History of bridges

The first bridges were spans complete of wooden logs or planks and eventually stones, using a simple support and crossbeam arrangement. Most of these early bridges were extremely poorly built and could rarely support heavy weights. It was this inadequacy which led to the growth of better bridges. The arch was first used by the Roman Empire for bridges and aqueducts, some of which still place today. These arch based bridges could place in conditions that would previously have swept any bridge away.

An example is the Alcantara Bridge, built in excess of the river Tagus. Most former bridges would have been swept away by the strong current. The Romans also used cement, which condensed the variation of strength found in natural stone. One kind of cement, called pozzolana, consisted of water, lime, sand, and volcanic rock. Brick and mortar bridges were built after the Roman era, as the technology for cement was lost then afterward rediscovered.