Methods to Improve the Durability of Laminated Rubber Bearings
To improve the durability of laminated elastomeric bearings, multi-dimensional optimizations are required in materials, design, construction, and maintenance. The specific methods and technical measures are as follows:
I. Material Optimization and Selection
Rubber Material Improvement
Aging-Resistant Rubber Selection: Use weather-resistant rubbers such as chloroprene rubber (CR) and ethylene propylene diene monomer (EPDM), which offer better resistance to UV rays, ozone, and chemical corrosion compared to natural rubber (NR).
Anti-Aging Additives: Incorporate anti-aging agents (e.g., amines, phenols) and anti-ozone agents into the rubber formula to inhibit molecular chain oxidation and 断裂 (breakage), delaying aging.
High-Damping Rubber Application: For structures requiring vibration reduction, use high-damping rubber (HDR), whose damping properties reduce fatigue damage from repeated deformation.
Steel Plate Anti-Corrosion Enhancement
Multi-Layer Rust Protection: Apply hot-dip galvanizing, chrome plating, or epoxy resin coatings to steel plate surfaces to isolate moisture and salt spray; use stainless steel plates (e.g., 316L) in coastal or corrosive environments.
Electrochemical Protection: For critical projects, combine sacrificial anodes or impressed current cathodic protection to prevent electrochemical corrosion of steel plates.
II. Structural Design and Protection Measures
Protective Layer Design
Outsourced Neoprene Sheath: Wrap the bearing with a weather-resistant sheath to isolate UV rays, rainwater, and chemicals, while reducing direct rubber-air contact (e.g., Japanese standards require sheath thickness ≥5mm).
Drainage and Waterproofing Structures: Install drainage grooves or waterproof eaves at the bearing installation site to avoid water accumulation; add waterproof sealing strips for important projects to prevent rainwater infiltration.
Structural Optimization
Stress Dispersion Design: Increase the bonding area between rubber layers and steel plates, and use stepped steel plate edges (non-right angles) to reduce rubber cracking caused by stress concentration.
Temperature Adaptation Design: Select high-temperature-resistant rubber (resistant to ≥120°C) for high-temperature environments (e.g., industrial plants), and use cold-resistant formulas (e.g., adding plasticizers) in low-temperature regions (below -40°C) to prevent rubber hardening.
Integration of Limiting and Energy-Dissipating Components
Combine sliding limit devices or metal dampers to share part of the deformation under seismic or wind loads, reducing repeated shear fatigue of rubber layers (e.g., lead-core rubber bearings reduce rubber damage through lead-core energy dissipation).
III. Load and Deformation Control
Rational Load Design
Avoid Long-Term Overloading: Ensure the vertical load safety factor of the bearing ≥2.5 during design (e.g., Chinese codes require ultimate bearing capacity ≥2 times the design load) to prevent permanent rubber compression deformation.
Limit Horizontal Displacement: Determine the maximum shear deformation of the bearing through structural calculations (typically controlling shear strain ≤250%) to avoid exceeding the rubber’s elastic limit (e.g., Japanese regulations specify shear strain ≤300% under seismic conditions).
Dynamic Load Buffering
For frequently vibrating structures (e.g., bridges), install elastic gaskets or dampers at the connection between the bearing and the structure to reduce rubber fatigue caused by high-frequency loads.
IV. Construction and Installation Specifications
Precise Positioning and Uniform Force Distribution
Use a level to calibrate the bearing plane during installation, ensuring verticality deviation ≤0.5% (as required by China’s Code for Design of Building Isolation) to avoid local stress concentration from eccentric loads.
When connecting the bearing to embedded steel plates, use high-strength bolts with uniform pre-tightening force to prevent loosening-induced extra vibration.
Environmental Isolation Measures
Avoid contact between the bearing and corrosive substances like oil and cement slurry during construction; install concrete protective covers or metal shields on the bearing top for outdoor installations.
V. Maintenance and Monitoring Systems
Regular Inspection System
Visual Inspection: Check the rubber layer for cracking (crack width >1mm requires attention) and steel plate corrosion annually, and measure bearing height changes (compression >5% requires evaluation).
Performance Testing: Detect bearing stiffness and damping ratio degradation through dynamic loading tests (e.g., low-cycle repeated loading) every 5-10 years, and use ultrasonic flaw detection for internal rubber defects if necessary.
Intelligent Monitoring and Early Warning
Install strain sensors, temperature sensors, and displacement meters to real-time monitor the bearing’s stress state and environmental parameters, and predict aging trends (e.g., rubber elastic modulus decline rate) through big data analysis.
Timely Maintenance and Repair
Surface Repair: Apply waterproof sealant to minor rubber cracks; remove rust from corroded steel plates and reapply anti-rust paint.
Overall Replacement: Replace the bearing promptly when stiffness degradation exceeds 20% or through cracks appear (e.g., Japanese regulations recommend comprehensive inspection and replacement of isolation bearings after 50 years of use).
VI. Environmental Adaptability Optimization
Targeted Measures for Special Scenarios
Coastal Areas: Use salt spray-resistant coatings (e.g., polyurea) for bearing sheaths, and adopt composite protection of hot-dip galvanizing + epoxy coating for steel plates.
Industrial Corrosion Environments: Use fluororubber (FKM) or fully sealed metal casings to isolate acid mist, oil, and other corrosions.
Climate Adaptability Design
Add sunshades to bearings in tropical regions to reduce solar heating; install thermal insulation layers (e.g., polyurethane foam) around bearings in cold regions to prevent rubber hardening at low temperatures.
Summary
Enhancing the durability of laminated elastomeric bearings requires a full-cycle approach covering “materials – design – construction – maintenance”. Through high-performance material selection, innovative structural protection, precise load control, and intelligent operation and maintenance systems, their actual service life can be extended to over 80 years (far exceeding the conventional 60-year design life), especially meeting the long-term safety needs of critical buildings such as nuclear power plants and hospitals.
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