Classification of Bridge Bearings
Bridge bearings come in a wide variety of types. According to structural forms, material properties, and functional characteristics, they can be divided into the following main categories:
I. Classification by Material
1. Elastomeric Bearings
Plain Plate Elastomeric Bearings: Made of natural or synthetic rubber, suitable for medium and small-span bridges. They adapt to displacement and loads through rubber elasticity.
PTFE Sliding Elastomeric Bearings: PTFE plates are pasted on the surface of plain elastomeric bearings to form low-friction sliding pairs with stainless steel plates, suitable for long-span bridges or those requiring frequent displacement.
Pot Elastomeric Bearings: Rubber is sealed in a metal pot, using the triaxial compression characteristics of rubber to bear high loads, often equipped with sliding components (such as PTFE + stainless steel), suitable for large bridges.
2. Steel Bearings (Mechanical Bearings)
Rocker Bearings: The bottom is a curved metal structure, realizing horizontal displacement through rocking, and the top hinge allows rotation, often used in steel bridges.
Pin Bearings: Fixed-type bearings that achieve rotation through steel pins while restricting translation, suitable for bridge nodes requiring fixed positions.
Roller Bearings: Realize longitudinal translation using metal rollers (single or multiple), suitable for medium-load bridges but requiring regular maintenance against corrosion.
3. Sliding Bearings
Metal Sliding Bearings: Early types using metal-to-metal planar contact sliding, now mostly obsolete.
PTFE Sliding Bearings: Using PTFE as the sliding surface with stainless steel plates, featuring low friction coefficients, suitable for bridges in high-temperature difference or seismic areas.
II. Classification by Function and Displacement Characteristics
1. Fixed Bearings
Restrict horizontal displacement and only allow rotation (e.g., pin bearings), used at fixed ends of bridges to transmit vertical loads and horizontal forces.
2. Expansion Bearings
Unidirectional Expansion Bearings: Allow translation in a single direction (e.g., longitudinal) and rotation, often used in long-span bridges to adapt to thermal expansion and contraction.
Multidirectional Expansion Bearings: Allow longitudinal and transverse translation and rotation, suitable for complex displacement requirements (e.g., curved bridges or bridges in seismic areas).
III. Classification by Structural Form
1. Plate Bearings
Simple in structure, made of rubber or composite materials in plate form, directly placed between the beam bottom and piers, suitable for small-span bridges.
2. Pot Bearings
Composed of a metal pot, rubber block, and sliding components, capable of withstanding high vertical loads and large displacements, commonly used in long-span bridges (e.g., highway and railway bridges).
3. Spherical Bearings
Achieve multidirectional rotation through a spherical metal structure, paired with PTFE sliding surfaces, suitable for bridges requiring three-dimensional displacement (e.g., cable-stayed bridges, suspension bridges).
IV. Special Function Bearings
1. Seismic Isolation Bearings
Contain damping elements (such as viscous dampers) to dissipate energy during earthquakes or vibrations, reducing bridge structural response and enhancing seismic performance.
2. Tensile Bearings
Designed to withstand upward tensile forces (e.g., at suspension bridge anchorages), preventing the bridge superstructure from detaching from the substructure.
3. Corrosion-Resistant Bearings
Made of stainless steel, anti-corrosion coatings, or special materials, suitable for corrosive environments such as coastal areas and chemical industrial zones.
V. Classification by Application Scenario
1. Highway Bridge Bearings
Focus on adapting to vehicle loads and temperature displacement, with common types including elastomeric bearings and pot bearings.
2. Railway Bridge Bearings
Need to withstand greater dynamic loads and impacts, mostly using steel bearings or high-performance pot/spherical bearings.
3. Long-Span Bridge Bearings
Such as suspension bridges and cable-stayed bridges, mostly using spherical bearings and high-capacity sliding bearings to meet complex displacement requirements.
VI. Other Classification Methods
By installation location: Pier top bearings, abutment bearings, anchorage bearings, etc.
By construction method: Cast-in-place bridge bearings, prefabricated assembled bearings.
Summary
Different types of bearings have distinct characteristics in load transfer, displacement adaptation, durability, and cost. When selecting a bearing type, comprehensive considerations should be given to bridge span, load conditions, environmental factors, and economic efficiency. With the development of material technology, new types of bearings (such as composite material bearings and intelligent monitoring bearings) are gradually being applied to meet higher engineering requirements.
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