Seismic Upgrade Strategies for Existing RC School Structures

The seismic assessment of existing strategic and highly occupied reinforced concrete buildings, such as schools located in moderate-to-high seismic regions, is a critical task, especially because they have been constructed in periods lacking performance-based seismic design requirements. Following a review of possible local and global structural strengthening strategies, this study presents the seismic evaluation and retrofit design of an existing reinforced concrete school building designed before the introduction of modern seismic codes. The assessment is supported by an in situ investigation campaign including destructive and non-destructive materials testing, geotechnical investigations, and a detailed survey of the original construction details. A three-dimensional numerical model, calibrated on the in situ survey and material test results, enables the evaluation of the building’s seismic performance in both the pre- and post-intervention configurations. The model also supports the optimization of retrofit costs: a constraint of relevance because the intervention was funded through a dedicated public budget allocated by the national authority and subject to public validation. This represents a procurement framework that explicitly links the achievable retrofit performance level to a fixed cost ceiling, unlike standard practice in most seismic-prone countries. A global strengthening strategy was implemented including new reinforced concrete shear walls structurally connected to the foundations of the existing walls, whose capacity was enhanced through the installation of micropiles. Fiber-reinforced polymer (FRP) wrapping was applied to improve both flexural and shear beam capacity, while steel jacketing was adopted for some vertical elements. The combined interventions significantly improved the seismic performance of the building, ensuring a safer and more reliable response under future seismic events, respecting the initial publicly available budget.