Conroy Lum, P.Eng. (BC), Lead Scientist – Sustainable Construction, FPInnovations
Conroy is a structural engineer by training. His area of expertise is in drafting codes and standards, namely those covering the performance evaluation and quality assurance of structural wood products. He has drafted standards for the Canadian Standards Association (CSA), American Society for Testing and Materials (ASTM), and the National Lumber Grades Authority (NLGA). He was formerly Chair of the CSA Technical Committee responsible for the CSA standards on a number of forest products standards, included glued-laminated timber and structural wood adhesives. He currently leads the timber bridge research project funded by the Province of British Columbia and Natural Resources Canada.
Supporting a Renaissance in Timber Bridge Construction
As a net producer of manufactured solid wood products, British Columbia lags other jurisdictions when it comes to the use of timber in prominent public infrastructure such as bridges. As a result of a number of factors, BC’s use of timber in bridges has diminished significantly over the last 50 years. Sourcing timber bridge solutions within BC is very limited to the point of being non-existent. Understanding of timber design, performance and inspection is correspondingly limited. Consequently, existing timber bridges are treated as liabilities to be replaced.
The value being placed on sequestering carbon wherever possible—to enable the overall economy to function close to a carbon neutral state—now provides an incentive for using more wood in man-made structures. With advances in understanding and research, a renaissance in wood buildings is underway in BC due to the efforts over a number of years to proof out the possibilities followed by code revisions to facilitate broader acceptance. We will soon see building code recognition of 12-storey wood based buildings: this a result of work on cross-laminated timber (CLT), now produced in BC, and a bold demonstration of CLT used in an 18-storey building that not only exceeded the height limits in the BC Building code for wood construction, but also resulted in a faster time to completion than a typical project. Effort is now being directed towards public bridge infrastructure seeking a similar outcome. Determining if it is reasonable and possible to re-establish a BC timber bridge supply chain, leveraging new technologies (or new ways of using existing technologies) are key questions being evaluated in the Next Generation Timber Bridges for Resource Roads project.
Developing this understanding requires confronting the issues that led to the gradual erosion of timber’s share of bridges (e.g. concerns with longevity, cost, supply of large timbers, timber design/fabrication/ construction expertise). This includes identifying new technologies and techniques to overcome these issues, and outlining a follow-up plan covering codes and standards revisions. Reversing the decline, which has occurred over a number of decades, will not be easy, particularly if there is a desire for benefits to be broadly based (e.g. multiple suppliers across BC) utilizing local resources. While it is understood standardization of new technologies will play a critical role in providing certainty among participants in an emerging timber bridge supply chain, a major consideration is how this supply chain can be economically viable in a competitive environment currently dominated by steel and concrete, and withstand the pressures arising from the normal business cycle.
We outline the initial steps being taken to restore the timber bridge supply chain in BC with focus on the fabrication quality assurance. Highlights from the timber bridge project, including the All Timber Proof of Concept Bridge to be constructed this summer will be used to present the key points.
- Timber bridge supply chain
- Quality assurance
- Carbon sequestration
- Improving timber performance
Conroy Lum, FPInnovations
Brian Chow, BC Ministry of Forests, Lands, Natural Resource Operations and Rural Development