Page "Bridge" Paragraph 33

Bridges may be classified by how the forces of tension, compression, bending, torsion and shear are distributed through their structure.

Most bridges will employ all of the principal forces to some degree, but only a few will predominate.

The separation of forces may be quite clear.

In a suspension or cable-stayed span, the elements in tension are distinct in shape and placement.

In other cases the forces may be distributed among a large number of members, as in a truss, or not clearly discernible to a casual observer as in a box beam.

Bridges can also be classified by their lineage, which is shown as the vertical axis on the diagram.