Earthquake: Frequently Asked Questions

What is an earthquake, and how does it effect buildings?
Earthquakes are caused due to movements of ‘plates’ under ground. In an earthquake, the ground shakes and suddenly starts to move backward and forward. This movement may be in any direction. Near the epicenter of the earthquake, there is also an upward and downward movement; because of which the foundation of the buildings move with the ground, but the interia of the rest of the building relays movement of upper part of the building. It is this delay which comes stresses in the buildings and cracking which is a typical of earthquake damage.

Is it possible to build "Earthquake proof" houses?
It is a misconception commonly shared that, houses could be made earthquake proof. The reality however is that by taking precautions, the earthquake resistance of the house can be increased finitely, making them capable to resist quakes of specific magnitudes. These houses, too, may fail once they face quakes of higher intensity than they are designed for.

How strong should buildings be made?
The purpose of earthquake resistant design is not to prevent all damage by a severe earthquake, for such an objective would result in unreasonably expensive structures. The first aim is to ensure against the loss of life or injury. Second step is to balance the cost of additional design strength against the probable cost of repair of damage over the expected life of the structure.

As money is a limited resource, the main objective should be to prevent collapse of building with consequent loss of life. One must expect buildings to crack and to need repair if there is a major earthquake.

Secondly, community buildings like schools, hospitals, power stations etc are more important than individual houses. Hence these buildings should be built more strongly than ordinary houses.

What are the important considerations in making a house more earthquake resistant?
(a) Reduce its mass and make it as light as possible

(b) The structures should be rigid enough, making sure that whole structure vibrates together as one unit. Schematically, in such units, the top portions are so joined to the bottom that all movements are transferred immediately from lower levels to the entire building and entire unit vibrates as one rigid body. Consequently, no disharmonious stresses are set up and structure remains safe. One way of doing so is by "tying" the structure using horizontal bands at plinth, cill, Lintel and roof level. Vertical reinforcement also makes structure more resistant.

International Conference on EcoMaterials

announces

"Ecomaterials for disaster prevention and Relief"

in

Quality Control and Assurance in Concrete Constructions
to be held in Santa Clara, Cuba

24th – 27th September, 2001

Main Themes

Materials, products and components for construction
Technologies, solutions and constructive systems
Urban and rural design and conditioning
Economic management of projects in disaster zones.

The organising Institutions are:

CIEDM
(Center for the Research and 
Development of Structures and Materials)

ISP JAE
(Polytechnic Institute 
"Jose A. Echevarria")
&

EcoSouth

For more informaiton contact:
Prof.Dr.Ing.Fernando Martirena
Tel/Fax: ++53 422 81539;
Email: F.Martirena@ip.etecsa.cu ecosur@nicanet.com.ni

 

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