temperatures are reported for three configuration of exposed timber surfaces. Auto-extinction of the compartment was observed in one case but this was not observed when the experiment was repeated under identical condition. This highlights the strong interaction between the exposed combustible material and the resulting fire dynamics. For large areas of exposed timber linings heat transfer within the compartment dominates and prevents auto-extinction. A framework is presented based on the relative durations of the thermal penetration time of a timber layer and compartment fire duration to account for the observed differences in fire dynamics. This analysis shows that fall-off of the charred timber layers is a key contributor to whether auto-extinction can be achieved.
This study which involves the development of fire loads and design fires for residential and non-residential mid-rise buildings is part of NEWBuildS’ “Rationalization o f Life Safety - Code Requirements fo r Mid-rise Buildings” project. The project is focused on analysing the code requirements that relate to fire resistance and the use of automatic sprinklers for mid-rise buildings built with combustible or non-combustible construction. The ultimate goal of the project is to come up with alternative solutions and, potentially, trigger changes in the code requirements for mid-rise buildings.
A review, compilation, and analysis of fire load survey data was conducted from available literature for residential and office buildings. A web survey of floor areas was also conducted for floor areas of mid-rise buildings. Fire loads and fuel packages for midrise buildings were developed based on previous surveys as well as the web survey. The fire load data in conjunction with statistical data was used to select fire scenarios from which design fire scenarios were chosen.
The fire characteristics of the selected fuel packages, such as heat release rate, and production of toxic gases, were analyzed using the two-zone fire risk analysis model, CUrisk, in order to develop appropriate design fires for mid-rise buildings.
This thesis studies the fire behaviour of Cross Laminated Timber (CLT) panels in partially protected rooms. A one-dimensional heat transfer model was developed to determine the fire resistance of CLT floor and wall panels. During this study, three room fire tests were conducted at Carleton University Fire Research Laboratory to determine the maximum percentage of unprotected CLT surface area that will yield similar results to that of a fully protected room. The rooms had a single opening and were constructed entirely using 3-ply, 105 mm thick CLT panels. A non-standard, parametric fire using furniture and clothing as fuel was used and 2 layers of gypsum board were used to cover the ceiling and the protected walls. The Heat Release Rate, temperature, charring rate and gypsum falloff time of each test was collected. The results obtained from the room test were then compared to the numerical heat transfer model to evaluate its accuracy.
Recent architectural trends include the design and construction of increasingly tall buildings with structural components comprised of engineered wood referred to by names including; cross laminated timber (CLT), laminated veneer lumber (LVL), or glued laminated timber (Glulam). These buildings are cited for their advantages in sustainability resulting from the use of wood as a renewable construction material. Previous research has shown that timber elements contribute to the fuel load in buildings and can increase the initial fire growth rate – potentially overwhelming fire protection system and creating more severe conditions for occupants, emergency responders, and nearby properties.
The overarching goal of this project Fire Safety Challenges of Tall Wood Buildings Phase 2 is to quantify the contribution of CLT building elements (wall and/or floor-ceiling assemblies) in compartment fires and provide data to allow comparison of the performance of CLT systems against other building systems commonly used in tall buildings.
The objective of the two tests described in this report was to evaluate the performance of cross-laminated timber (CLT) and nail laminated timber (NLT) construction protected with two layers of %-in. (16-mm) type X gypsum board when exposed to the thermal environment of a severe living room fire for the American Wood Council (Client), located in Leesburg, Virginia. The tests were conducted on September 3 and 15, 2015, at Southwest Research Institute's (SwRI) Fire Technology Department, located in San Antonio, Texas.
This report describes the testing of the assemblies that were evaluated and the results that were obtained. The results presented in this report apply specifically to the materials and products tested and in the manner tested.
The main objective of this preliminary study is to evaluate the heat release rate and fire growth contribution due to heat delamination characteristics of CLT manufactured with current certified ANSI/APA PRG-320 adhesives used for face bonding, when exposed to a constant radiant heat flux. The evaluation is performed using the principles of ISO 5660-1 “Reaction-to-fire tests - Heat release, smoke production and mass loss rate – Part 1: Heat release rate (cone calorimeter method)” . The American version of this test method is ASTM E1354 « Standard Test Method for Heat and Visible Smoke Release Rates for Materials and Products Using an Oxygen Consumption Calorimeter » .
The long-term objective is to determine which currently accepted test methods allow for a better evaluation of heat delamination characteristics of adhesives used in structural engineered wood products, based on their actual end-use applications (e.g. bending, compression, combined stress, cross-plies, etc.)
This paper documents the findings of a series of full-scale room fire tests, which includes tests on fully protected, partially protected CLT rooms as well as light-frame timber/steel rooms under real natural fires, aiming to investigate the fire behaviour and performance of CLT panels as an increasingly popular engineered wood product and to compare it to the performance of more traditional construction methods. Results show that the CLT panels when left unprotected get involved in the room fire as part of the combustible contents, responsible for over 60% of total heat release in the fully unprotected CLT room and double the heat release rate of a fully protected room fire where the CLT does not contribute. Partially-protected CLT rooms also demonstrates various levels of fire contribution. The amount of CLT exposure is also related to the occurrence of re-ignition and a second flashover after all the movable fuels are consumed. The behaviour of CLT delamination and charring as well as the performance of gypsum boards in fire are also discussed.
As timber buildings are constructed taller, architects and building owners are asking for more timber to be exposed. Addressing how exposed timber and in particular cross laminated timber, influences a fully developed fire through to self-extinguishment is a current and complex fire safety issue. There is limited research available on how exposed timber alters heat release rate, temperatures and fire duration. This paper provides a summary of the relevant research to understand similarities in findings and how the results of fire tests can be applied. Research shows that large areas of exposed timber has a significant impact on heat release rate, but limited areas of exposed timber can be accommodated within a fire safe design. The location of exposed timber and avoiding two or more adjacent exposed surfaces, is an important finding. It is evident from the limited testing that a single exposed timber wall of approximately 20% of the total wall area has little impact on a compartment fire. The development of a calculation methodology to account for the change in compartment fire dynamics when two or more surfaces are exposed is the next step in the advancement of exposed timber fire safety engineering.