Browsing by Author "İlki, Alper"

Now showing 1 - 4 of 4

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Assessment of Seismic Demand and Damping of a Reinforced Concrete Building After CFRP Jacketing of Columns
(Techno-Press, 2022) KOÇAK, PINAR İNCİ; Göksu, Çağier; Töre, Erkan; Binbir, Ergun; Ateş, Ali Osman; İlki, Alper
While the lateral confinement provided by an FRP jacket to a concrete column is passive in nature, confinement is activated when the concrete expands due to additional compression stresses or significant shear deformations. This characteristic of FRP jacketing theoretically leads to similar initial stiffness properties of FRP retrofitted buildings as the buildings without retrofit. In the current study, to validate this theoretical assumption, the initial stiffness characteristics, and thus, the potential seismic demands were investigated through forced vibration tests on two identical full-scale substandard reinforced concrete buildings with or without FRP retrofit. Power spectral density functions obtained using the acceleration response data captured through forced vibration tests were used to estimate the modal characteristics of these buildings. The test results clearly showed that the natural frequencies and the mode shapes of the buildings are quite similar. Since the seismic demand is controlled by the fundamental vibration modes, it is confirmed using vibration-based full-scale tests that the seismic demands of RC buildings remain unchanged after CFRP jacketing of columns. Furthermore, the damping characteristics were also found similar for both structures.
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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, Alper
Brittle 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.
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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, Alper
This 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.
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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, Alper
Past 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.