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Build a Safe House with Confined Masonry

Publication Type : Book

Publisher : Gujarat State Disaster Management Authority, Gandhinagar

Source : Gujarat State Disaster Management Authority

Year : 2012

Abstract : Most houses in rural India are masonry houses. The masonry walls are built with burnt clay brick or natural stone masonry. Many choices are made across India for the roof. For instance, a sloping roof with wood truss and burnt clay tile is adopted in Kachchh region of Gujarat (western state of India), and a flat roof with reinforced concrete (RC) slab in Tehri Region of Uttarakhand (northern state of India). These houses are constructed in the conventional manner known to masons. Technically, they are called Unreinforced Masonry (URM) Houses; it has plain masonry walls with no steel reinforcement embedded in them to improve their behaviour during earthquakes. Today, of the existing building stock in India, about 45% of houses are made of burnt clay brick and about 10% of natural stone. Thus, over half of India’s population lives in URM houses. Unreinforced masonry (URM) walls are pushed sideways during a strong earthquake, along their length and thickness directions. When shaken along their thickness, they collapse. And, when shaken along their length, they develop diagonal cracks along their length and/or separate at wall junctions. When walls collapse, they bring down the roof along with them. This is the main reason for large loss of lives during earthquakes that have occurred in different regions of the country. Despite houses collapsing in earthquakes, people still continue to reconstruct their houses in the age old method of unreinforced masonry, thereby making their houses vulnerable to future earthquakes. In cities, RC buildings constructed first by making the RC frame, and then by infilling the spaces between beams and columns with masonry walls made of burnt clay bricks or cement blocks, and cement mortar. To build a house this way requires high levels of technical skills, which usually are not available in small towns and villages. But, everyone, whether residing in a town or a village, wants a pucca house - a house with brick walls and RC roof, just like the buildings in larger towns and cities. This is reason enough to improve earthquake safety measures in these houses. Small, but significant, changes should be made in current method of construction of masonry houses in rural India. This improved method of house construction is called Confined Masonry Construction. Loss of life can be reduced considerably in masonry houses during future earthquakes. For this, masonry walls are confined on all four sides with (a) stiffer and stronger vertical elements made in RC, and (b) RC horizontal bands at discrete levels in the masonry walls along the perimeter of all the rooms of the house. Books providing technical information on confined masonry construction are exhaustive, but largely offer generic details. They have to be adapted for specific conditions at site. Often, this is difficult for a man building his house. An illustrated manual such as this is required, that follows the requirements of Confined Masonry Construction in an easy-to-follow language, and provides guidance on how to build a confined masonry house with specific functional design. Such a manual will enable the individual house owner or a 'practical technician' to build such a house. Also, the manual will help local authorities to construct houses under any social housing scheme sponsored by the Governments. This book illustrates the step-by-step construction of a Confined Masonry House of a specific design. It provides precautions to be taken and amount of material required to construct the house. Also, alternate specific designs are presented.

Cite this Research Publication : Iyer,K., Kulkarni,S.M., Subramaniam,S., Murty,C.V.R., Goswami,R., and Vijayanarayanan, A.R., (2012), Build a Safe House with Confined Masonry, Gujarat State Disaster Management Authority, Gandhinagar, pp 129

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