Earthquake resistant characteristics of traditional Khasi houses in Shillong, India

Shillong, the capital of the state of Meghalaya, is located in the highest risk zone (V) of earthquake vulnerability in India. The area has witnessed several earthquakes including the one that occurred in 1897 during which most of the town was destroyed. Some of the buildings that survived the earthquake included some traditional Khasi houses. The earthquake resistant features of such traditional buildings were studied. Basically, the traditional Khasi houses are built on raised platforms. The roofs are of thatch while the walls may be from materials such as stone masonry with lime mortars, lime rendered mud walls or thatch depending on prevailing weather conditions. Mud and stone walls are common in areas with heavy rainfalls. The structural system consists mainly of post and beam timber frames having pillars buried into the ground. The floor is supported at intervals by limestone or wooden pillars. Some of the characteristics of the traditional Khasi houses in Shillong that are in conformity with modern building code requirements include the fact that they are not usually built on hill tops and they have symmetrical oval shapes which are devoid of sharp corners, thereby avoiding stress concentrations which is a major source of failure at wall corners during earthquakes. Nails are not used in the constructions, and the grooves and tongues that are utilized allow for dissipation of seismic loads. The roofs are made of light materials so that fatalities from failed roofs are limited. Earthquake resistant features exist in traditional constructions in Shillong, which could be useful in building better earthquake resistant houses in modern times, especially for rural and urban poor settlements in earthquake prone countries.