Seismic evaluation of existing buildings and strengthening techniques

Abstract

Occurrence of recent earthquakes in India and in different parts of the world and the resulting losses, especially human lives, has highlighted the structural inadequacy of buildings to carry seismic loads. There is an urgent need for assessment of existing buildings in terms of seismic resistance. In view of this, various organizations in the earthquake threatened countries have come up with documents, which serve as guidelines for the assessment of the strength, expected performance and safety of existing buildings as well as for carrying out the necessary strengthening required. Can we identify those buildings that are likely to be damaged to an extent that would create unacceptable life-safety hazards for their occupants? Similarly, can we identify those buildings that, although they do not satisfy current design codes and standards, would be expected to perform satisfactorily in the next earthquake? These questions are faced daily by building owners, occupants, government officials and engineers. Consideration of the financial issues, such as the potential economic losses due to earthquake damage and the cost of the structural upgrading, complicates the problem further and makes decision making extremely difficult. Seismic evaluation of existing buildings in any region of seismicity constitutes a three-tiered process, viz. Screening Phase (Tier 1), Evaluation Phase (Tier 2) and Detailed Evaluation Phase (Tier 3). This paper deals with the details of methodology of seismic evaluation; which is applied to a four storey Hospital Building to understand the concept of evaluation.