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DEATHQUAKE;
THE WAY OUT
Preventing
Collapse
A
quake of similar intensity in Delhi or Mumbai could bring unparalleled
devastation. Better design and construction, and buttressing of existing
buildings, can keep casualties low.
By
Supriya Bezbaruah
In
a minute there is time, said Nobel laureate T.S. Eliot, that a minute
will reverse. Actually, it took less than a minute for towering buildings
in Ahmedabad and Bhuj to collapse on 20,000 lives. An earthquake itself
never kills people, it's the badly constructed buildings that kill, points
out V. Suresh, chairman of the Housing and Urban Development Corporation
(HUDCO). Proving his point, there was little damage to Ahmedabad's 30,000
Gujarat Housing Board flats, even as other prominent buildings like Shikhar
Towers and Mansi Apartments totally disintegrated. That is the real tragedy
in Gujarat today-that the devastation was avoidable, if only guidelines
for earthquake-resistant building construction, available since 1970,
had been followed. The greatest fear now is the realisation that none
of the other densely populated and earthquake-prone metros like Delhi
or Mumbai has regulated earthquake-resistant buildings. An earthquake
in these cities, experts fear, could be a calamity of unparalleled dimensions.
Delhi lies on four fault lines, and according to experts at least 50 per
cent of the buildings cannot resist quakes.
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| FAULT
LINE: Inferior construction can make a building vibrate like a tuning
fork, and fall apart |
The Gujarat
earthquake should not really have been a surprise. The Rann of Kutch has
been marked as an extremely high-risk earthquake zone since the first
seismic hazard surveys in 1935. Earthquake-resisting designs have been
known to structural engineers since the 1960s, and the National Building
Code of 1983 clearly identifies structural designs in terms of earthquakes
and cyclones. "For safety's sake, these guidelines should be part
of building laws," insists Suresh.
In fact,
knowledge is plentiful. Following the UN's Yokohama Strategy for a Safer
World in 1994, the Union Urban Development Ministry's Building Materials
and Technology Promotion Council carried out extensive surveys of all
natural disaster risks in every part of India. The result, titled the
Vulnerability Atlas of India, published in 1998 in two big volumes, details
the risks involved in different constructions, in every single district
of the country. It also includes recommendations for appropriate safety
techniques, bye-laws, practices and regulations for that region. No other
country has such a comprehensive vulnerability map. Two copies of smaller
volumes on each state were sent to the respective governments. So far,
not a single state has acted on any of the recommendations.
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| FLATTENED:
An aerial view of the devastated centre of Bachau town some 70 km
east of Bhuj. Constructing quake-resistant buildings does not add
much to the costs. |
Safety laws
may set the tone but public awareness is essential for their enforcement,
according to Suresh. Four out of five Indian homes are designed by the
owners themselves, and most do not realise that their homes may become
their tombs. Regulating engineers is also the need of the times, says
Mohinder Raj, a leading Delhi-based consultant engineer. Engineers have
no licensing system, so even a novice engineer can legally certify that
a building has been suitably built.
So how can
buildings be made earthquake-safe? Two essential factors are good design
and good construction, says Raj. The idea is to build structures in a
way that can absorb maximum force and still remain stable. Harvard-trained
architect Dikshu Kukreja of leading Delhi-based architecture firm C.P.
Kukreja and Sons, says, "If the beams and columns of the building
are properly joined, 50 per cent of earthquake design is taken care of."
This means if the builder has a tendency to save on concrete or steel,
the sturdiness of the building is at stake. As a thumb rule, in any building,
adding a steel frame and concrete, called reinforced cement concrete (RCC),
in the columns and beams and joining them well, adds to safety.
Pure geometric
shapes like squares, rectangles and triangles disperse the seismic forces
equally in all directions, so are safer. For similar reasons, a cantilever
or irregular shape results in uneven distribution of forces, causing such
buildings to collapse. Uneven structures can be safe, stresses Kukreja,
but they have to be appropriately reinforced to resist such forces.
Steel cross-beams
in high-rises are the latest techniques. A solid concrete core-such as
the lift-shaft in the centre-and sheer concrete walls, along with cross-beams,
are extremely earthquake resistant. Such structures dominate the San Francisco
skyline.
Building
materials are crucial too. The safest modern building would be all steel
as it is an extremely good shock absorber. Cellular lightweight concrete
and wood substitutes are frequently used by the quake veterans, the Japanese.
Traditional bamboo and wood used in Kashmir and the North-east, both seismic
hotbeds, are also sturdy and cause minimal damage. Glass is not earthquake-friendly
as a rule. However, says Kukreja, glass can be safe-the latest technology
suggests almost invisible but strong and lightweight plastic/silicon frames
to hold the glass, ensuring safety without subtracting from the aesthetics.
Fifty-four
per cent of India is earthquake prone. Only a major retrofitting movement
and laws can prevent another disaster. Building quake-resistant buildings
does not cost extra. But retro-fitting is expensive, costing up to 6-10
per cent of the building value, according to Suresh.
After Bhuj,
state governments are being reminded of the vulnerability atlases again.
Delhi has announced that it will make safety guidelines mandatory. Like
in California, which has had strict legally binding building codes in
place since a 1933 earthquake, with another legislation in 1992, and a
more comprehensive code established in 2000. Such concerns are now being
voiced at the highest levels in India. Preventing another catastrophe
depends on these voices not fading away with time like the cries of the
400 schoolchildren trapped under the rubble in Gujarat.
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