When the United States Armed Forces needs a bridge, they need something modular, lightweight and easy to install. They also need it to be able to carry substantial loads without having to think about whether there is sufficient structural capacity. The U.S. Army Corps of Engineers (USACE) is constantly looking for new technologies that simplify deploying bridges to an active theatre.
The inherent benefits of the Hillman Composite Beam (HCB®) made it an obvious choice for a technology that warranted consideration for military applications. To vet out the technology, the USACE elected to install an HCB bridge on the artillery range in Fort Knox, Kentucky.
Although U.S. military bridges are designed using American Association of State Highway and Transportation Official (AASHTO) codes, they are designed to carry substantially larger loads such as a HETS 115 vehicle to transport armored personnel carriers. These vehicular loads are in many cases almost twice the standard loads of a conventional AASHTO HL-93 design truck. One of the inherent benefits of the HCB is that it is ideally suited to applications with very high Live to Dead load ratios. The HETS 115 loads were easily incorporated into the design of the HCBs for this project.
In November 2012, Bridge No. 4 at Fort Knox was replaced with two new experimental spans. One span comprises steel girders with a FRP reinforced concrete deck. The second span comprises HCBs supporting a conventional reinforced concrete deck. Several new details were developed in order to adapt to the two-span configuration with the adjacent steel span, including the use of steel transverse diaphragms attached at the ends of the HCBs. It also included the novel use of Stay-In-Place (SIP) pultruded FRP forms to provide a lightweight and sustainable solution for the deck forming.
The five HCBs were pre-filled adjacent to the bridge with concrete by the All-Cities Construction/Salsman Brothers team to expedite the field installation. Even when filled, the HCBs weighed no more than the adjacent steel girders. The result is a rapidly deployed, modular bridge system that provides the military with a bridging solution that can even be containerized.
Project Specs:
HCB Piece Weight
Owner: U.S. Army Corps of Engineers (USACE)
Contractor: All-Cities Construction/Salsman Brothers
Completion date: November 2012
Project Sheet: Click here for downloadable PDF version