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Review of large-scale fire tests on cross-laminated timber
Abstract
Concerns about the environmental impact of building construction is leading to timber being more commonly used. However, it often faces scepticism regarding its safety in the event of fire. This article provides a point of reference on the fire performance of cross-laminated timber through a review of large-scale tests. Although adequately protecting CLT can make its contribution to fire insignificant, some of the internal surface of an enclosure can be exposed whilst still achieving adequate fire performance. Natural fire tests show that the charring rate and zero-strength layer
thickness are higher than commonly used in guidance documents. The type of adhesive used to bond lamellae influences performance where delamination can lead to secondary flashovers, particularly in smaller enclosures. Structural elements can potentially collapse without self-extinction and/or suppression intervention. Tests to date have focussed on a residential context and knowledge gaps remain regarding larger enclosures, such as office-type buildings.
... In the domain of burn-out and auto-extinction, many experimental campaigns have been undertaken which identify the importance of the enclosure energy balance, alongside other factors such as the impact of bond-line failure (BLF) on whether auto-extinction occurs or not. Ronquillo et al. [11] provide a summary of large-scale experimental studies on mass timber enclosures, reaching the following relevant conclusions: ...
... However, despite this, averting BLF and subsequent extensive/premature char fall-off is often seen as a condition imposed on designs as such events have the potential to cause "an undesirable feedback loop such as fire re-growth" [23]. As is noted in Ronquillo et al. [11], such observations emanate from enclosures where either multiple CLT surfaces were exposed or they had the potential to become exposed through encapsulation failures. In such situations, particularly where walls are exposed and able to suffer extensive char fall-off, it was often observed that collections of smouldering char at the base of the wall were sufficient to allow the walls to continue to undergo flaming combustion, subsequently impacting their ability to auto-extinguish. ...
This paper provides understanding of the fire performance of exposed cross-laminated-timber (CLT) in large enclosures. An office-type configuration has been represented by a 3.75 by 7.6 by 2.4 m high enclosure constructed of non-combustible blockwork walls, with a large opening on one long face. Three experiments are described in which propane-fuelled burners created a line fire that impinged on different ceiling types. The first experiment had a non-combustible ceiling lining in which the burners were set to provide flames that extended approximately halfway along the underside of the ceiling. Two further experiments used exposed 160 mm thick (40-20-40-20-40 mm) loaded CLT panels with a standard polyurethane adhesive between lamella in one experiment and a modified polyurethane adhesive in the other. Measurements included radiative heat flux to the ceiling and the floor, temperatures within the depth of the CLT and the mass loss of the panels. Results show the initial peak rate of heat release with the exposed CLT was up to three times greater when compared with the non-combustible lining. As char formed, this stabilised at approximately one and a half times that of the non-combustible lining. Premature char fall-off (due to bond-line failure) was observed close to the burners in the CLT using standard polyurethane adhesive. However , both exposed CLT ceiling experiments underwent auto-extinction of flaming combustion once the burners were switched off.
... The HRR contributed by square meter of exposed timber can also be evaluated analytically. The fire dynamics of timber compartments is a very complex issue that is still the focus of much research efforts [15,48,[87][88][89][90]. In this section, simplifying assumptions are adopted to allow a reasonable analytical evaluation of the heat output from burning timber in mass timber buildings; while the empirical data of Sect. 3 serves as a benchmark. ...
Estimation of design fires and thermal exposure conditions is an important step in structural fire engineering procedures. Mass timber, as a combustible
material, may contribute to the fire intensity, yet there lacks methods to estimate
design fires in compartments with exposed timber. This paper summarizes available
experimental data on the contribution of exposed timber to heat release rate,
describes a simple analytical method to evaluate this contribution, and discusses the
effects on time–temperature curves and required firefighting resources based on a case
study. Results show that the total heat release rate in compartments increases with
the surface of exposed timber. This total heat release rate can be conservatively estimated using empirical relationships for ventilation-controlled burning rate and charring depth. In estimating gas temperature–time curves, both external flaming and
extended fire duration combustion models can be applied to obtain an envelope of
fire severity inside the compartment and for external spread. The proposed assessment approach provides a method to evaluate realistic design fires in timber buildings
and to estimate the water supply required to put out these fires. Accurate modeling
of the contribution of timber to fire severity is important for the design of mass timber construction as well as for the safety of firefighters.
... Therefore, there is still room for a solution consisting of solid and completely pure wood, dovetail wood board elements (DWBEs) [23]. Numerous studies have been conducted in the literature on the technological, ecological, and economic aspects of EWPs in construction with different building solutions [24] such as [25][26][27][28][29][30], and there is limited understating of DWBEs, which mostly includes structural analysis of connection details (e.g., [31][32][33][34][35][36][37][38][39]). Here, the dovetail wood board elements (DWBEs) can be defined as solid/massive and pure wood structural elements such as floor 4 slabs that use plug-in dovetail form in the joint detail and do not use adhesives and metal connections. ...
Adhesives and metal fasteners have an important place in the content of engineered wood products (EWPs). However, adhesives may cause toxic gas emissions due to their petroleum-based nature, while metal fasteners may adversely affect the reusability of these products. These issues also raise important questions about the sustainability and environmental friendliness of EWPs. Thus, there is still room for a solution that is solid and completely pure wood, adhesive-and metal-connectors-free dovetail wood board elements (DWBEs). There are many studies on the technological, ecological, and economic aspects of these products in the literature, but no studies have been conducted to assess the technical performance of DWBEs. This chapter focuses on DWBEs by proposing various geometric configurations for horizontal structural members in multistory building construction through architectural modeling programs. In this architectural design phase, which is one of the first but most important stages, the proposed configurations are based on a theoretical approach, considering contemporary construction practices rather than structural analysis or mechanical simulation. Further research, including technical performance tests, will be undertaken after this critical phase. It is believed that this chapter will contribute to the dissemination of DWBEs for innovative architectural and structural applications, especially in multistory wooden structures construction.
... The configuration, scale and fire design of in-demand commercial buildings are, however, increasingly detached from research that has been conducted to date, which has tended to focus on experimentally investigating fire dynamics in combustible residential-type enclosures. An extensive review of current large-scale testing is provided in Ronquillo et al. [3]. This focus on residential enclosures has meant little knowledge has been generated for large enclosures, where the combustible elements typically only comprise a single surface, e.g., a CLT floor slab. ...
https://www.sfpe.org/publications/sfpeeuropedigital/sfpeeurope23/europeissue23feature4
... In the literature, many studies have been carried out on the technological aspects of wood with different construction solutions based on the use of EWPs products such as CLT (e.g., [29][30][31][32][33][34][35][36][37]). There is an extremely limited number of research on DWBE, and the literature about 'DWBE' is based on inadequate structural analysis and model testing of several types of jointing details rather than even evaluating the performance of a structural component, e.g., a shear wall or a whole structure. ...
Adhesives and metal fasteners play important roles in the composition and connections of engineered wood products (EWPs) such as cross-laminated timber and glue-laminated timber in the building construction industry. However, due to their petroleum-based nature, adhesives can cause toxic gas emissions, while metal fasteners compromise the end-of-life disposal and reusability of EWPs. These issues adversely affect the sustainable material properties of EWPs. Numerous studies have been conducted in the literature on the technological, ecological, social, and economic aspects of EWPs in construction with different construction solutions, but no studies have been conducted to evaluate the technical performance of dovetail wood board elements (DWBE) in multi-story or tall building construction. This study focuses on adhesive- and metal fastener-free DWBE as sustainable material alternatives for ecologically sensitive engineering solutions. Various preliminary design proposals are presented for DWBE using architectural modeling programs as an environmentally friendly approach intended for use in the timber construction industry. The research findings are based on a theoretical approach that has not yet been practically tested but is proposed considering existing construction practices that need further investigation, including technical performance tests. It is believed that this paper will contribute to the promotion and diffusion of DWBE for more diverse and innovative architectural and structural applications, particularly in multi-story timber building construction, as one of the key tools in tackling climate change challenges.
The use of mass timber in buildings instead of non‐combustible materials has benefits in sustainability, aesthetics, construction times, and costs. However, the uptake of mass timber in modern construction for medium and high‐rise buildings is currently hindered by uncertainty regarding safety and structural performance in fire. We attribute this to a lack of data. Insufficient understanding means that for building designs beyond the current range of experiments the fire performance is unknown. To address this uncertainty, we review the available data in the scientific literature from 63 compartment fire experiments with timber, the majority of which use cross‐laminated timber (CLT). We found that most experiments reached temperatures 80–180°C greater than in non‐combustible compartments. Timber ceilings have on average a 16% lower char rate than timber walls. The heat release rate contribution of timber has a positive linear relationship with charring rate, however is susceptible to significant uncertainty and variability. There are limits to the data available, particularly in large open‐plan compartments of floor areas larger than 100 m2 where a wider range of heating conditions occur. Other topics where further understanding is required are compartments with exposed timber areas greater than 75%, compartments with smaller opening areas, and the hazard of smouldering following the flames. Therefore, additional research is needed to design beyond the limits, specifically in compartment size, ventilation, and timber exposure. This paper identifies correlations in the current body of experimental research to improve fire‐safe design of timber buildings.
Construction fires are a big threat to worker safety and property safety. Mass timber buildings under construction are largely unprotected as they are not yet equipped with active fire protection systems. With the addition of Types IVA, B, and C, the 2021 International Building Code adopted stricter requirements for mass timber buildings that are under construction. Cross‐laminated timber (CLT) is used as the primary structural element for high‐rise mass timber buildings. However, to date, limited number of research studies investigated the impact of passive fire protection for CLT buildings that are under construction. To facilitate a better understanding of construction fires and their consequences, it is necessary to develop a numerical modeling solution for the early phases of a CLT construction project, which can be achieved by using building information models together with fire dynamics simulation (FDS). However, the numerical modeling technique must be benchmarked against experimental data first to then extrapolate the modeling technique to explore other parameters and conduct FDS analysis. Therefore, this paper develops and benchmarks a numerical modeling solution against a mid‐scale CLT compartment fire test by applying the FDS tool to simulate the fire behavior within the CLT compartment. The FDS analysis results are expected to validate the practicality of simulating the fire behavior in CLT structures using the numerical model proposed in this study. The overarching goal of this study is therefore to develop a comprehensive numerical modeling solution to simulate and assess passive fire protection sequencing in CLT buildings that are under construction.
Cross-laminated timber (CLT) is one of the most widely utilized mass timber products for floor construction given its sustainability, widespread availability, ease of fabrication and installation. Composite CLT-based assemblies are emerging alternatives to provide flooring systems with efficient design and optimal structural performance. In this paper, a novel prefabricated CLT-steel composite floor module is investigated. Its structural response to out-of-plane static loads is assessed via 6-point bending tests and 3D finite-element computational analysis. For simply supported conditions, the results of the investigation demonstrate that the floor attains a high level of composite efficiency (98%), and its bending stiffness is about 2.5 times those of its components combined. Within the design load range, the strain diagrams are linear and not affected by the discontinuous arrangement and variable spacing of the shear connectors. The composite floor module can reach large deflection without premature failure in the elements or shear connectors, with plasticity developed in the cold-formed steel beams and a maximum attained load 3.8 times its ultimate limit state design load. The gravity design of the composite module is shown to be governed by its serviceability deflection requirements. However, knowledge gaps still exist on the vibration, fire, and long-term behaviour of this composite CLT-steel floor system.
Mass timber buildings present fire hazards that are often not addressed by design codes and guidance documents, if the structure is permitted to contribute as a source of fuel. One such hazard is increased external flaming as excess fuel burns outside of openings.
This may have implications for a building’s fire strategy, be that in terms of storey-to-storey fire spread, or fire spread to adjacent buildings. This paper explores the development of a correlation between global equivalence ratio (GER) and external heat release rate (HRR), in function of the amount of internally exposed combustible surface area to a mass timber enclosure. The correlation is empirically calibrated against existing experimental data and is shown to give an adequate estimation of external HRR where the exposed surface area does not exceed c. 55% of the total enclosure surface area. A separate flame length correlation is developed and is shown to conservatively estimate the flame height from openings when benchmarked against an independent CLT enclosure fire test. However, further benchmarking is required against a larger range of experimental sources to establish the broad scope of applicability.
Structural fire resistance and charring behaviour of cross-laminated timber (CLT) have been well documented in the past decade. It was found from these standard fire-resistance tests that once the 1st lamination charred, the general trend is that the charring rate of the subsequent laminations increased, regardless of whether it was a floor or wall assembly. It was also found that the thickness of laminations and the performance at elevated temperatures of the adhesives played an important role in the charring behaviour of CLT. This behaviour is typically not observed for glue-laminated timber face-bonded with phenolic adhesives and resins. The objective of this research is to evaluate CLT face-bonded with adhesives that meet the new 2018 ANSI/APA PRG 320 with respect to elevated temperature requirements and their effects on the resulting charring rates when exposed to the standard time-temperature curve of CAN/ULC S101 (similar exposure to ASTM E119). The results obtained in this study suggest that CLT manufactured with an adhesive meeting the CSA O177 Annex A.2 flame test requirements could use the commonly-accepted one-dimensional charring rate of 0.65 mm/min during fire exposure. This study further suggests that the costly large-scale compartment fire test, as per Annex B in ANSI/APA PRG 320 (2018), may not be required for qualification purposes. It could, however, be suggested as an alternative qualification test method to CSA O177 Annex A.2, similar to glulam elements.
This paper presents a review of the pyrolysis, ignition, and combustion processes associated with wood, for application in tall timber construction. The burning behaviour of wood is complex. However the processes behind pyrolysis, ignition, combustion, and extinction are generally well understood, with good agreement in the fire science literature over a wide range of experimental conditions for key parameters such as critical heat flux for ignition (12 kW/m² ± 2 kW/m²) and heat of combustion (17.5 MJ/kg ± 2.5 MJ/kg). These parameters are key for evaluating the risks posed by using timber as a construction material. Conversely, extinction conditions are less well defined and understood, with critical mass loss rates for extinction varying from 2.5 g/m²s to 5 g/m²s. A detailed meta-analysis of the fire resistance literature has shown that the rate of burning as characterised by charring rate averaged over the full test duration is observed to vary with material properties, in particular density and moisture content which induce a maximum 18% variability over the ranges expected in design. System properties are also shown to be important, with stochastic phenomena such as delamination and encapsulation failure resulting in changes to the charring rate that cannot be easily predicted. Finally, the fire exposure as defined by incident heat flux has by far the largest effect on charring rates over typical heat fluxes experienced in compartment fires. Current fire design guidance for engineered timber products is largely prescriptive, relying on fixed “charring rates” and “zero-strength layers” for structural analyses, and typically prescribing gypsum encapsulation to prevent or delay the involvement of timber in a fire. However, it is clear that the large body of scientific knowledge that exists can be used to explicitly address the fire safety issues that the use of timber introduces. However the application of this science in real buildings is identified as a key knowledge gap which if explored, will enable improved efficiencies and innovations in design.
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.
Five full-scale fire experiments were conducted to observe the performance of a two-level apartment-style structure constructed of mass timber. Each level consisted of a one bedroom apartment, an L-shaped corridor, and a stairwell connecting the two levels. One of the primary variables considered in this test series was the amount and location of exposed mass timber. The amount of mass timber surface area protected by gypsum wallboard ranged from 100% to no protection. For each experiment, the fuel load was identical and the fire was initiated in a base cabinet in the kitchen. In the first three experiments, the fire reached flashover conditions, and subsequently underwent a cooling phase as the fuel load from combustible contents was consumed. The first three experiments were carried out for a duration of up to 4 h. In the fourth experiment, automatic fire sprinklers were installed. Sprinklers suppressed the fire automatically. In the fifth experiment, the activation of the automatic fire sprinklers was delayed by approximately 20 minutes beyond the sprinkler activation time in the fourth experiment to simulate responding fire service charging a failed sprinkler water system. A variety of instrumentation was used during the experiments, including thermocouples, bidirectional probes, optical density meters, heat flux transducers, directional flame thermometers, gas analyzers, a fire products collector, and residential smoke alarms. In addition, the experiments were documented with digital still photography, video cameras, and a thermal imaging camera. The experiments were conducted in the large burn room of the Bureau of Alcohol, Tobacco, Firearms and Explosives Fire Research Laboratory located in Beltsville, Maryland, USA. This report provides details on how each experiment was set up, how the experiments were conducted, and the instrumentation used to collect the data. A brief summary of the test results is also included. Detailed results and full data for each test are included in separate appendices.
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.
Cross-laminated timber (CLT) panels are relatively new engineered wood products that can be used as load bearing walls, floors and roof elements in innovative and high quality modern timber structures. The fire behavior of cross-laminated timber panels requires careful evaluation to allow the expansion of CLT elements usage in buildings. A University of British Columbia study has been conducted at the Trees and Timber Institute CNR-IVALSA in San Michele all’Adige, Italy to experimentally evaluate the fire performance of Canadian CLT panels. In total, ten loaded fire tests were performed using standard fire curves (ULC/ASTM and ISO) to study the influence of different cross-section layups on the fire resistance of floor and wall elements and to investigate the influence of different anchors on the fire behavior of wall elements. This paper presents the main results of the experimental analyses and discusses in particular the charring rate, one of the main parameters in fire design.
An extensive research project, called SOFIE and sponsored by the Italian Province of Trento, on the structural behaviour of timber buildings made of prefabricated cross-laminated solid timber panels is currently carried out at CNR-IVALSA in Italy. The research project aims at supplying documentation and information on the use of XLam timber panels as structural elements, in order to increase its use in particular for residential multi-storey buildings. Following the shaking table test of a full-scale 3 storey XLam timber building carried out in Tsukuba, Japan in June and July 2006, a natural fire test on the same building has been recently carried out at the Building Research Institute in Tsukuba. The paper presents the main results of the natural full-scale fire test.
The present study tested the charring rates for cross-laminated timber panels (CLT) exposed to standard and parametric fires. A series of fire tests were performed on horizontal cross-laminated timber panels exposed to EN 1991-1-2 Standard and Parametric temperature-time curves, and a "Swedish" curve. A large gas-fired horizontal furnace was used in the experiments. The char depth was measured through all stages of the fires. The objectives were; to examine the charring rate of CLT panels and whether the charring changed through the fire stages, to investigate if the charring rates for the various temperature-time curves were different, and if the rates were affected by the panel thicknesses. Timber panels of three different thicknesses were tested to investigate a thickness effect. The results illustrate that the charring rate for CLT panels exposed to various fires can vary greatly. Fast temperature growth gave faster charring rates. The thickness of the panels did not have an unambiguous effect on the charring rate. The charring rate of wood exposed to fires of long durations became constant after a while.
The results presented in this paper are part of a multi-partner collaborative project named ‘The Épernon fire tests’, the purpose of which is to analyse the different behaviours of combustible and non-combustible loaded structures when they are tested under standard and ‘natural’ fires. The project has several scientific objectives, such as quantification of the energy participation of combustible materials in fire tests1, the influence of combustible surfaces and ventilation factors on the dynamics of compartment fires2, and the thermomechanical behaviour of concrete and timber elements under natural fires. This paper focuses on the study of the thermomechanical behaviour of cross-laminated timber (CLT) slabs under standard and natural fires. The objective is to bring new experimental data to the complex study of the behaviour of unprotected CLT slabs exposed to fire. In addition, we propose a detailed analysis of the thermomechanical behaviour of the slabs, in order to better predict their loss of stability when subjected to fire.
This paper presents a discussion of the recent ‘ban’ on combustible cladding that has been implemented in England following the Grenfell Tower fire. The ban is discussed in terms of its context within the existing regulatory system in England and is analysed in terms of the intended and unintended consequences. Key intended consequences are identified as the prohibition of ‘Grenfell-type’ cladding, the banning of desktop studies for relevant buildings and the banning of some forms of engineered timber construction. Unintended consequences include the devaluation of private leaseholder’s homes, the potential for the problems with the construction industry to be perceived as ‘fixed’ and a raft of somewhat absurd administrative effects. The authors conclude that the ban has likely been effective in its overall aim but that its success is, ironically, inherently bound up with the efficacy of the very regulations that it was intended to fix. The authors also identify that the new ban is potentially susceptible to ‘gaming’ by unscrupulous parties within the construction industry.
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.
A large-scale fire test was conducted on a compartment constructed from cross laminated timber (CLT). The internal faces of the compartment were lined with non-combustible board, with the exception of one wall and the ceiling where the CLT was exposed directly to the fire inside the compartment. Extinction of the fire occurred without intervention. During the fire test, measurements were made of incident radiant heat flux, gas phase temperature, and in-depth temperature in the CLT. In addition, gas flow velocities and gas phase temperatures at the opening were measured, as well as incident heat fluxes at the facade due to flames and the plume leaving the opening. The fuel load was chosen to be sufficient to attain flashover, to achieve steady-state burning conditions of the exposed CLT, but to minimize the probability of uncertain behaviors induced by the specific characteristics of the CLT. Ventilation conditions were chosen to approximate maximum temperatures within a compartment. Wood cribs were used as fuel and, following decay of the cribs, self-extinction of the exposed CLT rapidly occurred. In parallel with the large-scale test, a small scale study focusing on CLT self-extinction was conducted. This study was used to establish: the range of incident heat fluxes for which self-extinction of the CLT can occur; the duration of exposure after which steady-state burning occurred; and the duration of exposure at which debonding of the CLT could occur. The large-scale test is described, and the results from both the small and large-scale tests are compared. It is found that self-extinction occurred in the large-scale compartment within the range of critical heat fluxes obtained from the small scale tests.
The consortium of Nordic Wood Structures, EBC and Yvan Blouin Architect are designing a 13-storey residential building using a mass timber structure. The project, named "Origine" is proposed to be located in the eco-neighbourhood of Pointe-aux- Lièvres in Quebec City and to start construction in spring 2015. The mass timber structure would be composed primarily of glue-laminated timber and cross-laminated timber (CLT). The cross-laminated timber consists of at least three orthogonally bonded layers of solid-sawn lumber that are laminated by gluing of longitudinal and transverse layers with structural adhesives to form a solid rectangular-shaped, straight and plane timber intended for floor, roof or wall applications. The National Research Council Canada (NRC) was requested to assist in the demonstration of an alternative solution to noncombustible construction as prescribed in the Québec Construction Code [1] and the National Building Code of Canada (NBCC) [2]. Three series of fire tests were conducted at NRC to investigate: the fire endurance (fire resistance) of CLT floor and wall assemblies [3], the fire performance of a CLT exterior wall assembly [4], and the fire demonstration of a CLT stair/elevator shaft for the proposed building. This report provides the description and results of the fire demonstration for the CLT stair/elevator shaft. This fire demonstration was funded by the Government of Quebec’s Ministère des Forêts, de la Faune et des Parcs through FPInnovations.
This consortium research project produced a large amount of technical information and data in the areas of fire safety, acoustics and building envelope performance for use in mid-rise (and taller) wood buildings. The results of the acoustics and building envelope performance are summarized in separate reports [8, 9]. This report consolidates the results of fire research activities (thrusts 1-3) conducted under the project. These include investigation of the encapsulation approach to protect the combustible structural elements, development of wood-based generic exterior wall assemblies to limit exterior fire spread, and development of generic fire resistant light-weight wood-frame wall assemblies for applications in lower storeys of mid-rise wood buildings.
A full-scale compartment fire test was performed to assess gypsum plasterboards and wood based panels as cladding materials for the fire protection of light and massive timber elements. The test compartment was constructed using both the timber frame and the cross laminated timber techniques; a wood crib was used to achieve realistic fire conditions. Temperature measurements and optical inspection evidence suggested that gypsum plasterboards offered adequate fire protection since they did not fail and no charring was observed in the timber elements. A free standing wall inside the test compartment, protected by wood-based panels, partially collapsed. Measured values of characteristic failure times, such as time to failure of fire protection cladding and time to onset of charring, were compared to relevant Eurocode correlations, achieving good levels of agreement. The obtained set of measurements, describing the time evolution of a large variety of physical parameters, such as gas and wall layer temperatures, can be used for validation of relevant advanced fire simulation tools.
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