Bridge bearing

The purpose of a bearing is to allow controlled movement and thereby reduce the stresses involved.

Possible causes of movement are thermal expansion and contraction, creep, shrinkage, or fatigue due to the properties of the material used for the bearing.

External sources of movement include the settlement of the ground below, thermal expansion, and seismic activity.

[2] The oldest form of bridge bearing is simply two plates resting on top of each other.

As the bridge expands, the bearing rocks to allow movement in the horizontal direction.

These bearings only allow rotation, and prevent movement in the horizontal and vertical directions.