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Performance of Various Types of Buildings during EarthquakeDifferent types of buildings suffer different degrees of damage during earthquakes and the same has been studied here.
1. Mud and Adobe Houses during EarthquakesUnburnt sun dried bricks laid in mud mortar are called adobe construction. Mud houses are the traditional construction, for poor and most suitable in view of their initial cost, easy availability, low level skill for construction and excellent insulation against heat and cold. More than 100 million people in India live in these type of houses. There are numerous examples of complete collapse of such buildings in 1906 Assam, 1948 Ashkhabad, 1960 Agadir, 1966 Tashkent, 1967 Koyna, 1975 Kinnaur, 1979 Indo-Nepal, 1980 Jammu and Kashmir and 1982 Dhamar earthquakes. It is very weak in shear, tension and compression. Separation of walls at corner and junctions takes place easily under ground shaking. The cracks pass through the poor joints. After the walls fail either due to bending or shearing in combination with the compressive loads, the whole house crashes down. Extensive damage was observed during earthquake especially if it occurs after a rainfall, (Krishna and Chandra, 1983). Better performance is obtained by mixing the mud with clay to provide the cohesive strength. The mixing of straw improves the tensile strength. Coating the outer wall with waterproof substance such as bitumen improves against weathering. The strength of mud walls can be improved significantly by split bamboo or timber reinforcement. Timber frame or horizontal timber runners at lintel level with vertical members at corners further improves its resistance to lateral forces which has been observed during the earthquakes.
2. Masonry Buildings during EarthquakesMasonry buildings of brick and stone are superior with respect to durability, fire resistance, heat resistance and formative effects. Masonry buildings consist of various material and sizes:
(i) Large block (block size >50 cm)-concrete blocks, rock blocks or lime stones
(ii) concrete brick-solid and hollow
(iii) Natural stone masonry.Because of its easy availability, economic reasons and the merits mentioned above this type of construction are widely used. In very remote areas in Himalayas buildings are constructed of stacks of random rock pieces without any mortar. The majority of new construction use mud mortar, however, few use cement mortar also.