Houses that hold on
At 2.53 am on October 25, 1991, a moderate earthquake measuring 6.6 on the Richter scale affected more than 425,000 people of about 2,100 villages in the districts of Uttarkashi, Tehri and Chamoli in what was then Uttar Pradesh and is now the hill state of Uttaranchal. Traditionally built timber houses proved to be the most effective at keeping damage at bay.
It would, however, be incorrect to say that the old-fashioned houses survived just because of materials used. The construction techniques, too, determined the amount of damage. Making houses for earthquake-prone areas is more about 'software' than 'hardware'. So, even if timber is not easy to come by, there are solutions.
A S Arya, head of the quake engineering cell of the Bureau of Indian Standards ( bis ), says an additional expenditure of 6-10 per cent during construction can make a building quake resistant.
Heavy roofs (slate tiles or RCC ) supported by weak walls (random rubble in mud mortar) proved to be deadly. Most new constructions were of this kind, which became popular in Uttarkashi region after the construction of the Maneri dam about 30 years ago. Older houses at higher elevations have timber roofs held together by timber 'tie-bands' -- horizontal timber beams spanning across the entire building, connecting the entire structure and giving it the character of a cage. Such houses suffered little damage despite the mud-and-stone masonry.
The Dehradun-based People's Science Institute has worked on popularising features that make houses stand up better to earthquakes. Such houses must have tie-bands just above the level of the floor, the level of the doors and windows, and another at the roof level, point out Ravi Chopra and Rajesh Kumar of the institute. Corners are the most vulnerable and ought to be strengthened. Elasticity of the structure can be enhanced with flexible steel rods or wood batons at corners. Doors and windows should be few, small and symmetrically placed away from the corners. The house should be as light as possible.
Anil Joshi of the Himalayan Environmental Studies and Conservation Organisation (HESCO) was involved in the construction of quake-resistant houses in Tehri and Rudraprayag districts after the 1991 Uttarkashi quake. He says all houses designed or guided by the renowned architect Laurie Baker remained intact even as many others in the vicinity collapsed during the 1999 Chamoli quake. Baker emphasises using local construction material. The poor masonry work and ignorance of traditional wisdom resulted in the losses in rural areas, Baker maintains.
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