In the wake of recent strong earthquakes in Croatia, there is a need for a detailed and more comprehensive post-earthquake damage assessment. Given that masonry structures are highly vulnerable to horizontal actions caused by earthquakes and a majority of the Croatian building stock is made of masonry, this field is particularly important for Croatia. In this paper, a complete assessment of an educational building in Zagreb Lower Town is reported. An extensive program of visual inspection and geometrical surveys has been planned and performed. Additionally, an in situ shear strength test is presented. After extensive fieldwork, collected data and results were input in 3Muri software for structural modeling. Moreover, a non-linear static (pushover) analysis was performed to individuate the possible failure mechanisms and to compare real-life damage to software results.

Recently, Zagreb was struck by a strong earthquake. Damage throughout the city was tremendous due to numerous aged and vulnerable masonry buildings. Many damaged buildings are under a certain level of cultural heritage protection. Hence, reliable assessment and effective rehabilitation are important to preserve cultural significance and mitigate risk for human life. With that in mind, the procedure of a detailed condition assessment of the building under heritage protection is presented. A detailed historical background of the case study building is shown, and observed damage and conducted in situ tests are discussed. The nonlinear static seismic analysis performed in the 3Muri software is extensively elaborated. Four different levels of reconstruction according to new Croatian law are briefly presented. Additionally, several strengthening scenarios are proposed with various strengthening techniques.

The focus of the study is on the renovation of a specific case study, which is a 19th century building under cultural heritage protection. It highlights the particular challenges faced by civil engineers in the structural renovation of buildings that are under heritage protection. Preserving the identity of these buildings limits the available methods for strengthening their seismic capacity. At the beginning, information about the seismic activity and the different post-earthquake evaluation procedures are presented to identify the damage and take appropriate further steps. Then, basic information about the building is given and supported by graphic attachments. In the following, the methods and materials are explained, focusing on in situ testing with the semi-destructive flat-jack method and the analysis of the structure with the nonlinear method implemented in the software. Subsequently, the obtained results are presented and discussed, accompanied by graphics. An approach for strengthening the structure is presented, which includes a combination of traditional methods and innovative solutions suitable for the preservation of cultural heritage. The discussion and conclusions emphasize the importance of assessing and retrofitting existing masonry structures due to their vulnerability, especially in earthquake-prone areas. Finally, this article also provides insights into the local context, cultural significance, and historical background of the building, along with the specific retrofitting solutions employed to address its unique requirements.

The vast majority of existing structures in Croatia, as well as in other European countries, are made of unreinforced masonry. The seemingly ideal building material presents a great challenge for engineers in earthquake-prone zones. Given that structural failure can have significant consequences in terms of loss of human lives as well as financial losses, a comprehensive structural reliability assessment is needed. Old existing masonry structures often do not have design documentation, and even when they do, the initial mechanical properties have almost certainly degraded over time. That is why in situ testing is of great importance, but masonry is also characterized by a large scattering of results. After recent severe earthquakes in Croatia, more than ever, there is a need for a more reliable assessment of existing masonry structures. This paper presents reliability approaches for resistance evaluation of existing masonry in a real case study where basic failure modes of the masonry were observed. First, the data recommended in standards were used, followed by the updated data obtained from the flat-jack test. Finally, the design value method (DVM) and the adjusted partial factor method (APFM) were used. These methods align with Eurocode standards for new structures but are also adaptable for the assessment of existing structures. Differences in the results between the existing and the new version of the standard were observed, as well as an increase in the obtained resistances with an increase in the complexity of the methods used. Also, the influence of in situ testing proved to be an important factor in the analysis.