# Risk and Resilience Assessment of Lisbon's School Buildings Based on Seismic Scenarios
## 1 Introduction
The Portuguese National Laboratory for Civil Engineering (LNEC) developed a research study on the seismic risk and resilience of public schools managed by the Lisbon City Council (CML). This paper describes the methodology and the main outcomes regarding the study of a subset of 32 schools, represented in Figure 1, that correspond to the secondary education and second and third cycles of basic education schools that are managed by CML. This group of schools includes the bigger and more complex schools of the CML school building portfolio. Based on the outputs of this research study, which was completed in 2021 [22], CML and LNEC jointly defined a risk mitigation intervention for this group of schools, whose main principles are also presented in this paper. The analysis of 77 elementary schools and kindergartens that are part of the CML school buildings portfolio is programmed for the near future. This relatively low number of schools (109 schools that are managed by CML) allows for a comprehensive and detailed risk assessment of each school building to be carried out. This detailed assessment provides information on the structural safety and seismic performance of the buildings, as well as useful knowledge for the optimization of a structural retrofitting intervention for specific seismic scenarios. Nevertheless, the risk assessment methodology should not require a numerical and computational cost that hinders its application to a broad portfolio of buildings. In other words, the risk assessment methodology should perfectly balance between complexity and engineering-based outcomes [6]. The risk assessment should allow for defining seismic risk prioritization strategies and identifying the archetype of buildings that require more detailed evaluations/analyses, as well as provide quantitative seismic risk estimates for one or more selected buildings in the database and design structure-specific risk-mitigation strategies, such as structural retrofitting. Nonlinear numerical models of the school buildings were developed based on the available information, namely design projects and drawings provided by CML or collected from other sources, such as the Atlas of Portuguese School Architecture [23], as well as visual inspections carried out by the LNEC team. The nonlinear response of the buildings in this research work is simulated using the SeismoStruct software [24], while the performance for various seismic intensity levels is obtained with the Capacity Spectrum Method (CSM) [25], which is one of the reference methods for seismic performance assessment of existing building structures in international guidelines. The research presented in this paper allowed for the defining, for each school, of a performance matrix that represents the fulfillment of the levels of seismic performance established for the various seismic intensity levels according to predefined performance objectives. These performance objectives are defined based on international guidelines (VISION 2000) [26] and specialized literature [27]. The evaluation of seismic risk parameters, namely estimated losses in terms of the built-up area, both expected annual losses and losses in a 50-year period, and recovery times for each school, which can be defined as the number of interdiction days of the school buildings due to earthquake damage, allows for the ranking of schools on the basis of their seismic risk and vulnerability. Additionally, a resilience analysis was developed, consisting of the estimation of the post-earthquake school building portfolio functionality as a function of time after the seismic event, for a set of seismic scenarios. The assessment based on the speed of recovery is one of the reference methods used to evaluate resilience [28]. Other methods are the assessment against thresholds that reflect program objectives, assessment against principles of good resilience, and assessment against peers (benchmarking).