This document introduces base isolation as a seismic retrofitting technique. It defines base isolation as decoupling a structure's superstructure from its substructure using structural elements. The document discusses the principle of base isolation, which is to isolate the structure from ground movement. It compares base isolation to other retrofitting techniques, noting advantages such as reduced structural damage and maintenance costs. The document also outlines different base isolation systems using elastomeric bearings and sliding systems. Examples of base isolation projects and companies utilizing the technique are provided. The document suggests government initiatives and training to develop base isolation in India.
2. Acknowledgement
Before going into this presentation , I would like to
thank my respected faculties here for their help , their
support and their guidance throughout the duration
and completion of this project.
3. Introduction
In this presentation, we are going to
Introduce Retrofitting
Describe its techniques with Base Isolation as an
example
Compare Base Isolation With other Retrofitting
techniques
Discuss about the government initiatives.
Discussion on how to make this technology
developed for future purposes.
4. Retrofitting
Seismic Retrofitting is the modification of
existing structures to make them more resistant
to seismic activity , ground motion, or soil failure
due to earthquakes.
6. Base Isolation
Base isolation, also known as seismic base isolation or base isolation system, is
one of the most popular means of protecting a structure
against earthquake forces.It is a collection of structural elements which should
substantially decouple a superstructure from its substructure resting on a
shaking ground thus protecting a building or non-building structure's integrity.
Base isolation is one of the most powerful tools of earthquake
engineering pertaining to the passive structural vibration control technologies. It
is meant to enable a building or non-building structure to survive a potentially
devastating seismic impact through a proper initial design or subsequent
modifications. In some cases, application of base isolation can raise both a
structure's seismic performance and its seismic sustainability considerably.
Base isolation system consists of isolation units with or without isolation
components, where
• Isolation units are the basic elements of a base isolation system which are
intended to provide the aforementioned decoupling effect to a building or
non-building structure.
• Isolation components are the connections between isolation units and their
parts having no decoupling effect of their own.
7. Principle Of Base Isolation
The main principal of base isolation is to try and
isolate the structure from the ground movement
so you could just about put it on ball bearings if
you like and the ground could move underneath
it and the building stays still.
9. Difference Between Base Isolation and
Other Retrofitting Techniques
Base Isolation Is Different Because..
• Applied under the structure rather than fitting it everywhere in the
building like other techniques of retrofitting.
• Saves a major amount of destruction.
• Maintenance Cost is less comparatively as it requires less look after.
• Buildings with base isolation are quite cost effective than a building which
is retrofitted.
10. Advantages
Structural Damage
restricted.
No Damage to indoor
services and
facilities(gas or water
pipelines).
Protects the structure
by preventing plastic
deformation of
structural elements.
Secondary damage
(Falling furniture) is
restricted.
Function of buildings is
ensured as super
structure is designed to
remain elastic even
after an earthquake
happens.
Deflections and
stresses generated are
lower.
Allows for a reduction
in structural elements
of buildings with less
ductile detailing
needed.
Protect the contents
inside the building.
Safe For occupants.
Protects the integrity of
internal structures e.g.
stairs, internal walls ,
and partitions.
Widely Held
Conception that Base
Isolation is expensive.
In some cases it results
in a lower construction
cost overall.
11. Disadvantages
• Cannot be applied partially to structures unlike other
retrofitting
• Challenging to implement in an efficient manner
• Allowance for building displacements
• Inefficient for high rise buildings
• Not suitable for buildings rested on soft soil.
• Coupled foundations allow motion of some modes of the structure
to include a participating soil mass which increases inertia for these
modes, and would also allow energy to radiate back into the soil. A
Base Isolated building is decoupled from the soil by the isolators.
The lower support stiffness of the isolators makes the building
more susceptible to wind induced motion.
12. Types of Base Isolation
Base Isolation systems which uses:
Elastomeric Bearings
Sliding Systems
13. Elastomeric Base Isolation System
• Most widely Used Base Isolator.
• Made of Natural rubber or neoprene.
• Consist of thin rubber sheets bonded onto thin
steel plates and combined with an energy
dissipation mechanism.
14. Sliding Base Isolation Systems
• It is the second basic type of isolator.
• Works by limiting the base shear across the isolator
interface.
15. Spherical Sliding Base Isolation
Systems
• Another type of base isolator in which the
building is supported by bearing pads that
have a curved surface and low friction.
• During an earthquake, the building is free to
slide both vertically and horizontally.
16. Friction Pendulum Bearing
• Specially designed base isolators.
• Works on the principle of simple pendulum by
increasing natural time period of oscillation.
18. Is it an economic solution?
• Base isolation allows for a reduction in structural elements of the building
with less ductile detailing needed
• Widely held misconception that seismic isolation is expensive
• E.g. Union House built in Auckland in 1983 with base isolation produced
an estimated 7% cost saving in the total construction cost of $6.6m which
included a construction time saving of 3 months due to the structural form
requiring less seismic force, ductility demands and structural deformations
• As a general rule the inclusion of all aspects of seismic isolation in a new
structure will add no more than 3% to total construction cost and
considerably less when assessed against the benefits of isolation
• Contrary to belief, seismic isolation devices require no maintenance during
the life of the building
• Following any significant event they should be inspected to ensure bolts
and load plates are still in place.
• Devices do not need replacing after an earthquake unless the event was in
excess of their design specification in which case we recommend the
removal of some devices for testing.
• Because the building is protected from major damage, repair costs
following an earthquake will be lower to non-existent
20. Comparison of Base Isolated Structures
From Fixed Base Structures
Analytically it has been show that lead rubber bearings can bring about
20% savings in the reinforcement used.
COMPARISON OF QUANTITY OF REINFORCEMENTS
21. Base Isolation In India
Bhuji Hospital is the only building in
India which has adopted the base
isolation technique.
It is supported by 280 lead rubber
bearings (LRBs) and can stand a
force 10 tremor on Richter Scale.
The system is maintenance free and
does not incorporate electronics, Its
just rubber and lead.
22. Famous Projects In The World Using
Base Isolation
MM 21,Japan
Xindian Hospital, Taiwan
Coronado Bay Bridge, USA
23. Famous Projects In The World Using
Base Isolation
Berkeley Public Safety Bulding
Asian Art Museum, USA
Utah State Capitol, USA
24. Name Of Some Companies Using Base
Isolation
Dynamic Isolation Systems, USA
Holmes Consulting Group, New
Zealand
ARUP Group Limited
Seismic Isolation Engineering
Incorporation, Emeryville, CA (USA)
25. Government Initiatives
Initiation of Base Isolation techniques in the concept of
new buildings in some required parts of India.
Setting up a full scale 3D Earthquake testing facility to
test the behavior of 2 to 3 stories models of isolated
buildings or retrofitted buildings before they are actually
developed in the project area
As we are fully aware that the labours in our country
have limited knowledge about technology going on in the
world, so we must need to train them and make them
aware of such kind of technologies.
26. A Suggestion By Me:
Base Isolation should be used in India, parts
where it is utmost required.(ex- Jammu and
Kashmir, Ran of Kutch etc.)
Use of scrap tires rubber pads as isolators can
also work in place of LRBs.
New or modified form of isolation
techniques(STRPs) can be used in India.
Case study shows that types of isolators can serve positive force
resisting capacity up to 150% shear strain when loaded with axial
pressure of 8.6MPa. In this regards, the STRP isolators can serve the
purpose of the base isolation system of low-rise residential buildings.
27. References
Commercial Internet
Sites:
• www.wikipedia.com
• http://www.youtube.com
• http://www.robinsonseismic
.com
• www.ijetch.org
Some Universities And
Organizations Papers
• ISET Journal Of Earthquake
Technology
• Journal of Engineering Research
and Applications
• International Journal of Emerging
Technology and Advanced
Engineering
• Indian Institute Of Technology
(Kanpur).
28. A video that says it all..
Reference to Dynamic Isolation Systems
