Presented by :Ashish MangalCivil Engg.10EJJCE003

USE OF ISOLATED BEARING

Innovation in Earthquake Engineering Base Isolation Fiber Wrap Dampers Steel Moment Frame Solution Capacity Design principles

In general what’s good for earthquake design helps resist blast loads

Base Isolation Technology

Base isolation systems reduce building vibrations during earthquakes.Normally, a building is supported directly on its foundation, and it is said to have a fixed-base. When base isolation is used, special structural bearing are inserted between the bottom of the building and its foundation. These bearings are not very stiff in the horizontal direction, so they reduce the fundamental frequency of vibration of a building.

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During an earthquake, a fixed-base building can sway from side to side. When a base isolation system is used, the sideways movement occurs mainly in the bearings

There are many types of bearings used for base isolation. Here are two of them.

Seismic isolation and damping can reduce force and displacement demands so structure remains elastic or “damage free”

The Goals of Base Isolation Protection of Life Additional benefits of Isolation

Protection of Building Frame Protection of Non-structural Components and Contents Protection of Processes and Function Provide for an Operational facility after the Earthquake.

During a Richter 8.0 Earthquake a Seismically Isolated Building will Behave as if it were Experiencing a 5.5 Earthquake

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Rubber bearings Rubber bearing are made from layers of rubber with thin steel plates between them, and a thick steel plate on the top and bottom. The bearings are placed between the bottom of a building and its foundation. The bearings are designed to be very stiff and strong for vertical load, so that they can carry the weight of the building. However, they are designed to be much weaker for horizontal loads, so that they can move sideways during an earthquake.

Seismic Isolator

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Friction Pendulum Bearings Friction pendulum bearing are made from two horizontal steel plates that can slide over each other because of their shape and an additional articulated slider. They are designed to be very stiff and strong for vertical load , so that they can carry the weight of the building.

Friction Pendulum Bearing

Application of Base Isolation 1st application in New Zealand in 1974. 1st US application in 1984 1st Japanese application in 1985. 1st Indian application in 2001.   (Bhuji Hospital, Gujarat Province, India)

Structural engineers Dunning Thornton Consultants from Wellington were part of the New Zealand design team and supervised installation of the first bearings on site in late 2001. Eventually, 280 lead-rubber bearings were installed.

Benefits of Base Isolation Base Isolation provides the highest level of Protection – ‘Operational’ – after a major earthquake.

Base isolation has significant benefits for the earthquake protection of historic structure.

Base Isolated building are capable of resisting GSA blasts loads and their ability to move reduces the overall impact of the blast force on the building.

CONCLUSIONSPassive isolation techniques have been widely applied to many structures, and those promise a certain level of control performance. The structural control application using passive isolations is able to reduce the story drifts but still induce the floor accelerations. To enhance the advantages of passive isolations, a hybrid control technology can be applied. The study presents the realization of this idea that a building model is isolated with the bearings and controlled by actuators in two different directions.

REFERENCES Chopra.R, Kumar.R, Chawla.K.S, T.P.Singh, “Traditional Earthquake Resistant Houses”, Honey Bee, Vol 11&Vol 12,Oct 2000-Nov 2001. Deodhar.S.V, Dubey.S.K, “Remedial Measures Against Earthquake disaster”, National Building Material and Construction World, Vol 2, Jan 2003. Ramallo, J. C., Johnson, E. A., and Spencer, J. F., “Smart base isolation system,” Journal of Engineering Mechanics,128(10), 1088-1099 (2002). Indian Standard IS 1893-20