Structural Characteristics of the Earthquake-Prone Building Stock in Istanbul and Prioritization of Existing Buildings in Terms of Seismic Risk-A Pilot Project Conducted in Istanbul

ABSTRACT

Earthquakes have caused catastrophic results in cities since the beginning of settled life, and the cumulative experience of these events has indicated that the lack of seismic resilience brings enormous economic losses and threatens human life. Consequently, the importance of seismic risk mitigation of earthquake-prone structures has arisen to reduce the primary and secondary losses resulting from seismic events in the last decades as developments in the earthquake engineering field occur. The first step for ensuring seismic resilience is the identification of risky buildings, which is a difficult challenge for metropolises like Istanbul since the building stock consists of over a million buildings. Applying code-based detailed assessments to so many buildings is not practical in terms of time and cost. Moreover, the current code-based detailed assessment methodologies such as Provisions for the Seismic Risk Evaluation of Existing Buildings under Urban Renewal Law (2019) and Turkish Building Earthquake Code (2018) provide discrete predictions for existing buildings as either risky or non-risky or satisfying life safety/controlled damage or not. However, a ranking system based on a reliable and realistic risk classification to prioritize the buildings is needed. Therefore, as a pilot project, nearly 23,000 reinforced concrete buildings in 37 different districts of Istanbul have been investigated by Istanbul Metropolitan Municipality (IMM) through PERA2019 performance-based rapid assessment methodology by considering the Design Level and Scenario-Based Earthquake cases. This is the most up-to-date and comprehensive site survey and analysis conducted in Istanbul up to now. In this paper, the characteristics of the building stock in Istanbul based on the conducted site work and the outcomes of the rapid seismic safety assessment efforts are summarized. Then, a discussion on the seismic risk evaluation of the existing residential buildings based on the prioritization of the examined buildings is presented through the results obtained for the Design Level and Scenario-Based Earthquake cases.

KEYWORDS:

• Building stock
• rapid seismic assessment
• reinforced concrete buildings
• resilience
• seismic
• sub-standard

Acknowledgment

The authors wish to thank Istanbul Metropolitan Municipality for supplying the structural parameters of the buildings and technical support. The authors of this paper also wish to thank the scientific advisory committee members Mehmet Nuray Aydınoğlu, Zekai Celep, Ufuk Yazgan, Kutay Orakçal, Nusret Suna, Recep İyisan, Mustafa Erdik, Sibel Özkan, Chamber of Civil Engineers Istanbul Branch and Turkish Earthquake Foundation. The valuable contributions of Kutay Orakcal, Nahit Kumbasar, Mucip Tapan, and Denizhan Ulugtekin during the development of the initial version of PERA method are highly acknowledged. The authors would like to thank to Oğuz Cem Çelik and Özgür Avşar for their invaluable comments.

Disclosure Statement

No potential conflict of interest was reported by the author(s).

Data Availability Statement

The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to legal restrictions.