A parametric pushover curve and fragility model for retrofitted masonry buildings

The European building stock is outdated and seismically vulnerable, particularly in earthquake-prone regions such as Slovenia. Masonry buildings, which make up approximately 65% of Slovenia’s building stock, are especially at risk. To better understand how retrofitting can reduce seismic vulnerability, this study introduces a parametric pushover curve (PPC) and fragility model for retrofitted masonry buildings. The PPC model relies on a set of parameters for both existing and retrofitted masonry buildings, providing a tri-linear pushover curve. It can be used to plan retrofitting measures such as mortar grouting/repointing, jacketing, or reinforced jacketing combined with vertical ties. While relatively general, its accuracy depends on the level of detail in assessing the model’s input parameters. In this study, the proposed model was implemented using limited knowledge about the building structure, relying only on building-by-building data from the public real estate register, with the remaining parameters inferred from construction practices in Slovenia. This approach enabled the assessment of seismic retrofitting impacts on several thousand masonry buildings. The estimated parametric pushover curves indicate that retrofitted buildings exhibit greater seismic resistance, as reflected in damage-state peak ground acceleration values, with improvements varying by retrofit method and construction period. Repointing/grouting and jacketing provide moderate enhancements, while reinforced concrete jacketing and vertical ties offer the most significant improvements, particularly in preventing collapse-level damage states. Additionally, the model enables the definition of fragility curves at the building class level, including estimates of the standard deviation of the logarithmic values of damage-state peak ground accelerations. A slight decrease in this standard deviation was observed in retrofitted buildings, particularly in multi-storey structures.