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  Home :: Vulnerability Reduction :: Retrofitting
SEISMIC RETROFITTING OF EXISTING NON-ENGINEERED LOAD BEARING STRUCTURES IN INDIA
   
  Background
 

India is a country that is frequented by disasters almost every year in one part or another. It witnesses much damage, destruction, injury and loss of life. A resource starved nation like India loses much of its scarce valuable resources on post disaster rehabilitation. There have been many moderate to high intensity earthquakes and cyclones in India during the past decade.

   
  Non-engineered Structures
 

In a developing country like India an overwhelming majority of houses, as also the infrastructure buildings, in towns and villages, are of non-engineered load bearing type. These structures, especially houses, have been traditionally built over the past century or longer, using the locally available materials and the locally practiced technologies that have been most common in the area including stone, bricks, earth, lime and timber for walls, and clay tiles, stone or mud for roofing supported on under-structure made of local timber such as Teak, Acacia, Neem, Deodar, Pine and also Bamboo. In the recently built structures one also finds a mix of the traditional and new materials/technology such as cement, concrete and steel. The structures have pitched roof or flat roof, and are single story or double story.

Baring exceptions a majority of these structures are of load-bearing type. There is, however, little or no engineering input in to these structures, and, the people who build them have no technical knowledge of the construction carried out by them. Hence, these structures are called non-engineered.

For various reasons most of these buildings have simply not been built to withstand the forces of an earthquake anticipated in the region.

   
  Relationship of Non-engineered Structures with Local Context
 

The non-engineered traditional construction commonly practiced in different areas of the country depends greatly on the respective local context of the area. In other words the technologies vary significantly from area to area. These technologies have evolved and as a result have got optimized

   
  Significance of Non-Engineered Construction
 

Non-engineered structures like these play a major role in meeting the basic but crucial needs of the society. This could be better understood through looking at aspects like (a) cost, (b) climate, (c) lifestyle and (d) economy. One could say with fair amount of certainty that a majority of building construction will continue to be done this way in a foreseeable future because of the eternal resource crunch and country’s huge population. Other technical options have become available in the past few decades and more will become available with time. But few will be as viable and optimized for the rural and semi-urban context as the options that have been in use all this time.

   
  Large Scale of Vulnerability
 

A study conducted by Prof. Arya, Prof. Emeritus from India Institute of Technology at Roorkee in India based on the Vulnerability Atlas of India 1997, in the Seismic Zone V alone there are over 11 million housing units that are vulnerable. Similarly in Zone IV this number could be as much as 50 million. By another count there are over 80 million houses in the country that are vulnerable. These counts, however, do not include the non-engineered infrastructure buildings in towns and villages as also those built with modern technologies but without any engineering input. In other words the number of structures that are vulnerable is extremely large, and the people that are at risk may amount to as much as 50% of the country’s population.

   
  Performance By Non-Engineered Structures in Recent Disasters
 

The performance of non-engineered structures with a variety of building systems and materials has been studied extensively in the past decade. All these types of buildings that were built without taking in to account the possible earthquakes in the area performed badly. The reasons for the bad performance are well known. These are (a) poor quality of construction, which reflects the violation of the basic rules of construction, and (b) absence of disaster resistant features in it.

Even if a structure were to be built with good quality, it is unlikely to withstand shaking from a strong earthquake if special features to overcome the inherent weaknesses of a non-engineered structure were not incorporated in the construction. These forces could be resisted if (a) all the elements are properly interconnected, (b) and are secured to the walls, and (c) the roof has elements that ensure diaphragm action.

   
  Concept of Retrofitting
 

With a high number of structures being vulnerable it is important that their vulnerability is tackled in order to reduce the undue hardship and losses that the people may suffer and the economic losses that the country may face in the event of a major earthquake. This could be achieved through the retrofitting of these structures. A number of tests have been carried out in India to study the effect of retrofitting of a variety of traditional structures. These include those carried out by Prof. Arya at Umerga near Latur in 1995, by Rajendra Desai of NCPDP at Latur in 1997, and by Prof. Arya and Rajendra Desai at Radhanpur bordering Kutchch, as well as those carried out at I.I.T., Roorkee. These tests effectively demonstrated that retrofitting of the non-engineered structures with simple elements like Ferro-Cement Belt installed at lintle or eave level, vertical single reinforcing bar in the corners, diagonal bracings in roof, reduction in roof dead load etc. significantly increase the resistance of the structures to withstand the seismic forces.

   
  Retrofitting Measures
  For each weakness that has been observed in an earthquake there is a remedy in the form of a retrofitting measure. These remedies are evolved on the basis of the information available in a number of books and Bureau of Indian Standards (BIS) Guidelines in India. In Gujarat since after the Kutchch Earthquake Prof. Arya had helped evolve a set of ready to use guidelines for the Gujarat State Disaster Management Authority (GSDMA) that are based on the BIS Guidelines and Codes mentioned above. These guidelines were used extensively for the retrofitting of new houses that were not built as per the government guidelines and also for the existing infrastructure buildings in the quake affected parts of the State.
   
  Economics & Advantages of Retrofitting
 

The past experiences with the economics of retrofitting show that the retrofitting index (or the ratio of the cost of retrofitting over the total cost of new construction) is as low as 5%. For retrofitting to be most advantageous it must be done in a proactive manner. In other words it is best if done before a disaster strikes. This would help save lives and losses, and prevent suffering. Thus far in India the approach to retrofitting, what ever little that has been carried out, has been retroactive. The past disasters show that retrofitting has not been a priority for most concerned parties. It has been observed that many house owners, donor agencies, and, at times, even government agencies want to demolish the structures that are little damaged or absolutely undamaged. But that proposition has been expensive, inconvenient and time consuming. Instead, the option of repair and retrofitting is faster, economical, and helps retain the conveniences that were created in the existing structure, be it a house or an infrastructure building. It is indeed the most economical option that one could exercise for ensuring one’s long-term safety. The option of building anew, although effective, involves the cost of (a) dismantling the existing structure, (b) carting of debris and, finally, (c) the cost of reconstruction. With the rapidly escalating costs the expenditure involved may be several times that of what was spent when the structure was first built. On the other hand, retrofitting costs a tiny fraction of it. Yet another important advantage of this option is its in-built flexibility. Of the several different measures that need to be applied one has a choice to apply

One or a few measures at a time to a part of the structure or,
One or a few measures to the whole structure, or
All the options to the whole structure in one go.
 
Thus one could take a decision based on the
(a) availability of funds,
(b) availability of time, and finally
(c) the convenience, while ensuring the technical soundness of the overall scheme.
Possibility of phasing in retrofitting of the whole structure greatly increases the accessibility of this option.
   
  Hurdles in Application of Retrofitting Measures to Non-Engineered Structures
 

There are several hurdles in the large scale application of retrofitting in the country, be it in the urban area or in rural. These could be listed as follows.

Few engineers understand the technicalities of a variety of load-bearing systems used in the country. Most of them consider them un-scientific, archaic, unreliable, un-safe, out of fashion and not modern. As a result in the event of making a choice between preserving a load bearing structure through repair & retrofitting versus building it anew, the choice falls on the later.
Decision by an engineer to recommend retrofitting, which is essentially a low cost option, is dictated at times by its economic attractiveness to the engineer whose advise is sought .
In the aftermath of a disaster the over abundance of funds tends to result in to the exclusion of this option in the favor of a more expensive option of dismantling and reconstruction.
House owners, in general, are ignorant about it and they lack confidence in it. Hence, they do not readily opt for it and invest their own funds.
The building artisans and contractors do not possess the necessary skills and knowledge, nor do they understand the economics of it.
There have been training programs for masons and engineers in the past in many areas of the country. Most of them have been classroom programs. It is vital that the training is carried out in the field.
Most training programs have been “one shot deals”. But this is simply not enough to begin work on one’s own. Much follow-up and refresher training is needed to prevent mistakes and the false sense of security that such wrong work may create.
Necessary materials such as welded wire mesh (galvanized or otherwise), 16 gauge GI wire, low shrink grout etc. are not available in most places. In other words the delivery system for retrofitting simply does not exist and needs to be created.
   
  Need of the hour
 

It is recognized around the world that retrofitting of the existing buildings is the most viable option for ensuring the long term safety of the most number of people against future disasters. Since, in a developing country like India bulk of the houses and infrastructure buildings are non-engineered and are executed in the informal sector, the focus of promoting this option must be aimed primarily towards the people at large including building artisans. The technical community, however, does have a marked influence on the psyche of the people and the artisans. Hence, the efforts of promotion must also focus on the technical community. The following is a list of things that ought to be taken up for the large scale promotion of the option of retrofitting.

   
 
Education of Engineers
 
Engineering curriculum addition/revision – Since the education curriculum lacks the vernacular systems of construction the engineers coming out of the colleges are totally ignorant about them. Load bearing building systems are also absent from curriculum of most colleges. On the other end the education over emphasizes the RCC and steel construction. As a result for most engineers these are the only legitimate construction systems worth using. Everything else is useless and must be discarded.
Continuing education – The practicing engineers also need to be exposed to the vernacular systems and ways to retrofit them.
Impart Visibility through demonstration of retrofitting on actual buildings in various locations.
Public Awareness campaign for creating felt-need among the people is a crucial step in evolving the delivery system for retrofitting.
Confidence Building Program could be organized tailor made for different audiences such as those from construction industry, common man, policy makers, children etc. need to be taken up
Training of Petty Contractors and Building Artisan – This forms the most important link in the whole delivery system. After all for a common man the mason and the petty contractor are the “engineers” that help him build his house
Clear and Positive Government Policy – The government invests the most amount of money in construction, as well as in the post disaster relief and rehabilitation work. Hence, the government must have a policy that promotes retrofitting to minimize future losses

The synergistic effect of all these programs on a sustained basis could bring the desired results in a foreseeable future.

  By
Rajendra Desai, Hon. Jt. Director
National Centre for Peoples’ Action in Disaster Prepreadness, (N.C.P.D.P.)
103 Antariksh, Panjarapol Char Rasta, Near Polytechnic, Ahmedabad 380015, GUJ. India
Tel/FAX: 091 79 2630 8843, E-Mail: mitigation@ncpdpindia.org

March 2004

   
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