The paper, based on the authors’ direct involvement in managing actual retrofitting design, reports on seismic vulnerability assessment, design and implementation issues related to the seismic retrofit of reinforced concrete buildings through base isolation. The retrofitting interventions design of damaged buildings involves three aspects: the damage survey, the assessment of the vulnerability of building in its original structural configuration, the design of intervention needed to reduce the building vulnerability up to a conventional level, normally indicated by the seismic standards. In the first part of the paper, the experience achieved in the retrofit of reinforced concrete buildings damaged by the Italian 2009 L’Aquila earthquake is presented by referring to a typical intervention designed by the authors. Topics related to conventional vs base isolation retrofitting strategies, structure’s performance, safeguard of human life, construction efficiency and repairing cost are analyzed with reference to actual case study. Lessons learned from the Italian experience have been critically applied to the design of retrofit intervention of a building, designed according to the current Nepal set of codes and under completion at the time of the earthquake, damaged by the Gorkha 2015 earthquake. In the second part of the paper activities carried out for the definition of a specific site seismic input, for the dynamic characterization of the building and for the design of the base isolation retrofit are presented.
Seismic Vulnerability Assessment of Existing Reinforced Concrete Buildings in Urban Centers