Cross-laminated timber (CLT) is well known as an interesting technical and economical product for modern wood structures. The use of CLT for modern construction industry has become increasingly popular in particular for residential timber buildings. Analyzing the CLT behavior in high thermal environment has attracted scholars’ attention. Thermal environment greatly influences the CLT properties and load bearing capacity of CLT, and the investigation can form the basis for predicting the structural response of such CLT-based structures. In the present work, the finite element method (FEM) is employed to analyze the thermal influence on the deformation of CLT. Furthermore, several factors were taken into consideration, including board layer number, hole conformation, and hole position, respectively. In order to determine the influence, several numerical models for different calculation were established. The calculation process was validated by comparing with published data. The performance is quantified by demonstrating the temperature distribution and structural deformation.
An experimental study of the influence of an exposed combustible ceiling on compartment fire dynamics has been performed. The fire dynamics in compartments with combustible cross-laminated timber ceilings vs non-combustible reinforced concrete ceilings in otherwise identical compartments with three different ventilation factors were investigated. The experimental results are compared against predictions from two theoretical models for compartment fire dynamics: (a) the parametric fire model given in EN 1991-1-2, and (b) a model developed at Technische Universität Braunschweig, which are the parametric fire models currently used in Germany. It is confirmed that the introduction of a combustible timber ceiling leads to higher temperatures within the enclosure, both under fuel-controlled and ventilation-controlled scenarios. It is also demonstrated that the theoretical models considered in this article require refinement in order to adequately represent all relevant scenarios when combustible ceilings are present. A refinement of the German model, by adding the fuel from the combustible ceiling to the occupancy fuel load, was shown to not adequately capture the response for the ventilation-controlled fires.
The vulnerability of any building, regardless of the material used, in a fire situation is higher during the construction phase when compared to the susceptibility of the building after it has been completed and occupied. This is because the risks and hazards found on a construction site differ both in nature and potential impact from those in a completed building; and these risks are occurring at a time when the fire prevention elements that are designed to be part of the completed building are not yet in place. For these reasons, construction site fire safety includes some unique challenges. Developing an understanding of these hazards and their potential risks is the first step towards fire prevention and mitigation during the course of construction (CoC).
This report contains test results for the fire-retardant-treatment (FRT) and hygrothermal effects on structural glued laminated timber (glulam). This is the second part of the collaborative research project between ABA - The Engineered Wood Association, Tacoma, WA, and USDA Forest Products Laboratory (FPL), Madison, WI. The first part of this project is related to FRT laminated veneer lumber (LVL) and the results are provided in a separate research report.
Selected mechanical properties, including tension, bending, and shear of the FRT glulam treated with the American Wood Protection ASsociation (AWPA) P49 and P50 fire retardants were evaluated in this study. These results are used to support the development of an ASTM standard for FRT glulam.
Cross-laminated timber (CLT) panels are broadly utilized as structural members in modern timber structures. Variation in the residual resistance of CLT walls after fire exposure may lead to disruption of vertical force transmission and, in turn, structural collapse. To investigate the residual compressive load-carrying capacity of CLT walls after exposed to one-side fire, a series of tests were conducted on 3-ply and 5-ply members: axial compression tests, fire tests, and residual compressive load-carrying capacity tests. Combining the initial geometric defects obtained from the test results and the effect of shear deformation, theoretical formulae describing the compressive load-carrying capacity were deduced. Further considering the different mechanical properties over the residual cross-section model after fire, and the relative position between Region A and CLT orthogonal configuration, the calculation method of the residual compressive load-carrying capacity after fire were derived. The results of the residual compressive load-carrying capacity tests showed that the failure mode of the CLT walls after one-side fire was the eccentric compression, and the nonlinear segments of the load-axial and load-lateral displacement curves after fire accounted for larger proportion than those of axial compression tests. For the same total section thickness, the reduction in residual capacity of the 5-ply walls after fire was less than that of the 3-ply walls. The calculation results of the eccentric compression formulae considering shear deformation and initial geometric defect showed good agreement with the test values of axial compression tests. The residual compressive load-carrying capacity after one-side fire was predicted appropriately, which could be used as reference for assessing the residual load-carrying behavior of CLT elements after fire.
"As an alternative option to conventional sprinkler system, water mist systems are considered for the protection of timber buildings because they use much less amounts of water compared to sprinkler systems. The effectiveness of high pressure water mist (HPWM) and low pressure water mist (LPWM) systems was investigated in comparison to sprinkler systems for a residential fire scenario involving mass timber structures. The most distinct characteristic of the HPWM and LPWM systems was fine water droplets generated from the nozzles, which demonstrated effective smoke cooling in the room. Although the water spray rate of the HPWM was four times lower than that of the sprinkler system, the water mist systems effectively control the fire and maintained the room tenable. Most systems (HPWM, LPWM and sprinklers) tested in this study did not prevent fire damage on the CLT walls, but the HPWM system with a wide spray angle demonstrated rapid fire suppression and protection of the CLT walls. In all tests, a large water pool formed on the floor, which appeared proportional to the total water spray discharge in each test, and the moisture contents measured on the surface and bottom edges of the CLT panels indicated that water can penetrate into the interface between the floor and the wall in a typical CLT assembly"--Executive summary, page 1.
This paper presents an experimental evaluation of the fire resistance of glued-in rod timber joints using epoxy resin, with and without modification. A heat-resistant modified resin was designed by adding inorganic additives into the epoxy resin, aiming to improve the heat resistance. Joints that were made using the modified epoxy resin at room temperature showed a bearing capacity comparable to those with commercial epoxy resin. Twenty-one joint specimens with the modified epoxy resin and six with a commercial epoxy resin were tested in a fire furnace to evaluate the fire resistance. The main failure mode was the pull-out of the rod, which is typical in fire tests of this type of joints. As to the effects of the test parameters, this study considered the effects of adhesive types, sectional sizes, stress levels, and fireproof coatings. The test results showed that the fire resistance period of a joint can be evidently improved by modifying the resin and using the fireproof coating, as the improvements reached 73% and 35%, respectively, compared with the joint specimens with commercial epoxy resin. It was also found that, for all specimens, the fire resistance period decreased with an increase in the stress level and increased with an increase in the sectional sizes.
"This report presents the findings from a simulation parametric study to investigate the use of water mist systems for a residential compartment fire involving exposed mass timber structures. The fire and suppression models were first validated against experimental data obtained from the NRC fire tests that were conducted under the same project. Seventeen simulations were conducted using Fire Dynamic Simulator (FDS) software. The following parameters were investigated: effect of fuel arrangement and location on fire severity in exposed wood compartment, effect of different finishing on fire severity in compartment, fire and suppression in open space vs compartment, effectiveness of water mist systems in fire suppression in compartments with different finishing. The results show the effectiveness of the water mist system in suppressing the fire in exposed wood compartments where a high heat release is expected due to the high fuel load"--Executive summary, page iv.
The overall objective of this work is to expand options for designers of mass timber buildings by reducing the dependence on concrete and gypsum board though the demonstration of adequate fire performance of mass timber assemblies.
This work is intended to demonstrate that mass timber surfaces can be left exposed in concealed spaces, under certain conditions, while still performing well to control flame spread; this could result in significant savings in construction. Flame spread testing will be completed to compare the performance of mass timber assemblies and concealed space designs that are currently allowed by the NFPA 13 to be exempt from the installation ofsprinklers.
Data is needed to support the use of exposed mass timber in concealed spaces by demonstrating limited flame spread in concealed mass timber void spaces. Flame spread testing has already shown that mass timber has lower flame spread ratings than typically found with thinner wood panels. This will lead the way in allowing unsprinklered 305 mm (12 in.) deep concealed spaces beneath mass timber assemblies or exposed mass timber in other concealed spaces such as hollow wood floor beams.
The goal is to generate data to support the use of exposed mass timber in concealed spaces. This data could be used in an Alternative Solution to gain approval for this type of design. Ultimately, this could lead to changing the NBCC to allow exposed mass timber in concealed spaces.
The fire resistance of cross-laminated timber (CLT) could be improved by treating the lamina with fire retardants. The major issues with this technology are the reduced bondability of the treated lamina with commercial adhesives. This study assessed several surface preparation methods that could improve the bondability and bond durability of fire-retardant treated wood with two commercial adhesives. Four surface preparation methods, including moisture/heat/pressure, surface planing, surface chemical treatment, and surface plasma treatment were assessed for their impact on the bondability and bond durability of lodgepole pine lamina. The block shear test results indicated that all surface preparation methods were somewhat effective in improving bond performance of fire-retardant treated wood compared to the untreated control wood samples, depending on the types of fire retardants and wood adhesives applied in the treatment process and bonding process. The selection of surface preparation, fire retardant, and wood adhesive should be considered interactively to obtain the best bond properties and fire performance. It may be possible to effectively bond the treated lamina with PUR adhesive without any additional surface preparation for the fire retardant used in the treatment at FPInnovations.
Fire safety regulations impose very strict requirements on building design, especially for buildings built with combustible materials. It is believed that it is possible to improve the management of these regulations with a better integration of fire protection aspects in the building information modeling (BIM) approach. A new BIM-based domain is emerging, the automated code checking, with its growing number of dedicated approaches. However, only very few of these works have been dedicated to managing the compliance to fire safety regulations in timber buildings. In this paper, the applicability to fire safety in the Canadian context is studied by constituting and executing a complete method from the regulations text through code-checking construction to result analysis. A design science approach is used to propose a code-checking method with a detailed analysis of the National Building Code of Canada (NBCC) in order to obtain the required information. The method starts by retrieving information from the regulation text, leading to a compliance check of an architectural building model. Then, the method is tested on a set of fire safety regulations and validated on a building model from a real project. The selected fire safety rules set a solid basis for further development of checking rules for the field of fire safety. This study shows that the main challenges for rule checking are the modeling standards and the elements’ required levels of detail. The implementation of the method was successful for geometrical as well as non-geometrical requirements, although further work is needed for more advanced geometrical studies, such as sprinkler or fire dampers positioning.
This paper describes selected observations, measurements, and analysis from a series of large-scale experiments on cross-laminated timber (CLT) slabs that were exposed to fire from below, using four different heating scenarios, with a sustained mechanical loading of 6.3 kN m per metre width of slab. The deflection response and in-depth timber temperatures are used to compare the experimental response against a relatively simple structural fire model to assess the load bearing capacity of CLT elements in fire, including during the decay phase of natural fires. It is demonstrated that the ventilation conditions in experiments with a fixed fuel load are important in achieving burnout of the contents before structural collapse occurs. A mechanics-based structural fire model is shown to provide reasonably accurate predictions of structural failure (or lack thereof) for the experiments presented herein. The results confirm the importance of the ventilation conditions on the fire dynamics, burning duration, and the achievement of functional fire safety objectives (i.e. maintaining stability and compartmentation), in compartments with exposed CLT.
Timber use is becoming more appealing in the recent years especially ‘exposed timber’; however, the information available on the performance of engineered timber after fire is limited. This paper explores the performance of timber elements exposed to well defined thermal boundary conditions and examines the extent of adhesive degradation after heating. Two different types of timber beams are explored; ‘glued laminated timber’ (Glulam) and ‘laminated veneer lumber’ (LVL). A subset of beams was exposed to radiant heat as per a modified ASTM E1321 heating procedure. An additional subset of beams also had an area of their cross-section carved away, equivalent to the char depth of the heated beams. The carved beams allow for the identification of degradation beyond the char layer, as theoretically both the carved and charred beams would have the same effective cross-sectional area. All beams were mechanically loaded to failure using a four-point loading setup. While the current allowance for degradation beyond the char layer is considered to be 7 mm for exposure times of 20 minutes and greater , the results herein indicate that for bending members this layer extends to at least a minimum of 11.7 mm for LVL and 12.3 mm for Glulam. The aim of this paper is to assess the post-fire performance of Glulam and LVL through looking at strength loss due to adhesive degradation, which may contribute towards enabling tall and unencapsulated engineered timber buildings.