PRAGYAN BHATTARAI
Take a look at recent seismic activity, and we might get the impression that Earth, perhaps a bit too over caffeinated, has a bad case of the shakes. The recent earthquake of 6 magnitude in Nepal and many others in the past have indicated the need of awareness that we need to incorporate for a new construction, retrofitting of existing structures and general safety.

Over the centuries, many researches have come to a conclusion that earthquakes don’t kill people; buildings do. Earthquake does cause buildings, bridges and other structures to experience sudden lateral acceleration but this solely is not responsible for their collapse. Many experts now believe we can get rid of this fearsome temblor through earthquake-resistant buildings which can prevent the total collapse and preserve life.

Today, the science of building earthquake-resistant structures has advanced tremendously and many developed countries have been practicing this approach. Discussing the issue of Nepal and its implementation phase, there is hardly any progress. To make this earthquake-resistant buildings possible in Nepal, the techniques are a bit different but the basic principles are the same. There are tremendous techniques from base isolation and damping process to resistant design techniques. In a developing country, expensive technology is quite difficult to incorporate whereas simple techniques which deal with the basic principles can be followed without any harsh investment.

Before approaching these techniques it’s also equally essential to understand earthquakes. Earthquakes do occur when tectonic plates move and rub against each other. The case becomes extreme when large earthquakes may hit sometimes as a result of this movement. They snap and rebound to their original position which is also coined as Elastic Rebound Theory. When this earthquake’s ground motion occurs beneath a building and it is strong enough, it sets the building in motion, starting with the building foundation, and transfers the motion throughout the rest of building in a very complex way. These motions in turn induce forces which can produce damage.

Our concern is to make our structure withstand such forces. Every building must withstand significant lateral force. We need to give our attention while designing the plan, section of a building, selecting the construction material and while implementing the ideas in the construction phase. There are tremendous techniques that can be embraced by a normal building. When dispatching the forces toward the footing from the structure, columns play a vital role than that of the beams so designing a structure with strong columns than beams is appreciated.

Structure might be of various shapes but for earthquake-resistant design, a simple and regular shape such as rectangular can be beneficial. Shear wall is a best walling system for earthquake-resistant buildings but it can be a bit expensive. In such cases, cross-bracing can be provided which also helps in dispatching the forces with great efficiency. While considering height of the building, the floor area and the overall width of the area must be in a decreasing form as stories increase. As all the load will be transferred to a base column, so the width of base column should also be properly reinforced. Proper spacing must be maintained between two buildings. Simple but good plans are always appreciated and are good to resist earthquake.

When stirrups are being bent for beams and columns, proper locking at the edge with at least 45 degree must be maintained as they form good bonding and resist the buckling phenomenon. Proper space between the bars to facilitate during concrete compaction, the interlocking of two beams with proper development length and mix design of concrete are also major considering point during the construction phase. Footing as per the soil condition must be identified and proper placing of footing must be done. Horizontal truss for the roofing system can be best choice in normal building. Identifying the safe region of a building can be beneficial at the time of emergency. Moreover obeying a country building code and getting assistance of experts can have a great advantage.

Proper selection of material for construction also plays a vital role. More economical material which is locally available, extracted from renewable resources can be eco-friendly in the construction and also add up tremendous aesthetical benefits. Light material can be used which makes the structure more strong in a non-load bearing structure. Retrofitting for existing structure in accordance with code can make the pre-existing structure safe. Being aware about the catastrophe well in advance is one of the means to get rid of the problems and implementing the safety in need and save lives.

As Nepal is in an earthquake-prone area, primary focus must be mainly on awareness program among all inhabitants in addition to the members of a family, students, staff and friends, besides building earthquake-resistant buildings.

source: BHATTARAI,PRAGYAN (2013),"Earthquake-resistant structures: Importance of design and safety", The Himalayan Times,5 Sep 2013
Bhattarai is an engineer at Basha Research Cooperation, Singapore
photo/art: The Himalayan Times