Technical Guide for Evaluation of Seismic Force Resisting Systems and Their Force Modification Factors for Use in the National Building Code of Canada with Concepts Illustrated Using a Cantilevered Wood CLT Shear Wall Example
The objective of this guideline is to provide a simple, systematic, and sufficient procedure for evaluating the performance of Seismic Force Resisting Systems (SFRSs) and to determine the appropriate ductilityrelated (Rd) and over-strength related (Ro) force modification factors for implementation in the National Building Code of Canada (NBC). The procedure relies on the application of non-linear dynamic analysis for quantification of the seismic performance of the SFRS. Note that the procedure is also suitable for assessing force modification factors (RdRo values) of systems already implemented in the NBC.
The audience for this guideline are those (called the “project study team” in this document) who submit proposals for new SFRSs with defined RdRo values to the NBC for inclusion in Subsection 4.1.8., Earthquake Loads and Effects, of Division B of the NBC. This guideline can also be used by a team performing an alternative design solution for a specific project and seeking acceptance from authority having jurisdiction. In such cases, not all aspects of this guideline (e.g., having different archetypes) will be needed.
The acceptable solutions in Division B of the anticipated 2020 NBCC limit the height of Groups C and D buildings of sprinklered encapsulated mass timber construction (EMTC) to 12 storeys in building height, and a measured building height of 42m. The recently published 2021 IBC contains provisions to permit buildings of mass timber construction under the IBC Type IV construction, surpassing the NBCC provisions by maximum building height, building area, occupancy groups, and interior exposed timber. The IBC mass timber buildings are permitted to have a building height of maximum 18 storeys, depending on the occupancy group. Within Type IV construction, four subdivisions are described to have varying maximum permissible building height, area, fire resistance rating (FRR), and interior exposed timber.
Through a comparison of mass timber provisions of both Codes, relevant research reports, test reports, industry standards, this report documents the consequential and inconsequential differences and developed conclusions on whether the NBCC can adopt the IBC provisions, and with what modifications so that the new provisions may fit the NBCC context.
FPInnovations’involvement in various codes and standards technical committees aims to monitor, contributeor propose changes for improvement as well as to create new standards to include new wood products and systems based on knowledge developed from FPInnovations’ research activities. Involvement also allows FPInnovations to be aware of any potential changes to codes and standards and to recognize and address threats and opportunities for wood use. Codes and standards exist to protect consumers but are written to reflect the current practices and knowledge based on a consensus agreement by committee members. FPInnovations’ involvement in codes and standards committees helps to align the coming changes with new wood products. This InfoNote reports on FPInnovations’ contribution to the floor vibration-control design methods on codes and standards implementation and research.
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).
The correlation between the bending elastic modulus of lumbers along the primary direction and that of the resultant cross-laminated timber (CLT) plates in the full size suitable for slabs or wallboards was investigated to verify the feasibility of predicting the bending performance during the manufacturing of heavy building structures of this new type of material. A batch of Canada hemlocks lumber was graded based on a vibrational test that measures longitudinal elastic modulus. The elastic modulus and shear modulus in the transverse direction were also measured using the scheme of a torsional modal analysis of a cantilever plate. CLT were fabricated using the graded lumbers in sizes suitable for slabs or wallboards. The elastic moduli of these CLT products were measured using a conventional four-point static bending test. Finally, the static measurements of the elastic moduli of the CLT were compared with their predicted values that were calculated with the aforementioned data collected from the lumber pieces. The predicted elastic modulus along the primary direction of a CLT product agreed with the measured values. Therefore, the mathematical model of the CLT plate and the equation of its elastic modulus are feasible for the bending performance prediction in industrial production of CLT.
In order to expedite market acceptance and facilitate the commercial uptake of wood products and systems in Canada, it is necessary to showcase such applications through high-rise and non-residential building demonstration projects. This paper presents recent initiatives by the Government of Canada focused on increasing use of wood as a green building material in infrastructure projects by supporting such demonstration projects. The objective of Green Construction through Wood (GCWood) program (launched in 2017) is to support the design and construction of several high-rise and non-residential timber demonstration buildings and bridges in Canada through expression of interest (EOI) calls. The program is also supporting research and development activities to facilitate acceptance of provisions that would allow for the construction of tall wood buildings in Canadian building codes and advanced wood education at engineering and architectural colleges and universities to help develop the future design capacity in Canada.
The rate at which flame spreads on the exposed interior surfaces or a room or space can have an impact on the rate of fire growth within an area, especially if the materials of the exposed surfaces are highly flammable. Therefore, the National Building Code of Canada (NBC) regulates the surface flammability of any material that forms part of the interior surface of walls, ceilings and, in some cases, floors, in buildings. Based on a standard fire-test method, the NBC uses a rating system to quantify surface flammability that allows comparison of one material to another, and the ratings within that system are called flame-spread ratings (FSR).
Fire separations and fire-resistance ratings are often required together but they are not interchangeable terms, nor are they necessarily mutually inclusive. The National Building Code of Canada (NBC)1 provides the following definitions: A fire separation is defined as “a construction assembly that acts as a barrier against the spread of fire.” A fire-resistance rating is defined as “the time in minutes or hours that a material or assembly of materials will withstand the passage of flame and the transmission of heat when exposed to fire under specified conditions of test and performance criteria, or as determined by extension or interpretation of information derived therefrom as prescribed in [the NBC].” In many buildings, the structural members such as beams and columns, and structural or non-structural assemblies such as walls and floors, are required to exhibit some degree of resistance to fire in order to prevent the spread of fire and smoke, and/or to minimize the risk of collapse of the building in the event of a fire. However, fire separations are assemblies that may or may not be required to have a specific fire-resistance rating, while structural members such as beams and columns that require a fireresistance rating to maintain the structural stability of a building in the event of a fire are not fire separations because they do not “act as a barrier against the spread of fire.”
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.
Over the past several decades, environmental issues have become an increasing priority for both government and private industry alike. Here in North America the emphasis has gradually broadened from site-specific environmental degradation to include the characterization of product burdens. Similarly, many private companies and/or their respective trade associations have increasingly emphasized environmental information and often share this information with their customers in the form of a environmental product declaration (EPD). Life cycle assessment (LCA) is the backbone on which a Type III EPD is based.
The use of LCA is growing in the mainstream as green building ratings systems (e.g., LEED V4 and Green Globes), government procurement policies, and pollution prevention programs are contemplating or already incorporating the use of environmental performance measures that can only be objectively provided through a thorough LCA study. Similarly, many product manufacturing companies are adopting “design for the environment” environmental management systems to either reduce the overall mass or material complexity of their products or to streamline their manufacturing processes and consequently reduce environmental burdens emanating from their plants, as well as making it easier for their products to be recycled at their end-of-life.
The Canadian Wood Council commissioned the Athena Sustainable Materials Institute to update the Institute’s 2012 cradle-to-gate LCA of Canadian LVL production in support of a joint N. American environmental product declaration (EPD) initiative. Consequently, the previous research has been updated with new primary gate-to-gate production data, revised background data, and this new report. This research has been completed in accordance with the most recent version of FPInnovations PCR for North American Structural and Architectural Wood Products.