This study on Circular Economy & the Built Environment Sector in Canada was carried out by The Delphi Group in collaboration with Scius Advisory and completed in March 2021 on behalf of Forestry Innovation Investment Ltd. (FII) in British Columbia and Natural Resources Canada (NRCan) as the co-sponsors for the research. The work identifies a broad range of current efforts across Canada and undertakes a deeper dive on design for disassembly and adaptability (DfD/A) best practices, including an analysis of the ISO Standard 20887:2020 (i.e., design for disassembly and adaptability) in line with current Canadian industry practice and market readiness.
Timber has been used for building construction for centuries, until the industrial revolution, when it was often replaced by steel and concrete or confined to low-rise housings. In the last thirty years however, thanks to the development of mass timber products and new global interest in sustainability, timber has begun to make a resurgence in the building industry. As building codes and public perception continues to change, the demand for taller and higher-performance timber buildings will only grow. Thus, a need exists for new construction technology appropriate for taller mass timber construction, as well as for fabrication and deconstruction practices that respect wood’s inherent sustainable nature. With this in mind, this research program aims to develop a new hybrid shear connection for mass timber buildings that allows for easy construction, deconstruction, and reuse of the structural elements.
This report includes results of Phase 1, which focused on connections consisting of partially threaded 20M and 24M steel rods bonded into pockets formed in CLT and surrounded by thick crowns of high-strength three-component epoxy-based grout. A total of 168 specimens were designed and fabricated, and push-out shear tests carried out with a displacement-controlled monotonic loading protocol. Strength and stiffness values were assessed and effective failure modes in specimens identified. These latter, along with the recorded load-deformation curves, indicate that it is possible to develop mechanics-based design models and design formulas akin to those already used for typical dowel-type fastener timber connections. Additionally, the specimens were easily fabricated in the lab and quickly fastened to the test jig by means of nuts and washers, suggested such connections have a strong potential for prefabrication, disassembly, and reuse.
Project contact is Lech Muszynski at Oregon State University
The aim of this project is to remove this vulnerability by thoughtful conceptualization of basic strategies for optimizing the design of mass timber buildings for successful post-use material recovery/reuse and end-of-life climate benefit. Research questions will include:
1. Is demolition of decommissioned mass timber buildings a viable end-of-life option at all?
2. Can deconstruction be conducted by following construction steps in reverse order?
3.What may be the extent of damage inflicted to the connection nests, connected edges and surfaces of MTP elements during a deconstruction?
4.Can original connection nests be safely reused in structures re-using deconstructed MTP elements?
5.What is the impact of techniques and technologies selected at the design, production, and construction stages on the EOL options and carbon cost of deconstruction,
6. What is the carbon impact of deconstruction on reuse or recycling of MTP elements?
7. Do the existing deconstruction companies in the Pacific northwest have capacity to process mass timber panels that could not be reused?
8. What is the carbon costs of transportation and repurposing/recycling of MTP elements for non-structural uses?