What are the 4 basic bridge structures?

1. Beam bridges. These are the simplest type of bridge, and consist of a horizontal beam supported by piers. Beam bridges are typically made of concrete, steel, or wood.

2. Arch bridges. These bridges consist of a curved arch that supports the weight of the bridge deck. Arch bridges are typically made of stone, concrete, or metal.

3. Suspension bridges. These bridges are supported by cables that are suspended from towers. Suspension bridges are typically made of steel.

4. Truss bridges. These bridges consist of a series of triangles that are connected together to form a rigid structure. Truss bridges are typically made of steel or wood.