12-04-2014, 03:07 PM
Seminar on ADVANCED EARTHQUAKE RESISTANT DESIGN AND TECHNIQUES
INTRODUCTION
An earthquake is the vibration of Earth produced by the rapid release of accumulated energy in elastically strained rocks
Energy released radiates in all directions from its source, the focus.
Energy propagates in the form of seismic waves.
Sensitive instruments around the world record the event.
What causes an earthquake?
Movement of Tectonic Plates
Earth is divided into sections called Tectonic plates that float on the fluid-like interior of the Earth. Earthquakes are usually caused by sudden movement of earth plates
Rupture of rocks along a fault
Faults are localized areas of weakness in the surface of the Earth, sometimes the plate boundary itself
Seismic Codes of India
IS: 13920:1993 Ductile Detailing of Reinforced Concrete Structures Subjected to Seismic Forces, BIS, New Delhi
IS: 1893 (Part1-5): 2002 Criteria for Earthquake Resistant Design of Structures, BIS, New Delhi
IS: 4326:1993 Earthquake Resistant Design and Construction of Buildings, BIS, New Delhi
Lead-rubber bearings
A lead rubber bearing is made from layers of rubber sandwiched together with layers of steel. In the middle of the solid lead “plug”. On top and bottom, the bearing is fitted with steel plates which are used to attach the bearing to the building and foundation. The bearing is very stiff and strong in the vertical direction, but flexible in the horizontal direction.
Base Isolation in Real Buildings
It has been in increased use since 1980’s
Base isolation has now been used in numerous
buildings in various countries
Base isolation is also useful for retrofitting
important buildings like hospitals and historic
buildings
In India
Two single storey buildings in Killari town were
built with rubber base isolators resting on hard
ground.
Commonly used Seismic Dampers
Viscous Dampers (energy is absorbed by silicone-based fluid passing between piston cylinder arrangement)
Friction Dampers (energy is absorbed by surfaces with friction between them rubbing against each other),
Yielding Dampers (energy is absorbed by metallic components that yield).
Viscoelastic Dampers (energy is absorbed by utilizing the controlled shearing of solids).
Conclusion:
Conventional approach to earthquake resistant design of buildings depends upon providing the building with strength, stiffness and inelastic deformation capacity. But the new techniques like Energy Dissipation and Active Control Devices are a lot more efficient and better.
In the coming years the work in the field of EQRD is very important to have safe structures which can take the effect of earthquake with less damage to the society.