Over the past years, FPInnovations has initiated projects aimed at reducing the effects of climate changes on access roads to resource. Among these projects is the evaluation of the use of advanced wood-based solutions to construct innovative timber bridges, which are considered as green infrastructure, as a way to mitigate impact on forest resources.
There is a long history of timber being used in resource road bridges. However, those timber structures are gradually being replaced with steel and concrete bridges. In order to mitigate this trend, FPInnovations has initiated a two-year project, funded by the province of British Columbia (through the Ministry of Forest, Lands, Natural Resource Operations and Rural Development). This project focuses on the use of timber-concrete composite (TCC) for the bridge deck.
The timber-concrete composite system in this study consists of two distinct layers made of timber and concrete joined together by shear connectors, with concrete being the top layer, therefore exploiting the best properties of both materials. TCC system can be a cost-competitive solution for longer span surfaces needed in bridge components since the two materials would be used efficiently to utilize their inherent mechanical properties.
Phase 1 of the project consisted in testing the decks, which were fabricated at FPInnovations from available green, unincised, and untreated Hem-Fir lumber; this enabled certain concepts to be quickly identified and refined. Phase 2, which included green but treated and incised lumber, allowed for a more accurate assessment of the concept. So far, tests performed have shown sufficient capacity to pursue more costly cyclic and environmental exposure tests.
Because the deck is built entirely with commercially available components using existing fabrication facilities (i.e. no further capital investment), the potential is high for subsequently developing an all-timber resource road bridge concept involving timber girders. Efforts are underway to evaluate high capacity glulam girders to support the decks; this will be followed by identifying and prioritizing potential code changes, assessing the supply chain with regard to training needs, and compatibility with existing capabilities. Lastly, additional laboratory testing supplemented with data from in-situ monitoring will be used to support code changes that will enable broader acceptance of the concepts.
Eventually, an all-timber bridge utilizing more advanced technologies will regain its position as a viable material for bridges, leading to an improved environmental footprint in resource roads.
To learn more about this project, please contact Conroy Lum, from FPInnovations’ Building system team.