The Ancient Roman Bridge, a Timeless Engineering Feat

Ancient Romans were the first major bridge builders. Through extensive use of the arch and concrete they perfected, they built the biggest and longest-lasting bridges of antiquity.

The Puente Romano de Mérida in Spain, completed in 117 AD, is the world’s longest surviving bridge of the ancient times. Ángel M. Felicísimo from Mérida, España, CC BY-SA 2.0, via Wikimedia Commons.

Stone arch after stone arch. That is the basics of an Ancient Roman bridge. Their shape and form don’t change much from that. Although it doesn’t sound fancy presented like this, it is yet another of the Ancient Romans' exceptional engineering feats. I’ll explain why.

The key to the Ancient Roman bridge was the “true” arch, built with stone, and the concrete they so expertly perfected, the Roman concrete or opus caementicium. Yet, alongside these two key components were important technological features and design details.

Origins

Arches were the first evolution away from the post-and-lintel structure that had existed for thousands of years in Neolithic civilizations (i.e.: until 2,000 BC in the Egyptian, Hellenistic, or Indian civilizations). It was initially a ‘corbel arch’ or ‘corbelled arch’, built as the higher the structure rose the more it offset towards the centerline. It is called a “false arch” because it is not self-supporting per sé.

The arch as we see it everywhere today, the “true arch”, appeared around 2,000 BC in Mesopotamia and it was built in bricks. An arch is a compression form, no tensile stresses happen (called “arch action”), transferring the forces all the way to the ground through the ‘springers’, the linear supports that begin when the curved part ends (e.g.: columns).

Completed in 3 BC, the bridge is in the pleasant countryside of southeastern France near Bonnieux, at the western edge of the Luberon Regional Natural Park. Its semicircular spans were built in stone blocks. . Photo by Hawobo, CC BY-SA 2.0 DE, via Wikimedia Commons.

Although the arch is self-supporting, there is a risk of collapse due to the lateral ‘thrust’. To avoid this, the structure is secured with ‘tie-rods’ or external supports such as abutments. Arches within a wall — or consecutive arches in a bridge — do not have that issue as there is another structure at its sides.

The arch requires a very simple construction method allowing for strength, flexibility, and aesthetics.