3rd Croatian Conference on Earthquake Engineering 3CroCEE

Building codes on earthquake-resistant design, construction, and retrofitting are being improved based on observations of building performance during strong earthquakes, with the aim of mitigating earthquake risk in proportion to the corresponding hazard, as highlighted in recent findings from the SeisRICHerCRO Croatian Science Foundation Research Project IP-2020-02-3531. In the Republic of Croatia, prior to introduction of Eurocodes in 2005 and 2011, an example is the earthquakes ML6.9 in North Macedonia in 1963 and ML7.2 in Montenegro in 1979, which resulted in the Regulation on Temporary Technical Provisions for Construction in Seismic Areas in 1964 and Regulation on Technical Standards for the Construction of High-Rise Buildings in Seismic Areas in 1981, respectively. The urban built environment was therefore constructed in compliance with building codes from different time periods, which do not provide the same level of earthquake protection as the most recent codes, and the buildings have not been subsequently retrofitted. Special attention is required for historical and cultural heritage buildings of outstanding significance, such as the Old City of Dubrovnik, which was included in the UNESCO World Heritage list after the ML7.2 earthquake in Montenegro in 1979 (IMCS,MAX = IX–X, and of very strong intensity, i.e., IMCS = VII in Dubrovnik). This led to the establishment of the Institute for the Restoration of Dubrovnik, which has been overseeing the retrofitting efforts. One of the most representative buildings in the Old City is the Rector’s Palace, which dates back to the 13th century but has been reconstructed several times throughout history. Due to severe structural damage sustained in the aforementioned earthquake, the building was comprehensively retrofitted on two occasions: 1982-1984 and 2015-2018. The objective of this study was to review the effectiveness of the retrofitted built heritage construction against contemporary design-level earthquake shaking (e.g., 475-year hazard level), focusing particularly on the atrium and arcades, which are the most vulnerable structural parts of the Rector’s Palace and possess significant architectural and sculptural value. The discussion will also address the structure's performance levels and provide recommendations for achieving reasonable earthquake protection within affordable means while avoiding irretrievable damage to heritage construction.