Evaluation and retrofit of the St. Lawrence Parish House in Petrinja that was damaged during the 2020 earthquakes in Croatia

Efforts to reduce carbon dioxide emissions globally are compelling the construction industry to prioritize sustainability. A key strategy is the prolonged use of existing building stock to minimize additional emissions from concrete production. Many European buildings, however, are constructed with unreinforced masonry (URM), which are known to be less resilient against seismic forces. Assessing the seismic behaviour and reinforcing vulnerable structures, particularly after earthquake damage, becomes crucial.

This thesis focuses on analyzing the seismic response of the St. Lawrence Parish House in Petrinja, Croatia, damaged during the December 29, 2020 earthquake. Employing an equivalent frame model (EFM), a dynamic response history analysis (RHA) using the open-source software OpenSees aims to characterize the structure’s seismic behaviour in its initial state. RHA results, compared against Eurocode 1998-1-1 and 1998-3 standards, confirm the building’s overall compliance with safety requirements.

However, a detailed study of out-of-plane (OOP) mechanisms reveals potential vulnerabilities not captured by global assessments. Utilizing the N2 method from EN 1998-1-1, it becomes evident that while the structure meets global safety limits, local OOP failure modes form a specific risk which prevents the structure from meeting Eurocode requirements. To address these concerns, reinforcement is deemed necessary. Specifically, the vaulted structures that support the first-floor slab are a source of vulnerability. An in-depth examination of introducing steel ties above the vaults is thus conducted. Global and local (OOP) analyses on the retrofitted structure assess the efficacy of these measures in securing the building. Additionally, two proposed reparation methods aim to restore the walls’ initial stiffness and strength, ensuring the safe future use of the Parish House.

In summary, this study underscores the importance of seismic assessment and targeted reinforcement in preserving and repurposing vulnerable historic structures.