Most builders in the capital say they are conforming to construction codes for Zone V seismic activity,although the NCR falls under Zone IV.PRABHAKAR SINHA talks to a few builders
Builders in the National Capital Region (NCR) claim that structurally,their constructions are safe in the region as they are earthquake-resistant buildings.Though most parts in the NCR are in the earthquake Zone IV,builders claim their buildings are built to resist Zone V seismic activity.Earthquake Zone V is more vulnerable to seismic waves than Earthquake Zone IV.
The government has classified the various area into different zones based on their vulnerability to earthquakes.A micro-zonation study of Delhi carried out by the Indian Meteorological Department (IMD) identified East and Northeast Delhi as most vulnerable because of newer alluvial soiltype found there.
The Chhattarpur basin is also at high risk due to a basin effect.Other than a very small strip of rocky ridge area,the remaining parts of Delhi are at a moderate risk.On the basis of these earthquake zonings,the government has codified the structural norms that builders have to follow to get their building plan,including the structural map,approved.The governments guidelines for building constructions prescribe the standards which are good enough to prevent a total collapse.But,they do not prescribe standards required to prevent loss of life.Therefore,even if a building is constructed following the governments prescribed guidelines,there could be loss of life in the event of an earthquake due to falling walls.In developed countries,to avoid loss of life due to falling walls,they prescribe use of only reinforced walls.In India,too,such norms should be followed.
However,for the safety of the structure,builders claim they follow stricter norms than what has been prescribed by the authorities.Sanjay Chandra,the MD of Unitech,says Unitech not only follows the building code as prescribed by the government but also has tied up with a Canada-based technology company,Pall Dynamics,to upgrade safety standards of its buildings.Pall Dynamics has developed a patented technology which uses particular type of braces,which are used as frictional dampener to reduce the effect of seismic waves on the building structure.He says the firm uses this material in all its highrise buildings.The company also gets its building maps approved by Pall Dynamics.
A DLF spokesperson also maintained that the firm,as a matter of principle,adopts the building code for Earthquake Zone V in the NCR.
Getamber Anand,the MD of ATS Group,who is also vicepresident of builders association CREDAI,says that most builders adopt Zone V specifications in their construction.He says while the NCR is in Zone IV,buildings constructed under Zone V specifications give them enough strength to withstand the worst case scenario in the region.The government implemented the building code in 2001,after the Bhuj earthquake.
It revised the code again in 2006,to make the norms even stricter.Anil Sharma,the CMD of Amprapali,says that under the new code,there are provisions for factor of safety.Under this,he says,a building structure is planned to bear three times the load that it is supposed to experience in an earthquake.This gives additional strength to the building.Not only this,under the new code,all the joints of beams and columns are made flexible so that they do not develop cracks in case of an earthquake.
Apart from all this,all the buildings in the NCR have used the concept of sheer wall,which is composed of braced panels to counter the effects of lateral load on a structure due to an earthquake.Sharma says that after the introduction of sheer wall in 1970s,buildings have become stronger to withstand an earthquake.
Sharma says that the good thing in India is that unlike Japan,which is prone to both frequent earthquakes and tsunamis,there are no regions which are prone to both earthquakes and tsunamis.Delhi is prone to earthquakes alone,for instance.Similarly,areas near the sea shore are prone to tsunamis but they are not prone to earthquakes.This makes an engineers job easy in planning safe structures here.Sharma says that Amrapali is planning to use pre-fabricated beams and columns to further improve the quality of the construction.Besides,the company will use more and more reinforced structures in construction of its project buildings.
Sanjeev Srivastva,the MD of Assotech Limited,who is implementing a highrise residential project Celeste Tower in Noida,says that most of the highrise buildings being constructed today have adequate protection against earthquakes and fire.The 121.6-metres tall Celeste Towers has an earthquake-resistant design and has followed all the mandatory norms as per the seismic code.
