By: Big R Bridge
Constructed in 2011, this is the longest single span box culvert of any material in North America. This was also the first large span steel buried bridge to take advantage of its flexible nature in the foundation design.
The original project documents called for a precast concrete arch, which required deep foundations due to the rigid structure having a low settlement tolerance.
Corrugated metal structures are flexible and able to accommodate a higher total and differential settlement than comparable sized precast structures and traditional bridges.
When a value engineered flexible buried bridge was proposed, the geotechnical engineer was asked to review site conditions and provide alternative foundation recommendations suitable for a flexible structure.
The result was an increase in the allowable bearing pressure that made spread footings feasible for the flexible structure while deep foundations were needed for the rigid precast concrete structure.
Even though the assembled costs of the two structures were comparable, there was an overall project savings of 45% with the flexible structure because of a much lower foundation cost.
This has revolutionized the industry in large span / low rise structures and made corrugated steel a viable cost and time saving alternative to precast concrete and traditional bridges.
In many ways, this structure has opened the eyes of many engineers and paved the way for increased use of flexible buried bridges in a market that has been dominated by precast concrete and traditional low to medium span bridges.