Question

Why do bridges have expansion joints built into them?
To stop bridges expanding and contracting.
Because bridges will expand and contract as temperature changes, and without expansion joints they might collapse.
To avoid collapse due to gusts of wind.
So that the bridge can be lengthened in the future.
Expansion joints aren't actually necessary.​

Answer 1

Answer:

Thermal expansion can affect bridges with either expanding or contracting the bridge (or, by essentially distorting it's shape). ... Expansion joints fill gaps within the bridge and act as a flexible, variable filler that help the bridge adapt to temperature changes without distorting.