Person: CÖMERT, MUSTAFA
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Dr. Öğr. Üyesi
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CÖMERT
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MUSTAFA
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Publication Metadata only Seismic Risk Assessment and Preliminary Intervention Cost-Benefit Analysis for the Building Stock of Istanbul(Springer International Publishing, 2022) Demir, Cem; CÖMERT, MUSTAFA; Aydoğdu, Hasan Hüseyin; İlki, AlperPast destructive earthquakes in highly seismic areas of the world have shown that the failure of earthquake-prone buildings endangers the lives of the inhabitants and may cause enormous financial losses. Management of the seismic risks through effective mitigation efforts requires the identification of risky buildings in our cities. However, this is a challenging task, since the building stock is generally too huge to be investigated by using detailed seismic assessment methods provided by current technical documents. On the other hand, available quick assessment methods such as street surveys may lead to remarkably erroneous estimations, particularly if the building stock is composed of substandard buildings constructed without proper engineering service and inspection. Thus, reliable rapid assessment methodologies are required for seismic risk identification and classification of buildings in big cities. In the scope of a recent campaign launched by the Istanbul Metropolitan Municipality (IMM), PERA2019 rapid assessment methodology has been employed on more than 20000 buildings from 33 different districts of Istanbul. In this study, firstly, the preliminary results obtained for those buildings by considering a Scenario-Based Earthquake case are summarized. Then, a preliminary cost-benefit analysis considering the pre-earthquake and post-earthquake intervention costs (such as retrofitting, reconstruction and structural and non-structural damage repairs) together with the secondary costs (such as interruptions on the use of damaged buildings) have been performed and discussed. The obtained results indicate that a synchronized effort orchestrating rapid assessment methodologies and intervention strategies may provide feasible and effective solutions for reduction of seismic risks in big cities like Istanbul.Publication Restricted Seismic Retrofit of Substandard RC Columns Using Sprayed Glass Fiber-Reinforced Mortar and Basalt Textile Reinforcement(Taylor & Francis Ltd., 2023) Ateş, Ali Osman; Hajihosseinlou, Saeid; Nasrinpour, Amin; Demir, Cem; CÖMERT, MUSTAFA; Maraşlı, Muhammed; İlki, AlperThis study investigates the seismic retrofit of substandard reinforced concrete (RC) columns through external jacketing of potential plastic hinge zones using sprayed glass fiber-reinforced mortar and basalt textile reinforcement. An innovative spraying method was used to apply the matrix material to the concrete surface. A total number of eight full-scale columns (four reference, four retrofitted) were tested under constant high axial load to capacity ratio and reversed cyclic lateral loading. Columns were constructed using low-strength concrete and transverse reinforcement with various spacing and inadequate hook detailing to mimic the columns in substandard structures. Test results are evaluated in terms of lateral load-drift ratio relationships, displacement ductility, stiffness degradation, energy dissipation, and residual displacements. Evaluation of the test results showed that the proposed technique is effective for seismic retrofit of substandard RC columns, particularly in terms of enhancement of displacement ductility, energy dissipation capacities, and reduction of residual displacements.Publication Restricted Seismic Collapse Performance of a Full-Scale Concrete Building with Lightly Reinforced Columns(Asce-Amer Soc Civil Engineers, 2021) Töre, Erkan; Demir, Cem; CÖMERT, MUSTAFA; İlki, AlperBrittle failure of lightly reinforced concrete columns is one of the primary reasons for partial or total collapse of substandard existing buildings subjected to earthquake loading. This study presents collapse performance of a full-scale building that was performed to gain insight into the seismic behavior and the collapse mechanisms of nonductile buildings with lightly reinforced concrete columns. The three-story building was tested under displacement-controlled quasi-static reversed cyclic loading followed by a lateral pushover loading up to realization of the total collapse. In addition to the poor reinforcement details, columns had high axial load-to-axial capacity ratios as also observed in many existing substandard buildings. During the test, severe structural damage was observed at 0.9% first-story drift ratio in the cyclic part of the lateral loading and the brittle total collapse of the building took place during the pushover loading at 1.45% first-story drift ratio. In this paper, after the introduction of the test campaign, the formation of structural damage and collapse mechanisms are discussed. In addition, an attempt to predict the behavior and performance of the test building is made by using a column model that considers flexural, slip, and shear deformations. Finally, the obtained analytical results are compared with the experimental observations and results.Publication Metadata only An Overview on the Structural Monitoring, Assessment and Retrofitting of Historical Structures with a Focus on 13th Century Monuments(Springer Science and Business Media B.V., 2024) Ilki, Alper; KOÇAK, PINAR İNCİ; Halici, Omer F.; Demir, Cem; CÖMERT, MUSTAFA; Kuran, FikretMonumental historical structures affirm natural and cultural identity and hence they should be transmitted to future generations. The protection and preservation of these structures against aging and natural hazards, particularly seismic actions, requires a comprehensive approach including diagnosis of the present condition of the structure and enhancement of structural capacity for disaster mitigation, if necessary. It is obvious that due to their historical values, any attempt towards the preservation of the monumental historical structures must be carried out with respect to the principles of integrity and authenticity. In this study, the structural performance assessment procedures, implementation of structural health monitoring systems and seismic strengthening strategies are discussed and described with reference to 13th-century monumental historical structures in Turkiye. The structural engineering aspects of recent activities for the restoration and preservation of the Great Mosque and Hospital of Divrigi (a world heritage listed structure) and Sivas Ulu Cami (Mosque) Minaret are briefly presented. In light of the structural analysis and monitoring results, recommendations for interventions to these monumental structures are outlined. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2024.Publication Restricted 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(Taylor and Francis Ltd., 2023) Aydoğdu, Hasan Hüseyin; Demir, Cem; CÖMERT, MUSTAFA; Kahraman, Tayfun; Ilki, AlperEarthquakes 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.