SeisRICHerCRO

Seismic Risk Assessment Of Cultural Heritage Buildings In Croatia

In many seismic prone areas there is unsustainable amount of vulnerable constructions and economic resources that are far to be adequate to protect them all. Thus, the risk assessment becomes a strategic tool for each community to establish priorities when planning construction retrofitting. This aspect becomes very important when the goods exposed to the risk are un-replaceable as in the case of cultural heritage.

The most earthquake prone area in Croatia are the coastal and the northwestern parts of Croatia. The earthquake catalogue shows that Dubrovnik area was repeatedly hit by strong earthquakes, while the continental part of Croatia are reported strong earthquakes around Zagreb and Ivanščica-Kalnik Mts. Therefore, it is considered as necessary to investigate selected cultural heritage buildings, and to develop a seismic risk assessment procedure that would be applicable to other cases of interest.
Characteristic locations were selected according to the highest level of seismicity criteria. As a target locations are chosen the old city center of Dubrovnik (comprising a multitude of churches, monasteries, palaces, etc.), the most significant architectural achievement of the 15th and 16th centuries in Croatia – the cathedral St. Jakov in Šibenik, and one of the most attractive castles in Croatia – Trakošćan Castle. The first two sites are on the UNSECO World Heritage list.

Based on the quantitative and qualitative analyses of listed monumental buildings and locations, the primary objective of the proposed research is development of ready transferable methodology and practical procedure for assessing the seismic risk of cultural heritage which include seismic risk assessments on urban scale (macro approach) – case of Dubrovnik old city center, and for individual monuments (micro approach) – cases of cathedral in Šibenik and Trakošćan castle. Both approaches will allow estimation of physical damage scenarios, economical and ethic losses.

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Publications

Earthquake Performance of a Cultural Heritage Building: The Jesuit College in Dubrovnik, Croatia

Aanis Uzair, Lars Abrahamczyk, Dagoberto Gómez, Kinda Elias, Ante Vrban, Davorin Penava, Snježana Markušić

Proceedings of the 2nd Croatian Conference on Earthquake Engineering - 2CroCEE

Zagreb, Croatia - March 22 to 24, 2023

DOI: https://doi.org/10.5592/CO/2CroCEE.2023.23

Cultural heritage buildings generally refer to the ancient structures having high cultural and historical significance. These buildings are constructed using obsolete practices and require special considerations with respect to the lateral resistance, especially in moderate and high seismic regions. This study focuses on the earthquake performance assessment of the Episcopal Seminary Building and Classical Gymnasium (Jesuit College) located in the Old City of Dubrovnik, Croatia (UNESCO World Heritage Site). The construction dates back to 1662 and was developed in different stages until 1765. During this period, Jesuit College suffered damages from two major earthquakes i.e., M7.6 Dubrovnik in 1667 and M6.9 Montenegro in 1979. The material composition, structural drawings, and fundamental frequencies of the building were previously obtained in the framework of the research project “Seismic Risk Assessment of Cultural Heritage in Croatia – SeisRICHerCRO”. The material is predominantly composed of irregular stone blocks laid in lime mortar. The structural details such as floor vaults, arches, flexible diaphragms, and spatially irregular openings are numerically modelled using the finite element method. The analytical model is calibrated by performing eigenvalue analysis to compute the material parameters i.e., elastic modulus and density (supported by extensive literature review) that allows the modal frequencies to match with the values obtained from the ambient vibration testing. The seismic performance is then evaluated using the linear analysis procedure in accordance with the current guidelines of the Eurocode 8 and the corresponding Croatian National Annex. For the design earthquake, critical damage zones are identified and recommendations for retrofitting measures are proposed.

Assessment of the Earthquake Performance of a Cultural Heritage Building: Episcopal Seminary Building and Classical Gymnasium in Dubrovnik, Croatia

Dagoberto Gómez Bonilla

This thesis presents a detailed modelling of the Jesuit College using finite element software. From ambient vibration measurements obtained by previous testing campaigns, the finite element model is updated and equivalent material properties for the masonry of walls and vaults are obtained. The earthquake performance of the case study is assessed from the results of a Response Spectrum Analysis, in compliance with the corresponding Eurocode and Croatian National Annex guidelines. The outcomes present the development of shear, tensile and compressive stresses in the linear range, from the application of seismic loads. It is possible to identify critical zones where the highest stresses are located, as well as the potential type of damage and development of cracking after verification of material stress limits. Based on the results, recommendations are provided for retrofitting measures that can improve the earthquake performance of the building, as well as proposals for further development of the work.

Assessment of the Earthquake Performance of a Cultural Heritage Building Applying the Equivalent Frame Method in Dubrovnik, Croatia

Kinda Elias

This thesis presents a detailed modelling of the Jesuit College using macro-modelling. The Equivalent Frame Modelling approach, which requires less computational effort, was used for the assessment of the building. The geometry is modelled using available data in the finite element modelling software. As part of the modelling process, all structural details such as vault systems in the first-floor slab and flexible diaphragms in the upper floors are represented, in addition to openings in the external and internal walls. Based on the modelled geometry and frequency obtained from the in-situ testing, the model updating process is performed in accordance with the results of the eigenvalues analysis to calibrate the Young's modulus E, shear modulus G and density ρ. The model updating is supported by reference material parameters based on observations from visual inspection. Following the calibration of the model, a global and local analysis of the building was performed with the help of the Response Spectrum Analysis, based on the guidelines from Eurocode and the Croatian National Annex. Then the Pushover Analysis was preformed, and the damage grades of the building were obtained based on the EMS98 scale. Following the Out-of-Plane analysis for certain walls was conducted and the critical peak ground acceleration for each case was defined. The main outcome of the study is identification of critical zones at the global and local levels. Based on this information, the earthquake performance of the Episcopal Seminary Building and the Classical  Gymnasium is evaluated. Furthermore, conclusions are drawn regarding the potential location of damage in the event that the expected design earthquake occurs. In addition, recommendations are made for improving the seismic performance of the building through retrofitting works, as well as proposals for further development of the work.