Flat-Pack PC Concrete Arch Bridge

Segmented-arches are an ancient form of construction. But after centuries of limited use, they are making a come-back. The example shown above is installed in sections to achieve the desired width of the bridge. After the foundation, abutment, and wing walls are built; the bridge portion itself can be placed in a day or so without the need for shoring, bracing, or formwork.

Known generally as a "flat-pack" the arch/beam is transported flat and falls into an arch under gravity when lifted. Each arch is a composite of pre-cast, trapezoidal, unreinforced concrete blocks or voussoirs, connected along the top by a high-tensile polymer membrane.

The spandrel above the arch is backfilled with rock or concrete and the finally the deck constructed on top. The longest crossing to-date is 53 feet, but longer spans, skew-spans, and double-arch radius spans are planned.

The cost of construction is about equal to conventional beam-and-span systems, but because there is no reinforcement, flat-packs are much more durable and have an anticipated service-life of 2 to 3 times a traditional bridge. Precast units typically make for shorter construction schedules as well.

Learn more: asce.org; youtube.com; gizmag.com; engineering.com; bridgeweb.com;