The document discusses base isolation techniques for earthquake-resistant building design. Base isolation involves separating the structure from its foundation using a suspension system to reduce seismic demand on the building. There are several types of base isolation devices that provide flexibility, damping and resistance to vertical loads, including elastomeric bearings, lead rubber bearings, and flat or curved slider bearings. Elastomeric bearings use layers of rubber between steel plates to support vertical loads while allowing flexibility under lateral earthquake forces.

1. BASE ISOLATION TECHNIQUES

2. What is the base isolation technique?
Base isolation is a state-of-the-art method in
which the structure (superstructure) is separated
from the base (foundation or substructure) by
introducing a suspension system between the
base and the main structure.

3. Purpose of Base Isolation
• Wind and Earthquake are the most predominant
loads that demands lateral design of a structure.
Again, earthquake load is not controllable and it
is not practical to design a structure for an
indefinite seismic demand.

4. • Base isolation takes an opposite approach, i.e.
to reduce the seismic demand instead of
increasing the capacity. Controlling ground
motion is impossible, but we can modify the
demand on structure by preventing/reducing the
motions being transferred to the structure from
foundations.

5. Response of base isolated & non-isolated
structure

6. Basic requirements
Basic requirements of an isolation system
are
– Flexibility
– Damping
– Resistance to Vertical or other service loads.

7. Type of Base Isolation Devices
There are Six major types of base
isolation devices which are widely adopted
for seismic base isolation.
– Elastomeric Bearings
– High Damping Bearings
– Lead Rubber Bearings
– Flat Slider Bearings
– Curved Slider Bearings or Pendulum Bearings
– Ball & Roller Bearings.

8. Elastomeric Rubber Bearings

9. Elastomeric Rubber Bearings
• Bearings formed of horizontal layers of synthetic
or natural rubber in thin layers bound between
steel plates. These bearings are capable of
supporting high vertical loads with very small
deformations. These bearings are flexible under
lateral loads. Steel plates prevent the rubber
layers from bulging. Lead cores are provided to
increase damping capacity as plain elastomeric
bearings does not provide significant damping.
They are usually soft in horizontal direction and
hard in vertical direction.

10. Roller and Ball Bearings

11. • For isolation applications in machinery
isolation, roller and ball bearing are used.
It includes cylindrical rollers and balls. It is
sufficient to resist service movements and
damping depending on the material used.

12. Springs