|
|
| 21 June 2008 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
CONSTRUCTION OF
EARTHQUAKE RESISTENT BUILDINGS
IN SEISMIC ZONES OF
Earthquakes occur due to movements along faults that have evolved through geological and tectonic processes. Often they occur without any prior warning and are, therefore, unpredictable. The large area of
 On the basis of occurrence of earthquakes of different intensities, the National Building Code of India divide the country into five seismic zones as described on the above map. The zone V is the highest risk zone where earthquakes of having intensity of 9 plus on the Richter scale can take place. Earthquake of an intensity between 8 to 9 can be experienced in Zone IV whereas earthquake can occur between 6 and 8 on the Richter scale in Zone III of India. The respective seismic zones of important urban centres of
The natural disasters like earthquake can not be prevented, but measures are required to be taken to reduce the extent of damage, especially in a vast country like The developed countries of the world are adopting new technique of construction of seismic proof buildings whereas under developed countries do not give much attention for the construction of seismic proof buildings due to shortage of resources. With the result world’s worst disasters always take place in underdeveloped and poor countries. Disasters cause enormous destruction and human sufferings. The losses due to occurrence of earthquakes reduce the pace of economic development and often lead to depletion of available resources. Effect of Earthquake Forces on Buildings:-
 During an earthquake, a building experiences two types of seismic forces : lateral and uplift. Lateral or shear forces are horizontal forces which cause back and forth movements Uplift forces are vertical forces which cause up and down movements. Using metal connectors, shear walls & fasteners strengthened the structural stability of the buildings. Retrofitting is the process of reinforcing the foundation of existing buildings to bring them at par with present norms of earthquake resistance. Recommendations :- The earthquake disasters can be averted with the construction of seismic proof buildings. Each building can be designed in such a way that it may withstand during severest quakes depending on the seismic zone it falls in. The multistoried structures are considered at a higher risk due to gravitational pull. A single storey or a multi-storied building may be equally prone to an earthquake but the fact is that a poorly designed single structure may crumble, while a well-designed multi-storey structure may only shake,”The National Disaster Management Authority (NDMA) has made it compulsory for all new constructions to be earthquake-resistant, especially in cities located in seismic zones. The guidelines have also recommended selective seismic strengthening and retrofitting of existing priority structures located in high-risk areas. The buildings retrofitted to withstand earthquakes survive better than those that have not been upgraded. Even simple efforts, such as bracing parapets, tying buildings to foundations, and anchoring brick walls at the highest, or roof level, have been proved extremely effective to protect buildings during earthquake. . It has also been proven that well maintained buildings have faired better than those in poor condition during and after an earthquake. Thus, maintenance and seismic retrofit are two critical components for the protection of historic buildings in areas of seismic activity. It makes no sense to retrofit a building without improvements. The subcontinent is sitting on the highly seismic Indian plate, with some major faults lines. In fact there is no seismically safe zone in
1. Implementation of Disaster Management Plan :-
The Disaster Management Bill, likely to be presented in the winter session of Parliament, will make it necessary for all states to have a disaster management authority and implement the national disaster plan. "Eventually disaster management is a state’s concern and the action plan has ultimately depend upon the state’s own concerns and ability to set up institutional and financial 2. Creation of Special Force At National Level :- At the national level, other measures are being planned. Eight battalions of 10,000 soldiers are being trained for being posted to eight different locations and money has also been sanctioned for buying aircraft for their use in cases of emergency. 3. Creation of Emergency Operation Centre :- is being equipped with state-of-the-art communication links and micro-zonation of 38 cities above 10-lakh population is being attempted in different phases. The micro-zonation of In words of Science and Technology Minister Kapil Sibal, the micro-zonation process is the government’s effort to take effective measures with proper research to minimise risk to existing buildings in the event of an earthquake. Micro-zonation, he says, will help bring area-wise changes in building bylaws to ensure quake resistant measures in the structural designs of high rises to minimise the risk of heavy damage and loss of life in event of an earthquake. While the government is attempting a paradigm shift in the disaster management from relief and rehabilitation to mitigation and prevention, to make it successful will eventually depend upon the civil society.
By
B.N. Sharma
Retd. Senior Town Planner of
Haryana Government |
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
