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A perfect recipe for disaster

india Updated: Oct 13, 2011 22:52 IST
Alpa Sheth

The Sikkim administration is relieved that only 60 people (0.01% of its population) died in the September 19 earthquake. An excellent report card when compared to Gujarat, where over 13,800 people (0.03% of its population) died in the 2001 quake.

However, it's perhaps for the first time in the earthquake history of India that government buildings have fared far more poorly than private buildings. I was in Sikkim recently on a damage-assessment trip and I saw scores of damaged government buildings in Gangtok and elsewhere. The most glaring example was the secretariat, which will now be razed to the ground. A pity since it can be retrofitted and reused for non-critical functions. The legislative assembly building, which had undergone expensive retrofitting just before the quake, also suffered widespread non-structural damage. The same is the state of the police headquarters and a hospital in Gangtok.

While the government may rejoice bec-ause of the low casualty, the extent of damage of the government buildings in this moderate intensity earthquake is unacceptable. The performance of these buildings needs to be reviewed because they, along with some hotels, industries and institutional buildings, are perhaps the only 'engineered' buildings in the state.

The state has been growing at a rate of over 8% annually. Almost 65% of its present stock of 13,000 buildings have mushroomed in the past 10 to 15 years and most of them are made of reinforced concrete. But there are only two private qualified structural engineers in Sikkim and so it's easy to see why most of the private buildings are usually non-engineered, reinforced concrete structures, one of the deadliest building typologies in an earthquake area.

And yet, to the surprise of many earthquake engineers, the apparent damage in Gangtok, the most populous city of Sikkim, is not as bad as it was feared. A majority of buildings have suffered some form of minor or significant non-structural damage which is reversible; few have suffered structural damages. Only three buildings collapsed, 57 have been put on notice for evacuation and 15 have been ordered full or partial demolition.

A layman constructing a multi-storey in Gangtok is not even aware of the need for a structural engineer. While granting permission to build a house, the relevant government department doesn't require the involvement of a structural engineer. So the homeowner, who has no clue about earthquake engineering or ductility requirements in a high seismic zone, constructs his house only with a grid of columns and beams.

Such houses with uniform stiffness and frames on regular grid behaved well in the moderate-intensity Sikkim earthquake, but they may not do so if the quake is a high-intensity one. Those buildings that had an open storey (floors where there were no partition walls causing a sudden change in stiffness of building) collapsed or had severe structural damage.

Sikkim's reinforced concrete homes face two challenges. Being on slopes, they are connected to the earth at numerous floors and are thus subject to shaking at multiple levels. This complicates a building's performance. The second is that they do not have access to machine-mixed concrete - almost all concrete used is hand-mixed, a complete no-no by engineering standards.

The performance of government buildings in the Sikkim earthquake and engineered buildings of Ahmedabad during the Bhuj earthquake have some lessons for us: first, there are problems with how we design and construct buildings; second, designers indulge architects and allow for a lot of things that they do not quite know how to handle; third, poor quality of materials and workmanship; and fourth, most engineers and developers seem to believe that an earthquake will never strike their area and, therefore, they don't follow proper building codes and earthquake designs.

The sad part is that despite having a huge repertoire of earthquake engineering knowledge, there is no will on the part of the engineering community or the stakeholders to implement these. The pressure for improved performance of engineered buildings during an earthquake must come from civil society.

Alpa Sheth is member of the Post-Earthquake Reconnaissance Team of the National Disaster Management Authority, Government of India. The views expressed by the author are personal.