Earthquakes and other natural disasters are common occurrences in the world since historic times. There are several methods that different civilizations use to avert the consequences of the disasters. In particular, earthquake is one such disaster that is not predictable, yet its impacts are great in the property and human life. Due to this phenomenon, the construction of house had to include earthquake resistant techniques. There are several methods that traditional societies use in constructing house that are earthquake resistant. Most of these methods utilize locally available materials. These include the following.
- Construction technology that use ductile construction materials as bamboo and other timber materials.
- Construction techniques using robust architectural methods and forms (Shape, and elevation of the houses)
- Techniques using resilient structural configuration
- Techniques using that reduce seismic forces (Ravi Sinha, Svetlana Brzev, and Gayatri Kharel, 2004).
Techniques that use ductile construction materials
These involve the use of material such as timber and bamboo. This happens in most of the temperate regions. The bamboo and timber in general are highly ductile and hence are capable to undergo huge deformations without failure. It is this property makes them ideal for construction of houses that are earthquake resistant. In the constructions, ductile materials are used to connect houses that make them resistant to earthquakes. China has used this technology to constructed houses that have lasted for more than 100 years. However, these materials are easily susceptible to decay. They thus require good maintenance to last for long. In most case, they are used to construct houses that are not required to last long. The timber can be treated to increase the longevity. A house whose main shock absorbers come from the construction materials other than the form and shape, utilize timber in most of its sections, there case of a whole house being made of wood in many parts of the world (Mendes-Victor, L, Ferrigni, F, Mauro, A, Pierotti, P, Helly, B, Rideaud A., 1997).
Construction techniques using robust architectural forms
The shape of the building determines the overall resistant to stress from earthquakes. Buildings with regular geometric shapes are symmetrical, and with a uniform elevation, they have greater strength to resist stress than irregularly constructed buildings. Therefore, houses that are rectangular, circular as are the most commonly build house in the past have higher resistant capabilities. The buildings with regular shapes remove re-entrant corners that may experience stress concentration in the event of earthquakes. The regular shapes also ensure that the centre of stiffness and centre of mass are coincidental reducing the effects of torsion. The uniform elevation in the buildings reduces concentration of forces in a particular location, and hence making the building stronger to resist stress from shockwaves. For example, cylindrical plans of story buildings are used in the Kutch region in India because the region is prone to earthquakes. This construction techniques differs from the other in that the shape of the house is the core engineering aspect been considered in the construction.
Construction structural configurations that is resilient
This involves the use of well distributed and load redundant resistant systems. In this case, the earthquakes is resisted thorough the walls and frame systems of the building. Locally available materials are used that are not very strong. They are tied with bands to make then an integral unit. The tying enables distribution of inertia forces from the earthquakes to all the walls. In some part of Kashmir, India, some buildings are constructed using interlocked stones without mortar in-between. During earthquakes, the stones just vibrate dissipating the earthquake forces. This can also include construction of houses using bamboo or timber with diagonal braces. For example, in Turkey, diagonal timber frames are used with timber braces to increase resistant to earthquakes (Erdik, M., 1984). The frame system in this construction technology is the core aspect. It however, has to use lighter materials in the frames to make the frame strong and capable of resisting stress from shock waves.
Construction techniques aimed at reducing seismic forces
The total mass of a building and the inertial forces of an earthquake are directly proportional. In Japan, traditional houses are constructed in such a way that the total mass of the house is significantly reduced hence reducing the effects of the seismic forces (Sinha, R, Shaw, R, Goyal, A, Choudhary, MD, Jaiswal, K, Saita, J, Arai, H, Pribadi, K, and Arya, AS., 2001). The walls have their weight reduced. The exterior walls have very heavy material but the interior walls are made of light materials. This reduces the overall weight of the house making it very resistant to stress caused by earth quakes. Timber raced house are common in India where the walls are made of a timber frame and stones in-between the stones.
These construction technologies may seem to have different angles, but they cannot be applied each individually to come up with an earthquake resistant building. They have to be used in combination to ensure that the houses constructed have the highest resistant. Therefore, the use of timber and bamboo combined with a regular geometric shape as rectangular house is used. In the construction, the weight of the walls is reduced greatly by having outer strong walls. The interior of the walls can be made of lither materials as ply wood. The elevation is also made uniform to reduce concentration of force at one point.
Mendes-Victor, L, Ferrigni, F, Mauro, A, Pierotti, P, Helly, B, Rideaud A. Ancient Buildings and Earthquakes, European University Center and Council of Europe 1997
Sinha, R, Shaw, R, Goyal, A, Choudhary, MD, Jaiswal, K, Saita, J, Arai, H, Pribadi, K, and Arya, AS. The Bhuj Earthquake of January 26, 2001, Indian Institute of Technology Bombay and Earthquake Disaster Mitigation Research Centre, Miki, Japan (Joint Publication) 2001.
Erdik, M. “Report on the Turkish earthquake of October 30, 1983.” Earthquake Spectra 1984; 1:151-172
Ravi Sinha, Svetlana Brzev, and Gayatri Kharel. Indigenous earthquake-resistant technologies – An overview; 13th World Conference on Earthquake Engineering Vancouver, B.C., Canada August 1-6, 2004.