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It all started with a small wooden bearing.

Pullout Mechanism

A laminated rubber pullout mechanism for seismic isolation


  • The horizontal performance of the laminated rubber does not change during normal actuation and flotation.
  • Can be installed using the conventional methods of fixation. Available for the entire lineup of LRBs and RBs.
  • The main body of the seismic isolator does not need to be larger in size.

Structure and action

The laminated rubber bushing has a pull-out mechanism that is attached to the lower flange of the laminated rubber.
When a tensile force acts on the seismic isolator, the rubber part of the bushing shears and deforms, causing the entire seismic isolator to float. This prevents excessive tensile force from acting on the laminated rubber body.
Horizontal forces are also transmitted to the bolts through the metal and rubber portions of the laminated rubber bushing.
In such an event, the compressibility of rubber is used to ensure that all bolts bear horizontal forces almost equally, resulting in a high degree of stability.

Basic characteristics

Confirmation of characteristics using an actual device

Characteristics are verified with an actual device using the LRBφ800.

Experiment with the LRBφ800

Experiment with the LRBφ800

Tensile test (compressive and tensile forces applied in the vertical direction)

The results of simple compression and simple tensile tests are shown in the figure.
Tensile force has a small slope compared to compression, and the tensile surface pressure is less than 1 N/mm2even when the surface is lifted 20 mm.

  • Experimental results
    Vertical displacement: 20.3 mm
    Tensile surface pressure of the laminated rubber: 0.62 N/mm2
  • Vertical tensile rigidity
    Designed value: 12.2 kN/mm
    (for 8 rubber bushings)
    Experimental value: 8.9 kN/mm
    (Tilt between 5 and 15 mm vertical displacement)
Compression/tension tests

Compression/tension tests

Shear test

Shear tests of approximately ±440 mm in the horizontal direction were conducted with the isolator floating, and results confirmed that there was almost no change in its characteristics from normal conditions.

Relationship between the horizontal load and horizontal displacement

Relationship between the horizontal load and horizontal displacement