What are the main functions of bridge expansion joints?

The primary role of bridge expansion joints is to accommodate movements that occur due to temperature fluctuations, settling of the structure, and other dynamic actions such as traffic loads. As materials expand and contract in response to temperature changes, they exert stresses on the bridge superstructure. Expansion joints provide a necessary gap that allows these movements and mitigates the potential for cracking, misalignment, or structural damage. By allowing for this flexibility, they significantly reduce stress on the bridge components, which contributes to the overall longevity and safety of the structure.

Other options do not appropriately address the main functions of expansion joints. While decorative modifications may be a consideration in some design aspects, they are not a core function of expansion joints. Increasing the weight capacity of a bridge isn't relevant to what expansion joints do, as these joints do not add strength or load-bearing capabilities. Lastly, while some joint systems may help control debris entry at certain locations, this is not the main function of expansion joints, which focus on allowing for movement and protecting structural integrity.