Bearing pads, a type of bridge bearing, are essential components used in bridge construction to safely connect the superstructure (the bridge deck and beams) to the substructure (the piers and abutments).
Their primary purpose is to transmit loads while allowing controlled movement between the two parts of the bridge.
Key Functions of Bearing Pads
Bearing pads perform several critical functions that ensure the safety and longevity of the bridge structure:
- Load Distribution: They provide a uniform surface to transfer the massive vertical loads from the bridge deck (including the weight of the structure, vehicles, and traffic) down to the supporting piers and abutments. This prevents localized stress concentrations that could damage the concrete or steel.
- Accommodation of Movement: Bridges are constantly subject to movement from various factors, and bearing pads are designed to accommodate these movements without transferring damaging stress to the structure:
- Thermal Expansion and Contraction: As the temperature changes throughout the day and year, the bridge deck expands and contracts. Bearing pads allow this horizontal movement to occur.
- Rotation: When the bridge deck deflects (bends) slightly under the weight of vehicles, it causes a small rotation at the ends of the beams. The flexibility of the bearing pad absorbs this rotational movement.
- Wind and Traffic Vibrations: They act as shock absorbers to dampen and isolate vibrations caused by wind and dynamic traffic loads, reducing wear and tear.
- Seismic Activity: In earthquake-prone areas, specialized bearing pads (like seismic isolators) are crucial for absorbing and dissipating seismic energy.