What are bearings in construction?

Bearings in construction are structural components that transfer loads and accommodate movements between a structure’s different parts. They ensure structural integrity and longevity. Bearings manage forces like expansion, contraction, rotation, and translation, caused by temperature changes, seismic activity, and live loads. The construction bearings market projects 5.62% CAGR growth from 2025 to 2035, reflecting the critical role these components, often from a specialized bearing factory, hold.

Key Takeaways

• Bearings in construction help buildings and bridges move safely. They handle changes from heat, wind, and earthquakes.
• Bearings move loads from one part of a structure to another. This stops too much stress and makes structures last longer.
• Different types of bearings exist for different jobs. Examples include elastomeric, pot, and spherical bearings.

Why Bearings are Essential in Construction

Bearings play a fundamental role in modern construction, ensuring the safety, stability, and longevity of structures. They perform several critical functions that make them indispensable components in various engineering projects.

Accommodating Structural Movement

Structures are not static; they constantly experience various movements. Temperature changes cause materials to expand and contract. Seismic activity, wind, and even the weight of people and vehicles induce dynamic forces. Bearings are specifically engineered to manage these movements. For instance, movement calculations for bridge bearings explicitly account for thermal expansion and contraction. They also consider other factors like concrete creep, shrinkage, and elastic shortening in prestressed structures.

Different types of bearings handle these movements in unique ways. Rocker Bearings allow rotation and some translational movement, specifically used in large bridges to accommodate thermal expansion and contraction. Roller Supports permit movement in one direction, typically horizontal, while restricting perpendicular movement. Engineers commonly use them in bridges and long beams to manage thermal expansion and contraction.

Other bearing types also offer specialized movement capabilities. Elastomeric Bearings accommodate displacements through their elastic deformation. Pot Bearings can be combined with sliding surfaces to allow translational movement. Spherical Bearings feature curved plates to support higher loads and movement, making them ideal for complex geometries and significant rotational demands.

Bearings are designed for specific ranges of movement. For example, RJ Watson Disktron Bearings have a rotational capacity exceeding 0.08 radians. Unidirectional bearings allow rotation in both longitudinal and transverse directions and displacement in one direction. Fixed bearings permit rotation in any direction but prevent any displacement. Multidirectional bearings accommodate rotation and displacement in any direction. Flexible guided bearings are designed for the displacement needs of curved girder bridges. Engineers even modified abutment bearings on the Hoover Dam Bypass Bridge for a longitudinal restoring stiffness over a movement range of 5 inches.

Efficient Load Transfer

Bearings are crucial for transferring loads effectively from one part of a structure to another. Structural bearings are devices installed in bridges to transfer loads from the superstructure to the substructure. They are designed to handle various design loads, including dead loads, live loads, wind loads, and seismic loads. This ensures a proper connection between different bridge components and facilitates the transfer of vehicular and external forces. Without bearings, concentrated loads would directly impact the supporting elements, potentially causing localized stress and structural failure. A specialized bearing factory manufactures these components with precision to meet stringent load-bearing requirements.

Reducing Stress and Extending Lifespan

By accommodating movement and facilitating efficient load transfer, bearings significantly reduce stress on structural elements. When a structure expands or contracts, or when it experiences seismic forces, bearings absorb and distribute these movements. This prevents excessive stress from building up in rigid connections, which could lead to cracking, fatigue, or even catastrophic failure. By mitigating these stresses, bearings protect the integrity of the entire structure. This proactive management of forces extends the overall lifespan of buildings, bridges, and other infrastructure, reducing maintenance costs and ensuring long-term safety.

Types of Bearings Used in Construction

Construction projects rely on various bearing types, each designed for specific load conditions and movement requirements. Understanding these differences helps engineers select the most appropriate solution for structural integrity and longevity.

Elastomeric Bearings

Elastomeric bearings are flexible components that accommodate movement through deformation. They typically consist of laminated neoprene rubber layers. Thin steel shims are interspersed within these layers. Some designs also include steel plates on their top and bottom surfaces. For example, bearings might feature rubber layers 8 mm or 12 mm thick, with steel layers measuring 3 mm or 4 mm, depending on the overall bearing size.

Engineers frequently specify elastomeric bearings for various applications. They commonly support concrete superstructures and transmit loads to substructures. These bearings also perform well in other material types and structures. They are particularly popular for short- to moderate-span prestressed concrete girder systems. This is due to their dependable performance, cost-effectiveness, and ease of installation. High-demand steel girder applications, especially those with long spans, large reactions, and complex movements, also benefit from elastomeric bearings. They often offer cost and performance advantages over pot or disc bearings in these scenarios.

Pot Bearings

Pot bearings are robust devices designed to handle high loads and significant rotations. Key components of a pot bearing include a steel pot, an elastomeric pad, a stainless steel plate, and a sealing ring. The operational principle involves an elastomeric pad enclosed within the steel pot. This pad behaves like a fluid under three-phase stress, allowing for large rotations. Horizontal displacement occurs through the relative motion between a PTFE plate on the piston and a stainless steel plate. A specialized bearing factory manufactures these components with high precision to ensure optimal performance.

Pot bearings offer impressive load capacities and rotational capabilities. They typically have a bearing capacity equal to 100% of their design capacity, with an allowance for 10% overloading. These bearings are designed for high loading, often exceeding 50,000 kN. They can also accommodate large rotations, ranging from 0 to 0.03 radians. For instance, some pot bearings can handle capacities up to 60 MN with longitudinal displacements of ±300 mm.

Spherical Bearings

Spherical bearings are ideal for structures requiring high load capacity and significant rotational movement in multiple directions. They feature a curved sliding surface that allows for large rotations and angular displacements. The material specifications for these surfaces are critical for performance.

The concave surface often features a woven PTFE fabric liner. This liner typically has a thickness between 0.020 inches (0.5 mm) and 0.125 inches (3.2 mm) after compression. The convex surface can be solid stainless steel. Alternatively, it might be carbon steel with a minimum 3/32 inch (2.4 mm) thick stainless steel weld overlay. Another option is hard chromium plating, applied according to Federal Specification QQ-C-320B Class 2, with a Rockwell C hardness of at least 60. This surface is then polished to a maximum 20 microinch (0.5 micrometer) finish. For maintenance-free spherical plain bearings, special sliding layers of modern, low-friction materials are incorporated, making them suitable for heavy loads with a constant direction.

Sliding Bearings (PTFE)

Sliding bearings, often utilizing Polytetrafluoroethylene (PTFE), facilitate translational movement with minimal friction. Engineers design these bearings to allow parts of a structure to slide over each other.

Design considerations for PTFE bearings are crucial. PTFE is typically applied between two flat stainless steel plates. The PTFE surface area is often smaller than the steel plates to prevent creep, which is deformation under sustained heavy loads. For larger rotations, exceeding 5 degrees, PTFE is applied to curved stainless steel surfaces. To mitigate creep, engineers use dimpled PTFE or recess it into a backing plate. This helps contain the material. Protecting the sliding surface from construction debris like weld spatter, paint, and metal filings during installation is also essential. Standard flat slide bearings primarily handle linear movement and accommodate only minor rotations, typically under 5 degrees. For significant rotations, specialized curved or spherical bearings are necessary. A complete slide bearing assembly requires a polished stainless steel plate as the mating surface. The PTFE or graphite pad slides against this surface, achieving a low coefficient of friction. PTFE thickness varies with temperature requirements; a 3mm layer is common for standard temperatures up to 130°C, while a 5mm layer set into a recessed plate is used for elevated temperatures up to 200°C.

The friction coefficient of PTFE in sliding bearings can vary. Chloride infiltration, for example, can cause the friction coefficient of the PTFE layer to increase from 0.05 to 0.12. Some studies show that the friction coefficient of polymers rubbing against metals decreases with an increase in load. Other research indicates the friction coefficient increases with an increase in load. This highlights the complex behavior of PTFE under different conditions.

Roller and Rocker Bearings

Roller and rocker bearings are two distinct types that accommodate movement in different ways. Roller bearings primarily facilitate linear movements along a single axis. They are highly effective for large translational movements but do not accommodate rotational movement well. Rocker bearings, conversely, accommodate both rotational and translational movements.

Historically, roller and rocker bearings have found applications in various sectors. While modern construction often favors other bearing types, these traditional designs still have niche uses. For example, roller rocker technologies are prevalent in passenger vehicles, commercial vehicles, and racing cars. They enhance engine efficiency, power output, and reliability. They also reduce engine wear and extend maintenance intervals. These bearings are also used in V6 and Inline-6 engines, as well as specialty vehicles and custom builds, where specific performance requirements demand tailored solutions.

Where Bearings are Used: Insights from a Bearing Factory

Bearings are fundamental components across diverse construction sectors. A specialized bearing factory produces these critical elements for various applications, ensuring structural integrity and longevity.

Bridges and Overpasses

Bridges, especially long-span structures, heavily rely on advanced bearing systems. Engineers specify fabric pad bearings for stiffer, heavier spans like post-tensioned box girder bridges. These bearings offer high load capacity and use a PTFE sliding surface for movement. High Load Multi-Rotational (HLMR) bearings, particularly disk bearings, handle extreme loads and large rotations, common in flexible steel plate girder bridges. Sliding bearings are also ideal for long-span bridges; they facilitate significant horizontal shifts. Bridge bearings overcome challenges in curved designs by allowing superstructures to adapt to directional and torsional forces. They manage horizontal deformations and maintain vertical stiffness in multi-span decks. Bearings also counteract dynamic responses from vehicle and seismic loading, address thermal expansion, and bear tensile stresses during seismic events. They mitigate environmental factors like moisture and corrosive agents.

Buildings and High-Rises

High-rise buildings utilize bearings to manage dynamic loads and enhance seismic resilience. Elastomeric bearings are vital; they manage sway from wind and provide flexibility without compromising strength. They improve foundation stability by accommodating ground shifts and reduce vibrations for occupants during earthquakes or strong winds. Skyscrapers like the Burj Khalifa demonstrate their effectiveness. Seismic isolation bearings, positioned between a building’s structure and foundation, allow the building to move independently during an earthquake. This minimizes seismic energy transfer, safeguarding the structure and its contents. These bearings offer horizontal flexibility for swaying while maintaining vertical stiffness. A bearing factory designs these systems for optimal performance.

Other Infrastructure Projects

Specialized infrastructure projects, such as stadiums and power plants, also employ advanced bearing solutions. These facilities often use seismic isolation bearings. Elastomeric bearings, composed of rubber and steel plates, provide flexibility and dissipate energy. Sliding bearings, frequently incorporating friction pendulum systems, allow controlled movement in large, heavily loaded structures. Hybrid bearings combine features of both elastomeric and sliding types, offering multi-axis isolation for complex structures where traditional solutions are insufficient.

Bearings are indispensable components for modern construction. They ensure the safety, integrity, and longevity of structures. These vital elements effectively manage loads and accommodate movements. Bearings help structures withstand environmental and operational stresses, making them crucial for modern infrastructure. A specialized bearing factory often produces these essential parts.

FAQ

What is the primary function of construction bearings?

Bearings transfer loads and accommodate movements between structural parts. They ensure a structure’s integrity and longevity by managing forces like expansion, contraction, and rotation.

How do bearings contribute to seismic safety in buildings?

Seismic isolation bearings allow buildings to move independently during earthquakes. This minimizes seismic energy transfer, protecting the structure and its contents from damage.

Which bearing types are commonly used in bridges?

Bridges frequently use elastomeric, pot, spherical, and sliding bearings. These types manage heavy loads, thermal expansion, and various movements effectively.