Elastomeric bridge bearings are crucial components in modern bridge design, accounting for approximately 80% of all bridge bearings used worldwide. These bearings provide support and flexibility to bridges, allowing for structural movement and load transfer. Understanding the characteristics, types, design considerations, and maintenance of elastomeric bridge bearings is essential for engineers, bridge inspectors, and maintenance professionals.
Elastomeric bridge bearings are characterized by their high elasticity and load-carrying capacity. They are typically made of natural or synthetic rubber, reinforced with steel or fabric layers. The elastomeric material provides flexibility and resilience, allowing the bearing to accommodate bridge movements due to thermal expansion and contraction, seismic forces, and traffic loads.
Key Characteristics:
Elastomeric bridge bearings come in various types, each designed for specific bridge structures and load conditions. The common types include:
The design of elastomeric bridge bearings involves careful consideration of several factors:
Regular maintenance and inspection of elastomeric bridge bearings are crucial for ensuring their proper functioning and longevity. Inspections should be conducted periodically, with the frequency depending on the bridge's condition and traffic volume.
Maintenance Tasks:
Inspection Procedures:
Replacing elastomeric bridge bearings typically involves the following steps:
Step 1: Bridge Jacking: Use hydraulic jacks to lift the bridge and relieve the load on the bearings.
Step 2: Bearing Removal: Remove the old bearings using appropriate tools and techniques.
Step 3: Bearing Installation: Install the new bearings in the designated locations.
Step 4: Load Transfer: Transfer the bridge load to the new bearings by carefully lowering the bridge.
Step 5: Inspection and Testing: Inspect and test the new bearings to ensure proper installation and performance.
Advantages:
Disadvantages:
Elastomeric bridge bearings play a vital role in the performance and longevity of modern bridges. By understanding their characteristics, types, design considerations, and maintenance requirements, engineers and bridge professionals can ensure the proper functioning and safety of these critical components. Regular inspections, preventive maintenance, and timely replacement are essential for maximizing the lifespan and reliability of elastomeric bridge bearings.
Property | Value | Unit |
---|---|---|
Density | 1.1 - 1.3 | g/cm³ |
Hardness (Shore A) | 50 - 70 | - |
Tensile Strength | 10 - 20 | MPa |
Elongation at Break | 250 - 400 | % |
Compression Set (22 hours, 23°C) | 20 - 40 | % |
Ozone Resistance | Excellent | - |
UV Resistance | Good | - |
Bridge Type | Load Range | Movement Range | Bearing Type |
---|---|---|---|
Small-Span Bridges | Low | Low | Plain Elastomeric |
Medium-Span Bridges | Medium | Medium | Reinforced Elastomeric |
Long-Span Bridges | High | High | Laminated Elastomeric |
Seismic-Resistant Bridges | Variable | Variable | Seismic Isolation |
Inspection Item | Criteria |
---|---|
Cracks | Any visible cracks in the elastomeric material |
Deformations | Excessive bulging, sagging, or tilting of the bearings |
Bolt Corrosion | Rusted or loose bolts and fasteners |
Seal Damage | Torn or damaged seals between the elastomer and metal components |
Extrusion | Elastomer material squeezing out from between the steel plates |
Contamination | Presence of dirt, debris, or other foreign materials on the bearings |
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