14 results
Search Results
Now showing 1 - 10 of 14
Article Citation - WoS: 18Creep and Shrinkage Behavior of High-Strength Concrete and Minimum Reinforcement Ratio for Bridge Columns(Precast/prestressed Concrete inst, 2010) Mertol, Halit Cenan; Rizkalla, Sami; Zia, Paul; Mirmiran, AmirThis paper summarizes the findings of an extensive research program that examined the shrinkage and creep behavior of high-strength concrete (HSC) up to a strength of 18 ksi (124 MPa). Creep and shrinkage strains of 60 specimens were monitored for up to two years. The variables considered in this investigation were the concrete compressive strength, specimen size, curing type, age of concrete at loading, and loading stress level. Research findings indicate that the current American Association of State Highway and Transportation Officials' AASHTO LRFD Bridge Design Specifications could be used to estimate the creep coefficient and shrinkage strain of HSC up to 15 ksi (103 MPa). However, the current AASHTO LRFD specifications do not provide appropriate predictions for concrete compressive strength greater than 15 ksi (103 MPa). A revised time-development correction factor is proposed to obtain better predictions for HSC up to 18 ksi (124 MPa). For HSC compression members, the current AASHTO LRFD specifications require an excessive amount of minimum longitudinal reinforcement to account for the long-term effects due to shrinkage and creep. Based on an analysis, a new relationship is proposed for the required minimum reinforcement ratio.Article Citation - WoS: 10Citation - Scopus: 10Evaluation of Masonry Buildings and Mosques After Sivrice Earthquake(Croatian Soc Civil Engineers-hsgi, 2021) Mertol, Halit Cenan; Tunc, Gokhan; Akis, TolgaThe evaluation of masonry and mosque type structures after the Sivrice Earthquake is presented in this study. Stone masonry buildings exhibited damage such as vertical cracks and splitting at corners, wedge shaped corner failures, diagonal cracking on walls, out-of-plane splitting of walls, and separation of walls from flooring/roofing systems. On the other hand, the separation of flags and caps of minarets was a common example of damage in mosques. Future earthquake damage can be prevented by following design codes and providing adequate supervision for new structures, while strengthening measures are recommended for the existing buildings.Article Farklı Geleneksel ve Çelik Lifli Beton Katmanlarına Sahip Betonarme Kirişlerin Eğilme Davranışı(2022) Mertol, Halit CenanBu çalışmada, farklı geleneksel ve çelik lifli beton katmanlarına sahip betonarme kirişlerin eğilme davranışı incelenmiştir. Boyutları 180×250×3500 mm olan toplamda 10 kiriş, iki grupa bölünerek dört nokta yüklemesi altında eğilme davranışı değerlendirmesi için test edilmiştir. Tüm kirişlerde çekme bölgesinde 416 donatısı kullanılmıştır. Bu araştırmadaki ana değişken kiriş yüksekliğince oluşturulan katmanlardaki beton tipidir. Kirişin yüksekliği her biri 50 mm olan 5 katmana ayrılmıştır. “F” grubunda bulunan geleneksel beton kullanılan kirişlerde, çelik lifli beton katmanları aşağıdan başlayarak geleneksel beton katmanlarının yerlerine yerleştirilmiştir. Örnek olarak, F15P10 kirişinin yüksekliği boyunca aşağıdan 150 mm’si çelik lifli betondan, yukarıda kalan 100 mm’si ise geleneksel betondan imal edilmiştir. “P” grubunda bulunan çelik lifli beton kullanılan kirişlerde ise, geleneksel beton katmanları aşağıdan başlayarak çelik lifli beton katmanlarının yerlerine yerleştirilmiştir. Örnek olarak, P10F15 kirişinin yüksekliği boyunca aşağıdan 100 mm’si geleneksel betondan, yukarıda kalan 150 mm’si ise çelik lifli betondan imal edilmiştir. Kirişlerin yük-sehim eğrileri elde edilmiş ve bu eğriler azami yük, kullanım rijitliği, tepe sonrası rijitlik ve eğilme tokluğu açısından değerlendirilmiştir. Araştırma sonucunda göre, yeterli sünekliğin çekme bölgesinde bulunan çelik lifli beton katmanı ile sağlanabileceği belirlenmiştir. Bu katmanın, çekme bölgesinde olduğu sürece yüksekliğinin ve yerinin davranışı önemli bir şekilde etkilemediği görülmüştür.Article Citation - WoS: 6Citation - Scopus: 6Influence of the Proportion of Frp To Steel Reinforcement on the Strength and Ductility of Hybrid Reinforced Concrete Beams(Taylor & Francis Ltd, 2023) Kartal, Saruhan; Kalkan, Ilker; Mertol, Halit Cenan; Baran, ErayThe present study pertains to the influence of variation of FRP (Fiber Reinforced Polymer) proportion in tension reinforcement on the flexural behavior of RC beams with FRP and steel reinforcing bars. A total of 25 beams, including FRP-, steel- and hybrid FRP-steel reinforced ones, were tested to failure under four-point bending. Two types of FRP bars, GFRP (Glass Fiber Reinforced Polymer) and BFRP (Basalt Fiber Reinforced Polymer), were used and both over- and under-reinforced beams were tested. The beams in each group were designed to have close flexural capacities to fully reveal the effect of FRP proportion in the tension zone on beam ductility for a fixed bending capacity. A new analytical model was developed for estimating the bending capacities of beams. Different deformation and curvature ductility definitions were adopted and an energy-based definition, revealing the expected tendency in beam ductility, was determined. The test results revealed that the presence of even a single FRP bar in the tension zone results in reductions up to 40% in beam ductility as compared to the beam with full steel reinforcement. Each additional replacement of a steel bar with FRP was found to cause a further decrease up to 20% in beam ductility.Article Citation - WoS: 19Citation - Scopus: 19Interaction Between Assembled 3d Honeycomb Cells Produced From High Density Polyethylene and a Cohesionless Soil(Sage Publications Ltd, 2012) Gurbuz, Ayhan; Mertol, Halit CenanAssembled 3D high-density polyethylene honeycomb cells, providing confinement to arrest spreading of the soil in cells and creating relatively stiff bed that redistributes footing pressure over wider area, were used in the present study to enhance load-carrying capacity and to reduce settlement of base materials under a foundation. The effects of various test parameters including width, height, number of layers of the 3D honeycomb cells, vertical distance between layers of the cells and depth of stress zone of the foundation were studied. The test results indicated that considerable improvement in the load-carrying capacity (congruent to 3.0) and reduction in settlement of the foundation (congruent to 62%) were obtained with the implementation of the single layer of the 3D cells into cohesionless soils. The optimum effective distance between two layers of the 3D cells was 0.142 times the width of foundation, the ratio of effective width of 3D cells to the foundation was about 4.2 and the depth of influence stress zone of the foundation was about two times the width of the foundation.Article Citation - WoS: 4Citation - Scopus: 4A Site Survey of Damaged Rc Buildings in Izmir After the Aegean Sea Earthquake on October 30, 2020(Croatian Soc Civil Engineers-hsgi, 2023) Mertol, Halit Cenan; Tunc, Gokhan; Akis, TolgaAn earthquake with a magnitude of Mw = 6.6 and a depth of approximately 16.5 km occurred on 30 October 2020 off the cost of Samos, a Greek island 35 km southwest of Seferihisar, a town in Izmir. The earthquake caused several collapses and severe structural damage in approximately 6,000 buildings, specifically in the Bayrakli District in Izmir Bay. This paper presents the observations and findings of a technical team that visited the earthquake -affected areas immediately after the earthquake. Eleven partially or fully collapsed and several severely damaged reinforced concrete buildings were investigated. Based on the site investigations, we observed that almost all of the collapsed or severely damaged reinforced concrete buildings in the region were built between 1975 and 2000. Site observations also confirmed that the construction of these collapsed or damaged buildings did not conform to the requirements outlined in the Turkish Earthquake Codes used at the time. The failures and severe damage to buildings in earthquake-affected areas are primarily related to inadequate reinforcement configuration, poor material quality, the absence of geotechnical studies, and framing problems related to their lateral load-carrying systems. Therefore, it is recommended that all the buildings located in and around Izmir Bay, particularly those built between 1975 and 2000, be structurally evaluated to prevent any further loss of life and property during future earthquakes.Article Citation - WoS: 3Citation - Scopus: 6Experimental Analysis of the Behavior of Composite Column-Reinforced Concrete Beam Joints(Springer Heidelberg, 2021) Tunc, Gokhan; Dakhil, Abdulrrahman; Mertol, Halit CenanThis study assesses the seismic performance of steel-reinforced concrete (SRC) composite columns connected to reinforced concrete (RC) beam joints, and their ability to dissipate seismic energy through inelastic deformations. In this article, experimental aspects regarding the seismic performance of high-ductility and low-ductility steel-concrete composite frame were investigated. The principle design parameter in this study was ductility, which is considered a conceptual framework in Efficiency-Based Seismic Engineering. Thus, attention was focused on assuring various ductility ranges of joints obtained through a detailed study of the Turkish Earthquake Code (TEC 18) [Ministry of Public Works and Housing.: Turkiye Bina Deprem Yonetmeligi (Turkey's Earthquake Code for Buildings). Official Gazette (2018) (in Turkish).]. After identifying deficiencies and the energy dissipation capacity in the newly proposed joints, two half-scaled frames with specific ductility-related designs were constructed, instrumented, tested, and analyzed. The specimens were tested under displacement-controlled lateral cyclic loading that incorporated constant axial loading to create cyclic tension and compression facets across the joint areas. The test results proved that the SRC column-RC beam frames employing an extra column reinforcement ratio exhibit slightly better seismic performance. Due to the presence of structural steel, the shear failure of the joint was effectively prevented, even after the formation of the plastic hinge on the interface of the beam. During the testing, the column rebars, to some extent, made a minor contribution to the joint strength of the specimen compared to the structural steel that absorbed almost all of the load applied to the frame.Article Citation - WoS: 6Citation - Scopus: 7Finite Element Analysis of Frames With Reinforced Concrete Encased Steel Composite Columns(Mdpi, 2022) Tunc, Gokhan; Othman, Mohammed Moatasem; Mertol, Halit CenanStructural frame systems that consists of concrete-encased-steel-embedded composite columns and reinforced concrete beams are typically used in mid-rise to tall buildings. In order to understand their overall structural behavior, a total of 12 frame models with high and low ductility features were constructed and analyzed using LS-DYNA software. Two of these models were validated using the results of previously tested frames. The remaining 10 models were studied to predict the behavior of frames with varying concrete strengths, reinforcement configurations, and structural steel sections under vertical and lateral loads. The results were investigated in terms of cracks and failure patterns, load-deflection relationships, energy dissipation, and stiffness degradation. The analytical results indicated that the high ductile frame models showed slightly better lateral load carrying performances compared to low ductility frame models. Moreover, the analytical studies demonstrated that the existence of structural steel in a column, regardless of its cross-sectional shape, was the most important parameter in improving the lateral load carrying capacity of a frame.Article Citation - WoS: 5Citation - Scopus: 7Lessons Learned From Four Recent Turkish Earthquakes: Sivrice-Elazığ, Aegean Sea, and Dual Kahramanmaraş(Springer, 2024) Tunc, Goekhan; Mertol, Halit Cenan; Akis, TolgaT & uuml;rkiye is located in an earthquake-prone region where almost all of its population resides in risky areas. In the past 100 years, there has been a strong earthquake every two years and a major one every 3 years. This study investigates the impact of four recent earthquakes, that occurred between 2020 and 2023, on reinforced concrete (RC) buildings. The first, Sivrice-Elaz & imath;& gbreve;, struck the eastern part of T & uuml;rkiye on January 24, 2020, with a moment magnitude of Mw = 6.8. The second, the Aegean Sea, hit the western part of the country on October 30, 2020, with an Mw of 6.6. The third and fourth are the February 6, 2023 dual Kahramanmara & scedil; earthquakes with Mws of 7.7 and 7.6, which struck the eastern part of T & uuml;rkiye approximately 9 h apart. Immediately following these earthquakes, a technical team investigated each of the damaged areas. This study summarizes their findings on RC buildings. It was discovered that the majority of the collapsed or severely damaged RC buildings were constructed before 2000. The main reasons for this included technological limitations, specifically on producing high-quality concrete, as well as a lack of public policies and enforced laws in the construction sector to maintain an acceptable international standard. Furthermore, the damage patterns of buildings from these four earthquakes indicated poor workmanship, low material quality, improper structural framing, a common appearance of soft and weak stories, the inadequate use of shear walls, and defective reinforcement configuration. The significance of soil studies and the enforcement of building inspections are also discussed, along with the earthquake codes. The study concludes that the maximum peak ground accelerations from the dual Kahramanmara & scedil; earthquakes were almost triple the code-prescribed values. Therefore, it is recommended that the current mapped spectral acceleration values be revised and that buildings constructed before 2000 should be prioritized while determining their structural performances.Article Citation - WoS: 21Citation - Scopus: 28Damage in Reinforced-Concrete Buildings During the 2011 Van, Turkey, Earthquakes(Asce-amer Soc Civil Engineers, 2014) Baran, Eray; Mertol, Halit Cenan; Gunes, BurcuTwo major earthquakes with magnitudes Mw=7.2 (ML=6.7) and ML=5.6 occurred in eastern Turkey on October 23 and November 19, 2011. The maximum measured peak ground accelerations for the two ground motions were 0.18g and 0.25g, respectively. The earthquakes resulted in various levels of damage to RC moment-resisting frame buildings ranging from minor cracking in brick partition walls to total collapse. This paper summarizes the field observations of the Atilim University Reconnaissance Team carried out in the region a few days after the two main shocks with an emphasis on the performance of RC buildings. A summary of the evolution of the Turkish seismic design code during the last 35 years is given, followed by an explanation of the behavior of RC buildings during the October 23 and November 9 earthquakes. The deformation types that were commonly observed in the heavily damaged or collapsed RC buildings include plastic hinging in columns attributable to stiffer beams, localization of damage in ground-story columns attributable to changes in the stiffness of the lateral load-resisting system caused by brick partition walls, and shear failure of columns caused by discontinuities in the partition walls adjacent to the columns. Poor concrete quality, inadequate development and lap splice length for reinforcement, and inadequate confinement in columns also contributed to the poor seismic behavior.
