Beam bridge

Beam Bridge

Multispan plate girder bridge deck on concrete piers.
Ancestor	Log bridge
Descendant	Box girder bridge, Plate girder bridge, trestle, truss bridge
Carries	Pedestrians, automobiles, trucks, light rail, heavy rail
Span range	Short
Material	Timber, iron, steel, reinforced concrete, prestressed concrete
Movable	No
Design effort	Low
Falsework required	No unless cast-in-place reinforced concrete is used

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 (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, prestressed or post-tensioned.

Types of construction could include having many beams side by side with a deck across the top of them, to a main beam either side supporting a deck between them. The main beams could be I-beams (also known as H-beams), trusses, or box girders. They could be half-through, or braced across the top to create a through bridge.

Because no moments are transferred, thrust, as from an arch bridge, cannot be accommodated, so leading to innovative designs, such as lenticular trusses & bow string arches, which contain the horizontal forces within the superstructure.