Nepal is one the most earthquake prone countries in the world and past earthquakes have caused huge destruction in Nepal. Now it is time to stand up and be prepared for the next big one by building an earthquake resistant structure to reduce damages.

April 25, 2015 (Baisakh 12, 2072 B.S.). On this day Nepal was hit by an earthquake of 7.8 Richter scale magnitude in broad daylight at around 11:56 AM.  Its epicenter was in Barpak, Gorkha, only 11km beneath the earth surface.  This earthquake destroyed houses mainly in Kathmandu, Bhaktpur, Lalitpur and other villages in Gorkha, Dolakha, Sindupalchwok.  More than 500 tremors (after shock) of magnitude greater than 4 Richter scale have been felt till date and the number is still increasing.   According to Home Ministry more than six million people were affected, more than 9000 people lost their lives, more than 20,000 people were injured and thousands were homeless.   On Magh 2, 1990 BS, 82 years ago, an 8.0 magnitude earthquake, named Nepal-Bihar earthquake had killed nearly 8,000 people, at a time when the total population of Nepal was only around 60,00,000.  Thus, Magh 2 is celebrated annually as the Earthquake Safety Day in Nepal.

Some of the major destruction of 2015 Earthquake was: losses of lives and property; collapse of historical Dharahara; cracked highway in Kathmandu; destruction of historical temples and buildings; landslides in numerous places.

During earthquakes it is usually man -made structures that kill people.  The extent of damage doesn’t depend only on magnitude of earthquakes, but also on the construction practices and construction materials used in the area.  To keep buildings standing, it is essential to follow prevalent building and planning codes, as well as use properly trained and certified professionals such as engineers, architects, and planners.  But having certification and codes on paper does not necessarily ensure implementation or compliance.  Laws and regulations must also be monitored and enforced.  This is not easy in a country such as Nepal, which has isolated villages, a history of conflict, and many governance difficulties.

Seismic venerability also increases with increase in height and weight of the building.  So it is desirable to use light weight material and low rise structure in earthquake prone areas unless they are properly designed and constructed by skilled professionals.

Most constructions in Nepal are non-engineered.  In towns or cities they are mostly RCC framed structures and in villages they are built in masonry.  In masonry buildings the connections between the roof and the walls, and between cross-walls are usually weak, rendering such buildings vulnerable to collapse.  A good connection and better earthquake resistance can be achieved by:

  1. Ensuring good interlocking of the masonry courses at the junction.
  2. Employing horizontal bands at various levels, particularly at the lintel level.
  3. Keeping the size of the doors and window opening small.  The smaller the opening, larger is the resistance offered by the wall.
  4. Limiting the length-to-thickness and height-to-thickness ratios as per design codes of the walls.  This reduces the tendency of walls to topple when pushed in the weak directions.

In the case of modern buildings, which are ‘framed’ (comprising a skeleton of columns and beams, typically made of reinforced concrete), or having shear walls, it is possible to ensure safety against collapse through proper structural design and detailing, to achieve the desired strength and ductility. And there must be proper supervision by skilled engineers throughout the construction of the building.

In case of old buildings, retrofitting might be a solution to increase the strength of building during an earthquake.  Ferrocement bands and embedded metal strips that run across the walls (horizontally and vertically) can preserve the integrity of the buildings to a large extent.

Designing Earthquake Safe Buildings and Structures

Great research has been carried out to determine what types of buildings and structures are able to withstand earthquake.  A few tips for earthquake-resistant design are:

  • For a building to remain safe during an earthquake, columns should be stronger than beams and foundations.
  • One of the most important characteristics behaviors of earthquake safe buildings and structures is flexibility. A rigid structure will crumble and collapse during the movement caused by an earthquake.
  • The building should have a simple geometrical plan such as rectangular.  Even in rectangular design, plans with excessively longer lengths in one direction should be avoided.  Buildings which have L, U, V, Y or H shape in plan should be avoided.
  • For a structure having floor area more than 1000sq ft., it must been designed as per relevant National Building codes of Nepal.
  • A R.C.C band of 4” thickness should be provided throughout the run along wall at lintel and sill levels, passing over doors and windows.
  • If the building has any columns that run within only floors and do not run all the way into the ground, such columns are called floating columns these types of columns can reduce the structural capacity during earthquakes.
  • The staircase is the only escape route during an earthquake, and should be designed so as to not fail during an earthquake.
  • The foundation of building should be at the same level as far as possible.
  • Buildings should not have a soft story.  A story in a building should not have a story of substantially less resistance, or stiffness, above or below it.
  • Buildings on solid earth, such as a bedrock, greatly reduces the amount of damage to such structures and buildings.
  • Sufficient development length must be provided for reinforcing steel.
  • Reinforcing steel should be clean, fresh and free form any dust, loose rust which may reduce its bond with concrete.

Thus, we can safeguard lives by adopting proper building designs and construction practices. And if you are planning to construct a new house, strictly stick with the following points:

  1. Consult an engineer before any planning and be sure your site is safe to construct a building.
  2. Consult an engineer about your building plans, they will suggest necessary modifications.
  3. Stick with Vastu Sastra as far as possible which will increase comfort in living.
  4. Get building design by a structural engineer.
  5. Provide continuous supervision by engineer throughout the construction of the building.
  6. Most importantly don’t use inferior materials.

Nepal is one of the earthquake prone countries in world, and past earthquakes have caused   huge destructions in Nepal.  Now it is time to stand up and be prepared for the next big one by building an earthquake resistant structure to reduce damages.