A parametric study on the use of a local seismic risk assessment form to determine the seismic vulnerability of local unreinforced masonry buildings

Abstract

According to Eurocode 8 (EN 1998-1), the return period for earthquakes capable of causing severe damage to infrastructure is 475 years. It has been around 325 years since the last major event occurred in the Maltese Islands, and thus, statistically there is a high probability that another similar event may occur within the following 150 years. One critical issue with the post-earthquake behaviour of buildings is their usability in terms of safety for the occupants or their evacuation by Civil Protection Department personnel. In order to limit the time required to inspect each individual building, inspection forms containing a “check list” format were recently created by the University of Malta so as to provide an immediate empirical judgement of the safety level for the building structure. These forms do not normally require thorough calculations to be carried out, and since they tend to be based on simple visual inspections, they are qualitative in nature and follow a descriptive approach. The safety classification acquired from this form applies only as a temporary status for buildings, mainly until any required emergency procedures are carried out (Baggio et al., 2007). Previous academic studies based on the Equivalent Frame Method have proposed a “safe number of floors” or a “safe building height limit” for local unreinforced masonry (URM) buildings containing building characteristics that contribute to their seismic vulnerability such as the presence of a soft storey at basement level, vertical setbacks, and double volume spaces, particularly at the lower floors of the building. This dissertation assesses the relation between these afore-mentioned studies focusing on the safety classification obtained from the local seismic risk assessment form. In this way, the adequacy of this recently-developed seismic risk assessment form may be assessed, including the observation of any possible shortcomings and suggested improvements to the form.