Seismic retrofit of existing buildings led by NON-LINEAR DYNAMIC analyses

Although still little used in practice, the non-linear time-history (NLTH) analysis is the most powerful method to design new earthquake-resistant buildings. This kind of analysis may even help the designer to assess the seismic performance of existing buildings and suitably plan their retrofit. With reference to a pre-seismic-code r/c building and to a suite of Italian spectrum-consistent earthquakes, the paper highlights the advantages of adopting NLTH analyses to evidence critical features in the seismic response of existing buildings and to assess in advance the effectiveness of their retrofit strategy. To this purpose, the behaviour of the retrofitted building should be suitably modelled. This paper shows how this can be done when carbon fibre reinforced polymer is used to strengthen the critical sections. Two advanced finite element programmes are adopted in parallel to carry out the numerical analyses: SAP2000 and SeismoStruct. The differences involved in the numerical model are discussed and the main advantages of a three-step procedure based on the NLTH approach are evidenced.