Bearings are structural devices positioned between the bridge superstructure and the substructure.
Their principal functions are as follows:
1. To transmit loads from the superstructure to the substructure, and
2. To accommodate relative movements between the superstructure and the substructure.
The forces applied to a bridge bearing mainly include superstructure self-weight, traffic loads, wind loads, and earthquake loads. Movements in bearings include translations and rotations. Creep, shrinkage, and temperature effects are the most common causes of the translational movements, which can occur in both transverse and longitudinal directions. Traffic loading, construction tolerances, and uneven settlement of the foundation are the common causes of the rotations.