नेपाली   | English

Retrofitting existing structure to resist Earthquake


Nepal has progressed significantly in spreading the awareness about the earthquake through different programs, advertisement, conferences etc to prepare at the time of emergency. We have already celebrated the Earthquake day with all type of awareness spreading techniques. Many organizations, collages and government have drag their interest in making people aware about this stuff.  The workout that many organization in Nepal are proceeding with in order to combat the enormous potential disaster for future earthquake hazards is also appreciable. Tremendous work in order to remind the people about the catastrophic earthquake of 1934, and the subsequent earthquake occurred in various parts and lesson to be learned from those by preparing in advance for such disasters are being carried on. Now the question arises “Are these activities enough to combat the catastrophic earthquake?”. Simple awareness programs are not enough for Nepal in this circumstance; we need to have strong plans and policies for the existing buildings as well as upcoming buildings to resist the upcoming earthquake. It is expected that the buildings or any construction should be as per the code; every countries do have their own building code as per the geographical condition of a country. It is also mandatory to upgrade the code as per the condition to keep abreast with the current research and development in the structural design and analysis, construction industries with new construction materials, and the state-of-the-art technological advancement nationally and internationally. When we concentrated to the code of Nepal then there are no remarkable changes since the building code of 1994. The feasibility study of the code is not being embraced effectively time and again in Nepal.

United Nation study has enlisted Nepal among the top 10th position for earthquake prone countries which indicates the need of regular updates of codes and also reflects the need of sustainable and innovative planning for safe future. Existing building which are not as per the stander also can be retrofitted in order to sustain the normal earthquakes. The building code normally outlines the necessary minimum design and construction standards that are required to meet the earthquake-resistant building criteria. Certainly, following the appropriate earthquake resistant building code helps reduce the damage and collapse of buildings, and hence the losses and damages that would have caused by such collapse. Following the basic construction method and basic principles of construction in term of design is enough for constructing earthquake resistant buildings, and it’s also as economical as building a nominal house. For the existing buildings the retrofitting procedure and standers are also to be standardized by code but this practice is still lacking in Nepal. Tremendous number of old unreinforced- masonry building in Kathmandu itself indicates the need of retrofitting code in Nepal. Many countries are practicing separate code for retrofitting such as Uniform Code for Building Conservation in USA, Building energy and conservation code in Europe etc. Many countries have set the example that to resist the earthquake, not only used of advance technology such as base isolation, damping process are effectives but simple plans and astute implementation of basic principles also can handle earthquake with great efficiency. This application was endorsed by Chile where Chile’s strict building code faced the earthquake of magnitude 8.8 on Feb 27, 2010 resulting less destruction whereas in Haiti earthquake of magnitude 7 on Jan 12, 2010 wash away with great loss. This instance can be an inspiring fact to acknowledge the important of simple and safe building techniques.

There can be simple and innovative techniques for retrofitting existing buildings, having the knowledge about such techniques can be beneficial for everyone. Many old buildings which are to be retrofitted are made up of stone, unfired bricks with non-reinforcement.  Incorporating simple techniques which are as simple as creating a one-meter square grid of punched holes in the stone wall, which is then covered with a 10 cm mesh of bamboo on the inside and outside; the net is secured to the wall by means of 12-gauge gabion wire, (a form of riprap contained in a wire cage that is very useful in erosion control.), which is inserted through the holes and fastened strongly; it is covered with a stucco of mud, which is used in rural areas in order to ensure longer life for the bamboo mesh. Providing the columns for the buildings as per the feasibility, patching up of defects such as cracks and fall of plaster, repairing doors, windows, replacement of glass panes, repairing non-structural walls, boundary walls, re-plastering of walls as requires, rearranging disturbed roofing tiles, injecting epoxy like material which is strong in tension into the cracks in walls, columns, beams, addition of reinforcing mesh on both faces of the cracked wall holding it to the wall through spikes or bolts, demolish the weakness sources that can make stress concentration in several parts, avoiding of excessive openings, making the building as a unity by tying together all components of building, avoiding brittle failure by re-arranging, adding reinforcing bar, increase lateral strength by adding walls and columns etc. In this way many other innovative and simple techniques must be well known to all and this can be endorsed at the time of need. Engineering is not an expensive approach instead its implementation of basic principles for safe lifestyle. All these can be taken after the proper survey of the existing structure is done properly then after analysis of the whole plan is to be done and in accordance with the conclusion, suitable methods can be identified and can be implemented. These all techniques helps in increasing the stiffness, strength, ductility, energy dissipation of existing structure which modify the character of the ground motion transmitted to the building and also helps in reducing the occupancy expose.

Concentrating more in basic design, simple and attractive plans, good site location, regular design and plans, symmetry of building, good enclosed area, good structural design including strength, stiffness and ductility, fire resistance and proper selection of materials can be beneficial and these leads us for the construction of earthquake resistant buildings. When it comes with the construction of roads then proper stabilization of ground level, reinforcement of stabilization of weak soil with proper reinforcing materials, proper compaction avoids unnecessary cracks due to shacking. We all must be aware about the basic design concept and implementation knowledge irrespective of our profession. Understanding the nature of material to be used and its advantages to environment and human life makes us wiser in selection of astute material for construction. The basic knowledge in these can make our construction more effective, economical and earthquake resistant. We may encounter the hit of earthquake at any instant so cleaver mind for safe approach would be the intellectual step.  More and more ambitious retrofitting campaign need to be undertaken by the government as well as organization working actively for earthquake in Nepal rather than limiting it to awareness campaign and program.

Note- Writer is Research Civil Engineer and Assistant Editor In Chief of International Journal of Engineering Research and General Science


The Article Published in The Himalayan Times, OP-ED Section 2014/2/26

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