Final answer:
A beam bridge is only good for covering short distances because its strength diminishes with length. Thermal expansion is also factored into the design, with small changes in length being managed across many expansion joints to prevent damage. For longer spans, additional supports such as piers are needed to ensure the bridge's stability.
Step-by-step explanation:
A beam bridge is a type of bridge that consists of a simple span supported at its ends without any intermediate supports. This design limits the distance it can span, as the strength of a beam diminishes with length, a concept rooted in Physics and Engineering. For this reason, a beam bridge is only good for a short distance. Longer spans require additional support structures, like piers or suspension cables, to handle the increased loads and the bending moments that come with an extended length.
Thermal expansion is an important factor in bridge design, including for beam bridges. Materials used in bridge construction can expand and contract with temperature changes. Engineers must design expansion joints to accommodate this movement. Although the change in length is small, especially compared to the total length of a bridge, ignoring thermal expansion could lead to structural damage or even bridge failure.
For example, in a bridge supported by two piers, as noted in the provided reference, each pier must provide an upward force to counteract the bridge's weight and the loads it carries. If the bridge span is too long for a simple beam bridge design, the forces might not be distributed evenly, leading to excessive stress on the bridge material, which could increase the risk of collapse.