Seismic analysis and strengthening of Pico Island Churches

Abstract

The proposed study addresses the development of an integrated strategy for modelling, experimental calibration, numerical analysis and seismic strengthening carried out in two churches of the Pico Island, Azores, namely the Bandeiras and the Madalena churches. Following an initial description of the observed damages resulting from the 1998 earthquake, the modelling option for the churches' structures is outlined. Reference is made to the use of ambient vibration tests that led to the definition of the experimental vibration frequencies and mode shapes which were then compared to the numerical ones for calibration purposes. Seismic analyses were carried out using the actual records of the referred earthquake and the obtained results were analysed in light of the real observed damages. Numerical findings were then used to support proposals for seismic strengthening strategies which are also described and illustrated. The proposals follow a design based approach in the sense that very refined analysis may not be indispensible if the seismic strengthening of this type of structures is mainly directed towards the improvement of the global structure response by enforcing a "box-type" behaviour through simple and not very expensive interventions.