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https://hdl.handle.net/20.500.12587/8653

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Thermal impacts on the erosion of compacted bentonite under flow rate
(Springernature, 2024) Bülbül, Süleyman; Sedighi, Majid; Sevim, Özer
Compacted bentonite is widely used as a filling and barrier material for underground storage of spent nuclear fuel waste due to its favorable properties. Over its design life, this compacted clay may be exposed to groundwater from the surrounding host rock. Depending on the modeling approaches and assumptions, the temperature to which the compacted bentonite will be exposed can vary. This paper presents the findings of laboratory investigations on the erosion of compacted bentonite at ambient temperature (26 degrees C) and elevated temperature (80 degrees C) temperatures. The compacted bentonite samples, with dry densities of 1.72 g/cm3 and 1.73 g/cm3 were subjected to erosion under a flow rate of 0.22 ml/min at 26 degrees C and 80 degrees C, respectively. The dynamic light scattering (DLS) method was employed to measure the size and quantity of the eroded particles. The amount of daily erosion and the size of the eroded particles were determined from effluent samples. The results indicate that the amount of eroded bentonite particles increased significantly with increasing temperature. Additionally, as temperature increased, the size of bentonite particles in the effluent decreased within a specific range. At 26 degrees C, particle sizes ranged from 59 to 6358 nm, whereas at 80 degrees C, the particle size distribution narrowed.
Thermal and Compressive Strength Properties of Sepiolite Substituted Autoclaved Aerated Concrete
(Gazi Univ, 2014) Savaş, Musa; Demir, Ilhami; Güzelküçük, Selahattin; Şengül, Cağrı Göktuğ; Yaprak, Hasbi
Aerated concrete is a lightweight concrete which has porous structure. In this study, effects of usage of sepioliteas a raw material instead of quartzite on the thermal and compressive strength properties of aerated concrete were investigated.G2/04 class aerated concrete, which has been commercially produced as a wall component, has been focused. Aerated concrete samples have been prepared by substitution of sepiolite instead of quartzite in %5, %10, %15, %20 and %25. Sepiolite has been provided from Eskisehir mine field. After 4 hours cure at 60 degrees C, samples moved to treat in autoklave in the temperature of 180 degrees C and pressure at 11 bar for 6.5 hours. Thermal conductivity and compressive strength properties of samples were determined. As a result, increasing the rate of sepiolite in aerated concrete decreases the compressive strength and increases the thermal conductivity.
The forecasting of air transport passenger demands in Turkey by using novel meta-heuristic algorithms
(Wiley, 2021) Korkmaz, Ersin; Akgüngör, Ali Payidar
The imbalance between modes of transport in our country appears as the most important problem. Therefore, in air transportation, which has a significant increasing trend, estimating the passenger demand with directly related parameters and novel algorithms is important for Turkey. In this study, different prediction models were developed applying for the first time with five different meta-heuristic algorithms which are Flower Pollination Algorithm (FPA), Artificial Bee Colony Algorithm (ABC), Crow Search Algorithm (CSA), Krill Herd Algorithm (KH), and the Butterfly Optimization Algorithm (BOA) to estimate Turkey's air transport demand. While developing the models, Fuel Price, Gross Domestic Product per Capita, Seat Capacity, and Annual Fuel Consumption were selected as the model parameters. Although each model developed using different approaches is applicable, quadratic and power models developed using CSA showed the highest performance. For this reason, future projections were based on these models. Air transport passenger demand was examined using two scenarios in a process until 2035. In the first scenario, according to model forms, Turkey's future air transport passenger demand will reach about 460 and 490 million passengers, respectively. In the second scenario, the number of passengers will reach approximately 375 and 660 million for quadratic and power models, respectively. The results of this study will contribute to the evaluation of the current investment plans and the development of strategic plans that will meet the demands. Additionally, they will help take necessary measures and introduce some necessary regulations to ensure the income and expense balance so that the efficiency of airline companies can be improved.
The effect of sea water on the properties of concrete with silica fume admixture
(Stowarzyszenie Producentow Cementu, 2010) Demir, İlhami; Yaprak, Hasbi; Şimşek, Osman
Two series of concrete samples with silica fume addition were produced from the mixtures with tap water or sea water, as mixing water. It was found that sea water has no harmful influence on the concrete mix properties, but increase the rate of concrete hardening. This caused the increase of concrete strength, which was observed till the end of measurements i.e. till 90 days. However the increase of strength after 90 days was smaller than after 28 days.
The Effect of Magnetized Water on the Fresh and Hardened Properties of Slag/Fly Ash-Based Cementitious Composites
(Mdpi, 2023) Sevim, Özer; Demir, İlhami; Alakara, Erdinç Halis; Güzelküçük, Selahattin; Bayer, Ismail Raci
The physicochemical structure of the mixing water used in concrete has a significant effect on the physical and mechanical properties of cementitious composites. The studies on the effect of magnetized water (MW) on the properties of FA/BFS-based cementitious composites are still in their infancy. This study explores the effect of MW on the fresh and hardened properties of fly ash (FA)/blast furnace slag (BFS)-based cementitious composites. A total of 22 different mixture groups having FA/BFS (0, 5, 10, 15, 20, and 25%) by weight of cement were produced using tap water (TW) and MW. The fresh-state properties (the initial and final setting times and the consistency) and hardened-state properties (the compressive strength, water absorption properties, and rapid chloride ion permeability test) of produced cementitious composites were investigated. The development of hydration products was analyzed using scanning electron microscopy (SEM) and the mercury intrusion porosimetry (MIP) test. The results reveal that the fresh- and hardened-state properties of cementitious composite samples produced with MW are significantly improved. The properties of the samples utilizing MW showed that FA and BFS could be used at a higher rate for the same target properties in cementitious composites by using MW as mixing water. Using up to 25% FA/BFS in cementitious composites prepared with MW is recommended.
The Effect of Fiber Type and Ratio on the Physical and Mechanical Properties of Marble Powder Added Fiber Concrete
(Gazi Univ, 2022) Şimşek, Osman; Demir, Şükrü
In this study, it is aimed to determine the effect of steel and macro synthetic fibers used in different ratios and types on the physical and mechanical properties of concrete. For this purpose; Macro synthetic fiber was used at 0.25%, 0.30% and 0.35% by volum4, steel fiber at 0.50%, 0.75% and 1.00% by volume. Chemical additives and marble powder were used in fixed proportions. In the study, the water / cement ratio was taken as 0.54 constant according to the fiber concrete TS 802 mixture. In this research, beams of 10 x 10 x 40 cm and 15 cm cube samples were produced for fresh and hardened concrete properties. The effect of fiber type and ratio was investigated by performing physical and mechanical tests on the produced samples. As a result of the study, as the fiber ratio of fiber mixes in fresh concrete increased, workability and unit volume weights decreased. As a result, as the fiber ratio in fresh concrete increases, the fiber ratio has negatively affected the workability and the unit volume weights decreased. In hardened concrete; In hardened concrete; As the fiber ratio increased, the initial crack stress and bending stress increased. The highest mechanical and physical properties were given by 1.00% steel fiber and 0.35% macro synthetic fiber concretes.
The Effect of Different Aggresive Condition on Mortars of Cem I, Cem II and Boron Cement
(Gazi Univ, 2014) Yaprak, Hasbi; Demir, İlhami; Kaplan, Gökhan
This study investigates the sea water and ammonium nitrate resistance of cement mortars when subjected to different exposure conditions. Cement mortar samples were prepared using Boron, CEM I and CEM III/A cements. Mortar specimens were stored under three different conditions: continuous curing in lime-saturated tab water, continuous exposure to sea water, and continuous exposure to 5% ammonium nitrate solution (AN), at a temperature of 20 +/- 3 degrees C, for 2, 7, 14, 28 and 90 days. Prisms with dimensions of 25x25x285 mm, to determine the expansions of the mortar samples; and another set of prisms with dimensions of 40x40x160 mm, were prepared to calculate the compressive strength of the samples. For all environmental conditions and ages, the lowest expansion is found for CEM III/A cement mortars. It has been observed that CEM III/A cement mortars have the highest resistance for both sea water and environments with ammonium nitrate.
Suspended sediment load prediction in river systems via shuffled frog-leaping algorithm and neural network
(Springer Heidelberg, 2024) Katipoglu, Okan Mert; Aktürk, Gaye; Kılınç, Hüseyin Çağan; Terzioğlu, Zeynep Özge; Keblouti, Mehdi
Suspended sediment load estimation is vital for the development of river initiatives, water resources management, the ecological health of rivers, determination of the economic life of dams and the quality of water resources. In this study, the potential of Feed Forward Neural Network (FFNN), Genetic Algorithm (GA), Particle Swarm Optimization (PSO), and Shuffled Frog Leaping Algorithm (SFLA) models was evaluated for suspended sediment load (SSL) estimation in Ye & scedil;il & imath;rmak River. The heat map of Pearson correlation values of meteorological and hydrological parameters in 1973-2021, which significantly impacted SSL estimation, was examined to estimate SSL values. As a result of the analysis it was developed a prediction model with three different combinations of precipitation, stream flow and past SSL values (M1: streamflow, M2: streamflow and precipitation, M3: streamflow, precipitation, and SSL). The prediction accuracy of the models was visually compared with the Coefficient of Determination (R2), Bias Factor (BF), Mean Absolute Error (MAE), Mean Bias Error (MBE), Root Mean Square Error (RMSE), Akaike Information Criterion (AIC), Kling-Gupta Efficiency (KGE) statistical criteria and Bland-Altan plot, boxplot, scatter plot and line plot. Based on the analyses, the PSO-ANN model in the M1 model combination showed good estimation performance with an RMSE of 1739.92, MAE of 448.56, AIC of 1061.55, R2 of 0.96, MBE of 448.56, and BF of 0.29. Similarly, the SFLA-ANN model in the M2 model combination had an RMSE of 1819.58, MAE of 520.64, AIC of 1069.9, R2 of 0.96, MBE of 520.64, and BF of 0.19. In the M3 model combination, the SFLA-ANN model achieved an RMSE of 1423.09, MAE of 759.88, AIC of 1071.9, R2 of 0.81, MBE of 411.31, and BF of -0.77. Overall, these models can be considered good estimators as their predicted values are generally close to the measured values. The study outputs can help ensure water structures' effective lifespan and operation and take precautions against sediment-related disaster risks.
Stress Analysis Of Double Skin Composite Beams By Finite Element Analysis
(Pamukkale Univ, 2007) Doğan, Orhan; Büyükkaragöz, Alper
Double skin composite (DSC) construction consists of a layer of a plain concrete, sandwiched between two layers of relatively thin steel plate, connected to the concrete by welded stud shear connectors. This results in a strong and efficient structure with certain potential advantages over conventional forms of construction. The main aim of the present study is to provide additional numerical solution to compare with previous researches and to develop appropriate functions of optimum design depending on double skin composite beams. Ansys 5.4 program has been used for finite element analysis.
Spatiotemporal Analysis of Historical Droughts in the Central Anatolia, Turkey
(Gazi Univ, 2014) Yıldız, Osman
The spatiotemporal characteristics of meteorological droughts in the Central Anatolia, a semiarid region in Turkey, are determined utilizing the Standardized Precipitation Index (SPI) as a measure for drought severity. Using the temporal and spatial characteristics of monthly SPI, drought intensity-areal extent-frequency curves for various return periods are constructed for the region, and then the spatiotemporal characteristics of selected historical droughts are evaluated. The results indicate that the region is usually under the influence of droughts with low return periods, in other words, high frequency droughts during the study period (from 1953 to 2004). However, the areal extent of drought may be significant because of its negative impact on the water resources in the region. The overall evaluation of study results reveal that this method can provide useful information for spatial and temporal variations of droughts and can be utilized for water resources management in this region.
Simultaneous Measurement and Analysis of Noise Levels in Flexible and Rigid Pavements
(Pamukkale Univ, 2014) Yıldırım, Hakan; Açık, Selin; Akgüngör, Ali Payidar; Doğan, Erdem
Although concrete roads have been used worldwide for years, the same improvement could not exist in Turkey and therefore, bituminous (hot mix) asphalt roads were preferred instead. In this paper, the vastly built HMA (Hot Mix Asphalt) roads and rarely preferred concrete roads were compared based on their level of noise. For this purpose, the concrete road at the length of 2 kilometers between Afyonkarahisar and Emirdag; also the transition point to the HMA road (which continues after the concrete road) was observed. Both concrete and HMA road ends of this transition point was equipped with a noise measurement device and a camera was installed separately for providing minimum level of noise interference. Consequently, change in the noise levels depending on the building material of roads was recorded simultaneously. These factors was analysed and various models related to the sort of coating was provided. At this stage, the distance between set up points was kept as short as possible in order to prevent different results in the density of traffic and also in the flow rate. Result of various measurements and analysis provided the noise levels of concrete roads being 4 dB(A) less than HMA roads in the comparison based on the same level of vehicle composition and traffic flow. Encouraging the construction of concrete roads in our country is emphasized accordingly.
Shear and Bending Performances of Reinforced Concrete Beams with Different Sizes of Circular Openings
(Mdpi, 2023) Özkılıç, Yasin Onuralp; Aksoylu, Ceyhun; Hakeem, İbrahim Y.; Özdöner, Nebi; Kalkan, Ilker; Karalar, Memduh; Stel'makh, Sergey A.
The present study pertains to the effects of transverse opening diameters and shear reinforcement ratios on the shear and flexural behavior of RC beams with two web openings across different spans, i.e., a single opening in each half-span. Within the scope of the study, a total of 12 RC beams with five different opening diameter-to-beam depth ratios (0, 0.20, 0.27, 0.33, 0.40, and 0.47) and two shear reinforcement ratios were tested to failure under four-point bending. The load capacities, ductilities, rigidities and energy dissipation capacities in the elastic and plastic ranges of beam behavior were compared. Furthermore, the load capacities of the beams were compared to the existing analytical shear strength formulations in the literature. The test results indicated that whether an RC beam with openings has adequate or inadequate amounts of shear reinforcement, the frame-type shear failure becomes much more pronounced with increasing opening diameter. The reductions in the load capacity and modulus of toughness with increasing opening diameter are more considerable in the presence of inadequate amounts of shear reinforcement, while the beam ductility is less affected in shear-deficient RC beams with openings as compared to the ones with adequate shear reinforcement.
Seismic performance and damage assessment of bridges during the 2023 Kahramanmaras, Türkiye earthquakes (Mw = 7.8, Mw = 7.6)
(Sage Publications Inc, 2024) Baş, Selçuk; Hunt, Jeffrey; Gençtürk, Bora; Jampole, Ezra; Sönmezer, Yetiş Bülent; Chancellor, Brent; Bassal, Patrick
This article presents a summary of the damage observed in bridges in the regions affected by the 6 February 2023 Kahramanmaras, T & uuml;rkiye earthquake sequence. A bridge database was developed based on the observations from multiple reconnaissance groups that visited the bridges. These reconnaissance groups collectively visited 140 individual bridges that were subjected to various intensities of ground shaking. The severity of the observed damage ranged from no damage to total collapse. The types of damage to bridge components mainly included cracking and shifting of abutments, failure of pier cap shear blocks, shifting or dislodging of bearing pads, cracking of girders and loss of prestress, plastic hinging at pier bases, residual pier drift, and distress to deck surfaces, handrails, and carried utilities. Recorded and estimated seismic intensity measures are presented for each bridge site, and statistical information and correlations were developed considering the intensity of shaking, bridge parameters, and observed damage. Observations from a few visited sites are presented as case studies to illustrate the common failure mechanisms. The bridge database and presented results are expected to serve as a reference for further analysis, such as statistical verification, correlation, or damage estimations, and discussion regarding the mitigation of the observed vulnerabilities of bridges in T & uuml;rkiye and those with similar construction worldwide.
Robust-LSTM: a novel approach to short-traffic flow prediction based on signal decomposition
(Springer, 2022) Doğan, Erdem
Intelligent transport systems need accurate short-term traffic flow forecasts. However, developing a robust short-term traffic flow forecasting approach is a challenging task due to the stochastic character of traffic flow. This study proposes a novel approach for short-term traffic flow prediction task, namely Robust Long Short Term Memory (R-LSTM) based on Robust Empirical Mode Decomposing (REDM) algorithm and Long Short Term Memory (LSTM). Short-term traffic flow data provided from the Caltrans Performance Measurement System (PeMS) database were used in the training and testing of the model. The dataset was composed of traffic data collected by 25 traffic detectors on different freeways' main lanes. The time resolution of the dataset was set to 15 min, and the Hampel preprocessing algorithm was applied for outlier elimination. The R-LSTM predictions were compared with the state-of-the-art models, utilizing RMSE, MSE, and MAPE as performance criteria. Performance analyses for various periods show that R-LSTM is remarkably successful in all time periods. Moreover, developed model performance is significantly higher, especially during midday periods when traffic flow fluctuations are high. These results show that R-LSTM is a strong candidate for short-term traffic flow prediction, and can easily adapt to fluctuations in traffic flow. In addition, robust models for short-term predictions can be developed by applying the signal separation method to traffic flow data.
Reduction of propeller jet flow scour around a pile structure by using collar plate
(Pergamon-Elsevier Science Ltd, 2021) Cihan, Kubilay; Hafızoğulları, Ayşe Hazel
In this study, the effect of the collar plate usage on local scour around a pile due to propeller jet flow was investigated experimentally. Experiments were carried out for unconfined conditions, only existence of a pile and a pile with collar plate. Three different collar plate widths (W) and two different locations of the collar plate with respect to the seabed (hc) were used to determine the effect of the collar plate on scour. Three different rotational speeds were used and scour around a pile was measured by using an Acoustic Doppler Velocimeter Profiler (ADVP). Since the experiments were completed before reaching the equilibrium state, present study can be considered as a short-term study. The results of the experimental studies show that the amount of reduction of scour around a pile is sensitive to the collar plate width and location of the collar plate. A collar plate application is an effective way for reducing scour around a pile. The most effective type of collar plate was determined as a condition in which W/D and hc/y0 are equal to 3 and 0, respectively. The amount of reduction in scour around a pile was observed as 75%.
PVC and POM gripping mechanisms for tension testing of FRP bars
(Techno-Press, 2021) Başaran, Boğaçhan; Yaka, Harun; Kalkan, İlker
The present study pertains to the introduction of two new types of grip adaptor for universal testing machines, namely Polyvinyl Chloride (PVC) and Polyoxymethylene (POM) grip adaptors, and their application to tension testing of FRP bars with different fiber and surface finish types. The tabs are connected to the FRP bar sample with the help of mechanical anchors, i.e. bolts. These new adaptors offer vital superiorities over the existing end tab designs (anchors with filling material or mechanical anchorage), including the reduction in the time and labor for production, reusability and the mild nature, i.e. low hardness of the tab material, which retards and even prevents peeling and crushing in the gripping regions of an FRP sample. The methods were successfully applied to FRP bars with different types of fiber (CFRP, GFRP and BFRP) and different types of surface texture (ribbed, wrapped, sand-coated and wound). The test results indicated that the both types of end caps prevented slip of the bar, crushing and peeling in the gripping zone. The mechanical properties from the material tests with the new caps were in perfect agreement with the ones from the material tests with steel tubular caps.
Bezier Search Differential Evolution algorithm based estimation models of delay parameter k for signalized intersections
(Wiley, 2022) Akgüngör, Ali Payidar; Korkmaz, Ersin
This article presents a new methodology for estimating delay parameter k, and proposes analytical models which are used artificial intelligence technique for signalized intersections that considers the variation in traffic flow with under-saturated and over-saturated conditions. The delay parameter k has been expressed as a function of the degree of saturation in the proposed analytical models. Using the Bezier Search Differential Evolution algorithm (BeSD) algorithm, four different model forms were developed separately for under-saturated conditions (x <1) and over-saturated conditions (x > =1). Among the model forms developed as linear, quadratic, power, and logarithmic, the quadratic model presented the best results in both traffic conditions. In the validation of the models, a total of 140 different traffic conditions were determined, 56 of which cover the under-saturated and 84 the over-saturated traffic conditions. According to the statistical results, using k values depending on the proposed model instead of using a constant k value (0.5) provides 1.5 and 4.3 improvements for RMSE and MAPE values in under-saturated traffic conditions respectively, while these improvements in over-saturated traffic conditions have reached 9.5 and 6, respectively. As a result, using k values depending on the proposed model will be effective in obtaining a more accurate delay value. This effect is more evident, especially in over-saturated traffic conditions.
Bending Behavior of RC Beams with Regular Web Openings and Non-corroding GFRP Reinforcement
(Springer, 2024) Kartal, Saruhan; Kısıklı, Emin
The present study pertains to the flexural behavior of RC beams with openings and non-metallic (GFRP) reinforcement. The main goal of preferring GFRP reinforcement over the conventional steel reinforcement was to safeguard the beams against the reinforcement corrosion. The presence of multiple regular transverse openings throughout the beam length increases the susceptibility of reinforcing bars to corrosion as the larger contact area in these beams with the outside environment increases the ingress of corrosive agents. Within the scope of the study, a total of 8 RC beams, including two reference beams without web openings, were tested under four-point bending. The test parameters were the flexural reinforcement ratio, the presence of short stirrups in the chords, and the presence of diagonal reinforcement spiraling around the openings. Since GFRP stirrups are difficult to bend, each stirrups was formed by connecting four individual FRP bars around the longitudinal bars. The opening circular geometry was adopted to avoid stress concentrations around the sharp corners of opening and to facilitate the placement and fixing of different schemes of reinforcement in the beams. The present tests depicted that the diagonal reinforcement around the openings have considerable contribution to the flexural behavior of RC beams with GFRP reinforcement and with multiple regular transverse openings. The RC beams with openings were able to approach their analytical flexural capacities in the presence of diagonal reinforcement for both moderately and heavily reinforced beam groups. The analytical deflection predictions of GFRP-RC beams with openings showed a good agreement with experimental data.
An experimental study to determine the optimum depth of steel anchors in RC subjected to shear force
(Elsevier Science Inc, 2022) Odacıoğlu, Orhan Gazi; Doğan, Orhan; Kale, Fulya
Unlike existing in-plane strengthening RC shear-walls, anchors are used in strengthening of RC buildings to attach out-of-plane RC shear-walls or steel profiles. It is necessary to know the shear capacity as well as the ductile and nonlinear behavior of the anchor bolts as a connector to be used in the transfer of the shear force between the existing and new elements in strengthening. Considering that the existing RC structures in Turkiye are designed, according to the earthquake codes, with C14 concrete compressive strength until 1998, C18-20 until 2007, C20 until 2018 and also C25 after 2018, knowing the optimum anchorage depth depending on the concrete strength is of great importance in the strengthening analyzes of these structures. In this study, it was aimed to determine the shear performance and optimum anchorage embedment depth of steel sleeve expansion anchor bolts in RC. For this purpose, a total of 72 push-shear tests were conducted on M10 bolts for 6 different classes of low and normal strength concrete and 4 different anchorage depths. As a result of the experiment, it was observed that the shearing capacity of the anchor bolts increased with the increase of concrete strength and anchorage depth. However, for an optimum anchorage embedment depth, it has been observed that the anchor shear capacity reaches the maximum and remains constant without being affected from increment of the embedment depth and the change in concrete strength.
An analysis of Type I dilemma zone at signalised intersections
(Fac Transport Silesian Univ Technology, 2021) Akgüngör, Ali Payidar; Mercan, Elif Zahide
Intersections, for vehicles coming from different directions, are conflict points in road networks. When a driver approaching a signalised intersection encounters the yellow light, he/she is in a dilemma either to safely stop or to pass through the intersection during clearance time. The decision to stop or to pass may change depending on some factors such as duration of yellow light, deceleration and acceleration rate, width of intersection, speed and length of vehicle, etc. This study aims to put forth the effects of some related factors affecting the length of the Type I dilemma zone. To perform this study, five factors including vehicle speed, maximum deceleration rate, perception-reaction time, clearance time, the total intersection width-vehicle length were considered and a total of 648 different traffic cases were investigated. The study results showed that the Type I dilemma zone length increased with the increase of speed, total intersection width-vehicle length and perception-reaction time, but decreased with the increase of clearance time and deceleration rate.

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