archbridge

An arch bridge is a bridge whose primary structural element is a curved arch that transfers loads to the supports through compression. The arch redirects vertical forces into thrust along the curve and into the abutments at its ends, allowing spanning with masonry, brick, or other relatively strong materials. The resulting thrust is contained by stable foundations, making arches inherently durable.

Historically, arch bridges have ancient roots, but Roman engineers popularized stone arch bridges by employing carefully cut voussoirs and a keystone to lock the arch in place. After antiquity, masonry and brick arch bridges continued to be built through the medieval and early modern periods, with later adaptations using reinforced concrete and steel to achieve longer spans and different load conditions.

Design and construction hinge on geometry and centring. Each voussoir is shaped to fit its neighbors, creating a continuous arch that distributes compressive forces. A keystone seals the arch, and abutments resist outward thrust. For construction, temporary falsework or centring supports the arch until the keystone is placed and the structure becomes self-supporting.

Materials and forms vary. Stone and brick were common in older arches, while reinforced concrete and steel enabled segmental and longer-span arches. Arch bridges can be deck arches (the deck sits on top of the arch), through arches (the deck passes through the arch), or hybrids. Common arch types include semicircular, segmental, and pointed (Gothic) arches.

Notable examples include the Iron Bridge of Coalbrookdale, one of the first major cast-iron arch bridges; the Ponte Vecchio in Florence; and the Rialto Bridge in Venice. In modern practice, arch bridges remain a versatile choice for moderate to long spans where durable compression members are advantageous.