Intro: India need a beginning with open mind to put through all the measures required to retrofit old constructions and issue a stringent practical guideline to protect our future generations.
In India, half of the total money spent on construction activities is spent on buildings for residential, industrial, commercial, administrative, educational, medical, and municipal and entertainment purpose.
It is estimated that in coming times about half of the total outlay on buildings would be on housing. It is imperative that for such a large national investment, optimum returns are assured and wastage in construction is avoided.
|Steps to mitigate Earthquake disaster:
The loss of life and disaster in Nepal quake should be a reminder to India that itself lies in high seismic activity zone to devise guidelines to develop earthquake resistant buildings in urban areas. It is no hidden fact that earthquake causes significant damage to the development process of country and society. It not only brings massive economic burden but its sociological and physiological effects are long lasting and even more damaging
It is important to mention here that some of the largest earthquakes of the world have occurred in India and that the earthquake engineering developments in the country started rather early. According to reports, formal teaching and research in earthquake engineering started in late 1950’s. But despite an early start, the seismic risk in the country has been increasing rapidly in the recent years
More than about 60 per cent of the land area is considered prone to shaking of intensity VII and above (MMI scale). In fact, the entire Himalayan belt is considered prone to great earthquakes of magnitude exceeding 6.0. In a short span of about 75 years many earthquakes have occurred: 1897 Assam (M8.7), 1905 Kangra (M8.6), 1934 Bihar-Nepal (M8.4), 1950 Assam-Tibet (M8.7), 1975 Kinnaur, Himachal Pradesh (M6.8) and 1991 Uttarkashi, Uttarakhand (M7.0). Similarly the non Himalayan earthquakes which are remembered as tragedies of recent past are 1993 Latur, Maharashtra (M6.2), 1997 Jabalpur, Madhya Pradesh (M6.0), 2002 Bhuj, Gujarat (M7.7), 2009 Andaman Nikobar (M7.7), 2012 Andaman Nikobar (M7.7). The details of all earthquakes in India can be found on Indian Metrological Department (IMD) website.
The Geological Survey of India (GSI) carried out the scientific studies of earthquakes in India and published catalogue of Indian earthquakes after the investigations of the Cachar (Assam) earthquake of 1869.
Indian National Building Code was first published in 1970 and revised in 1983. Subsequently, the first revision of this Section was modified in 1987 through Amendment No. 2 to the 1983 version of the Code to bring this Section in line with the latest revised loading code. It covers basic design loads to be assumed in the design of buildings. The live loads, wind loads, seismic loads, snow loads and other loads, which are specified therein, are minimum working loads which should be taken into consideration for purposes of design. The latest revised earthquake code, IS 1893 (Part 1): 2002 ‘Criteria for earthquake resistant design of structures: Part 1 General provisions and buildings’, has been incorporated, due implementation of the provisions of which are applicable in seismic zone of the country. This needs to be duly adhered to by the authorities. The standard needs to be improved by substantiating practical methodology. No sense in issuing a guideline and demanding additional properties without offering practically affordable solution will result in avoidance and corruption as it is prevailing in civil construction industry and is always criticised after any catastrophe.
In the world, Japan and California are major seismic zones, they never report high mortality rate in high intensity earthquakes. Historically prior to the introduction of modern seismic codes in the late 1960s for developed countries (US, Japan etc.) and late 1970s for many other parts of the world (Turkey, China etc.), many structures were designed without adequate detailing and reinforcement for seismic protection. In our country a lot needs to be addressed towards this issue. This is no longer alone a civil engineer or architects job. We need to form and collaborate with organisations that develop model building codes to make seismic design parameter and values available to engineers. At the same time industry should be ready with modern tools and materials.
A forum-based mechanism is required for dealing with the complex regulatory, technical, social, and economic issues involved in developing and propagating building earthquake hazard mitigation regulatory provisions that are national in scope. At least hospitals and School buildings need guidelines and implementation on priority basis; hospitals for immediate relief and rescue operation in case of any eventuality and schools to protect our future generation.
Major question arises in our mind, what to do with the old structures built in past, when we did not have knowledge of the subject? The solution is seismic retrofitting. Seismic retrofitting is the modification of existing structures to make them more resistant to seismic activity, ground motion, or soil failure due to earthquakes. With better understanding of seismic demand on structures and with our recent experiences with large earthquakes near urban centers, the need of seismic retrofitting is well acknowledged. In view of the imminent problem, various research works have been carried out. State-of-the-art technical guidelines for seismic assessment, retrofit and rehabilitation have been published around the world – such as JSCE-E 533-1995 of Japan, the ASCE-SEI 41 and the New Zealand Society for Earthquake Engineering (NZSEE)’s guidelines. These codes must be regularly updated, for example the 1994 Northridge Earthquake brought to light the brittleness of welded steel frames. Research has shown that these older concrete frame structures are approximately 40 times more susceptible to seismic collapse. There are ongoing debates among engineers and policy-makers about whether policies should be adopted to encourage or require owners of these structures to undertake risk assessment and mitigation.
In India rural structures can be categorised as seismically unreinforced earth and masonry; they have no reliable strength in tension, and are brittle in compression. Generally, they must be suitably reinforced. This call for our own Indian design of reinforcement be it Jute or Coir based and evaluated with modern scientific methods.
Experience in past earthquakes has demonstrated that many common buildings and typical methods of construction lack basic resistance to earthquake forces. Adherence to these simple rules will not prevent all damage in moderate or large earthquakes, but life threatening collapses also can be prevented, and damage limited to repairable proportions.
Dr Milind M Khandwe & Kapil M Khandwe (The writers have a record of over 25 years providing the strategic direction/vision using innovative product and process development in Advance Polymeric Materials)