The cost and complexity of forming reinforced concrete arches often discourages their use in short-span bridges. However, economical inflated forming methods and the use of precast arch sections have helped some local agencies to overcome these objections and to make cost-effective arches part of their bridge program. Footings prepared in advance of arch construction may be either precast or cast in place. Typically the smaller arch structures are backfilled to desired grade and the roadway cast in place over the backfill.
Three systems are described in this article. The first uses an inflated forming method similar to the shotcreting technique that utilizes an inflated closed-end cylindrical balloon. The contractor sets up the inflatable form on temporary foundations, inflates it, and straps it to the desired shape. A second technique involves plant precasting of standardized sections. A newer system originating in the United States expands the arch-box system to bridge spans. The three-sided structural members are rigid frames with vertical sidewalls and arched top wall. The backfill restrains the tendency of the culvert to flex outward.