Today’s timber bridges are simply superior to the low-quality timber bridges you may have seen in the past, thanks in part to advancements in preservative treatments and corrosion-resistant hardware. Timber can provide solutions to maintenance issues, aesthetics, design objectives, logistical problems and construction time limits. Given these advantages, engineers can no longer assume that concrete or steel is the material of choice for their clients. For example, 16 prefabricated concrete and steel bridges were originally specified for the Big Canoe development north of Atlanta. But the owners persuaded the engineers to further investigate timber, because this was their first choice.
Previous timber bridges located in the Big Canoe development were antiquated; when the decking on the bridges needed to be replaced, the bridges were closed for an extended period of time. York Bridge Concepts (YBC) addressed this concern immediately by utilizing longer-life, treated timber and designing a wear deck on top of the structural deck. Should the wear deck needs to be replaced, the structural integrity of the bridge will not be compromised and the repair time will be minimal. The second objective dealt with the aesthetics of the bridges—in this wooded community, the developers knew timber best suited the surroundings. In addition, a design that included a super-elevated and curved 160-ft vehicular bridge was needed in order for the bridge to tie in at the abutments. This design could not be accomplished using the prefabricated concrete, but was easily achieved with timber.
Another issue for Big Canoe was the logistics of transporting large prefabricated concrete structures to the mountainous, undeveloped site. The use of timber also met this challenge; the individual pieces and parts of the bridge were transported to the site for YBC carpenters to completely construct the bridges on site, from start to finish.
The construction time for this project also was greatly shortened. Timber, a readily available resource, did not delay this project like steel fabrication or concrete procurement might have. In fact, YBC built in 4-6 months less time than projected for the originally specified structures.
Finally, timber never compromised the structural integrity or durability of the bridges. Four bridges were built to AASHTO HS20-44 standards, while 12 trail bridges were built to H-10 capacity to allow emergency vehicles access to the trail system.
