The latest developments in seismic design philosophy in modern urban centers have moved towards the development of new types of so called “resilient” or “low damage” structural systems. Such systems reduce the damage to the structure during an earthquake while offering the same or higher levels of safety to occupants. One such structural system in mass timber construction is the “Pres-Lam” system developed by Structural Timber Innovation Company (STIC) and Prestressed Timber Limited (PTL), both from New Zealand. FPInnovations has acquired the Intellectual Property rights for the Pres-Lam system for use in Canada and the United States.
Braced mass timber (MT) frames are one of the most efficient structural systems to resist lateral loads induced by earthquakes or high winds. Although braced frames are presented as a system in the National Building Code of Canada (NBCC), no design guidelines currently exist in CSA O86. That not only leaves these efficient systems out of reach of designers, but also puts them in danger of being eliminated from NBCC. The main objective of this project was to develop the technical information needed for development of design guidelines for braced MT frames as a lateral load resisting system in CSA O86.
In the first year of the project, the seismic performance of thirty (30) braced MT frames with riveted connections with various numbers of storeys, storey heights, and bay aspect ratios were studied by conducting non-linear pushover and dynamic time-history analyses. Also, fifteen (15) glulam brace specimens using bolted connections with different slenderness ratios were tested under monotonic and cyclic loading. Results from this multi-year project will form the basis for developing comprehensive design guidelines for braced frames in CSA O86.