Earthquake Resistant Design and Safety
To make a earthquake resistance design, a technique are bit different but the principal are same .
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. Recent earthquake of 6 magnitude in Nepal and many others in the past has indicated the need of awareness that we need to incorporate for a new construction, retrofitting of existing structure and general safety. Kathmandu has been enlisted in the most active seismic zones because of the unplanned settlement, improper construction of new buildings, annual population growth etc. Revising our history, we had a tragic loss of life and assets in 20th century and this situation can reoccur at any instant. This continuous earthquake hits seem to suggest an ominous future with a shaking, quivering crust and earthquake. Over the centuries, many researches have been progressed with 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 collapse. Many experts now believe we can get rid of this fearsome temblor through earthquake – resistant building which can prevent 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 resistance building 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 for these techniques it’s also equally essential to understand earthquake. Earthquakes do occur when tectonic plates move and rub against each other. The case become extreme and large earthquake may hit when sometime to this movement, they snap and rebound to their original position which is also coined as Elastic Rebound Theory. When this earthquake ground motion occurs beneath a building and it is strong enough, it sets the building in motion, starting with the buildings 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.
Now 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 structure, columns plays vital role than of beams so designing a structure with strong columns than beam is appreciated than that of strong beams than columns. Structure might be of various shapes but for earthquake resistant design, a simple and regular shape such as rectangular can be beneficial. Construction of soft story for the parking or other purposes is also not convenient for building. Separate parking can be beneficial or any other alternative can be taken. Shear wall is a best walling system for earthquake resistant building 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 overall width of the area must be in decreasing form as storied get increase. As all the load will be transferred to a base column so width of base column also should be properly reinforced with more in number. Normally space between structures is also main cause for the collapse of the building as one building get in contact with another so proper spacing must be maintained between two buildings and set back also must be proper. Simple and good plans are always appreciated and are good to resist earthquake. When stirrup are being bended for beam and column proper locking at the edge with at least 45 degree must be maintained which form good bonding and help from 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 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 expert can have a great advantage.
The Article is published in The himalayan times, Op-Ed Section, National paper of Nepal
