Sunday, March 1, 2009

Houses in Earthquake zone

by Charles Roring in Manokwari of West Papua - Indonesia



wooden-house-minahasa.jpgHouses that are built in active earthquake zone must possess high modulus of elasticity to withstand the ground movement. Usually for traditional houses, people use wood as the framework of their houses. Wood although strong and elastic in nature is combustible. Therefore, for modern building, walls are built from concrete whereas the wood pillars are covered with concrete or other non-combustible materials to prevent them from getting burned during a fire accident.


In tropical region, wood is one of the most favorite home building materials. Besides it is strong enough to support the dead and live loads of the building, wood can stabilize the indoor temperature of the house. Unfortunately, special design concept and wood treatment have to be applied to wooden houses to prevent them from being wholly consumed by the termite.


Earthquakes are mostly tectonic and volcanic. When a volcano erupts, it will release sulphur ash that is corrosive to metal roof. In Indonesia, villagers use earth roof tile or palm leaves as roofing materials. They are resistant to sulphur ash. Palm leaves are called daun atap or atap rumbia. They need to be replaced by new ones every three or five years. Sometimes during the rainy season, the owner of the house has to insert some new palm leaves to mend the leaks. Palm leaves as roofing material is very combustible. It is not recommended to be applied in big cities due to many electrical lines running near the roofs of the houses.


Houses that are constructed in earthquake zone are usually reinforced by the application of steel frames inside the concrete walls to prevent them from bending and fail during an earthquake.


In addition, the height of the walls which are normally 3.5 meters will be reduced to between 2.8 and 3.0 meters to minimize the risk of failure during the earthquake. Reducing the height of the walls will create an impression of hot in tropical houses. As a solution, many homes in quake zones have many windows that are reinforced with wood to support the dead loads of the wall and roof structure.


If I have to choose between wood and steel as reinforcing materials for home, I will choose wood. Also read: Archicad and Revit for House Design