Assessment of the seismic performance and retrofitting strengthening techniques of local heritage buildings

Abstract

This dissertation presents the results of a study carried out upon the seismic retrofitting strengthening techniques and the analysis of local unreinforced masonry heritage belfry towers in the event of an earthquake. The study starts out with a general overview and chronological history of seismic events in the Maltese islands. The study then focuses upon the main structural failure and collapse mechanisms of belfry towers subject to seismic loading. A general overview of the current, most common retrofitting techniques used to strengthen unreinforced masonry structures is presented together with an assessment of two foreign case studies of existing slender unreinforced masonry belfry tower structures, namely the Bell Tower of San Sisto Church and the Belfry Tower of Santa Maria del Carmine, both situated in Italy. The study then considers the analysis of two local case studies which possess an important heritage value, namely the belfry towers at St. Paul’s Anglican Pro-Cathedral in Valletta and at the Madonna Ta’ Pinu Sanctuary in Gozo. Structural modelling and analysis of the latter two belfry towers was carried out under earthquake loading corresponding to local seismic conditions together with an assessment of possible retrofitting strengthening techniques for the belfry tower at the Madonna Ta’ Pinu Sanctuary in Gozo. The numerical results of this dissertation showed that unreinforced masonry belfry tower structures in the Maltese islands are particularly vulnerable to seismic effects, in spite of the relatively low local seismicity conditions. Furthermore, retrofitting systems for such slender masonry structures may produce limited beneficial strengthening unless major interventions using high performance modern materials are carried out.