Durability of Laminated Elastomeric Bearings
I. Basic Performance of Durability
Design service life
Typically designed for a service life of no less than 60 years. Under normal operating conditions (e.g., loads and ambient temperature meeting design requirements), it can maintain good mechanical properties and seismic isolation functions for a long time.
Durability advantages of materials and structure
Rubber materials: Natural rubber or high-damping rubber is used, which has good anti-aging properties after vulcanization. Natural rubber has excellent weather resistance and oxidation resistance, and high-damping rubber can also meet long-term use requirements through formula optimization.
Steel plate interlayers: The steel plates are usually treated with anti-rust measures (such as galvanizing or coating) to prevent rusting in humid or corrosive environments, ensuring long-term stable bonding with the rubber layers.
II. Key Factors Affecting Durability
(1) Material Factors
Rubber aging
Aging mechanism: Long-term exposure to oxygen, ultraviolet rays, temperature changes, and ozone can cause molecular chain breakage or cross-linking in rubber, leading to reduced elasticity, hardening, and brittleness (such as cracking).
Countermeasures:
Use anti-aging rubber formulas (e.g., adding antioxidants and anti-ozone agents);
Wrap the bearing with a protective layer (such as a neoprene sheath) to isolate ultraviolet rays and environmental erosion.
Steel plate corrosion
Corrosion risk: If the steel plate anti-rust treatment is improper, or in humid and salt 雾 (salt spray) environments (such as coastal areas), the steel plate may rust, causing a decline in the overall mechanical properties of the bearing (such as stiffness changes and bonding failure).
Countermeasures:
Galvanize the steel plate surface or apply an anti-corrosion coating;
Ensure the interior of the bearing is dry during design to avoid water accumulation.
(2) Environmental Factors
Temperature impact
High temperature: Long-term exposure to high temperatures (e.g., exceeding 60°C) accelerates rubber aging and reduces elasticity;
Low temperature: Rubber may harden and lose elasticity at low temperatures, affecting deformation capacity (when designing, select appropriate rubber types, such as low-temperature-resistant rubber, based on the temperature range of the use area).
Chemical corrosion
When in contact with chemical substances such as acids, alkalis, and oils, rubber may be corroded, leading to performance degradation;
Countermeasures: Avoid direct contact between the bearing and corrosive media, or add a protective layer to the exterior.
(3) Load and Deformation Factors
Long-term vertical load
If overloaded for a long time, the rubber layer may produce permanent compressive deformation, affecting the bearing height and horizontal stiffness;
During design, control the vertical compressive stress within the allowable range (e.g., the vertical compressive stress of natural rubber bearings is typically ≤10MPa).
Repeated horizontal deformation
Repeated shear deformation caused by earthquakes or wind loads can lead to fatigue damage inside the rubber, and long-term accumulation may cause cracks;
During design, limit the horizontal displacement amplitude (e.g., shear strain ≤250%) and verify fatigue performance through tests.
III. Durability Assurance Measures
Material and process optimization
Select high-quality rubber raw materials and anti-corrosion steel plates, strictly control the vulcanization process (temperature, pressure, time), and ensure firm bonding between rubber and steel plates;
High-damping rubber or lead-core bearings enhance anti-fatigue and anti-aging capabilities through formula adjustment.
Structural design improvement
Add external protective layers (such as concrete casings or rubber sheaths) to isolate environmental erosion;
Design a drainage system to prevent the bearing from being immersed in water for a long time.
Regular inspection and maintenance
Inspection contents: Evaluate the bearing performance through visual inspection (such as rubber cracking and steel plate corrosion) and mechanical property tests (such as stiffness and damping ratio);
Maintenance measures: Timely repair damaged protective layers, remove rust and apply anti-corrosion treatment to rusted steel plates, and replace severely aged bearings when necessary.
IV. Durability Cases in Practical Applications
Bridge engineering: In bridges of seismic-prone countries such as Japan and New Zealand, laminated elastomeric bearings have been used for more than 40 years, and tests show they still maintain good performance;
Building isolation: In some isolated buildings in China (such as hospitals and schools in Yunnan and Sichuan), the bearings have shown no obvious degradation after more than 20 years of use, verifying their long-term durability.
Conclusion
The durability of laminated elastomeric bearings is ensured through material selection, structural design, and maintenance measures, meeting long-term engineering needs under normal use conditions. However, pay attention to the impact of environmental erosion, overloading, and other factors, and further extend the service life through regular inspection and maintenance.
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