presentation about the basic isolation techniques that related to structural dynamics that occurs from earthquake.

1. BASIC
ISOLATION
TECHNIQUE
PRESENTED BY;-
RAHUL KUMAR(22PCE040)

2. Objectives
Abstract
Response of Base Isolation Buildings
Spherical sliding isolation system
Types of bearings
Maintenance and Management of the Isolation System
Factors which enable the use of base isolation
Conclusion
Refernces

3. Abstract
Base isolation is one of the most popular means of protecting a structure against earthquake
forces. It is one of most powerful tools of earthquake engineering pertaining to the passive
structural vibration control technologies.
It is easiest to see the principle at work by referring directly to the most widely used of these
advanced techniques, known as base isolation.
The concept of base isolation is explained through an example of building resting on frictionless
rollers. When the ground shakes, the rollers freely roll, but the building above does not move.
Thus, no force is transferred to the building due to the shaking of the ground; simply, the
building does not experience the earthquake.

4. Abstract
Now, if the same building is rested on the flexible pads that offer resistance against lateral
movements, then some effect of the ground shaking will be transferred to the building.
If the flexible pads are properly chosen, the forces induced by ground shaking can be a few
times smaller than that experienced by the building built directly on ground, namely a fixed base
building.
The flexible pads are called base-isolators, whereas the structures protected by means of these
devices are called base-isolated buildings.

5. Abstract

6. Response of Base Isolated
Buildings
The base-isolated building retains its original, rectangular shape. The base isolated building
itself escapes the deformation and damage-which implies that the inertial forces acting on the
base isolated building have been reduced.
 Experiments and observations of base-isolated buildings in earthquakes to as little as ¼ of the
acceleration of comparable fixed-base buildings.
 Acceleration is decreased because the base isolation system lengthens a buildings period of
vibration, the time it takes for a building to rock back and forth and then back again.
And in general, structures with longer periods of vibration tend to reduce acceleration, while
those with shorter periods tend to increase or amplify acceleration.

7. Response of Base Isolated
Buildings

8. Spherical sliding isolation system
Spherical sliding isolation systems are another type of base isolation. The building is supported
by bearing pads that have a curved surface and low friction. During an earthquake the building is
free to slide on the bearings.
Since the bearings have a curved surface, the building slides both horizontally and vertically.
 The forces needed to move the building upwards limits the horizontal or lateral forces which
would otherwise cause building deformations.
And also by adjusting the radius of the bearings curved surface, this property can be used to
design bearings that also lengthen the buildings period of vibration.

9. Types of bearings:
Generally the Bearing are 2 types:-
1. Elastomeric Bearing,
The elastomeric bearing are 3 types are:-
a) Natural Rubber Bearing (NRB)
b) Synthetic Rubber Bearings
c) Lead Rubber Bearing (LRB)
2. Friction Pendulum Bearing,
The friction pendulum bearing are 2 types:-
a) Flat Slider Bearing
b) Curved Slider Bearing

10. Elastomeric Bearing
Elastomeric bearing is the most widely used base isolator. This isolation system consists of a
layer either made of natural or synthetic rubber sandwiched between the mild steel plates. This
together acts as a single unit.
The steel plates help the rubber layer to prevent bulging during the earthquake action. It is the
component that provides vertical load capacity and stiffness to the unit.
When the unit is subjected to movements that result in vertical deformation, it is granted as
horizontal movements by the bearings. The shearing deformability of the rubber sheets provides
horizontal flexibility. This movement is not restrained by the steel plates.

11. Elastomeric Bearing
a) Natural Rubber Bearing (NRB)
b) Synthetic Rubber Bearings
c) Lead Rubber Bearing (LRB)

12. Friction Pendulum Bearings
A friction pendulum bearing is the most extensively used kinematic systems in base isolation,
the pendulum system has a globe that is placed in two steel concave curved surfaces. Instead of
a globe, a cylinder member with a global contact surface can also be used. This type of isolation
system make use of special metals.
This isolation system have all advantages of a rubber bearing with sliding property on a global
concave surface. This system by assuming a position elevates the building during the seismic
lateral motion. This hence reduces the effect of an earthquake on the building a lot.
The friction pendulum system is widely used in heavy roof systems with large spans, in
buildings. As these systems use special metals, it can be employed in building construction in
cold regions were a high danger of freezing is expected.

13. Friction Pendulum Bearings

14. Friction Pendulum Bearings
a) Flat Slider Bearing
b) Curved Slider Bearing

15. Maintenance and Management of
the Isolation System
The isolation system must remain operational for the world expected lifetime of the structure
under all possible environmental effects. These may corrode the metallic parts of the isolation
system and deteriorate the elastomer; such effects may be reduced by using a protective rubber
cover.
The maintenance of the isolation system, and especially that of the seismic gap, must be
frequent to ensure the vertical loads which they must sustain. When the construction of a
diaphragm is not possible, the bearings must be designed in proportion to the magnitude of the
lateral forces carried by the members above them.
It is difficult to take into account such design issues due to the uncertainties involved; therefore, the
construction of a diaphragm above the isolation level must be anticipated.

16. Factors which enable the use of
base isolation
Several factors favor the development and practical application of seismic isolation. First of all
there are increased requirements for the performance of structure in severe earthquakes which
are not met by current conventional design philosophy. These are crucial to structures
containing sensitive and expensive equipment vulnerable even to micro tremors.
Second, the advance of computer technology and modern structural analysis method enables
the development of reliable software to stimulate the response of structures.
The development of seismic engineering and earthquake engineering to level where reliable
prediction can be made for expected earthquakes, is another important factor. In addition, the
construction of shaking tables which can stimulate actual earthquake excitations makes possible
the experiment validation of the behavior of seismic isolation system.

17. Factors which enable the use of
base isolation
The study of other minor loads such as wind load and the reliable quantifications of their
expected intensities and frequency of occurrence, also enables the use of seismic isolation.
Finally, development, manufacture and extensive research in the area of structural material
enable the reliable use of modern material for seismic isolation device.
The development of device which decipate energy and provide the restoring force to avoid
permanent displacement also allow the practical implementation of the seismic isolation
concept.

18. CONCLUSION
We can use base isolation technique to construct the earthquake resistant building.
Proper materials and design should be selected to get the best result.
The safety of people should be the main aim.

19. REFERNCES
P. Komodromos- Seismic isolation for earthquake resistance structure.- Henry J. Lagorio
Earthquake – An architect’s guide to nonstructural seismic hazards.- Charles K. Erdey
Earthquake Engineering.-Yousef Bozorgnia & Vitelmo V. Bertero
Earthquake Engineering-Wai – Fan Chen & Charles Scawthorn

20. Thank You!