AT the Lal Tekri area in Bhuj, an apartment block teeters over the road traffic at an angle of over 30o. Major Y.S.S. Rao of 12 Madras Sappers has been given the go ahead to bring down the four-storey structure, which he does with all the fine sse of a professional, systematically demolishing the structural pillars to achieve the objective.
The building symbolises the worst in terms of construction ethics. It was built over a deep nullah (an open drain) without reinforcement support, and so its foundations were incessantly subjected to erosion by the flowing water. When it collapsed, part of the structure sank into the nullah. Rescue teams had to crawl underneath to look for survivors.
The use of inferior construction materials was noticeable in practically every collapsed structure. Concrete slabs crumbled easily, for flat strips of non-load bearing mild steel had been used to make them, instead of steel rods of the requisite size.
While building in earthquake-prone zones (as a relevant aside, the British Geological Survey has said that the subcontinent should expect heightened further tectonic activity), a minimum of six kg of steel per square foot of built-up area needs to be use d. In Mumbai, builders use just 5 kg for a ground-plus-ten-storey structure and in Bhuj they used a mere 2.5 kg. For buildings in the earthquake-hit area that have been declared safe, further safety measures could include column strengthening by means of grouting or steel meshing.
There is no disputing the earthquake's severity or its capacity to leave even a well-constructed structure damaged. Central government buildings, built by the Central Public Works Department, are meant to be designed as earthquake-proof ones but at least some of these did not survive the quake. Yet, engineers and architects emphasise that adherence to rules of engineering and architecture would have resulted in lower casualty figures.
AT the Vivekanand Research and Training Institute (VRTI) in Mandvi, an experiment is in progress. Soon after the earthquake a team set out to work with the primary intention of creating a structure that could be in turns temporary, semi-permanent and the n permanent. The structure would have a high degree of strength in terms of the materials used and the inherent design qualities. It is expected to double as emergency shelters after being used to house people and store materials while permanent homes ar e being rebuilt for them.
It was inevitable that the team would settle on the dome. Not because a dome is entirely earthquake-proof but because "it's a handy structure and very stable", say the team-members (who prefer to see their work as that of a collective and therefore reque st anonymity).
Using Buckminster Fuller's (the U.S. architect and inventor) geodesic dome principles, the team recreated a model with the pentagon as a starting point. The roof of the dome is five-sided. Steel strips radiate from this, resulting in a wall face of hexag rams. For further verification of its usability, the team fed data into an engineering software programme and subjected the structure to a virtual stress analysis of situations and pressures that it would be likely to encounter on the ground. It passed a ll the tests.
As a temporary shelter the dome would be like an upturned basket, covered with tarpaulin. The covering would be held in place by nuts and rubber washers. The dome would rest on the ground and entry to it would be gained simply by lifting it. Once inside, there would be enough headroom to sit up.
As a permanent shelter the dome would rest on a circular, column-based, stone or block masonry wall. The roof would be a three-or-four-inch thick slab of ferro cement (a wire mesh covered with mortar of sand and cement). The team envisages a dome 20 feet in diameter and loaded with a five-tonne roofing slab whose weight is distributed evenly over the dome. Even with such a heavy load, the computer analysis shows the deflection factor bearing up very well - just a 1.7 mm dip on the entire span. A dangero us deflection level would have been upwards of 25 mm.
The finer points regarding the dome are being worked out - would it be better to transport the dome in its entirety to the affected areas, or would it be better to let the recipients assemble it at the site itself? Both ideas have their pros and cons, bu t a strong reasons to opt for the latter is the fact that assembling their own shelter would give the affected people a strong sense of involvement and of getting to grips with their own rehabilitation - bolting together 400 strips of foot long metal str ips to make a patchwork of hexagons would take a group of three people about two hours.
The issue of relevant architecture has always been a matter of debate among civil engineers, architects, building contractors and real estate agents, all projecting their own points of view. In the process, the safety factor has often been ignored.
The traditional architecture of Kutch is typified the bhunga - a round-walled, single-room structure with a conical roof of grass. The walls are a mesh of sand, limestone, stones and grass. An eco-conscious, climate-friendly, socially-oriented str ucture with sound engineering features - this will be an accurate description of a bhunga. Mutva Miya Husen Gulbeg, sarpanch of Dhordo village proudly points out: "When bhungas fall they fall outwards - not on the people who built them."
Not that bhungas are the answer to the modern imperatives of space and amenities that towns such as Bhuj, Anjar, Bhachau and Mandvi need. But the VRTI team believes that construction in Kutch does not have the space restrictions of other areas of the country. One of the ways to deflect the effects of an earthquake of vast magnitude is to build low-standing structures. The less the height, the less the shear on the columns.
There is one factor that plays a large part in the damage to structures by an earthquake. This is called resonance, and refers to the interaction of the intensity of the vibrations with a structure at a particular point. It is possible to design for reso nance, but the requirements are at odds with commonly practised construction methods.
To some extent advanced geological mapping can point out areas that might be subjected to certain pressures, but since tectonic activity is mutable this would be a futile exercise as far as long-term construction plans are concerned. It does, however, go a long way in explaining why some buildings fell and others didn't in Kutch.
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