Structure and application of bowl bearings

In major projects such as large bridges and building structures, the support system is a key component that connects the upper structure with the lower foundation. It not only has to bear huge loads, but also needs to adapt to the displacement and rotation of the structure. As a typical pressure bearing rotating support, bowl bearings play an irreplaceable role in modern engineering due to their high load-bearing capacity, flexible rotation, and smooth displacement.

1、 Basic structure of bowl bearings
The design of bowl bearings cleverly draws on the concept of "bowl", and its structure is mainly composed of the following parts, each performing its own duties and working together:

Pot:

This is the core pressure bearing component of the bearing, usually milled from high-strength steel. It is a circular container that serves to fix and constrain other components, and disperses and transmits massive concentrated forces to the lower bridge piers or foundations.

Elastomeric Pad:

A circular plate made of polytetrafluoroethylene (PTFE) or chloroprene rubber located inside the steel basin. It is the key to achieving rotation. Under the action of pressure, the rubber plate undergoes elastic deformation inside the sealed steel basin, providing flexible rotational ability for the upper structure.

PTFE Slide Plate:

Usually embedded on the bottom surface of a component called a 'middle steel lining plate'. PTFE material has an extremely low coefficient of friction and is known as the "solid material with the smallest coefficient of friction". It is paired with stainless steel plates to form a low friction pair, thereby achieving horizontal displacement of the support.

Upper support plate (Piston or Top Plate):

Also known as a piston or top plate, it directly contacts the upper structure (such as a box girder) and transfers the load downwards. Its bottom surface is connected to a PTFE skateboard, while its top surface is fixed to concrete or steel structure.

Sealing Ring:

A rubber ring tightly installed in the groove of the upper opening of the steel basin, its function is to wrap around the pressure bearing rubber plate inside, prevent it from being squeezed out of the steel basin, and prevent dust, moisture and other impurities from entering the basin, ensuring long-term reliability.

Stainless Steel Plate:

It is usually fixed with the upper or lower support plate and forms a sliding pair with the PTFE sliding plate to ensure smooth horizontal sliding.

2、 Working principle of bowl bearings
The core function of bowl bearings is to withstand loads, allow rotation, and adapt to displacement.

Pressure bearing function: Vertical loads are transmitted to the PTFE sliding plate through the upper support plate, and then spread to the steel basin and lower foundation through the pressure bearing rubber plate. The steel basin and the pressure bearing rubber plate jointly bear extremely high pressure.

Rotation function: When the beam body bends or rotates due to load, temperature changes, or other reasons, the force will act on the upper support plate. Due to its excellent elasticity, the pressure bearing rubber plate can undergo uneven compression deformation under the constraint of the steel basin, allowing the upper support plate to rotate at a slight angle and release the bending moment inside the beam.

Displacement function: When the beam needs to undergo horizontal displacement due to thermal expansion and contraction, concrete shrinkage and creep, etc., the low friction pair between the PTFE sliding plate and the stainless steel plate begins to work. Even under extreme pressure, they can generate relative sliding with minimal friction, guiding the beam to move smoothly horizontally and releasing internal stress.

3、 Main characteristics of bowl bearings
Extremely high bearing capacity: Due to its large pressure bearing area and the use of high-strength steel, the bearing capacity of a single support can reach tens of thousands of tons, which can meet the needs of super large bridges.

Good rotational performance: The elastic deformation of the pressure bearing rubber plate in a closed space provides a stable and reliable rotational mechanism, with strong angular adaptability.

Large displacement: By designing skateboards of different sizes, it is possible to meet large displacement requirements ranging from a few centimeters to over one meter.

Easy maintenance: compact structure, good sealing, basically maintenance free, long service life.

4、 Application fields of bowl bearings
Basin bearings are mainly used in situations where they need to withstand huge loads and adapt to large displacements and rotations:

Large highway and railway bridges: This is the most classic application field of bowl bearings, especially in the positions of piers and abutments of long-span continuous beam bridges, arch bridges, cable-stayed bridges, and suspension bridges.

Large building structures: roof supports for large-span buildings such as sports halls, exhibition centers, and terminals, used to adapt to deformation caused by temperature changes.

Hydraulic structures: supports for structures such as dams and gates.

Special structures: such as nuclear power plant facilities, elevated warehouses, and other structures that require seismic and displacement resistance.

5、 Summary
Basin bearings, with their scientifically reasonable structural design, perfectly solve the coordination problem of force and deformation in large engineering structures. It is not only a hub for transmitting loads, but also a key "joint" for releasing constraints and ensuring structural safety. From bridges spanning rivers and canyons to magnificent modern buildings, bowl shaped bearings silently support the stability and safety of these super projects. They are indispensable components in the hands of structural engineers and demonstrate the outstanding wisdom of human beings in the combination of engineering mechanics and materials science.