BASE ISOLATION

THE KEY TO A SAFER AND STABLE HOME .

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.

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.

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.

Types Of Retrofitting Techniques

Base IsolationBase 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.

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.

Principle Of Base Isolation

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.

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.

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.

Types of Base IsolationBase Isolation systems which uses: Elastomeric Bearings

Sliding Systems

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.

Sliding Base Isolation Systems• It is the second basic type of isolator.• Works by limiting the base shear across the isolator

interface.

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.

Friction Pendulum Bearing

• Specially designed base isolators.• Works on the principle of simple pendulum by

increasing natural time period of oscillation.

Materials Used In Base Isolation

LEAD

STEELRUBBER

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

Comparison of Base Isolated Structures From Fixed Base Structures

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

Base Isolation In IndiaBhuji 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.

Famous Projects In The World Using Base Isolation

MM 21,Japan

Xindian Hospital, Taiwan

Coronado Bay Bridge, USA

Famous Projects In The World Using Base Isolation

Berkeley Public Safety Bulding

Asian Art Museum, USA

Utah State Capitol, USA

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)

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.

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.

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).

A video that says it all..Reference to Dynamic Isolation Systems

THANK YOU