Development of seismic vulnerability assessment methodologies over the past 30 years

Models capable of estimating losses in future earthquakes are of fundamental importance for emergency planners and for the insurance and reinsurance industries. One of the main ingredients in a loss model is an accurate, transparent and conceptually sound algorithm to assess the seismic vulnerability of the building stock and indeed many tools and methodologies have been proposed over the past 30 years for this purpose. This paper takes a look at some of the most significant contributions in the field of vulnerability assessment and identifies the key advantages and disadvantages of these procedures in order to distinguish the main characteristics of an ideal methodology. Among these methods, an innovative methodology proposed by the authors for seismic vulnerability assessment of urban areas, comprising both unreinforced masonry and reinforced concrete types of construction, is presented. Following the evident correlation between building damage and lateral displacements, the main concept of the proposed methodology is to compare the displacement capacity of the building stock and the imposed displacement demand from the earthquake. A probabilistic framework has been incorporated into the methodology to account for the epistemic (knowledge-based) uncertainty and the aleatory (random) variability in both the capacity parameters and the seismic demand. The proposed approach has several advantages over alternative methods for loss estimation, though perhaps the most important is the possibility to be calibrated for use in different locations all over the world. At the same time, however, the method has been validated on a relatively low number of case studies, and a larger number of comparisons are needed for further development and improvement of the procedure.