Earthquakes are among the most devastating natural disasters. Traditional seismic design relies on the strength of structures to "resist" seismic forces, often leading to cracking or even collapse of beams and columns. Modern seismic isolation technology takes a different approach: placing isolation bearings between the building foundation and the superstructure. By introducing a flexible layer, it extends the structural period, dissipates energy, and isolates seismic input from affecting the building. In this "flexibility against rigidity" seismic revolution, high-damping silicone rubber is becoming an important choice for new-generation isolation materials due to its superior durability, stability, and large deformation capacity.

1. Principles of Seismic Isolation: Letting Buildings "Float"

The core functions of seismic isolation bearings include:

Horizontal Flexibility: Lowering the structure's natural frequency to avoid earthquake energy concentration bands (typically 0.2–1.0 Hz);

Vertical Stiffness: Supporting the weight of the building without change;

Damping Energy Dissipation: Consuming seismic energy through internal friction within the material or additional dampers.

Traditional seismic isolation bearings commonly use laminated rubber bearings (LRB), made by alternating layers of natural rubber and steel plates vulcanized together. However, natural rubber ages easily under ultraviolet light, ozone, and high temperatures, limiting its lifespan. Silicone rubber, with its inorganic backbone structure, offers inherent advantages in weather resistance.

2. Unique Advantages of Silicone Rubber

Superior Durability: Silicone rubber is virtually immune to UV, ozone, and humidity. Accelerated aging tests show that its performance degradation rate is much lower than that of natural rubber. For projects designed for a 100-year lifespan like bridges and nuclear power plants, silicone rubber isolation bearings significantly reduce lifecycle maintenance costs.

Wide Temperature Range Stability: From -50°C in cold regions to +70°C in tropical environments, silicone rubber exhibits minimal hardness changes (ΔShore A < 5), ensuring consistent isolation performance. Natural rubber hardens at low temperatures and softens at high temperatures, affecting isolation effectiveness.

High Damping Designability: By adding nano-fillers (such as modified silica or carbon nanotubes) or constructing interpenetrating networks (IPN), the damping ratio (tanδ) of silicone rubber can be increased to 0.15–0.30, approaching the level of lead-core rubber bearings, eliminating the need for additional dampers and simplifying construction.

Large Shear Deformation Capacity: With elongation exceeding 500%, silicone rubber can withstand over 300% horizontal shear strain during rare earthquakes without breaking, ensuring safety standards ("no collapse in major earthquakes").

3. Typical Structural Forms

Pure Silicone Rubber Laminated Bearings: Composed of silicone rubber layers bonded to stainless steel plates through vulcanization, combining load-bearing and isolation functions.

Silicone Rubber-Lead Composite Bearings: Incorporate a central lead core to provide initial stiffness and additional energy dissipation.

Maintenance-Free Full Silicone Rubber Bearings: Used for historical building preservation to prevent metal corrosion contamination.

Currently, pilot projects in Japan and Europe have begun using silicone rubber bearings in critical facilities such as hospitals and data centers.

4. Challenges and Prospects

Higher Costs: Raw material prices are about 3–5 times those of natural rubber.

High Requirements for Bonding Processes: Special primers are needed to ensure strong adhesion between silicone rubber and metal plates.

Incomplete Standards System: Current seismic isolation codes (e.g., GB 50011) mainly focus on rubber bearings; long-term creep and fatigue data for silicone rubber need supplementation.

As high-performance silicone rubber enters mass production and demand for green buildings increases, its application in seismic isolation is expected to shift from a "high-end option" to a "mainstream solution."

Conclusion

The essence of building seismic isolation lies in humility and wisdom towards natural forces. Silicone rubber seismic isolation bearings do not rely on brute force but instead use their flexible nature to mitigate immense pressures. They lie quietly between the earth and buildings, silently safeguarding countless families' safety—becoming an invisible yet highly reliable "life buffer zone" during every earthquake.



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