Seismic vulnerability of the contemporary loadbearing masonry building typology

Abstract

No major earthquake has been recorded in the Maltese Islands since the emergence of the contemporary loadbearing unreinforced masonry building typology around 50‐60 years ago, so the behaviour of this typology under seismic excitations is unknown. Notwithstanding the low‐to-moderate seismicity of the region, seismic considerations are ignored in the structural design of most residential buildings pertaining to this construction category. This, in conjunction with the prevalence of specific building characteristics (such as, a soft basement storey) and construction details which could potentially impair the seismic resistance of this building typology, highlights the necessity of a deeper understanding of the building response to seismic actions. This thesis investigates the seismic vulnerability of this masonry building typology through the identification of building characteristics which affect its seismic response. Hence, a preliminary assessment form for the estimation of the seismic vulnerability of this building typology is developed in this study and is applied in the evaluation of 183 buildings in two Test Sites, including the comparison of the resulting ratings to those obtained from three existing assessment methods. The statistical analysis of the data collected in the Test Sites results in the identification of eleven characteristics as significant predictors of the final rating. Furthermore, the examination of the variation in dynamic properties and seismic response parameters, resulting from non‐linear time‐history analyses of numerical models, investigating the influence of six characteristics on the seismic response through the Applied Element Method, indicates, in particular, the impairment of the seismic resistance of this building typology in the presence of a soft storey, higher building heights and clay‐predominant subsoils. The adequacy of a non‐linear static analysis which, by default, assumes a box‐like behaviour of the analysed structures, for the seismic assessment of the masonry building typology under study is also investigated. While further detailed studies are required, the conclusions from this study provide a clear indication of the seismic vulnerability of the URM building typology under investigation and the applicable numerical analysis methods.