Seismic vulnerability of masonry heritage buildings in Malta

Abstract

The understanding of the level of integrity of masonry heritage buildings that could be subjected to seismic action is essential in preparing conservation strategies. Since Malta lies in a seismic zone, it is crucially important to assess the vulnerability of such buildings to seismic action. Extant masonry heritage buildings, predating the major historical earthquakes of 1693, 1743 and 1856 survived, some with minor and others with major repairs. This does not mean that masonry heritage buildings have an adequate of seismic resistance to any future strong earthquake. The aim of the study was to determine the seismic vulnerability of Maltese masonry heritage buildings using numerical structural modelling, by focussing the study on the Annunciation Chapel, at rtal Millieri, limits of Zurrieq, a simple, yet typical heritage masonry building which predates all documented historical earthquakes. The selection of the numerical structural modelling technique to be used entailed a detailed evaluation of the two major groups of software used, namely Finite Element Method (FEM) and Discrete Element Method (DEM). The Applied Element Method (AEM) numerical structural modelling technique was selected on the basis that it can simulate the behaviour of the building from the initial loading stage to the total collapse of the building. The process of modelling the Chapel in AEM entailed a detailed study of the structure, and modelling every 3D masonry unit of each structural element. The AEM model of the Chapel was subjected to a range of seismic actions based on possible earthquake intensities. The results of the seismic analysis were calibrated with the natural frequency of the actual Chapel. The resilience of the Annunciation Chapel was observed in all seismic analyses results, although in some instances, there was permanent deformation and in others minor col apse of the structure.