The seismic vulnerability of reinforced masonry building aggregates with soft storey basements in the Maltese Islands

Abstract

In this day and age, reinforced masonry (RM) walls in buildings on the Maltese Islands are not commonly used, except sometimes for lift shafts. This is because, for the most part, unreinforced masonry (URM) walls are much cheaper to construct than reinforced masonry walls. Locally, URM buildings tend to be designed with rules of thumb that only consider the axial vertical gravity loading of the structure, without due consideration being given to the effects of horizontal loading, such as wind loading and/or seismic (earthquake) loading. Local load-bearing URM buildings, as they are currently being designed and built, especially when they have open plan soft storey basements for car parking, are particularly vulnerable in the presence of lateral loading, particularly in the case of an earthquake. Reinforced masonry concrete blockwork walls provide more lateral stiffness to the contemporary local masonry building. In spite of this, by no means does it imply that there is no limit to the number of floors that can be safely carried by local masonry buildings during an earthquake event. In previous research studies, the focus has been placed upon the seismic resistance of both URM structures and reinforced concrete structures in the Maltese Islands. However, no studies have focused on reinforced masonry structures. In this dissertation, a parametric study was conducted on RM buildings using three different types of ground materials to compare with results obtained from previous studies of URM and RC buildings, in terms of a safe number of floors under seismic loading. In order to carry out this research study, the Equivalent Frame Method was adopted, so as to provide a better understanding of the corresponding seismic vulnerability of RM buildings having different structural typologies. The results obtained show that, while RM buildings have an improved seismic resistance compared to URM buildings, there are nonetheless safe RM building heights beyond which the structural lateral stability of such buildings may be compromised during a strong seismic event. Finally, suggestions for future research studies, which emerge from the conclusions drawn from this dissertation, are also presented.