roundarches

Round arches, or semicircular arches, are arches whose curve forms a segment of a circle. The arch is built from wedge-shaped stones called voussoirs, arranged around a central keystone at the crown. In a round arch, forces are primarily compression, allowing relatively wide spans with sturdy walls and straightforward construction in stone, brick, or concrete.

History and use. Semicircular arches are a hallmark of Roman engineering, where the arch enabled durable bridges, aqueducts, and large vaults. The Romans’ use of concrete and precise voussoirs facilitated impressive spans and relatively thin walls. After antiquity, round arches remained common in Western Europe during the Romanesque period (roughly the 10th to 12th centuries), appearing in church portals, arcades, and vaults. They also occur in Byzantine and early Islamic architecture, though many Islamic arches are horseshoe-shaped or otherwise varied. In Gothic architecture, round arches were eventually superseded by pointed arches, which better distribute thrust and allow taller structures, but round arches continued to be used in revival styles and in contexts seeking a classical appearance.

Structure and variants. The key elements of a round arch are the voussoirs, the central keystone, and the arch’s curvature, which distributes weight into the supporting walls or piers. Materials commonly used include stone, brick, and concrete. While less prevalent in modern high-rise design, round arches remain a feature in neoclassical and monumental architecture, and are frequently employed for bridges, gateways, and porticoes to evoke classical antiquity.

Notable examples. The Arch of Titus, the Colosseum, and Pont du Gard illustrate the Roman utilization of semicircular arches, while Romanesque churches such as Speyer Cathedral show their enduring medieval use.