Publications

Located on multiple active fault lines, Turkey frequently experiences devastating earthquakes. In recent years, seismic metamaterials have emerged as an innovative isolation technique in earthquake engineering due to their ability to create band gaps that prevent the propagation of seismic waves within specific frequency ranges. Periodic foundations composed of such materials can reduce structural responses by dissipating in seismic energy before it reaches the structure. This study experimentally investigated the damping performance of metamaterial-based periodic foundations. A uniaxial shaking table capable of horizontal motion along the x-axis, driven by a 0.75 kW servo motor, was used as a vibration source. The motor's motion was simulated through Arduino IDE programming. Servo motor control signals with step counts of 5000, 4000, and 3000 representing three different vibration frequency profiles were applied to three test specimens for 20.667 seconds. Accelerometers placed on the top layer of each specimen recorded acceleration responses at 80-millisecond intervals. The recorded data were analyzed in the time domain (acceleration-time) and the frequency domain (via Fast Fourier Transform). The test specimens consisted of: (i) a conventional foundation made of reinforced concrete plates, (ii) a one-dimensional periodic foundation composed of rubber and concrete plates, and (iii) a one-dimensional periodic foundation embedded with piezoelectric sensors. All specimens were scaled to represent soil- layer bonded using a polyurethane-based adhesive. Experimental results revealed that periodic foundations were more effective in suppressing vibration energy than conventional ones. Furthermore, the piezoelectric sensor-integrated foundations exhibited vibration-induced energy harvesting potential, offering multifunctional benefits for structural applications in seismic environments.

In reinforced concrete (RC) structures, corrosion of the reinforcement due to environmental factors or concrete components poses significant risks to both structural integrity and safety. Reinforcement corrosion, can be visually detected through cracks in the concrete cover, and this situation offers a practical approach to associating corrosion-induced cracks with structural parameter degradations caused by the corrosion mechanism. In this study, a total of five RC frame specimens were fabricated, with one specimen not exposed to corrosion and four specimens exposed to different levels of corrosion through the accelerated corrosion method, all having the same cross-section and material properties. In the experiments conducted under a constant 20 % axial load and cyclic repeated load effects, the structural performance indicators of the RC frame specimens were examined. Within the scope of the study, two experimental models are proposed. The first model aims to estimate the loss in the cross-sectional area of the reinforcement bar based on crack width, while the second model was oriented towards estimating the energy consumption capacity of the specimen for a specific displacement ratio based on the loss in the cross-sectional area of the reinforcement. The results revealed that as the corrosion ratio increased, the crack widths of the specimens also increased, and after a 1.5 % drift ratio, there was a significant decrease in the energy consumption capacities of the corroded specimens.

Technical investigations carried out after the devastating earthquakes in Turkey in the last 25 years show that one of the main causes of damage to reinforced concrete structures is reinforcement bar corrosion. The deterioration caused by reinforcement corrosion in reinforced concrete elements reduces the parameters that define the performance level of the structure, such as ductility, stiffness, bond-slip relationship, load carrying capacity, and energy absorption capacity. Therefore, determining the specified performance levels of reinforced concrete structures exposed to corrosion before any seismic activity occurs is of great importance in preventing loss of life and property. Cross-section behavior in reinforced concrete structures represents the load-bearing element behavior In order to accurately determine the section behavior, the Moment-Curvature relationship must be defined. In this study, the structural behavior of reinforced concrete frames exposed to corrosion was examined experimentally and analytically. For this purpose, 4 of the 5 reinforced concrete frame specimens constructed were corroded at different ratios using the accelerated corrosion method. After the corrosion process was completed, in the experimental part of the study, all specimens were tested under the effect of a 20% constant axial load and reversal-cyclic loading. In the analytical study, as a result of the cross-sectional analyzes carried out by taking into account the material-mechanical properties changing with the effect of corrosion, it was determined that the calculated moment values were in high predicted with the experimentally measured moment values.

This research aimed to evaluate the freeze-thaw performance of waste rubber substituted concretes with two different water/cement ratios. Different ratios of waste rubber were used in concrete by substituting fine and coarse aggregates. The weight and compressive strength losses of rubberized concrete and control concretes subjected to freeze-thaw were experimentally examined. The changes in the microstructure of the concrete were analyzed by using a Scanning Electron Microscope (SEM). Furthermore, ANOVA was used to test the significance of the selected parameters statistically. The control concrete with a 0.5 water/cement ratio had eight times higher mass loss compared to the rubberized concrete. The SEM analysis results were consistent with the freeze-thaw test results. ANOVA that the waste rubber substitution ratio had a significant effect on the freeze-thaw performance of rubberized concrete. Water/cement ratio, together with the waste rubber substitution ratio, is an effective parameter on the freeze-thaw resistance of rubberized concrete.

In this study, it was aimed to determine the traffic and agricultural activity-induced heavy metal including arsenic (As), cadmium (Cd), cobalt (Co), chromium (Cr) and lead (Pb) pollution of sugar beet plants (Beta Vulgaris) grown along the Erzincan-Erzurum D100-25 highway and to reveal the possible change in the amount of heavy metals in sugar beet plants depending on distance to the highway. For this purpose, sugar beet plants were collected from 5 points of 10, 20, 30, 40 and 50 meters away from the highway and heavy metal levels of the samples were determined by inductively coupled plasma mass spectrometry (ICP-MS). The results showed that sugar beet plants were contaminated with various heavy metals such as Cr (585.5-2687.8 µg kg-1) > Co (143.4-500.7 µg kg-1) > Pb (52.1-476.7 µg kg-1) > As (9.1-112.4 µg kg-1) > Cd (4.4-65.2 µg kg-1) depending on the distance from the highway. It was determined that heavy metal pollution levels in sugar beet plants decreased with distance from the motorway and there was a high correlation (As: 0.977; Cd: 0.944; Co: 0.995; Cr: 0.989 and Pb: 0.999) between distance and heavy metal content.

In this paper, degradation of Direct Blue 71 (DB71) by Fenton's oxidation process was investigated. The effect of initial pH, dosages of Fe2+ and H2O2, dye concentration and temperature on the color and Chemical Oxygen Demand (COD) removal was studied in a batch reactor. The optimal conditions for the decolorization and COD removal of DB71 were determined as pH = 3.0, Fe2+ = 3 mg L−1 and H2O2 = 125 mg L−1. Under the optimal conditions 94% color and 50.7% COD removal efficiency of the dye in 100 mg L−1 aqueous solution were achieved after 20 min of reaction. Results indicated that the removal efficiency was strongly dependent on initial pH, initial concentration of Fenton's reagents, initial DB71 concentration and reaction temperature. Additionally increasing the reaction temperature from 20 to 60 °C showed a positive effect on the decolorization efficiency of DB71. The experimental data were analyzed using the first and second-order and Behnajady–Modirshahla–Ghanbery (BMG) kinetic models. BMG model provides the best correlation of the data. The present study can provide guidance to relational industry operators and planners to effectively treat the DB71 contaminated wastewater by Fenton's oxidation process.

Modeling of data is critical in the analysis and evaluation of hydrological behavior. River flow data is one of the most important data in explaining hydrology. Management of water resources; It takes place in the literature as an area that needs to be investigated in order to provide early warning for undesirable situations such as floods and drought. For this reason, it is of important to develop different techniques for the estimation and modeling of river flow or to make comparisons between techniques. In this study, the flow data of fourteen stations located in the Euphrates-Tigris basin between 1981 and 2010 were used. Adaptive Network Based Fuzzy Inference Systems (ANFIS), Support Vector Machine (SVM) techniques that are frequently used in the literature, and newly introduced Gaussian Process Regression (GPR), Extreme Learning Machine (ELM) and Emotional Neural Network (ENN) artificial intelligence techniques are compared. In addition, considering all performance indices, it was determined which technique gave better results with rank analysis. Although all models worked well, it was seen that the methods were ranked as ELM, GPR, ENN, SVM and ANFIS starting from the best. This has shown that ELM, GPR and ENN methods, which have been used recently in flow modeling, give better results than traditional methods with complex structures. In addition, flow values were used in the whole study and these values were examined in 3 different combinations. It was seen that the model structure that gave the best performance was the model structure that used the flow data from one, two and three days ago as an estimator. The results were analyzed with a Taylor diagram and time series graphs.

The protection of digital data is becoming increasingly critical due to the rise in cyber threats. Particularly, image-based data is vulnerable to unauthorized access and cyberattacks, necessitating their protection. Today, image data is used in various fields, from credit card information to biometric data, military satellite imagery to medical images, and the security of this data is of great importance. Therefore, image encryption is considered an effective method for ensuring data privacy and security. The security of digital images is a critical issue for both individual and corporate users. While individuals seek to protect their personal photos and private documents, companies strive to safeguard trade secrets and customer information. Encrypting images is a widely used method to enhance data security and prevent unauthorized access. With the increasing use of social media, digital photography has become widespread, significantly increasing the need for large storage capacities. Thanks to technological advancements, storage processes are now largely carried out through cloud systems. Cloud storage systems allow different types of data to be stored virtually and cater to a broad user base. However, these systems often do not apply any encryption processes to ensure the privacy and security of stored photos (Liu & Dong, 2012). Encryption is a protection method that transforms data into an unreadable format, thereby securing it. This ensures that only authorized individuals can access the data, maintaining security and privacy. Authorized individuals can access encrypted data using specific decryption methods. Ensuring the security of multimedia data transmitted over digital networks has become an important topic for researchers and security experts today (Kumari et al., 2017). Today, ensuring data security and protecting it during transmission has become a fundamental requirement for many sectors. Images used in medical, military, and remote sensing fields can contain important and sensitive information (Ceyhan et al., 2021). Encryption techniques are used to ensure the integrity of such data and prevent potential security breaches. Encryption methods vary based on criteria such as speed, processing load, complexity, memory requirements, cost, information loss, and resistance to attacks. Therefore, the selection of the correct encryption method plays a crucial role in ensuring data security

The sonocatalytic degradation of Direct Blue 71 (DB71) azo dye has been studied in the presence of low-frequency ultrasound (20 kHz). An initial concentration of 50 mg L−1 of dye, within the range of typical concentration in textile wastewaters, was used. Batch sorption studies were conducted to study the effects of various parameters such as Zero-Valent Iron (ZVI) dose, pH, and effect of different power levels (20, 55, and 95 W), on DB71 oxidation. Oxidation of DB71 with the assistance of ultrasound was enhanced with the increase in ZVI initial concentration and ultrasonic power, and with the decrease in pH. It was observed that the color removal efficiency was influenced by the solution H2O2 amount. Accordingly, removal of 91.2% color and 97.2% total organic carbon (TOC) of dye was achieved by applying the optimal operational parameters with 0.3 g L−1 of catalyst, 2.5 pH and 25°C, during 20 min. In hybrid study, the color removal yield of 100% was obtained by combination of US/ZVI/H2O2 at dyestuff concentration of 100 mg L−1. The amount of catalyst and power levels had an important effect on the color removal yields (p < 0.05).

A total of four reinforced concrete (RC) columns were tested to compare the structural capacities of RC columns produced by natural perlite aggregates and conventional concrete. The structural performance of the RC columns made from natural perlite aggregates were compared for to conventional RC columns regarding the same concrete strength levels, sectional properties, and reinforcement layouts of conventional RC columns. The RC columns were tested under a combined constant axial load ratio of 30% with cyclic loading for two concrete strength levels, namely, of 25 and 40 MPa. Load-displacement curves, energy absorption capacities, stiffness degradation, the moment-curvature relationship, the plastic hinge mechanism and the ductility index were experimentally obtained at two different concrete types along with the measured stress-strain properties of the conventional and perlite concrete. The test results showed that the construction of the RC columns using only perlite may become possible in future by providing an adequate concrete stress-strain capacity, which will be improved.

Abstract The rapid increase in the number of electronic products worldwide, in terms of both variety and advanced technology, together with the decrease in costs, has led to the generation of a large amount of electronic waste (e-waste), which has significantly increased environmental pollution. This study was conducted to investigate the hypothesis that the adhesion of polymer binders and plastic origin e-waste will be more effective and stronger, and therefore have a positive effect on the permeability properties of polymer concrete and its behavior against aggressive solutions. For this purpose, quartz aggregates and gravel used as an aggregate in polymer concrete were replaced with 0%, 3%, 6%, 9%, 12% and 15% e-waste. In the study where unsaturated polyester resin was used as a binder, the changes in the permeability properties (capillary water absorption, rapid chloride permeability) of the e-waste polymer concrete and its behavior against aggressive solutions (acid and sulfate attacks) were evaluated after 7, 28 and 90 days. In addition, mechanical experiments were conducted and comparisons were made. After the control concrete, the highest compressive strengths were obtained from the polymer concrete specimens using 3% e-waste, measured as 59.05 MPa, 64.5 MPa and 73.05 MPa after 7, 28 and 90 days, respectively. The research showed that polymer concretes with capillary water absorption coefficient values close to zero after 90 days can be produced with using up to 9% e-waste. The use of e-waste as an aggregate in polymer concrete at 3%, 6% and 9% e-waste, in particular, produced concrete with a high resistance to acid and sulfate attacks. The hypothesis of the study was confirmed after extensive experiments. Graphical Abstract

Boyar maddelerin yaygın kullanımından kaynaklanan boyalı atık suların arıtılması önemli bir çevre sorunudur. Bu nedenle boyar madde içeren tekstil endüstrisi atık sularından renk giderim prosesleri ekolojik açıdan önem kazanmaktadır. Günümüzde büyük hacimli atık sulardaki boyar maddelerin etkili ve ekonomik bir şekilde giderilebilmesi için alternatif yöntemlere gereksinim vardır. Bu çalışmada tekstil atık sularında yaygın olarak bulunan Crystal Violet (CV)’in buğday kepeği üzerine adsorpsiyonu incelenmiştir. Kepeğin CV boyar maddesinin adsorpsiyonu üzerinde etkilerini belirlemek için; farklı başlangıç boya konsantrasyonları, pH değerleri, adsorbent konsantrasyonları ile sıcaklık parametreleri denenmiş ve optimum koşullar sağlanmıştır. En yüksek giderimin doğal pH (6.24)’da olduğu gözlemlenmiştir. Adsorbent miktarı belli bir değere kadar arttıkça boyar madde giderimi de artmıştır. Ayrıca, adsorpsiyonun 120. dakikada dengeye geldiği ve boyar madde konsantrasyonu arttıkça giderim veriminin düştüğü görülmüştür. Bununla birlikte, sıcaklığın 25°C’den 45°C’ye arttırılması boyar madde giderimini artırmıştır. Bunun yanında deneysel verilerin Langmuir ve Freundlich izotermler ile yalancı birinci ve ikinci derece kinetik modellere uygunluğu araştırılmıştır. Bu modellere ait parametreler ile adsorpsiyon prosesine ait termodinamik parametreler hesaplanmıştır. Karakterizasyon çalışmaları kapsamında buğday kepeği için adsorpsiyon öncesi ve sonrası Fourier Transform Infrared (FTIR) ve Scanning Electron Microscopy (SEM) analizi yapılarak biyosorpsiyon mekanizmasındaki fonksiyonel gruplar incelenmiş ve biyosorpsiyon sonrası oluşan yapısal değişikliklerin varlığı görülmüştür.

Korozyona maruz kalmış betonarme yapılarının sismik performanslarının tahmin edilmesi geleneksel yapılara göre oldukça zordur. Yapılan bu deneysel çalışmayla birlikte korozyona maruz kalmış betonarme elemanları üzerine yapılacak olan çalışmalara ışık tutulması amaçlanmıştır. Beş adet tam ölçekli betonarme kolonu hızlandırılmış korozyon yöntemi kullanılarak farklı korozyon oranları için paslandırılmıştır. Bu çalışmaya konu olan beş adet betonarme kolonu bu çalışmanın yazarları tarafından yürütülmekte olan TÜBİTAK 3501 ve 116M162 numaralı proje kapsamında üç farklı beton basınç dayanımı (C8, C20 ve C30), iki eksenel yük ve dört farklı korozyon oranı için deneyleri gerçekleştirilen paslandırılmış betonarme kolonlarının başlangıç hasar seviyelerinin tespiti için tersinir yükleme programının ve betonarme kolon hasar indekslerinin tespit edilmesi için yürütülmüştür. Betonarme kolonlarındaki gerçek korozyon oranları yükleme deneylerinden sonra betonarme kolonlarının kırılarak ve içlerinden tüm betonarme donatılarının çıkartılması ile elde edilmiştir. Deneyleri gerçekleştirilen betonarme kolonları sabit eksenel yük altında monotonik yüklemeye tabi tutularak, akma ve nihai yükleri, süneklilik oranları ve enerji yutma kapasiteleri deneysel olarak elde edilmiştir. Yapılan deneysel çalışma sonucunda, monotonik yüklemenin tersinir tekrarlanır yüklemeye göre zayıf yönleri her bir deprem parametresi için değerlendirilmiştir. Elde edilen deneysel sonuçlar doğrultusunda ileriki korozyon çalışmaları için önemli önerilerde bulunulmuştur. Yapılan bu çalışma kapsamında, korozyonun sağlamış olduğu sargı etkisi nedeni ve buna bağlı olarak aderans dayanımdaki artışlar, akma dayanımdaki azalış, süneklik oranları ve enerji yutma kapasitelerindeki artış ve azalışlar nedeniyle korozyona maruz kalmış betonarme elamanlarının değerlendirilmesinde hasar indekslerinin belirlenmesi gerektiği sonucuna varılmıştır.