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9 records – page 1 of 1.

Analysis of Cross-Laminated Timber Charring Rates Upon Exposure to Non-Standard Heating Conditions

https://research.thinkwood.com/en/permalink/catalogue136
Year of Publication
2015
Topic
Fire
Material
CLT (Cross-Laminated Timber)
Author
Bartlett, Alastair
Hadden, Rory
Bisby, Luke
Law, Angus
Organization
Fire and Materials
Year of Publication
2015
Format
Conference Paper
Material
CLT (Cross-Laminated Timber)
Topic
Fire
Keywords
Charring Rate
Heat Release Rate
Fire Resistance
Conference
Fire and Materials 2015
Research Status
Complete
Notes
February 2-4, 2015, San Francisco, United States
Summary
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.
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Auto-Extinction of Engineered Timber as a Design Methodology

https://research.thinkwood.com/en/permalink/catalogue1676
Year of Publication
2016
Topic
Fire
Material
CLT (Cross-Laminated Timber)
Author
Bartlett, Alastair
Hadden, Rory
Bisby, Luke
Lane, Barbara
Year of Publication
2016
Format
Conference Paper
Material
CLT (Cross-Laminated Timber)
Topic
Fire
Keywords
Extinction
Fire Propagation Apparatus
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 22-25, 2016, Vienna, Austria p. 3934-3941
Summary
Engineered timber products such as cross-laminated timber (CLT) are gaining popularity with designers due to attractive aesthetic, sustainability, and constructability credentials. The fire behaviour of such materials is a key requirement for buildings formed predominantly of exposed, structural timber elements. Whilst design guidance focuses on the residual structural capacity of timber elements exposed to a ‘standard fire’, the fundamental characteristics of CLT’s performance in fire, such as ignition, flame spread, delamination, and extinction are not currently considered. This paper focuses on the issues relating to increased fuel load due to a combustible building material itself. Whilst an increasingly common protection solution to this conundrum is to fully encapsulate the timber elements, there is limited supporting test data on this approach. Through understanding these concepts from a fundamental, scientific perspective, the behaviour can be properly understood, and, rather than limiting design, can be incorporated into design to satisfy suitable performance criteria. In this paper therefore, the concept of auto-extinction – a phenomenon by which a timber sample will cease flaming when the net heat flux to the sample drops below a critical value – is explored experimentally and related to firepoint theory. A series of c.100 small scale tests in a Fire Propagation Apparatus (FPA) have been carried out to quantify the conditions under which flaming extinction occurs. Critical mass loss rate at extinction is shown to occur at a mass flux of 3.5g/m2s or a temperature gradient of 28K/mm at the charline. External heat flux and airflow were not found to affect the critical mass loss rate at the range tested. This approach is then compared with a compartment fire with multiple exposed timber surfaces. With further testing and refinement, this method may be applied in design, enabling architects’ visions of exposed, structural timber to be safely realised.
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Effects of Exposed Cross Laminated Timber on Compartment Fire Dynamics

https://research.thinkwood.com/en/permalink/catalogue1340
Year of Publication
2017
Topic
Fire
Material
CLT (Cross-Laminated Timber)
Application
Rooms
Author
Hadden, Rory
Bartlett, Alastair
Hidalgo, Juan
Santamaria, Simón
Wiesner, Felix
Bisby, Luke
Deeny, Susan
Lane, Barbara
Publisher
ScienceDirect
Year of Publication
2017
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Application
Rooms
Topic
Fire
Keywords
Compartment Fires
Heat Release Rate
Temperature
Exposed Timber
Auto-Extinction
Combustible Material
Heat Transfer
Research Status
Complete
Series
Fire Safety Journal
Summary
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.
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Effects of Fuel Load and Exposed CLT Surface Configuration in Reduced-Scale Experiments

https://research.thinkwood.com/en/permalink/catalogue2047
Year of Publication
2018
Topic
Fire
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Author
Bateman, Christopher
Bartlett, Alastair
Rutkauskas, Lukas
Hadden, Rory
Organization
The University of Edinburgh
Year of Publication
2018
Format
Conference Paper
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Topic
Fire
Keywords
Auto-Extinction
Fuel Load
Delamination
Conference
World Conference on Timber Engineering
Research Status
Complete
Summary
With increasing regularity, compartments with exposed timber boundaries are being proposed in high-rise buildings. However, due to the combustible nature of timber, the fire-specific risks associated with these decisions must be thoroughly explored. In particular the requirement that the timber stops burning after the imposed fuel load has been consumed must be fulfilled. By means of reduced scale experiments it was determined that sustained burning was dependent on both the configuration of exposed faces and, to a lesser extent, the imposed fuel load. The principal factor for auto-extinction or otherwise was found to be in the configuration of exposed surfaces, with two exposed walls (in this case back and side wall) consistently resulting in sustained burning. When a wall and the ceiling were left exposed (wall opposite the compartment opening and ceiling), auto-extinction occurred for all but the highest fuel load considered. The occurrence of char fall-off (delamination) was significant in promoting sustained burning and was observed to cause a transition from apparent extinction back to flaming in one experiment.
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Needs for Total Fire Engineering of Mass Timber Buildings

https://research.thinkwood.com/en/permalink/catalogue1674
Year of Publication
2016
Topic
Design and Systems
Fire
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Author
Bartlett, Alastair
Wiesner, Felix
Hadden, Rory
Bisby, Luke
Lane, Barbara
Lawrence, Andrew
Palma, Pedro
Frangi, Andrea
Year of Publication
2016
Format
Conference Paper
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Topic
Design and Systems
Fire
Keywords
Fire Safety
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 22-25, 2016, Vienna, Austria p. 3888-3897
Summary
Fire safety is widely perceived as a barrier to implementation of tall timber buildings, particularly for engineered mass timber buildings with significant areas of exposed timber and timber structural framing. This negative perception is exacerbated by a lack of scientific data or experimental evidence on a range of potentially important issues that must be properly understood to undertake rational, performance-based engineering design of such structures. With the goal of delivering fully engineered structural fire designs, this paper presents and discusses a framework for using scientific knowledge, along with fire engineering tools and methods, to enable the design of timber buildings such that, when subject to real fire loads, their performance is quantified. The steps in this framework are discussed with reference to the available literature, in an effort to highlight areas where additional knowledge and tools are needed.
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A Review of Factors Affecting the Burning Behaviour of Wood for Application to Tall Timber Construction

https://research.thinkwood.com/en/permalink/catalogue2504
Year of Publication
2019
Topic
Fire
Design and Systems
Application
Wood Building Systems

Structural Capacity in Fire of Laminated Timber Elements in Compartments with Exposed Timber Surfaces

https://research.thinkwood.com/en/permalink/catalogue2105
Year of Publication
2019
Topic
Fire
Mechanical Properties
Material
CLT (Cross-Laminated Timber)
Application
Rooms
Author
Wiesner, Felix
Bisby, Luke
Bartlett, Alastair
Hidalgo, Juan
Santamaria, Simón
Deeny, Susan
Hadden, Rory
Publisher
ScienceDirect
Year of Publication
2019
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Application
Rooms
Topic
Fire
Mechanical Properties
Keywords
Compartment Fire Test
Temperature
Thermal Penetration
Charring
Load Bearing Capacity
Exposed Timber
Research Status
Complete
Series
Engineering Structures
Summary
In compartment fires with boundaries consisting of exposed mass timber surfaces – for example in compartments with exposed cross-laminated timber (CLT) walls or floors – the thermal penetration depth, i.e. the depth of timber heated to temperatures significantly above ambient behind the char-timber interface, during fire exposure may have a significant influence on the load bearing capacity of structural mass timber buildings, particularly in the decay phase of a real fire. This paper presents in-depth timber temperature measurements obtained during a series of full-scale fire experiments in compartments with partially exposed CLT boundaries, including decay phases. During experiments in which the timber surfaces achieved auto-extinction after consumption of the compartment fuel load, the thermal penetration depth continued to increase for more than one hour, whilst the progression of the in-depth charring front effectively halted at extinction. A simple calculation model is presented to demonstrate that this ongoing progression of thermal penetration continues to reduce the structural load bearing capacity of the CLT elements, thereby increasing the potential for structural collapse during the decay phase of the fire. This issue is considered to be most important for timber compression elements. Currently utilised structural fire design methods for mass timber generally assume a fixed ‘zero strength layer’ depth to account for thermally affected timber behind the char line; however they make no explicit attempt to account for these decay-phase effects.
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Structural Response of Cross-Laminated Timber Compression Elements Exposed to Fire

https://research.thinkwood.com/en/permalink/catalogue1338
Year of Publication
2017
Topic
Fire
Mechanical Properties
Material
CLT (Cross-Laminated Timber)
Application
Walls
Author
Wiesner, Felix
Randmael, Fredrik
Wan, Wing
Bisby, Luke
Hadden, Rory
Publisher
ScienceDirect
Year of Publication
2017
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Application
Walls
Topic
Fire
Mechanical Properties
Keywords
Reduced Cross-Section Method
Axial Load
Compressive Load
Deformation
Temperature
Zero-Strength Layer
Research Status
Complete
Series
Fire Safety Journal
Summary
A set of novel structural fire tests on axially loaded cross-laminated timber (CLT) compression elements (walls), locally exposed to thermal radiation sufficient to cause sustained flaming combustion, are presented and discussed. Test specimens were subjected to a sustained compressive load, equivalent to 10 % or 20 % of their nominal ambient axial compressive capacity. The walls were then locally exposed to a nominal constant incident heat flux of 50 kW/m2 over their mid height area until failure occurred. The axial and lateral deformations of the walls were measured and compared against predictions calculated using a finite Bernoulli beam element analysis, to shed light on the fundamental mechanics and needs for rational structural design of CLT compression elements in fire. For the walls tested herein, failure at both ambient and elevated temperature was due to global buckling. At high temperature failure results from excessive lateral deflections and second order flexural effects due to reductions the walls’ effective crosssection and flexural rigidity, as well as a shift of the effective neutral axis in bending during fire. Measured average one-dimensional charring rates ranged between 0.82 and 1.0 mm/min in these tests. As expected, the lamellae configuration greatly influenced the walls’ deformation responses and times to failure; with 3- ply walls failing earlier than those with 5-plies. The walls’ deformation response during heating suggests that, if a conventional reduced cross section method (RCSM), zero strength layer analysis were undertaken, the required zero strength layer depths would range between 15.2 mm and 21.8 mm. Deflection paths further suggest that the concept of a zero strength layer is inadequate for properly capturing the mechanical response of fire-exposed CLT compression elements.
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Structural Response of Fire-Exposed Cross-Laminated Timber Beams under Sustained Loads

https://research.thinkwood.com/en/permalink/catalogue1364
Year of Publication
2016
Topic
Fire
Mechanical Properties
Material
CLT (Cross-Laminated Timber)
Application
Beams
Author
Lineham, Sean
Thomson, Daniel
Bartlett, Alastair
Bisby, Luke
Hadden, Rory
Publisher
ScienceDirect
Year of Publication
2016
Format
Journal Article
Material
CLT (Cross-Laminated Timber)
Application
Beams
Topic
Fire
Mechanical Properties
Keywords
Flexural Loading
Reduced Cross-Section Method
Zero-Strength Layer
Char Depth
Eurocode
Load Bearing Capacity
Deflection
Heat Flux
Research Status
Complete
Series
Fire Safety Journal
Summary
Cross-laminated timber (CLT) is a popular construction material for low and medium-rise construction. However an architectural aspiration exists for tall mass timber buildings, and this is currently hindered by knowledge gaps and perceptions regarding the fire behaviour of mass timber buildings. To begin to address some of the important questions regarding the structural response of fire-exposed CLT structures in real fires, this paper presents a series of novel fire tests on CLT beams subjected to sustained flexural loading, coincident with non-standard heating using an incident heat flux sufficient to cause continuous flaming combustion. The load bearing capacities and measured time histories of deflection during heating are compared against predicted responses wherein the experimentally measured char depths are used, along with the Eurocode recommended reduced cross section method and zero-strength layer thickness. The results confirm that the current zero-strength layer value (indeed the zero-strength concept) fails to capture the necessary physics for robust prediction of structural response under non-standard heating. It is recommended that more detailed thermo-mechanical cross-sectional analyses, which allow the structural implications of real fire exposures to be properly considered, should be developed and that the zero-strength layer concept should be discarded in these situations. Such a novel approach, once developed and suitably validated, could offer more realistic and robust structural fire safety design.
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9 records – page 1 of 1.