Flaws in the construction of high-rise buildings in many important cities in this country have made the people vulnerable to the serious dangers involved at times of earthquakes. It is high time, that this fact was grasped by the Public. During the last two years there have been several conferences and workshops on the topic of reducing risk from earthquakes. People from the Scientific and Engineering Community are interacting on issues related to earthquakes.
There is unanimous agreement among the engineering fraternity in pinpointing the category of buildings which are mainly at risk among all the buildings in India. It happens to be the buildings on stilts. It happens to be buildings which have an open ground floor area that is often used as a car park.
It is a fact that most of the buildings on stilts would fall should there be a big earthquake whether in seismic zones 3, 4 or 5. Almost 60 percent of the Indian landmass belongs to these zones with the greatest danger being in zone 5. There are four zones and zone 2 is the least dangerous. Zones 3, 4 and 5 include most of our important cities of Mumbai, Delhi, Hyderabad, Pune, Chandigarh and Kolkata.
Adding to the problem, it is a fact that the buildings on stilts are all multi-storied. This makes the rate of casualty even higher than a low-rise building. If the Government is conscious of this grave problem what is it doing regarding this?
It seems that such a problematic issue is easier to sweep under the carpet. Even though the people in authority are aware of the situation it just seems to get bigger with more unsafe buildings being added in the cities.
However, it can be resolved, if faced in a methodical and timely way. Awareness must be awakened among the masses that all buildings on stilts are to be counted as unsafe till a safety certificate is given by a structural Consultant. The majority of Indian cities have multi-storied buildings constructed on 9 m to 12 inch (22.5 cm to 30 cm) thick columns and this is very inadequate even for zone 3. If there is a major quake, these structures are bound to collapse and crash.
The Owners or Occupants should have a structural check done for their building in order to pinpoint those that need to be upgraded by a structural retrofit. For this, the giant task India possesses thousands of structural Engineers who can be of Assistance. Small cells of individual consultants working on a building each would be very successful in a public-private partnership representation.
The majority of buildings in Indian cities and particularly those on stilts are deficient in stiffness. If any building is known to be lacking in stiffness, it can easily be compensated by using concrete jacketing or additional columns. One has to take care and check whether that jacketing is done right down to the foundation. It must meet the criterion of minimum stiffness. But, it should not be made too stiff as that it will draw greater forces from earthquakes and be harmful.
A retrofit tactic can be recommended by the Engineer on the basis of computer analysis which can be communicated to the building Owners to be implemented. After this process, the Owners should be burdened with the responsibility of keeping the building the safe. The Government may think of giving an incentive in tax for the money used on retrofit of residential buildings.
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