This article presents a test method that was developed to screen adhesive formulations for finger-jointed lumber. The goal was to develop a small-scale test that could be used to predict whether an adhesive would pass a full-scale ASTM E119 wall assembly test. The method involved loading a 38-mm square finger-jointed sample in a four-point bending test inside of an oven with a target sample temperature of 204°C. The deformation (creep) was examined as a function of time. It was found that samples fingerjointed with melamine formaldehyde and phenol resorcinol formaldehyde adhesives had the same creep behavior as solid wood. One-component polyurethane and polyvinyl acetate adhesives could not maintain the load at the target temperature measured middepth of the sample, and several different types of creep behavior were observed before failure. This method showed that the creep performance of the onecomponent adhesives may be quite different than the performance from short-term load deformation curves collected at high temperatures. The importance of creep performance of adhesives in the fire resistance of engineered wood is discussed.
The growing diffusion of cross-laminated timber structures (CLT) has been accompanied by extensive research on the peculiar characteristics of this construction system, mainly concerning its economic and environmental benefits, lifecycle, structural design, resistance to seismic actions, fire protection, and energy efficiency. Nevertheless, some aspects have not yet been fully analysed. These include both the knowledge of noise protection that CLT systems are able to offer in relation to the possible applications and combinations of building elements, and the definition of calculation methods necessary to support the acoustic design. This review focuses on the main acoustic features of CLT systems and investigate on the results of the most relevant research aimed to provide key information on the application of acoustic modelling in CLT buildings. The vibro-acoustic behaviour of the basic component of this system and their interaction through the joints has been addressed, as well as the possible ways to manage acoustic information for calculation accuracy improvement by calibration with data from on-site measurements during the construction phase. This study further suggests the opportunity to improve measurement standards with specific reference curves for the bare CLT building elements, in order to compare different acoustic linings and assemblies on the same base. In addition, this study allows to identify some topics in the literature that are not yet fully clarified, providing some insights on possible future developments in research and for the optimization of these products.
This project aims to support the construction of tall wood buildings by identifying encapsulation methods that provide adequate protection of mass timber elements; the intention is that these methods could potentially be applied to mass timber elements so that the overall assembly could achive a 2 h fire resistance rating.
FPInnovations initiated this project to demonstrate the ability of wood exit stairs in mid-rise buildings to perform adequately in a fire when NBCC requirements are followed, with the intent of changing perceptions of the fire safety of wood construction. The objective of this research is to investigate further the fire safety afforded by exit stair shafts of combustible construction, with the ultimate objective of better consistency between the provincial and national building codes with respect to fire requirements for exit stair shafts in mid-rise wood-frame construction.
FPInnovations conducted a research project to study the construction of mid-rise wood exit shafts in Ontario and Québec. The scope of the project included an investigation into the concerns that have been raised in regards to the use of wood exits in mid-rise buildings, an analysis of recent Canadian fire statistics in residential multi-family structures, and a fire demonstration of a mass timber wall and supported light-frame floor. This report describes the fire demonstration completed as part of this project; this report acts as a supplement to the full project report.
FPInnovations carried out a survey with consultants and researchers on the use of analytical models and software packages related to the analysis and design of mass timber buildings. The responses confirmed that a lack of suitable models and related information for material properties of timber connections was creating an impediment to the design and construction of this type of buildings. Furthermore, there is currently a lack of computer models and expertise for carrying out performance-based design for wood buildings, in particular seismic and/or fire performance design.
In this study, a sophisticated constitutive model for wood-based composite material under stress and temperature was developed. This constitutive model was programmed into a user-subroutine which can be added to most general-purpose finite element software. The developed model was validated with test results of a laminated veneer lumber (LVL) beam and glulam bolted connection under force and/or fire.
The objective of this research is to address a knowledge gap related to fire performance of midply shear walls. Testing has already been done to establish the structural performance of these assemblies. To ensure their safe implementation and their broad acceptance, this project will establish fire resistance ratings for midply shear walls. Fire tests will provide information for the development of design considerations for midply shear walls and confirm that they can achieve at least 1-hour fire-resistance ratings that are required for use in mid-rise buildings.
This research will support greater adoption of mid-rise residential and non-residential wood-frame construction and improve competition with similar buildings of noncombustible construction. This work will also support the development of the APA system report for midply walls, which will be a design guideline for using midply walls in North America.
Le présent rapport décrit une partie des activités de recherche et développement (R&D) en lien avec la démonstration de la résistance au feu ainsi que les études sur la performance acoustique effectuées dans le cadre de la construction du bâtiment Origine. Ce bâtiment est la tour résidentielle en bois massif la plus haute au Québec. Sa réalisation a débuté en 2015 à la suite des analyses préliminaires de faisabilité technique-économique qui se sont étalées pendant toute l’année 2014. La construction et l’installation se sont finalisées vers la fin de 2017.
En premier lieu, le rapport présente les démarches liées à la réalisation d’un exercice de démonstration d’incendie pour une cage d’escaliers/ascenseur avec une chambre d’habitation adjacente, l’analyse de résultats et les principales conclusions en lien avec la pertinence de l’utilisation du bois massif pour des édifices de grande hauteur. En ce qui concerne la performance acoustique, le rapport présente la méthodologie d’étude et d’analyse des résultats des tests acoustiques pour des assemblages de mur et de plancher utilisés dans le projet Origine. De plus, ce rapport facilite la compréhension des activités réalisées et permet de montrer objectivement la capacité des produits en bois massif à offrir un environnement sécuritaire et confortable aux occupants de bâtiments multi-étagés.
Les principaux résultats indiquent que les cages d’escaliers/ascenseur faites en bois massif, conçues pour une résistance au feu équivalente à celle faites en béton, peuvent offrir une excellente performance et servent d’alternatives adéquates pour les bâtiments multi-étagés. En ce qui concerne le développement d’assemblages acoustiques pour les murs et les planchers en bois massif, il a été prouvé qu’une approche multicritère permet d’offrir des solutions performantes à des coûts raisonnables.
Finalement, il est clair que ce projet constitue un jalon très important dans le chemin d’acceptation des bâtiments multi-étagés en bois massif au Québec et au Canada. Sa construction, faite presque entièrement en bois, a nécessité de nombreux efforts économiques, de R&D, de conception et d’installation. De plus, les activités réalisées pour l’acceptation de ce type de construction ont permis de mettre en place de nouvelles technologies et des techniques de conception qui faciliteront la réplication de ce type de projet partout en Amérique du Nord.
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.
The key objective of this study is to analyze full-scale fire-resistance tests conducted on structural composite lumber (SCL), namely laminated veneer lumber (LVL), parallel strand lumber (PSL) and laminated strand lumber (LSL). A sub-objective is to evaluate the encapsulation performance of Type X gypsum board directly applied to SCL beams and its contribution to fire-resistance of wood elements.
The test data is being used to further support the applicability of the newly developed Canadian calculation method for mass timber elements, recently implemented as Annex B of CSA O86-14.
In this study, new design models for cross-laminated timber (CLT) are developed to verify the fire resistance up to 120 minutes. This is done aiming for the popular Effective Cross-Section Method using a so-called zero-strength layer (ZSL) to account for losses in strength and stiffness. This was done using a method earlier presented at WCTE 2010 and discussed with the European industry. To allow for improvements, (a) the current CLT product portfolio was analysed and thermal and mechanical simulations were done accordingly for initially unprotected and unprotected members. Further, (b) new definitions for the ZSL were used to allow for a higher accuracy of the simplified models. As anoutcome, a model with (1) tabulated data between 7.0 and 12.0 mm for the effective ZSL only considering longitudinal layers and (2) a simplified model “twelve and two” is proposed for CLT members in bending.
Comprehensive guide to engineered wood construction systems for both residential and commercial/industrial buildings. Includes information on plywood and oriented strand board (wood structural panels), glulam, I-joists, structural composite lumber, typical specifications and design recommendations for floor, wall and roof systems, diaphragms, shear walls, fire-rated systems and methods of finishing.
In this project, a conceptual but realistic 20-storey building of hybrid construction incorporating massive timber panels and other structural materials was identified. The project team, consisting of three practicing consultants and 6 graduate student and post-doctoral researchers from NEWBuildS, undertook an analysis and engineering design of the demonstration building. An advisory group that includes FPInnovations scientists, NEWBuildS supervisors of the graduate students and Post Doctoral Fellows, provides technical support to the project team. The performance attributes addressed in the project were structural performance under seismic and wind load, fire resistance and building envelope. . This publication documents the analysis and design of the demonstration building, and identifies technical issues that require further study.
Wood beam-column connections have traditionally been designed as simple shear connections, ignoring their potential moment capacity. A major reason for not utilizing such moment connections is linked to the brittle limit states that wood components exhibit. The purpose of this research was to develop and test a ductile and high-strength wood moment frame connection. A design procedure for such a connection is presented herein.
The proposed glulam beam-column connection utilizes an embedded steel knife plate with a reduced section that acts as a ductile yield link, thus limiting the moment that can be transferred through the connection. This configuration is intended to fail through yielding of the ductile link, thus preventing non-ductile failure mechanisms of wood from occurring. In addition, the connection provides more wood cover over the embedded steel plate, which potentially may increase the connection's fire rating as compared to typical connections.
Two specimens, based on a baseline connection developed using the design procedure presented, were monotonically loaded until failure. Unlike the first specimen, the second was reinforced in the perpendicular-to-grain direction using self-tapping screws. Failure mechanisms were analyzed, and performance characteristics related to the connection's strength, stiffness, and ductility were evaluated. Results indicated that the reinforced specimen exhibited higher strength, stiffness, and ductility compared to the unreinforced specimen. The reinforced specimen showed improvements of 9.49% and 42.2% in yielding and ultimate moment, respectively, compared to the unreinforced specimen. Moreover, an improvement of 31.3% in ductility was obtained using perpendicular-to-grain reinforcement.
Cross-laminated timber (CLT) became a popular engineered wood product in recent years for highquality and innovative timber buildings. As for any building product, the fire behaviour of CLT panels requires careful evaluation in the design of such buildings. The adhesive used in the bond lines of CLT plays an important role in the fire design. However, currently, European standards do not provide a test method to assess the adhesive performance in CLT exposed to fire. This paper presents a series of fire tests performed with CLT panels glued with different adhesives. It is shown how the mass loss of the CLT panels in standard fire resistance tests can be used to assess the adhesive performance in CLT exposed to fire.
During the past few years, a relatively new technology has emerged in North America and changed the way professionals design and build wood structures: Cross-laminated Timber (CLT). CLT panels are manufactured in width ranging from 600 mm to 3 m. As such, fastening them together along their major strength axis is required in order to form a singular structural assembly resisting to in-plane and out-of-plane loading. Typical panel-to-panel joint details of CLT assemblies may consist of internal spline(s), single or double surface splines or half-lapped joints. These tightly fitted joint profiles should provide sufficient fire-resistance, but have yet to be properly evaluated for fire-resistance in CLT assemblies.
The experimental portion of the study consisted at conducting ten (10) intermediate-scale fire-resistance tests of CLT floor assemblies with four (4) types of panel-to-panel joints and three (3) CLT thicknesses. The data generated from the intermediate-scale fire tests were used to validate a finite element heat transfer model, a coupled thermal-structural model and a simplified design model. The latter is an easy-to-use design procedure for evaluating the fire integrity resistance of the four commonly-used CLT floor assemblies and could potentially be implemented into building codes and design standards. Based on the test data and models developed in this study, joint coefficient values were derived for the four (4) types of CLT panel-to-panel joint details. Joint coefficients are required when assessing the fire integrity of joints using simple design models, such as the one presented herein and inspired from Eurocode 5: Part 1-2.
The contribution of this study is to increase the knowledge of CLT exposed to fire and to facilitate its use in Canada and US by complementing current fire-resistance design methodologies of CLT assemblies, namely with respect to the fire integrity criterion. Being used as floor and wall assemblies, designers should be capable to accurately verify both the load-bearing and separating functions of CLT assemblies in accordance with fire-related provisions of the building codes, which are now feasible based on the findings of this study.
This report begins with a discussion of the mechanisms of flame spread over combustible materials while describing the NBCC prescriptive solutions that establish the acceptable fire performance of interior finish materials. It is noted that while flame spread ratings do give an indication of the fire performance of products in building fires, the data generated are not useful as input to fire models that predict fire growth in buildings.
The cone calorimeter test is then described in some detail. Basic data generated in the cone calorimeter on the time to ignition and heat release rates are shown to be fundamental properties of wood products which can be useful as input to fire models for predicting fire growth in buildings.
The report concludes with the recommendation that it would be useful to run an extensive set of cone calorimeter tests on SCL, glue-laminated timber and CLT products. The fundamental data could be most useful for validating models for predicting flame spread ratings of massive timber products and useful as input to comprehensive computer fire models that predict the course of fire in buildings. It is also argued that the cone calorimeter would be a useful tool in assessing fire performance during product development and for quality control purposes.
Forest Service/USDA Wood Innovations Grants
Recipient Point of Contact: Karl R. Englund
Location: Pullman, Washington
Summary
The durability of wood has always limited mass adoption into many markets. With CLT, wood’s perceived ineffective performance when exposed to bio-deterioration and fire has many customers hesitant to commit to a mass timber structure. Our project will evaluate a commercial ready process to pretreat the lamstock of CLT panels with a variety of borate-based treatment options. By treating the lamstock prior to CLT fabrication, a more homogeneous treatment is realized, making a more durable panel that can be implemented in areas prone to high humidity and mitigate risks associated with durability. Our work will provide a commercial-ready solution that can be easily implemented in-line, lowering costs and not interrupting process flows or outputs.
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.
Over the past 60 years, the materials traditionally used to construct temporary military structures have become less effective in operational theaters that require greater force protection from ballistic and blast events. Cross-laminated timber (CLT), an engineered wood product that has recently grown in popularity due to its strength and ease of assembly, has the potential to serve as an alternate or replacement building material. However, its viability for use in temporary military structures not only depends on its well-documented performance under normal design loads, but also its less-understood performance under ballistics and blast loading conditions. To better characterize CLT under such conditions in the absence of historical data, a series of ballistic experiments were conducted at the United States Army Engineer Research and Development Center (ERDC) to measure the penetration depth or residual velocity of munitions fired at various velocities. Based on the 152 initial ballistic experiments, new enhanced cross-laminated timber (ECLT) samples were developed using known armor materials and evaluated in terms of constructability and ballistic performance. During construction, heavy plate armor was significantly less compatible in bonding with CLT configurations and in some cases required mechanical connections, whereas the more fibrous materials developed for use in lightweight armor bonded well to the CLT with an epoxy mixture. The most promising ballistic performances came from the ECLT samples using flexible fibrous materials. In general, the testing showed that increased ballistic performance is attainable by enhancing CLT, but such improvements have consequences such as increased weight or material cost. Therefore, compromise on acceptable protection levels during the design process using cost-benefit analysis is necessary. Ultimately, ECLT samples modified with fiberglass fabric showed greatest cost-benefit potential.
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