The Dillman Bridge in Meaghers Grant was put out for tender in 2019 as a Design Build project. The old bridge had been decommissioned for over two years, after a vehicle accident on the bridge rendered the bridge unusable. This forced the local residents to take a 17-minute detour. The bridge site is located in one of the highest exposed and embedded corrosion zones in the world, making steel and concrete products much more susceptible to the elements than timber. Upon winning the tender, Timber Restoration Services contracted Wood Research and Development for the design work.
Wood Research and Development designed a 35 m long by 7.6m wide with a load rating of CL-625, tu gas a TL-4 crash proof rail system and an Alaskan Yellow Cedar handrail. The substructure consists of driven timber piles with a glulam timber back wall specifically designed for timber bridges. The superstructure is comprised of glulam laminated deck panels sitting on eight glulam girders which have two fixed end movement connections that were assembled onsite. The use of High Strength Fiber (FiRP®) and advanced techniques make this light-weight option not only a cheaper alternative, but also provides additional longevity. All fasteners and hardware are hot dipped galvanized.
The bridge was manufactured and assembled in our state-of-the-art manufacturing plant prior to treatment. This allows preservative uptake in all through bolt fastener holes, pre-drilled holes and edges, resulting in no bright wood being exposed. All fasteners are installed, where possible, either horizontally or vertically from underneath to help with moisture penetration. The structure is then disassembled, and sent for preservative treatment. The hardware and fasteners are sent for galvanization at the same time.
Once this is done the components are placed on a truck and sent to the project site. This method is not only best for extending longevity of the structure but also allows for an accelerated schedule for on-site installation.
This timber bridge will have a life span of at least 100 years, far outlasting any concrete or steel structure.