The foundation and support of these bridges is very important. The work of a bridge is to support itself and its load against the pull of gravity (stress). Stress on a material usually results in strain or a change in the material's shape. There are two types of stress: compression and tension. In a bridge, stress is also caused by the pull of gravity; the amount of stress is determined by the weight of the bridge plus its load. Compression occurs when an object is holding weight. Tension occurs when an object is being pulled or stretched.
The type of bridge designed is directly connected to the kind of stress that will be placed on the bridge. If the bridge will be a pedestrian bridge only then it would not need to be as strong as one that would carry trucks and cars. Steel may not be used. A bridge carrying many cars and trucks at the same time would need to be made sturdy and tough.
Steel, the strongest of all bridge materials may very well be used as well as others. Reinforced concrete is often used. Wood tends to bend and may split so it is unreliable when used in the construction of bridges, especially large bridges.
Assessment:
Name as many parts of bridges as you can.
Which would be used in the construction of your bridge?