Incremental seismic rehabilitation of RC buildings: An application to the school buildings of Basilicata region (Southern Italy)

During the last decade, comprehensive assessment programs have been carried out in Italy especially on public and strategic structures like hospitals and schools. Most of these seismic vulnerability assess-ments for non-seismically designed existing school buildings were carried out in the aftermath of the 2002 Molise earthquake, in compliance with the Or-dinances of the Italian Prime Minister (OPCM) 3274/2003 and 3362/2004. The main purpose of these assessments was the construction of priority lists in order to effectively set up strengthening intervention programs. The huge amount of resources needed to retrofit all vulnerable structures requires accurate studies for setting up strategies able to reduce the seismic risk to allowable levels optimizing the use of the available resources. To this end, the choice of seismic upgrading instead of full retrofit appears to be advisable and even mandatory, the former being less expensive and time-consuming thus allowing to obtain a more diffuse and rapid improvement of the seismic safety. With this aim, the assessment results on a non-seismically designed school building located in Basilicata region (Southern Italy) has been analysed in order to find out whether or not an Incremental Seismic Rehabilitation strategy could be effectively applicable. An application of the proposed procedure has been made on a case study school building with RC structure designed only to gravity loads. The structure has been firstly evaluated through non linear static analysis and, based on its performance and, specifically, on the sequence and type of local failures, a design for a staged seismic rehabilitation has been prepared. The design critical choices adopting an incremental seismic re-habilitation, quite different from a single-staged re-habilitation usually adopted by professional engineers, have been identified and discussed.