Project contact is Christian Dagenais at Université Laval
The structural elements of a building must provide fire resistance in order to prevent collapse and to provide an escape route for occupants. The basic philosophy is that components that support elements with a degree of fire resistance must also offer the same degree of resistance. It is also assumed that the connections between these elements provide at least the same degree as the supported elements. Traditionally, heavy timber construction used ingenious construction principles and assemblies made of cast iron. With the advent of innovative fasteners (eg self-tapping screws), the principles of assembly have changed greatly and are now similar to a metal frame. So, several studies have been carried out in recent years in order to increase knowledge of the fire behavior of these assemblies (Audebert et al., 2012, Dhima 1999, Frangi et al. 2009, Peng 2010, Ohene 2014, Ali et al. 2014 , Moss et al. 2008). Although a significant amount of information is available in the literature, it often indicates short-term flammability resistance (± 30 min), which is largely insufficient for buildings having to provide a degree of fire resistance of at least 2 hours. The objective is to carry out a literature review in order to fully understand the factors influencing the fire performance of assemblies in wood construction. A model of thermomechanical behavior and a simplified analytical approach would have to be developed.
With the arrival of innovative fasteners (e.g. self-tapping screws), assembly principles have greatly changed and now resemble a metal framework. Although a significant amount of information is available in the literature, it often indicates short-term flammability resistance (± 30 min), which is largely insufficient for buildings that need to provide a fire resistance rating of at least 2 hours. The objective is to carry out a literature review to understand the factors influencing the fire performance of assemblies in wood construction. A modeling of thermomechanical behavior and a simplified analytical approach should be developed. Testing from an intermediate furnace is likely to be required to validate model assumptions.
FPInnovations is involved in a large research project regarding CLT construction. One objective of this research is the creation of a design methodology for calculating the fire-resistance of CLT assemblies/construction. This methodology will foster the design of fire-safe buildings of wood or hybrid construction. In order to establish such calculation methods, a series of experimental tests has been undertaken. A total of eight full-scale CLT fire resistance tests have been conducted at the NRC fire laboratory where the panels were subject to the standard ULC S101  fire exposure. The series consisted of three wall and five floor tests. Each test was unique using panels with a different number of plies and varying thicknesses. Some of the assemblies were protected using CGC Sheetrock® FireCode® Core Type X gypsum board while others were left unprotected.
Advanced wood building systems form a significant market opportunity for use of wood in taller and larger buildings, which are currently required to be of non-combustible construction in accordance with provisions set forth in Part 3 of Division B of the National Building Code of Canada (NBCC).
In order to evaluate the surface burning characteristics of massive timber assemblies, flame spread tests on CLT assemblies have been conducted in accordance with ULC S102 test method. Three series of 3-ply CLT panels of 99 mm in thickness, V2 stress grade as per ANSI/APA PRG-320 (i.e., manufactured with Spruce-Pine-Fir (SPF) lumber) have been evaluated for flame spread and smoke developed classification. Fully exposed CLT specimens (99 mm) provided much lower flame spread ratings (FSR of 40), when compared to thinner similar products.
A research project, Wood and Wood-Hybrid Midrise Buildings, was undertaken to develop information to be used as the basis for alternative/acceptable solutions for mid-rise construction using wood structural elements. The effectiveness of the encapsulation approach in limiting the involvement of wood structural materials in fires was demonstrated in this research project through bench-, intermediate- and full-scale fire experiments. These results for encapsulated lightweight wood-frame (LWF) systems and encapsulated cross-laminated timber (CLT) systems are documented in a series of reports [3, 4, 5, 6].
In addition to developing the encapsulation approach for protecting the wood structural materials to meet the above code intent, research was undertaken to examine standard fire resistance of encapsulated wood structural assemblies for use in mid-rise wood/timber buildings. One of the major differences between structural LWF assemblies used in mid-rise wood buildings (5-6 storeys) and low-rise wood buildings (= 4 stories) is the wall assemblies for the lower storeys. For mid-rise wood buildings, loadbearing wall assemblies on the lower storeys have to be designed to resist higher axial loads due to the self-weight of the upper storeys, which often result in the need for larger-size stud members and/or a greater number of studs, and higher lateral loads in case of seismic events or wind loads, which often requires the use of wood shear panels within the wall assembly. These wall assemblies very often will need to meet standard fire resistance requirements, and therefore, information regarding their standard fire-resistance ratings should be developed. This report documents the results of fullscale furnace tests conducted to develop standard fire-resistance ratings of encapsulated LWF assemblies for use in mid-rise applications.