WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7150
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Article Art and Construction Related Qualities of 14th‒15th Century Monuments in a Rural Landscape on the Western Coast of Türkiye(KeAi Communications Co., 2024) Hamamcıoğlu Turan, Mine; Aktaş, Engin; Toköz, Özge DenizThis study aims to contribute to the understanding of the evolution of art and construction in the early settlements established by Turkish communities on the far west Asian coast by focusing on two developed examples in Urla Peninsula. Conventional surveying and evaluation techniques of architectural restoration and civil engineering were utilized. Key findings include the understanding of the hierarchy of rural settlements in the studied landscape: old Çesme the most developed village of peninsula in the 16th century. It was positioned along a valley in distance to coast, but in control of harbor that played significant role in commerce between Europe and Asia. Its mosque and tomb, dated to late 14th – early 15th centuries, used to crown it. Cylindrical minaret tower of mosque, domed tomb tower on a cubical base and squinch in the transition zone of mosque are evidences for Central Asian roots. Usage of local lime stone, re-usage of andesite blocks, framing of the stone blocks with bricks, and pendentive in tomb refer to Roman-Byzantine constructions. The study presents the development of Turkish art and construction on the far west Asian coast in the 14th‒15th centuries. Findings will be a guide for related conservation management in similar contexts. © 2024 The Author(s)Article Citation - WoS: 3Citation - Scopus: 3Ensemble and Optimized Hybrid Algorithms Through Runge Kutta Optimizer for Sewer Sediment Transport Modeling Using a Data Pre-Processing Approach(Elsevier, 2023) Safari, Mir Jafar Sadegh; Gül, Enes; Dursun, Ömer Faruk; Tayfur, GökmenUncontrolled sediment deposition in drainage and sewer systems raises unexpected maintenance expenditures. To this end, implementation of an accurate model relying on effective parameters involved is a reliable benchmark. In this study, three machine learning techniques, namely extreme learning machine (ELM), multilayer perceptron neural network (MLPNN), and M5P model tree (M5PMT); and three optimization approaches of Runge Kutta (RUN), genetic algorithm (GA), and particle swarm optimization (PSO) are applied for modeling. The optimization and ensemble hybridization approaches are applied in the modeling procedure. For the case of hybrid optimized models, the ELM and MLPNN models are hybridized with RUN, GA, and PSO algorithms to develop six hybrid models of ELM-RUN, ELM-GA, ELM-PSO, MLPNN-RUN, MLPNN-GA, and MLPNN-PSO. Ensemble hybrid models are developed through coupling the ELM and MLPNN models with the M5PMT algorithm. The data pre-processing approach is applied to find the best randomness characteristic of the utilized data. Results illustrate that the RUN-based hybrid models outperform the GA- and PSO-based counterparts. Although the MLPNN-RUN and MLPNN-M5PMT hybrid models generate better results than their alternatives, MLPNN-M5PMT slightly outperforms MLPNN-RUN model with a coefficient of determination of 0.84 and a root mean square error of 0.88. The current study shows the superiority of the ensemble-based approach to the optimization techniques. Further investigation is needed by considering alternative optimization techniques to enhance sediment transport modeling. © 2023 International Research and Training Centre on Erosion and Sedimentation/the World Association for Sedimentation and Erosion ResearchArticle Citation - WoS: 7Citation - Scopus: 5Meteorological Drought and Trend Effects on Transboundary River Basins in Afghanistan(Springer, 2023) Hayat, Ehsanullah; Tayfur, GökmenAfghanistan, as a landlocked country located within central and southwestern Asia, has an arid to semi-arid climate. Most of the people are involved in agricultural activities, and a major part of the country's gross domestic product depends on agriculture, but the country has the lowest water storage capacity. Consecutive periods of drought and rapid snowmelt due to climate change have made it more challenging for suitable water resource management practices. This study investigates the historical meteorological drought characteristics across the whole country by employing the Reconnaissance Drought Index for the period 1979-2019 using data from 55 meteorological stations. Trends in precipitation and temperature are also investigated using the Mann-Kendall's and the Sen's slope statistical tests. A four-decadal countrywide drought map is generated. Extreme and severe droughts were observed in 1999 and 2000 across the whole country. Moderate drought events have started to occur with a frequency of 3 to 5 years since 1999. The decadal annual rainfall values in each river basin indicate that rainfall has decreased in the last two decades with a significant decline in 1999-2008. The trends of increase in temperature and decrease in precipitation are indications of rapid climate change in the country, especially in the south, west, and southwest regions. Due to the intensity and frequency of the droughts, river flow rates have decreased; and therefore, there is a need for the upstream and downstream neighboring countries to come to terms with the phenomenon of a new normal in the hydrological cycle and accordingly revise new water sharing treaties.Article Modeling Plasticity and Damage in Fiber Reinforced Composites by a Crystal Plasticity Based Approach(Elsevier, 2023) Dizman, E. Aybars; Özdemir, IzzetIn very thin ply laminates, delamination failure initiation occurs at much higher stress levels as compared to conventional ply laminates. This results in significant plastic deformation in the matrix accompanied by large fiber rotations. A closer look reveals that microstructure of fiber reinforced composites at large strains do not rotate with the plastic spin induced by the total deformation gradient and therefore inelasticity of such materials requires dedicated constitutive models. This paper focuses on inelastic response of such composites by using a recently proposed crystal plasticity based modeling framework and extents it by a non-local continuum damage mechanics formulation. As opposed to existing works related to composites, adapted crystal plasticity model is formulated and implemented in an implicit manner. To address the initiation and evolution of damage observed at large strains, localizing implicit gradient damage (LIGD) framework is used to degrade the slip resistance and hardening mechanisms on longitudinal and transverse slip systems by means of two separate damage variables. A user element (UEL) subroutine encapsulating all the components of the model is developed and integrated within the commercial finite element solver Abaqus. Capabilities of the model are assessed at material point, ply, and component levels by comparisons with analytical solutions and selected experimental results from the literature.Review Citation - WoS: 42Citation - Scopus: 49Utilization of Waste Materials in the Stabilization of Expansive Pavement Subgrade: an Extensive Review(Elsevier, 2023) Tanyıldızı, Muhammed; Uz, Volkan Emre; Gökalp, İslamExpansive soils, also known as swell-shrink soils, are one of the most problematic soils in highway construction and exhibit significant volume changes by swelling and shrinking while wet and dry, respectively. These changes in soil cause cracks, heaves, differential settlements, and damages to the overlying pavements leading to high maintenance costs. The annual average maintenance cost of structures built on expansive soils ranges from $9 to $15 billion, with 50% of the expenses associated with highways and streets. Chemical stabilization techniques such as cement and lime stabilization are one of the most efficient ways to treat expansive soils. However, there is a need to develop environmentally friendly approaches to stabilize expansive soils due to worldwide growing interest in sustainable developments and concerns about greenhouse gas emissions and climate change. In this context, using waste materials in soil stabilization has been considered an important issue for sustainability concerns. The aim of the current study is to review the relevant studies performed to improve the geotechnical and engineering properties of expansive subgrade soils of pavements by using waste materials arising from industrial, agricultural, and other activities in the last decade. In the organization of this study, characteristics of expansive soils including plasticity, compaction, strength & stiffness, microstructural characteristics, shrink-swell properties, and durability were focused to point out the effect of the waste materials. The overall results obtained throughout the scope of the current study indicated that the use of waste materials in soil stabilization improves the engineering properties of expansive soils, significantly. This paper also provides key information and creates awareness for researchers and sector representatives about sustainable soil stabilization.Article Citation - WoS: 9Citation - Scopus: 13Analysis of Adhesively Bonded Joints of Laser Surface Treated Composite Primary Components of Aircraft Structures(Elsevier, 2023) Martin, Seçkin; Nuhoğlu, Kaan; Aktaş, Engin; Tanoğlu, Metin; İplikçi, Hande; Barışık, Murat; Yeke, Melisa; Türkdoğan, Ceren; Esenoğlu, Gözde; Dehneliler, SerkanThe performance of the adhesively bonded aerospace structures highly depends on the adhesion strength between the adhesive and adherents, which is affected by, in particular, the condition of the bonding surface. Among the various surface treatment methods, as state of the art, laser surface treatment is a suitable option for the CFRP composite structures to enhance the adhesion performance, adjusting the roughness and surface free energy with relatively minimizing the damage to the fibers. The aim of this study is the validation and evaluation of the adhesive bonding behavior of the laser surface-treated CFRP composite structures, using the finite element technique to perform a conservative prediction of the failure load and damage growth. Such objectives were achieved by executing both experimental and numerical analyses of the secondary bonded CFRP parts using a structural adhesive. In this regard, to complement physical experiments by means of numerical simulation, macro-scale 3D FEA of adhesively bonded Single Lap Joint and Skin-Spar Joint specimens has been developed employing the Cohesive Zone Model (CZM) technique in order to simulate bonding behavior in composite structures especially skin-spar relation in the aircraft wing-box.Article Citation - WoS: 15Citation - Scopus: 17Effects of Nanosecond Laser Ablation Parameters on Surface Modification of Carbon Fiber Reinforced Polymer Composites(SAGE Publications, 2023) Martin, Seçkin; İplikçi, Hande; Barışık, Murat; Türkdoğan, Ceren; Yeke, Melisa; Nuhoğlu, Kaan; Esenoğlu, Gözde; Tanoğlu, Metin; Aktaş, Engin; Dehneliler, Serkan; İriş, Mehmet ErdemRemoval of contaminants and top polymer layer from the surface of carbon-fiber-reinforced polymer (CFRP) composites is critical for high-quality adhesive-joining with direct bonding to the reinforcing fiber constituents. Surface treatment with a laser beam provides selective removal of the polymer matrix without damaging the fibers and increasing the wettability. However, inhomogeneous thermal properties of CFRP make control of laser ablation difficult as the laser energy absorbed by the carbon fibers is converted into heat and transmitted through the fiber structures during the laser operation. In this study, the effect of scanning speed and laser power on nanosecond laser surface treatment was characterized by scanning electron microscope images and wetting angle measurements. Low scanning speeds allowed laser energy to be conducted as thermal energy through the fibers, which resulted in less epoxy matrix removal and substantial thermal damage. Low laser power partially degraded the epoxy the surface while the high power damaged the carbon fibers. For the studied CFRP specimens consisting of unidirectional [45/0/?45/90]2s stacking of carbon/epoxy prepregs (HexPly®-M91), 100 mJ/mm2 generated by 10 m/s scanning speed and 30 W power appeared as optimum processing parameters for the complete removal of epoxy matrix from the top surface with mostly undamaged carbon fibers and super hydrophilic surface condition. © The Author(s) 2023.Article Citation - WoS: 9Citation - Scopus: 8Effect of Drainage Conditions on Cpt Resistance of Silty Sand: Physical Model and Field Tests(Springer, 2023) Ecemis, Nurhan; Arık, Mustafa Sezer; Taneri, HazalThe influence of drainage conditions on cone penetration test (CPT) resistance and the excess pore pressure during cone penetration in sand and silty sand are examined using field and physical model tests. Drainage can generally occur in saturated clean sand and silty sand under certain conditions. This work aims to understand and explain the effect of sand and silty sand drainage conditions on CPT resistance and pore pressure through the coefficient of consolidation (c h) and penetration rate (v). The physical model test results indicate the significant effect of excess pore pressures and their dissipation rates, depending on the coefficient of consolidation (silt content) and the penetration rate on cone resistance. For the same relative density, normalized CPT resistance decreases as there is a reduction in c h (or an increase in silt content) or an increase in penetration rate. The difference in CPT resistance in silty sand is attributed to drainage conditions. Finally, the results revealed in this study and the field test data reported in the literature were combined to develop an equation for the effect of drainage conditions on excess pore water pressure and CPT resistance. © 2023, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.Article Citation - Scopus: 1Relationship Between Abrasion, Fragmentation and Thermal Weathering Resistance of Aggregates: Regression and Artificial Neural Network Analyses(Springer, 2023) Gökalp, İslam; Kaya, Orhan; Uz, Volkan EmreFor being used in pavement construction, properties of aggregates must satisfy the minimum requirements specified by highway agencies or institutions. The properties of the aggregates are determined by many tests lasting anywhere between a couple of hours to a few weeks depending on the type of the test. If good correlations can be established between the tests taking longer time and the ones taking comparably shorter time, there might be no need to conduct these longer time-taking tests for the sake of time. The aim of this study is to investigate the relationships between abrasion, fragmentation, and thermal weathering resistances of different aggregate types. To accomplish this aim, aggregates with different origins (natural and slags) were tested and correlative analyses utilizing regression analysis and artificial neural network (ANN) models were performed to establish relationships between the results of these test methods. It was found that good correlations can be established especially with ANN models and significant amount of time and effort can be saved with these developed models. © 2023, The Author(s), under exclusive licence to Chinese Society of Pavement Engineering.Article Citation - WoS: 4Citation - Scopus: 53d Modelling of Surface Spreading and Underground Dam Groundwater Recharge: Egri Creek Subbasin, Turkey(Springer, 2023) Şahin, Yavuz; Tayfur, GökmenThis study investigated surface spreading and underground dam recharge methods to replenish groundwater in Turkey's Egri Creek Sub-basin of the Kucuk Menderes River Basin. A three-dimensional numerical model was employed for this purpose. Field and lab data are provided to the model for realistic simulations. Pumping test results were used to determine the aquifer parameters. The laboratory works involved sieve analysis, permeability tests, and porosity and water content prediction. The numerical model's boundary conditions were determined from the geological and hydrogeological characteristics of the study area. Initial conditions were expressed regarding water content and pressure head in the vadose zone. The numerical model was satisfactorily validated by simulating water levels in three different pumping wells in the study area. Seven different scenarios, each having a different pool size, were investigated for the surface spreading recharge method. The results showed that a pool size of 30 x 30 m with a 6-m depth basin was the most optimal choice, raising the groundwater level to about 29.3 m. On the other hand, it was found that an underground dam could raise the levels by an average of 9.5 m, which might not be significant to warrant the construction.