A clapper bridge is an ancient form of bridge found on the moors of the English West Country (Bodmin Moor, Dartmoor and Exmoor) and in other upland areas of the United Kingdom including Snowdonia and Anglesey, Cumbria, Derbyshire, Yorkshire, Lancashire, and in northern Wester Rossand north-west Sutherland in Scotland. It is formed by large flat slabs of stone, often granite or schist. These can be supported on stone piers across rivers, or rest on the banks of streams.
Beam bridges are the simplest structural forms for bridge spans supported by an abutment or pier at each end. No moments are transferred throughout the support, hence their structural type is known as simply supported.
The simplest beam bridge could be a log (see log bridge), a wood plank, or a stone slab (see clapper bridge) laid across a stream. Bridges designed for modern infrastructure will usually be constructed of steel or reinforced concrete, or a combination of both. The concrete elements may be reinforced or prestressed. Such modern bridges include girder, plate girder, and box girder bridges, all types of beam bridges.