Assessment and mitigation of seismic risk at the urban scale: an application to the historic city center of Leiria, Portugal

Abstract

The implementation of a culture of seismic risk preparedness is becoming increasingly critical in Europe as the building stock ages and the awareness about seismic risk rises. In this context, the assessment of the seismic vulnerability of existing buildings, followed by the implementation of appropriate retrofitting solutions, can help to substantially reduce the levels of physical damage and economic impact of future events. The central region of Portugal is particularly susceptible to large seismic events and is characterized by the prevalence of historic masonry buildings. This work aims to validate assessment methods for the risk of historical city centers in order to propose management strategies for municipalities and assess the economic impact of large-scale seismic retrofitting. To do this, an application of these methods was performed on the historical city center of Leiria. An in-depth inspection was performed of the entire center and the results were compiled into a database. Using an index-based seismic vulnerability assessment approach, a vulnerability assessment was made for each building. Based on vulnerability and predicted damage, estimates of human and economic losses were made for the city center before and after retrofitting to justify interventions on a broad scale.

Assessing and Managing Risk in Historic Urban Areas: Current Trends and Future Research Directions

“…In fact, the selection of descriptors is another crucial aspect to get representative semantic models (Ramírez Eudave and Ferreira, 2021a). Thought to evaluate each construction characteristic relevant for the analysis, several datasheets (such as the one of Blyth et al (2020) for the city of Leiria, Portugal) were constructed in the form of checklists organised into different categories: building identity and use of the building, general information, openings, layout, elements connected to the façades and also connections and damages Anglade et al (2020).…”

“…According to this formulation, each parameter is evaluated based on four increasing vulnerability classes (A, B, C and D) and weighted through a series of weights, p i whose value illustrates the relative importance of that parameter (building feature) to the overall seismic vulnerability of the building. Although the application of this method is limited to the building typologies for which those correlations were obtained, it has been successfully adapted and applied in countless vulnerability assessment works in many countries and contexts, including Coimbra (Vicente et al, 2011), Seixal (Ferreira et al, 2013), Horta (Ferreira et al, 2017b) and Leiria (Blyth et al, 2020) As presented in Figure 4, the vulnerability, expressed here in the form of a vulnerability curve, makes the bridge between the hazard and the probability of reaching discrete levels of damage for different seismic intensity levels. According to the schematisation illustrated in the figure, for such, a probability density function associated with a discrete seismic hazard value should be first defined.…”

“…A very suitable method in the context of historic city centres is the ARICA method-an acronym for FIGURE 5 | Mapping of the probability of collapses for an intensity VIII in the 1998 European Macroseismic Scale (EMS-98) (A), and collapse and building unusable probability curves obtained from the mean value of the vulnerability distribution (B). For details on how these outputs were obtained please refer to Blyth et al (2020).…”

An Improved Seismic Vulnerability Assessment Approach for Historical Urban Centres: The Case Study of Campi Alto di Norcia, Italy

“…Their limit otherwise lies in the constructions' scenario to which they can be applied: their reliability progressively decreases when applied to structures considerably different respect to the ones used for the method's calibration [12]. In addition, the lack of information coming from a survey may overlook critical epistemic uncertainties, influencing the results [13,14]. Since these methods are applied through external onsite inspections, the level of confidence concerning the geometric composition, the material properties, the boundary conditions and loads involved among the orthogonal walls of the construction analysed, depends on the available data and the experience of the technician [13,[15][16][17][18].…”

Experimental Investigations and Numerical Simulations for the Seismic Assessment of a Masonry Building

“…The seismic events of the last decades [1][2][3][4] underlined the high vulnerability of the masonry patrimony, that represents the largest part of the south Europe city centers, and the necessity of preserving this patrimony firstly to avoid human loss, and also the failure of historical testimonies.…”