Anti-vibration rubber design

Rubber as a polymeric elastomer material can reduce the intensity of earthquake damage. It has been used in the field of earthquake resistance since the 1950s. The practical application results show that the seismic effect is excellent and the application surface is expanding, and it has developed into a mature product.

This kind of seismic products is built on the principle of “base isolation” and is called “damping rubber isolation bearing”. Usually, the support is placed or fixed between the building and the foundation, and its structure is formed by alternately stacking multiple layers of film and steel plate. The steel plate is made of 45# steel, which acts as reinforcement, reinforcement and bearing. The thickness of each layer of steel plate is ≥ 2mm, and the number of layers is usually around 15. When an earthquake occurs, the support absorbs the vertical vibration energy from the underground source and mitigates the vibration energy caused thereby.

The role of rubber and reinforced steel plates is complementary. Normally, when the support is stressed (from the load of the building), the rubber can withstand the vertical gravity of the top-down building and then pass it to the building foundation. In addition, rubber plays another role, that is, when the building is subjected to lateral (such as earthquake or typhoon) external forces, it can be adapted by adjusting the lateral deformation to reduce lateral swaying. Therefore, the rubber isolation bearing has the dual characteristics of “vertical rigid and lateral softness” as the seismic element. In general, the performance of the support is required to be stable and durable under normal conditions; and in the event of an earthquake, it is required to withstand the test of destructive power.

Design Principle

(1) Design parameters

For laminated vibration-isolating rubber bearings, the shape factor is a very important design parameter. There are two types of such parameters:
1 first shape factor S1
In the formula S₁=D-D₁∕nt_R, D-D₁ is the difference between the outer diameter D of the support minus the diameter D of the inner cavity (for lead injection), the unit is mm; and is the thickness of the single-layer glue; and is the number of layers. The larger the value of the obtained coefficient S₁, the stronger the reflection layer is, and the greater the vertical stiffness.

2 second shape factor S₂

S₂=D/nt_R , as seen by the formula, the less n (the number of layers), the flatter the shape of the support and the better the stability.
According to the application practice, S₁ is suitable for >15, and S₂ should be between 3 and 6.

(2) Damping performance

The damping performance refers to the fact that after the external vibration energy is input, the amplitude of the rubber is gradually reduced due to the hysteresis effect of the rubber, and part of the vibration energy is converted into heat energy, thereby reducing the amplitude of the resonance wave and reducing the damage intensity of the earthquake.