Abstract
Prioritization of seismic risk mitigation at a large scale requires rough-input methodologies able to provide an expedited, yet conventional, assessment of the seismic risk corresponding to the portfolio of interest. In fact, an evaluation of seismic vulnerability at regional level by means of mechanics-based methods is generally only feasible for a fraction of the portfolio, selected according to prioritization criteria, due to the sheer volume of information and computational effort required. Therefore, conventional assessment of seismic risk via simple indices has been proposed in literature and in some guidelines, mainly based on the comparison of code requirements at the time of design and current seismic demand. These indices represent an attempt to define a relative seismic risk measure for a rapid ranking to identify the part of the portfolio that deserves further investigation. Although these risk metrics are based on strong assumptions, they have the advantage of only requiring easy-to-retrieve data, such as design year and location as the bare minimum, making them suitable for applications within the risk analysis industry. Moreover, they can take both hazard and vulnerability into account, albeit conventionally, and can be manipulated in order to account for exposure in terms of individual or societal risks. In the present study, the main assumptions, limitations, and possible evolutions of existing prioritization approaches to nominal risk are reviewed, with specific reference to the Italian case. Furthermore, this article presents the software NODE (available to interested readers), which enables the computation of location-specific code-based seismic performance demands, according to the Italian code and the evolution of seismic classification since 1909. Finally, this study intends to contribute to the ongoing debate on strategies for large-scale seismic assessment for building stock management purposes.
Highlights
The most critical aspect to date in seismic risk assessment of large-size structure portfolios, is the evaluation of structural vulnerability
The authors noted that employing the above-defined index in the first screening procedure, led to measures of seismic risk coarsely related with those obtained in the second step, by means of Eq (6), when the PGAC value is taken from the Gruppo Nazionale Difesa dai Terremoti (GNDT) approach
In order to appreciate the advantage of considering the demand to capacity ratio, it is possible to take into consideration two different structures: a first one designed for 0.8 g spectral acceleration and subjected to a modern hazard estimate equal to 1.0 g, and a second one designed for 0.1 g, while it should be 0.3 g according to current standards
Summary
The most critical aspect to date in seismic risk assessment of large-size structure portfolios, is the evaluation of structural vulnerability. In order to overcome the inherent difficulty in retrieving data, expert judgment-based methods have been developed in the literature, based on the identification of pre-defined structural vulnerability indicators within the building stock, resulting in expert-based DPMs (ATC 1985) or score assessment procedures (ATC 2004) Critical aspects of such approaches are the definition of the relative importance of the adopted indicators and their use to get quantitative estimates of the seismic risk. A software, namely NODE—NOminal DEficit—v.1.1 beta, enabling a rapid evaluation of the horizontal performance requirements (due to earthquake and wind) for Italian constructions at any site between 1909 and today, is introduced It allows to assess location-specific code-based design standards, to automatically compute nominal risk proxies for large populations of buildings, which may contribute to nation-scale risk maps (Crowley et al 2009).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
