Bridges are constructed of different materials whose properties and costs vary. Some materials are strong against compression forces but weak against tension forces; some materials resist fire, corrosion or weathering. Materials commonly used in bridge design include wood, rope, aluminum, concrete and steel.
In the design of structures there is a need to consider factors such as function, materials, safety, cost and appearance.
Bridges can be designed in different ways to withstand certain loads and potentially destructive forces.