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Q. Aseismic structures are touted as a viable solution to combat earthquake destruction. In this context, highlight the need of a National Program on Seismic Retrofitting of Buildings and Structures in India.

Approach:

• Give a brief introduction about aseismic structures and their earthquake-resistant properties.
• Write about the need of a National Program on Seismic Retrofitting of Buildings and Structures in India.
• Conclude with some challenges in the context and way forward.

Answer:

India has experienced several major earthquakes in the past few decades with around 56 percent of its land in Zone V, IV, and III and 44 percent in Zone II. Over 95 percent of fatalities in past earthquakes in India have occurred in non-engineered houses and structures.

• A large number of existing buildings across the country do not seem to have adequate earthquake resistant features specified in Indian Standard codes and criteria related to earthquake resistant buildings.
• In this context, aseismic structures are touted as viable solutions to combat earthquake destructions as these are designed and built with the objective to absorb the shocks of earthquake without collapsing thus reducing loss of life and property.
• Aseismic structures are generally constructed on top of flexible pads that isolate the foundation from the ground. These buildings are also shock absorbers and vibrational control devices and pendulum dampers.
• They are made with shock absorbing and ductile materials like steel and wood. Also, reinforcing the existing building with certain retrofitting also makes them aseismic structures. Countries like New Zealand are adopting aseismic structure.

On similar lines, the National Disaster Management Authority has brought the guidelines for the Seismic Retrofitting of Buildings in India. Retrofitting is fitting a building or structure in retrospect (after it is built) to make it capable to withstand the effects of earthquake shaking.

In this regard, there is a need for National Program on Seismic Retrofitting of Buildings and Structure in India owing to various factors:

• As per latest seismic map of BIS, 59 percent of land in India is vulnerable to moderate to severe seismic hazard.
• India’s major and critical infrastructure have been built long back. Many of the critical railway bridges are from the British era. Various important buildings are also from the same time.
• To avoid any loss of critical and lifeline structures, an umbrella policy is required to strengthen this structure so that they can withstand serious earthquake shocks.
• Rapid urbanization in the last few decades has increased load on various old buildings in metros and other cities making clusters of highly dense population, thus increasing vulnerability for any hazard from even minor earthquakes.
• Further a special class of buildings exist across the country, called Open Ground Storey Buildings. These do not conform to prevalent Indian standards for earthquake safety.
• These buildings are flexible and weak in the open ground storey compared to storey above. A large number of these low strength reinforced concrete buildings collapsed during the 2001 Bhuj earthquake.
• A large number of similar buildings exist in urban and semi-urban areas of India, which require retrofitting.

However, there are challenges in terms of disruption, planning, availability of funding and technology, designing, implementing and monitoring. Also, retrofitting strategy would prove to be more costly than making new structures. India needs to spend more on research on this front and conduct risk assessment and prioritize inventory of structures. In this regard, India can learn and adopt best practices from other countries to mitigate the loss during earthquakes.