The massive earthquake that struck Gujarat on the morning of January 26, 2001 caused extensive damage to life and property. The worst damage was concentrated in the old city of Bhuj. Jubilee Hospital, the main hospital in the city, was levelled and so were many other medical facilities across Kutch.

Many of the injured had to be flown to Mumbai and Pune for medical treatment. The poor medical response led to high casualties. The incident highlighted the need to strengthen and retrofit lifeline structures such as hospitals that play a key role in relief activities in the event of a major disaster and insulate them from damage. Experts participating in a training programme organised by the Institute of Land and Disaster Management in Thiruvananthapuram earlier this month stressed the need to ensure the survival of critical infrastructure, such as hospitals and health facilities, major financial institutions, schools, fire stations and offices of the civic administration, necessary for disaster relief and rescue operations.

Engineers, doctors, urban planners and representatives of various government agencies participated in the sessions. Speakers at the programme said lifeline structures that offer critical services during disasters, such as earthquakes, cyclones, building collapse or chemical accidents, were particularly important for a multi-hazard-prone State such as Kerala. Hari Kumar, national coordinator, Geohazards International, a non-profit organisation working for earthquake safety, says retrofit involves reinforcing a building to make it more earthquake-resistant.

Structures not conforming to BIS codes are candidates for retrofitting. It is estimated that there are 12 crore buildings in seismic zones 3, 4 and 5 representing moderate risk, high damage risk and very high damage risk, respectively, in India. The buildings that require retrofitting are those with poor construction quality, those that have not been designed according to the code. Mr. Kumar says soft-storey buildings, a term used to refer to multi-storey structures with one floor marked by large openings such as a parking garage, floor-to-ceiling shop windows or commercial spaces unhindered by pillars, are especially vulnerable to collapse during earthquakes. The inadequately braced level is less resistant to seismic force and consequently suffers structural damage or total collapse.

Soft-storey failure is primarily responsible for the damage caused to multi-storey buildings in seismic zones. Retrofit measures include addition of shear walls and braced frames, enhancement of the performance of existing elements such as concrete columns, improving connection between components, isolation or damping of elements subjected to strain and removal of selected components. Mr. Kumar says technical issues such as strength, stiffness, ductility and connectivity will suggest structural schemes, while other considerations such as construction cost, performance, disruption, long-term planning and aesthetics will govern selection of the scheme.

K.G. Thara, member, State Disaster Management Authority, points out that Kerala is in the same earthquake intensity zone as Latur (Zone III, where earthquakes of 6.5 on the Richter scale can be expected). “In Latur, the buildings collapsed because of faulty design, weak construction materials and poor maintenance, whereas in Bhuj, it was because of non-compliance to the seismic regulations and construction codes.” As per Union government reports, 61 per cent of the houses in Kerala belong to Category A (rural structures, un-burnt brick houses, clay houses and so on), which are at a moderate seismic risk (intensity VII earthquakes). Ms. Thara says a seismic evaluation of existing buildings in Kerala is overdue.

A structural safety audit will reveal geometric irregularities. The guidelines issued by the National Disaster Management Authority (NDMA) recommend a structural safety audit and retrofitting of select critical lifeline structures. The State governments have been advised to have these buildings assessed and where necessary, retrofitted.

T. Nandakumar