BASE ISOLATION

BASE ISOLATIONENGINEERING DESIGN ISSUESEarthquake.Wind. Blast / Progressive collapse.Green Engineering.Sensitivity to historic preservation issues.

INNOVATIONS IN EARTHQUAKE ENGINEERINGBase isolation.Fiber wrap.Dampers.Steel moment frame solutions.(Redundancy help of progressive collapse)Capacity design principles.

BASE ISOLATION TECHNOLOGYOne of the most significant development in earthquake engineering in past 35yrs.It provides the design profession, the ability to design a building is operation after a major earthquake.

Goals of base isolationProtection of life Current code.Additional benefits of isolation1. Protection of building.2. Protection of building non-structural components and contents.3. Protection of processes & function.4. Provide for an operational facility after the earthquake.BASIC ELEMENTS OF SESMIC ISOLATION SYSTEMSA flexible mounting so that the period of vibration of the total system is lengthened sufficiently to reduce the force response.A damper or energy dissipaters so that the relative deflections between the building and ground can be controlled to a practical design level.A means of providing rigidity under low load levels such as wind & minor earthquakes.BASE ISOLATION HOW IT WORKS

Most types of Isolators exhibit nonlinear behaviorLengthening of the Structures Period and increased Damping that result in a large scale decrease of the Seismic Response

During a Richter 8.0 earthquake a seismically isolated building will behave as if it were experiencing a 5.5 earthquake.BENEFITS OF ISOLATION RETROFITINGWork may be confined to basements.

Building can continue to be occupied.

Often the most economic solution.TYPES OF BASE ISOLATION SYSTEMFPS.RB system.LRB (N-Z system).R- FBI system.1.Friction Pendulum System:-

The P-F or sliding-joint system is classified as the simplest device because it uses only the stick-slip mechanism.

Exploded View of Ball-N-Cone Bearing. (FrictionPendulum)

2. The RB system:-

3. The LRB system

The RB system may not be able to resist the required displacements for the seismic isolation. A lead-plug insert provides hysteretic energy-dissipation, therefore, the damping required for a successful seismic isolation system can be incorporated in a single compact component with the RB system.4.The R-FBI system:-

The R-FBI system makes use of the parallel action of resiliency of rubber and the friction of Teflon coated plates. Similar to the P-F-system, it does not slide below the frictional resistance. Unlike the P-F system, however, it has an additional resistance to an increase of deflection and a recovering force by rubber after slidingAPPILICATION OF BASE ISOLATION SYSTEM1st application in New Zealand in 1974.1st US application in 1984.1st Japanese application in 1985.US 80 buildings & 150 Bridges.Japan 1000 buildings & 500 bridges.

San Francisco Airport International TerminalWorlds Largest Isolated Building

Base Isolated StructureConventional StructureApplication of ForcesApplication of Forces

Base Isolator Subjected to Forces:-

After DeformationBefore deformation

Before deformationAfter Deformation

Without Base IsolationWith Base IsolationCONCLUSIONSBase isolation provides the highest level of protection- operational after a major earthquake. It has significant benefits for the earthquake protection of historic structures.Base isolated building are capable of resting GSA blast loads & their ability to move reduces the overall impact of the blast force on the building. Scope of Future Work

Analysis And Design Of Unsymmetrical Base Isolated Buildings.Analysis And Design Of Base Isolated Structure, Considering Superstructure As Flexible.Non-linear Dynamic Analysis And Design Of Isolator Subjected To Earthquake Forces.

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