Taming the beast: Designing Alaska's longest bridge over the Tanana River
With the construction of the Tanana River Bridge in Salcha, Alaska, 1 million acres of U.S. military training facilities have been connected to the rest of Alaska; it also marks the completion of the first phase of the Alaska Railroad Corporation's (ARRC) Northern Rail Extension, which creates an 80 mile rail network between the North Pole and Delta Junction. Challenges to construction of the bridge included its remoteness, its location at potentially active seismic faults, as well as wind, stream flow and debris pressures, river bed scour, sheet ice, and severe flooding. As well, temperatures range from 90degF to lows near 70degF. The project was achieved through collaboration, careful design planning, selection of the appropriate piers, overcoming logistical issues, and enabling a cold climate pour of the concrete. The long term plan is to use the bridge to support rail traffic, as well as military vehicles, and this played an important role in designing the bridge deck.