Building up a dangerous trend
JUST 55 seconds in duration, it left 1,000 people dead. The earthquake, measuring 6.1 on the Richter scale, which devastated the hills of Uttarkashi, Tehri Garhwal and Chamoli districts in UP last October, also left 20 per cent of the houses in the region totally destroyed or severely damaged.
What was most alarming was that about 80 per cent of the buildings in 40 out of the 175 villages in Uttarkashi district could not withstand even the first shock. The high death toll in the region is directly related to this fact and indicates the severe structural limitations that the houses of this region suffer from.
Traditional building technology had, over the years, evolved earthquake resilient measures. Unfortunately, there has been a steady departure from these age-old norms, caused partly by increasing unavailability of traditional building materials and partly by the indiscriminate assimilation of modern house- building practices. It is this which has rendered the existing houses extremely vulnerable to seismic shocks.
Can conventional, earthquake-resistant construction techniques be replicated while reconstructing the damaged houses of this region? Alternatively, can modern housing technologies be adapted to local lifestyles so that the local population can afford them? In order to answer these questions it is important to understand why these shelters collapsed in the first place.
Careless construction The last earthquake in the region having occurred way back in 1905, the local people have become increasingly indifferent to precautionary measures while building houses. Traditionally, the most common building materials of the region for roofs and walls have been slate, stone, thatch, timber and mud. But because of increasing depletion of forests and stricter institutional controls over the mining of slate and the chopping of wood, the use of some of these materials has declined considerably.
Most of the houses that had collapsed were built with mud mixed with inadequate quantities of cement. The rubble used in them constituted stones collected from river-bed or quarried. "These stones," says R Ambalagan of the department of earth science (DES) in the University of Roorkee, "are mostly rounded schists which slide under the slightest pressure because of their low frictional quality."
According to the residents of the worst-affected villages of Jamak, Ganeshpur, Dhedsari and Maneri Bhali, the stone walls of their houses collapsed at the very first shock. This indicates both the poor mortar strength of the half-dressed walls and the very weak frames. Pratima Bose, reader in the university"s department of earthquake engineering (DEE), puts it this way: "The irregular shapes and sizes of the stones used in the masonry walls have different dynamic properties. So, when a multidirectional motion like an earthquake sways the structure, the force generated in it creates tension at the corners and the walls get torn apart."
DEE engineers point out that the heavy mass of large boulders and very stiff buildings attract a large seismic inertia force. When the structures are not well-integrated because of weak connections between construction elements, they obstruct the balanced transmission of forces. Such obstruction causes the buildings to sway and collapse. The absence of strong and continuous vertical reinforcements in the form of beams and columns in most of the stone masonry houses contributed to the devastating impact of the earthquake as the walls could not withstand the bending and shearing effects.
Moreover, the structures had very weak vertical joints between walls which were not properly filled with mortar. The low tensile strength of these structures, thanks to the poor quality of the mortar used, made them even more vulnerable to prolonged and intense ground motion.
The situation got further aggravated by the overall asymmetry in the plan and elevation of the buildings. A major drawback of the asymmetrical plan was that the cross walls, being taller than the side walls, failed to hold together in a box-like fashion when rocked. The tangential roofs added to the problem since they were unable to sustain the vibration. Consequently, the roofs got flattened out and pushed the walls outward. Mixture of technologies
Among the worst-hit houses were those which employed an odd mixture of old and new technologies. The rubble walls meant for supporting lighter roofs were burdened with concrete slabs. The sharp increase in use of cement in Uttarkashi is attributed to the increasing building activities in the region. Mahendra Pant, coordinator of the Roorkee-based Appropriate Ecotechnology Group (AEG), feels that the Tehri dam project has been largely responsible for the massive import of cement to the area. Huge quantities of pilfered cement allegedly found its way to the villages, where unskilled masons used them for building houses.
It was noticed in almost all the damaged houses that the cement plaster was falling off leaving the masonry exposed. The stone and sand used in them were found to be sub-standard by The Action Research Unit (TARU), an NGO, which prepared a draft action plan for house reconstruction in Garhwal. Usually, the roof slabs were over-reinforced, and the supporting columns were under-reinforced with inadequate bar spacing. While the traditional slate roofs collapsed in segments allowing people to escape, the RCC slabs collapsed at one go, pinning the people under them.
While the vulnerability of the buildings can be largely attributed to these technological blunders, some villagers held developmental activities in the vicinity responsible for the further weakening of the structures. Residents of Jamak, where the reported number of deaths was the highest, claimed that cracks had appeared on their walls because of blasting work at the nearby Maneri dam site.
Houses built along traditional lines have proved to be better adapted to withstand climatic stress. Some of the old buildings in Ranwai and Dharali villages in the Yamuna Valley are three storeys high and supported by intricate wooden frames with beams. Members of the Uttaranchal Bhukamp Pirit Sahayta Samiti, a voluntary agency, even found a five-storeyed house standing tall and intact amidst the rubble of newer structures.
What went into the making of these old buildings? Scientists, to their surprise, have discovered in some of these buildings a large number of structural modifications suggested in recent times. Apparently, after the earthquakes of 1803 and 1905, local people took measures to make their dwellings more resistant to seismic shocks. They placed bonding stones or chul intermittently to hold the walls together. A wooden belt encircling the entire breadth of the house was in common practice, as is evident from houses in the Yamuna Valley and the upper reaches of Uttarkashi.
According to Santi Thakur, a social worker from Uttarkashi, the foundation of these buildings had two parallel planks, or chewal, which were placed horizontally along the entire length of the base. The space between them were filled with rubble. Wooden rings, encircling the whole structure, were then placed at half- metre intervals. Planks were used for the supporting frame. Timber was hardly used as a roofing material in Uttarkashi. Its use in walls was also limited: today it is evident only in nine per cent of the houses. However, it was quite extensively used as flooring panel, especially in the upper storeys of the buildings.
Old temples in the area provide valuable clues to the building methodology of the past. For instance, the Vishwanath temple, a local attraction, has a conical dome built on wooden planks piled one above the other in a hexagonal fashion. While the modern structures in the temple complex have collapsed, the temple itself has survived with only superficial cracks on its walls. According to the temple"s mahant, the secret lies in the mishala (mortar) used in the structure. A lime mortar was prepared without any mud and then mixed with a paste of jaggery and pulses. But high costs and the erosion of traditional skills have rendered such technology obsolete.
The earthquake has also manifested another facet of the problem: the non-availability of timber for construction of houses. After the earthquake, people have preferred to build safe and light structures and wanted wood for the purpose. One of the reasons behind their renewed faith in wood is the fact that the kothars or granaries made of wood withstood the earthquake very well.
But the scarcity of construction timber almost stalled the reconstruction work. In a bid to meet the demand for timber, the Forest Development Corporation (FDC) of UP offered sleepers to villagers at subsidised rates. But the people have refused them on the grounds that they should be allowed to make use of the wood from the forests as a matter of right. Hari Singh, a former block pramukh and Congress activist from Ganeshpura, asks angrily, "If we can have trees from our forests as part of our rights, then why should we pay a sum of Rs 600 or Rs 700 for sleepers sawn from our own trees, transported to the plains and brought back to us for a high price?" There is also considerable discontent over the type of timber being allotted. The villagers want deodar for its load- bearing qualities and not the chir and kail that are presently being supplied by the forest department.
But officials feel that this sudden demand for construction timber will intensify the deforestation process. They point out that it takes about 60 to 80 years to generate sufficient timber for supply after meeting the customary rights of the local people. But this argument does not wash with the local people. They argue that 80 per cent of the Uttarkashi region is under forest cover and question the officials" plea that timber is scarce when the state FDC earns as much as 70 per cent of its income from this area.
While proven materials like wood, grass and bamboo have become scarce and the suitability of new materials is being questioned, various housing and technology groups have suggested different housing models for the region. For instance, the DEE has recommended the use of cement and sand in a ratio of 1:6 for greater mortar strength as well as the inclusion of tie belts, vertical steel reinforcements and bonding stones to hold the stone blocks together. Emphasis has been laid on building smaller, single-storey houses with walls of shorter length and minimum openings. It has also been suggested that the houses be built at least two metres away from the slope face of a hill.
The CBRI has even built a model stone building in Uttarkashi town incorporating precautionary features like concrete bands at the plinth, lintel and roof levels and using cement mortar for stone masonry.
But the additional cost involved in procuring cement and steel may make their use quite prohibitive. Dharam Singh and Rameshwar Singh Chauhan of Jamak village say, "We are totally dependent on what is being given to us by the government for relief and rehabilitation. Otherwise, the purchase and transportation costs of cement and other materials are beyond our means."
The other problem is that these new house-building technologies will require largescale technical assistance from outside. As Ravi Chopra of the People"s Science Institute (PSI), Dehradun, observes, "People are pushing ideas and a dozen-odd principles, but the application of even some of these would require a massive inflow of technical assistance." He, therefore, proposes to organise camps in the villages to train local mistrys (masons).
This view is also shared by Hem Gairola of Bhubaneshwari Mahila Ashram. "Rebuilding will have to be done by the affected members of the community as hiring labour from outside is neither feasible nor economical. The community will have to take up rebuilding and be trained in precautionary methods," she says.
In its reconstruction plan for Uttarkashi, the New Delhi- based School of Planning and Architecture (SPA) also recognises the limitation of inadequate manpower in the hills. According to its survey, there are no more than 2,000 skilled workers in the entire affected area encompassing around 1,800 villages.
Various rehabilitation agencies have suggested a new model for rebuilding homes: single-storeyed structures supported by a steel dome frame, covered with tin sheets and partitioned to create two rooms and a kitchen. But the plan has failed to impress the majority of villagers in the region. Nagi Ram"s reaction to this model was typical: "We are not government babus who can live with just one bed and a briefcase."
The designers, while emphasising the safety and economy aspects, have failed to take the traditional lifestyle of the people into consideration. Traditional houses are usually double- storeyed ones, with the cattle being housed in the lower storey. While these closed enclosures protect the cattle from the cold and wild animals, the local people also feel that having the animals close by helps in the thermal conditioning of their homes. Besides, the traditional designs are extremely economical in their use of space.
Naturally, those who have lost everything in the earthquake have no other option but to adopt the models suggested by the "outsiders", which can be built in the shortest possible time. But those who can afford to wait are planning to build their houses along conventional lines. This has led to yet another problem: how do the authorities ensure that these houses incorporate earthquake resistant measures?
Building designs in India are based on codes laid down by the Bureau of Indian Standards (BIS) corresponding to different earthquake zones. According to a DEE note to the Uttarkashi public works department, "Very few of the buildings have followed earthquake resistant designs and construction codes". Pratima Bose, however, faults the BIS codes themselves, pointing out that they are only recommendations which are not mandatory and, therefore, largely ignored by the municipal authorities. As a result, most of the the public buildings in urban Uttarkashi have suffered heavily in the earthquake. The collapse of the State Bank of India building in Uttarkashi town is an example of the disastrous consequences.
Interestingly, the building laws for Uttarkashi were framed in 1954 and have not been revised since then. But earthquake- resistant design recommendations have been revised repeatedly in 1966, 1970, 1977 and 1984.
Uttarkashi has not yet recovered from last October"s earthquake. Rebuilding its ravaged houses will take both time and effort. But if there is a lesson to be learnt from the experiences of the past it is that local people must be involved in rebuilding their homes. Building experts and architects sitting in Delhi or Bombay may come up with theoretically correct models, but unless their designs meet the lifestyle requirements of the people they are meant for, their efforts will remain just blue lines on tracing paper.
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