SEISMIC RATINGS FOR EXISTING BUILDING

Abstract

Earthquake is a natural hazard but unlike other natural hazards such as floods, tornadoes etc., which give pre intimation of their arrival, earthquake strikes without any warning. zt can occur at any time and at any place. The recent oceuralo,ees of earthquakes at Koyna (Dec. 1967) and Broach (Jan. 1971) have shown that earthquakes can occur even in the supposedly aseismic areas. The art of prediction of an earthquake is still in its infancy, but considerable research work is in progress throughout the world. Even if such an event can be predicted, it is )r actually impossible to prevent - _.its oocurance. The best that can be done is to mini-mise its disastrous consequences.gineers all over the worldhave been exercising their minds to evolve better and better methods of combating the hazards of the earthquake which are duly reflec- ted in national building code provisions for earthquake resistant design and construction. The present day philosophy for the design and construction of a building may be summarised as, that the building must be capable of: i) resisting minor earthquakes with no damages, ii) resisting moderate earthquakes with no structural damage but with minor non-structural damages, and iii) resisting major earthquakes with structural and non-structural damages but without collapse.