Browsing by Author "Demir, Abdullah"

Now showing 1 - 14 of 14

Methods for Multi-Segment Continuous Cable Analysis
(2023) Demir, Abdullah; Polat, Ugur
Cables are invaluable members for some applications of engineering. The specialty is due to its behavior under transverse loads. Having almost no rigidity in transverse direction makes cables different from other structural elements. In most applications, cables are assumed to be two force members. However, not only its weight but also its application with roller supports makes them different structural elements. Generally, cables are assembled as single-segmented cables (SSC) where they are fixed at their ends. However, in most of the SSC applications, cables have intermediate supports which can be rollers or sliders. These type of cable applications are called as multi-segment continuous cables (MSCC). In MSCC systems, the cable fixed at its ends and supported by a number of intermediate rollers. Total length of cable is constant, and the intermediate supports are assumed to be frictionless and stationary. In this prob-lem, the critical issue is to find the distribution of the cable length among the segments in the final equilibrium state, so reactions at all supports can be found. Two methods are proposed for the segment length adjustment based on the stress continuity among the cable. These methods are named as direct stiffness method and tension distribu-tion method (relaxation method). Results calculated from the proposed methods are verified by both the reference benchmark problems and commercial finite element program.
A Sustainable Decision-Making Framework to Evaluate Land and Seaside Disposal Options for Tunnel Spoil: A Case Study of Trabzon
(Science Press, 2025) Dincer, Ali Ersin; Demir, Abdullah; Ozturk, Sevki; Yilmaz, Kutay
Sustainable urbanization is essential for developing cities. To ensure the success of planned construction projects, designers must prioritize sustainability by lowering emissions and reducing costs. Tunnel projects are common worldwide, but disposing of the excavated material presents a significant challenge due to unsuitable geographic conditions. While coastal cities with mountainous terrains have historically used spoil for sea filling, this study offers alternative landside options to promote sustainability. By using a conventional analytical hierarchy process (AHP) method for multi-criteria decision-making (MCDM), the study evaluates land use, sustainability, slope, and drainage lines as constraints for the AHP method. The transportation-related greenhouse gas (GHG) emissions are also considered to reduce environmental damage. Particle swarm optimization is used to determine the minimum transportation distance from the excavation zone to the dumpsite. As a sub-criteria of land use, the seaside is also considered a dumpsite compared with other options on the land side. The spatial analysis results of the case study show that suitable landside sites are available for the Trabzon tunneling project. Although coastal areas in Trabzon have been used for spoil dumping for filling purposes in the past, landside deposition is a viable alternative. The suitability ranks of land and coastal filling options are relatively similar, and selecting the seaside as the dumpsite for the Trabzon tunneling project reduces CO2 emissions. By adopting sustainable practices, we can realize a better future for our cities and the environment.
A Fully Coupled Numerical Model for Unbonded Post-Tensioned Timber Structures
(Springer, 2024) Dincer, A. Ersin; Demir, Abdullah
The paper presents a fully Lagrangian mesh-free solver to simulate the dynamic behavior of post-tensioned timber structures. Weakly Compressible Smoothed Particle Hydrodynamics (SPH) is employed to model both the timber and the tendon. An efficient and simple coupling method between the timber and the tendon is proposed by considering the numerical stability. Besides, the same coupling algorithm is used to model the interaction between column and beam elements. Although the column is treated as rigid in the simulations, the coupling algorithm accounts for the initial compression of the column resulting from post-tensioning. For the verification of the code for solids and material nonlinearity of timber, benchmark problems available in the literature are used. Finally, the solver's capability is demonstrated through dynamic analysis of post-tensioned timber structures. The solutions obtained for all the cases are in good agreement with the experimental and theoretical data, which indicates the applicability and accuracy of the solver.
Citation - WoS: 16
Citation - Scopus: 17
A Novel Procedure for the AHP Method for the Site Selection of Solar PV Farms
(Wiley, 2024) Demir, Abdullah; Dincer, A. Ersin; Yilmaz, Kutay
This study proposes a novel approach to enhance the analytic hierarchy process (AHP) for the selection of suitable sites for solar photovoltaic (PV) farms. This approach is particularly beneficial when it is possible to establish a predefined objective relation in the final weights of the AHP method. The methodology focuses on achieving this predefined relation introducing a systematic revision of the constants of related constraints. In this study, the costs of constructing a unit transmission line and road in the Kayseri Province are objectively related, and the initial constant matrix of the AHP method is iteratively revised until the relation of the final weights converges to the predefined one. The suitability of solar PV farm locations is classified into five classes, revealing approximately 28% (40-100% of suitability) of the province as favorably suitable and designating about 67% as restricted zones. The findings reveal notable distinctions between the revised weights and those derived from the conventional AHP method. The disparity in weights for various constraints varies from 13.5% to 7.2%. Consequently, the alterations in the area of suitability regions range from 3.4% to 50%. The revision of AHP weights results in a reduction in higher-suitability areas, coupled with a significant expansion in the region exhibiting lower suitability. Notably, the extent of change in the suitability map increases when the difference in ratios between two criteria obtained from the AHP and the predefined objective relation is high. The proposed method demonstrates its applicability in regions like Kayseri where an objective relation between criteria can be established. Given the inherent subjectivity of the AHP method, the proposed procedure becomes essential to attain more objective weights. Since the methodology objectively adjusts weights based on known ratios, it increases the accuracy and reliability of site selection studies.
Citation - WoS: 11
Citation - Scopus: 11
Hydro-Elastic Analysis of Standing Submerged Structures Under Seismic Excitations With SPH-FEM Approach
(Latin Amer J Solids Structures, 2020) Demir, Abdullah
In this paper, a fully coupled fluid structure interaction (FSI) method is used to investigate the hydro-elastic response of a fully submerged standing structure under seismic excitations. Two different domains (solid and fluid) are modelled by mesh based and meshless methods, respectively. Solid domain is modeled by finite element method (FEM) and fluid domain is modeled by smoothed particle hydrodynamics (SPH). Coupling between FEM and SPH is implemented via contact mechanics, and this method differs from others in the way of coupling mechanism. Invading SPH particles are solved together with finite elements by using contact mechanics, then, a fully coupled method is achieved. In the scope of this research, different seismic excitations are applied to a rectangular tank. Half of the tank is filled with water and a submerged rubber plate is attached to its mid bottom. Thus, two-dimensional motion of rubber plate and water is investigated experimentally and simulated numerically. [GRAPHICS] .
Batık Minarelerde Su Seviyesinin Yapıya Olan Etkisinin Sayısal Olarak İncelenmesi
(2021) Dinçer, Ali Ersin; Demir, Abdullah
Baraj göllerinin, sular altında bıraktığı yerleşim yerlerinin, su üstünde kalan son mirasları minarelerdir. Türkiye’de iki adet batık minare bulunmaktadır ve su üstünden görülebilmeleri ile cazibe merkezleri haline gelmişlerdir. Uzun yıllar sular altında kalması bu yapıların malzeme kalitesinin düşmesine sebep olmuştur/olacaktır. Bunun yanında; olası bir deprem esnasında var olan zemin hareketine ek olarak suyun çalkalanma etkisinin de eklenmesi bu minarelerin davranışlarının öngörülmesini daha da zorlaştırmaktadır. Yüksek Deprem riski barındıran bölgelerde yer alan her bu yapıların deprem esnasında su ile yapacağı etkileşimin sonuçlarının irdelenmesi gerekmektedir.Bu kapsamda su altında kalan minarelerin davranışlarını incelemek için idealleştirilmiş 2 boyutlu model oluşturulmuş ve yakın fay hareketleri uygulanmıştır. İdealleştirilmiş modelin analizi için tam akupajlı bir yapı-sıvı etkileşim (FSI) modeli kullanılmıştır. Bu modelde yapı kısmın modellenmesi için sonlu elemanlar yöntemi (FEM), sıvı kısmın modellenmesi için ise yumuşatılmış parçacık hidrodinamiği (SPH) kullanılmıştır. Bu iki farklı yöntem ile modellenen alanların etkileşimi için ise kontak mekanik kullanılmıştır. Kullanılan FSI yöntemi birçok problemin çözümü ile doğruluğu kanıtlanan geçerli bir yöntemdir. Farklı su seviyeleri ile oluşturulan idealleştirilmiş modeller, geliştirilen FSI yöntemi ile analiz edilmiş ve sonuçlar karşılaştırmalı olarak sunulmuştur. Elde edilen sonuçlar batık minarelerde su kütlesi etkisinin yakın fay altında ne kadar yüksek olduğunu ortaya koymaktadır. Su seviyesindeki değişim ile bu etki doğal olarak değişim göstermektedir. Çalışma kapsamında farklı su seviyeleri incelenerek batık minareler üzerindeki su kütlesi etkisi ayrıntılı olarak incelenmiştir.
Ardıl Baraj Yıkılmasının Mansapta Bulunan Elastik Yapı Üzerindeki Etkisinin Yapı-Sıvı Etkileşim Yöntemi ile İncelenmesi
(2020) Dinçer, Ali Ersin; Demir, Abdullah
Bu çalışmada yazarlar tarafından geliştirilen bir yapı-sıvı etkileşim yöntemi idealize edilmişardıl baraj yıkılması problemi için test edilmiştir. Bu doğrultuda geliştirilen yöntemde, sıvı kısımyumuşatılmış tanecik hidrodinamiği (smoothed particle hydrodynamics - SPH) ile, katı kısım ise sonluelemanlar (finite element – FE) yöntemi ile modellenmiş ve katı ile sıvı arasındaki akupaj, kontakmekanik kullanılarak gerçekleştirilmiştir. Aynı geometrideki ardıl barajlar aralarında mesafebırakmaksızın yerleştirilmiştir. En yüksek konumdaki barajın doluluk oranındaki değişim dikkatealımıştır. Yıkılan barajların mansaptaki elastik bir yapıya etkisi hem yapının deformasyonu yönündenhem de akışkandaki basınç dağılımları yönünden test edilmiştir. Ayrıca serbest akışkan yüzeyi profillerive su hızı profilleri de çalışmada sunulmuştur.
Citation - WoS: 12
Citation - Scopus: 12
Numerical and Experimental Investigation of Sloshing in a Water Tank With a Fully Coupled Fluid-Structure Interaction Method
(Inderscience Enterprises Ltd, 2021) Demir, Abdullah; Dincer, Ali Ersin; Ozturk, Sevki; Kazaz, Ilker
In the present study, the harmonic movement of fluid flow and the behaviour of elastic structure under this movement are investigated. Accordingly, a recently developed fluid-structure interaction method in which fluid and structure are simulated with smoothed particle hydrodynamics (SPH) and finite element method (FEM) is used. The interaction between fluid and the structure is satisfied with the contact mechanics. In order to validate the numerical model under harmonic movement, different experiments are used. First, the structure is assumed to be rigid and the pressures calculated on the structure are compared with the experimental data available in the literature. Similarly, free-surfaces are also validated with novel experiments carried out in the context of this study. In addition, the interaction between an elastic structure and fluid is investigated in the novel experiments in which a water tank having an elastic buffer in the middle is moved under harmonic horizontal movement and the deflection of the elastic buffer and free-surface profiles are measured. Comprehensive results are given for all validation cases. According to the results, the numerical method is successful and can be used in these types of problems.
Citation - WoS: 3
Citation - Scopus: 3
Application of Smoothed Particle Hydrodynamics to Structural Cable Analysis
(MDPI, 2020) Dincer, A. Ersin; Demir, Abdullah
In this study, a numerical model is proposed for the analysis of a simply supported structural cable. Smoothed particle hydrodynamics (SPH)-a mesh-free, Lagrangian method with advantages for analysis of highly deformable bodies-is utilized to model a cable. In the proposed numerical model, it is assumed that a cable has only longitudinal stiffness in tension. Accordingly, SPH equations derived for solid mechanics are adapted for a structural cable, for the first time. Besides, a proper damping parameter is introduced to capture the behavior of the cable more realistically. In order to validate the proposed numerical model, different experimental and numerical studies available in the literature are used. In addition, novel experiments are carried out. In the experiments, different harmonic motions are applied to a uniformly loaded cable. Results show that the SPH method is an appropriate method to simulate the structural cable.
Measuring Disaster Resilience in MENA Countries and Its Impact on Disaster Losses
(Nature Portfolio, 2025) Demir, Abdullah; Dincer, Ali Ersin; Dincer, Nazire Nergiz
Disaster resilience is a protective feature aimed at reducing the effects of natural disaster events and losses resulting from these events. This study develops a Disaster Resilience Index (DRI) for MENA countries to assess resilience across ten dimensions, including economic, social, institutional, infrastructural, and environmental factors. Unlike most prior studies, which focus on individual countries or use narrower sets of indicators, this study provides a multi-country, region-specific framework tailored to MENA's socio-economic and environmental heterogeneity. The index integrates geospatial data on disaster risk from geographic information systems (GIS) and a natural hazard risk dimension. Validation using disaster-related fatalities, supported by a dual PCA-based sensitivity analysis, confirms the robustness of the DRI and reveals that countries with stronger governance, higher human capital, and robust infrastructure tend to exhibit greater resilience, while fragile states and resource-dependent economies are more vulnerable. Notably, the DRI calculated using both dimension-specific and all-indicator PCA produces closely aligned values, indicating the choice of conducting PCA at the dimension level does not significantly alter the overall assessment of disaster resilience. These insights provide a foundation for targeted disaster risk reduction strategies and highlight areas where international cooperation and policy interventions can strengthen resilience in the region.
Citation - WoS: 59
Citation - Scopus: 60
A Novel Method for the Site Selection of Large-Scale PV Farms by Using AHP and GIS: A Case Study in Izmir, Turkiye
(Pergamon-Elsevier Science Ltd, 2023) Demir, Abdullah; Dincer, Ali Ersin; Yilmaz, Kutay
Effective and sustainable climate-friendly policies to reduce carbon dioxide emissions in line with the 2020 European Green Deal are necessary. Accordingly, renewable energies assumed a critical role, rendering the site selection of these systems very crucial. The present study proposes a novel approach to the site selection of large-scale photovoltaic (PV) plants using a combination of analytic hierarchy process (AHP) and geographic infor-mation system (GIS). In the study, the weights of criteria used for selecting solar PV panels are adjusted according to the installed capacity of the PV plant. The land of cost is included as a criterion in the AHP for the first time in PV plant site selection. Besides, a novel method called optimality-based site growing (OBSG) is introduced to further analyze the suitable sites obtained from GIS simulations and to determine the most suitable locations of PV farms. The proposed method is demonstrated with a case study of Turkiye, and the results show that the method effectively determines the most suitable locations for large-scale PV plants.
Citation - WoS: 1
Citation - Scopus: 1
A Cleaner Demolition Scheduling Methodology Considering Dust Dispersion: A Case Study for a Post-Earthquake Region
(Elsevier Sci Ltd, 2024) Dincer, Ali Ersin; Demir, Abdullah; Dilmen, Omer
In the present century, pollution is a primary concern for billions, prompting governments to advocate cleaner ways of production. Demolition activity is often an indispensable solution for structures that have completed their economic life. However, there are no regulations for the scheduling of demolition, except those related to the method of demolition and ensuring worker safety. Older buildings incorporate hazardous materials, such as asbestos, silica, and lead. These materials not only carry inherent risks, but high levels of aerosols in the air also adversely affect health. In this study, a demolition scheduling method is proposed, considering the dust dispersion. This research is pioneering, providing a structured demolition schedule to minimize the impact on both humans and the environment. In the methodology, a dispersion model is used to calculate the region exposed to dust and the concentration distribution throughout that area. In addition to the dust effect map, a vulnerability map is created using Analytical Hierarchy Process (AHP), aiding in determining interrelations between vulnerable sites. Thus, the dust effect map is derived by considering both dust exposure and the vulnerability map. The region affected by dust and the concentration of dust vary based on wind characteristics. By knowing the dust effect maps for the site (or all subsites) during specified time periods, a schedule can be defined. As a case study, schedules causing the absolute minimum and optimum dust effect rates are established for Kahramanmaras,, , , T & uuml;rkiye which recently experienced a devastating earthquake. The findings of the case study show that the dust effect on humans and the environment is significantly reduced. Consequently, by adhering to the proposed scheduling plan, human exposure to demolition dust is minimized, resulting in reduced medical expenses even without increasing the cost of the demolition.
Citation - WoS: 13
Citation - Scopus: 14
Comparative Analysis of Hybrid Geothermal-Solar Systems and Solar PV With Battery Storage: Site Suitability, Emissions, and Economic Performance
(Pergamon-Elsevier Science Ltd, 2025) Fedakar, Halil Ibrahim; Dincer, Ali Ersin; Demir, Abdullah
Renewable energy integration has become a critical focus in the global effort to reduce carbon emissions and diversify energy sources. In regions with distinct geographic features, such as Turkiye, combining different renewable technologies can offer enhanced energy security. This study investigates the site suitability and economic and environmental performance of hybrid geothermal-solar systems and solar PV systems with battery storage across the provinces of Osmaniye, Hatay, and Kilis, of Turkiye. Using the fuzzy-AHP method, site suitability is evaluated, addressing a key gap in comparing these systems' adaptability to varying geographic conditions. This study is the first to directly compare these two renewable energy technologies in terms of site suitability. The findings reveal significant differences in site suitability, with solar PV systems with battery storage demonstrating broader applicability across the region. The suitable sites (20-100 % suitability) cover 1260.82 km(2) for solar PV systems with battery storage and only 122.18 km(2) for hybrid geothermal-solar systems. In terms of environmental impact, hybrid geothermal-solar systems exhibit significantly lower carbon emissions, averaging 44.6 kg CO2/MWh, compared to 123.8 kg CO2/MWh for solar PV systems with battery storage. Economically, hybrid geothermal-solar systems also outperform with a lower levelized cost of electricity of $0.091 kWh versus $0.254 kWh for solar PV systems. These results highlight the environmental and economic advantages of hybrid geothermal-solar systems, while also emphasizing their limited scalability to regions with geothermal activity. Conversely, solar PV systems, despite their higher emissions and costs, offer greater flexibility and potential for widespread deployment.
Citation - WoS: 24
Citation - Scopus: 24
Wind Farm Site Selection Using GIS-Based Multicriteria Analysis With Life Cycle Assessment Integration
(Springer Heidelberg, 2024) Demir, Abdullah; Dincer, Ali Ersin; Ciftci, Cihan; Gulcimen, Sedat; Uzal, Nigmet; Yilmaz, Kutay
The sustainability of wind power plants depends on the selection of suitable installation locations, which should consider not only economic and technical factors including manufacturing and raw materials, but also issues pertaining to the environment. In the present study, a novel methodology is proposed to determine the suitable locations for wind turbine farms by analyzing from the environmental perspective. In the methodology, the life cycle assessment (LCA) of wind turbines is incorporated into the decision process. The criteria are ranked using analytical hierarchy process (AHP). The study area is chosen as the western region of Turkiye. The obtained suitability map reveals that wind speed is not the sole criterion for selecting a site for wind turbine farms; other factors, such as bird migration paths, distance from urban areas and land use, are also crucial. The results also reveal that constructing wind power plants in the vicinity of Izmir, canakkale, Istanbul, and Balikesir in Turkiye can lead to a reduction in emissions. Izmir and its surrounding area show the best environmental performance with the lowest CO2 per kilowatt-hour (7.14 g CO2 eq/kWh), to install a wind turbine due to its proximity to the harbor and steel factory across the study area. canakkale and the northwest region of Turkiye, despite having high wind speeds, are less environmentally favorable than Izmir, Balikesir, and Istanbul. The findings of LCA reveal that the nacelle and rotor components of the wind turbine contribute significantly (43-97%) to the environmental impact categories studied, while the tower component (0-36%) also has an impact.