This study illustrates the range of possible wood construction approaches for school buildings that are up to four storeys in height. As land values continue to rise, particularly in higher-density urban environments, schools with smaller footprints will become increasingly more necessary to satisfy enrollment demands. There are currently a number of planned new school projects throughout British Columbia that anticipate requiring either three-or four-storey buildings, and it is forecasted that the demand for school buildings of this size will continue to rise.
This study is closely related to the report Risk Analysis and Alternative Solution for Three- and Four-Storey Schools of Mass Timber and/or Wood-Frame Construction prepared by GHL Consultants, which explores the building code related considerations of wood construction for school buildings that are up to four storeys in height. Though wood construction offers a viable structural material option for these buildings, the British Columbia Building Code (BCBC 2018) currently limits schools comprised of wood construction to a maximum of two storeys, while also imposing limits on the overall floor area. As such, the reader is referred to the GHL report for further information regarding building code compliance (with a particular emphasis on fire protection) for wood school buildings.
As part of Fast + Epp’s ongoing work to push the boundaries of Tall Wood construction in seismic zones, this testing program aims to develop a new dissipative system for use in timber braced frames or other timber lateral systems where the connections provide energy dissipation. The connections are designed to dissipate energy through ductile steel plates to provide robust and well understood dissipative systems. In collaboration with the Advanced Research in Timber Systems’ team at the University of Alberta, Fast + Epp is working on a four-phase testing program for cyclic and monotonic testing of various configurations of perforated plate connections. Small scale tests have been completed on perforated plates, and entire connections will be examined in advance of a full-scale timber brace frame test to evaluate the overall behaviour. One phase of physical testing was completed in January 2020, with the next 3 phases intended to be completed in 2021. Initial data analysis of the first phase testing has resulted in tuning of the system in advance of later phase testing. Results on the first two or three phases of testing are anticipated to be completed in 2020 with initial publication of the results in early 2021.
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.