Civil Engineering Association

Seismic Assessment of Masonry Buildings

As per the Census of India 2001, masonry housing units constitute 84.7% of the total 249 million housing units in India. Observations in all the past earthquakes in the country as well as in the other earthquake-prone SAARC countries have shown that masonry buildings are the most vulnerable to damage and collapse under earthquake Intensities MSK VII or more. Therefore, it has been realized that such existing buildings will need upgrading of seismic resistance by appropriate retrofitting techniques. The first step in this direction is proper seismic assessment to determine the weaknesses and deficiencies in such buildings which will require action to increase the strength and remove the deficiencies. This paper deals with this subject in two stages:
First, Method of Rapid Visual Screening which could be carried out by a site inspection and noting some crucial data about the building under consideration and its comparison with the damageability
observed through MSK/European Macro Intensity Scales would give the damage vulnerability level of the building. Second, a more detailed methodology is provided for carrying out the assessment of the building by comparing the actual construction details with the safe details recommended in IS:4326-1993. By this comparison, the weaknesses and deficiencies can be listed for improvement.
In some cases material testing, particularly that of the mortar quality, may have to be carried out for taking the final decision about the retrofitting methodology.