Fragility Functions for Seismic Risk in Regions with Moderate Seismicity

Current seismic risk evaluations are mostly based on approximate vulnerability curves. Damage prediction is improved by considering structural characteristics of building. Such improved fragility functions do not exist for many structures, especially in countries with moderate seismicity. Typical structures of these regions, such as unreinforced masonry buildings URM, differ notably from structures usually considered in seismic risk. Due to low perceived seismic hazard, these types of structures have not been adequately investigated. Moreover, experimental investigations have shown that their deformation capacity is often underestimated. As a consequence, advanced methodologies have not yet been developed. This paper describes the results obtained with an analytical displacement-based methodology to assess the seismic risk in existing buildings through fragility functions. The study is based on URM existing buildings, common in North Western Europe. These low or mid-rise buildings with basements generally do not have significant structural plan irregularities. The impact and the accuracy of several parameters (such as the damage grade definition, the prediction of the ultimate drift, and the strength of the walls) are addressed. The fragility curves obtained are compared to those obtained using empirical methods in a typical existing URM building.