26th ISET Annual Lecture SEISMIC EVALUATION AND RETROFITTING OF BUILDINGS AND STRUCTURES

Recent earthquakes in the Indian subcontinent have led to an increase in the seismic zoning factor over many parts of the country. Also, ductility has become an issue for all those buildings that were designed and detailed using earlier versions of the codes. Under such circumstances, seismic qualification of existing buildings has become extremely important. Seismic qualification eventually leads to retrofitting of the deficient structures. Pushover analysis and evaluation of performance of building using Capacity Spectrum Approach or Displacement Coefficient Method are increasingly used for this purpose. There is a need to look at certain important issues for incorporation in the Indian codes before uniformity of approach can be achieved. This, in turn, needs an in-depth understanding on what has gone into ATC-40 (ATC, 1996) or FEMA-356 (FEMA, 2000), and making appropriate modifications to suit the Indian conditions. It is necessary that the debate on this is started and completed early to achieve the desired results. Pre-disaster preparedness strategies lead to repair/retrofitting of the reinforced concrete structures for ensuring satisfactory performance during earthquakes. Repairs can lead to increased stiffness, strength, and failure-deformation. There is a need to quantify the performance of the structure after the repairs have been carried out. Performance factors have been suggested for such quantification. These are adequate in certain cases but may not be totally satisfactory in others. A large-scale experimental programme undertaken at SERC has shown that if there are inherent weaknesses in the detailing of the original structure, it may not be possible to improve the performance to the desired levels. In these cases, the performance factors may depend on the state of deformation considered for evaluation and may not be unique. There is a need to address this issue, so that suitability of repair measures can be satisfactorily evaluated