İnşaat Mühendisliği Bölümü Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/205

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Analysis of the probability of failure for open-grown trees during wind storms
(ELSEVIER SCI LTD, 2014) Ciftci, Cihan; Arwade, Sanjay R.; Kane, Brian; Brena, Sergio F.; 0000-0001-9199-6437; AGÜ, Mühendislik Fakültesi, İnşaat Mühendisliği Bölümü; Ciftci, Cihan
Although trees convey important environmental, economic, and sociological benefits on humans and society, they can also cause significant economic and societal disruptions, especially when subjected to wind storms in urban environments. Tools for proper assessment of the risk of these disruptions can be of significant benefit to society. In this research an approach to quantifying the failure probability for trees subject to wind storms is presented and illustrated by application to two specific maple trees in Massachusetts, USA. The approach entails four specific steps: (1) Random wind time history samples were generated using a modified Ochi–Shin spectrum, (2) these wind time histories were used as loading time histories on finite element models of the example trees in both summer (in-leaf) and winter (leafless), (3) maximum bending moments generated by the random wind time histories were compared to the failure (yield) moment of the tree at 1.4 m above ground, (4) the failure/fragility curves of the trees were estimated by Monte Carlo simulation for a range of average wind speeds and for 1000 independent wind time histories at each wind speed.
Effect of ambient temperature on the flexural behavior of 3D printed composite beams
(Soc. for the Advancement of Material and Process Engineering, 2018) Yıldırım, Afşin Talha; Eroglu, Fatih; Yesilyurt, Ogulcan; Albayrak, Kubilay; Sas, Hatice S.; Ciftci, Cihan; 0000-0001-9199-6437; AGÜ, Mühendislik Fakültesi, İnşaat Mühendisliği Bölümü; Yıldırım, Afşin Talha; Eroglu, Fatih; Yesilyurt, Ogulcan; Albayrak, Kubilay; Ciftci, Cihan
Adaptation of the additive manufacturing technology with 3D printers may lead to a new track in the manufacturing of composite materials. This additive manufacturing technology aims to mitigate manufacturing challenges and related design limitations of traditional composite manufacturing methods. The implementation of 3D printing of composite materials has the potential of decreasing the material cost by developing scientific methodologies to understand and optimize this printing process. This study focuses on understanding the flexural behavior of 3D printed composite beam elements and providing material data of both matrix and reinforcement components of composite materials. In this study, the flexural performance at different thermal conditions is experimentally investigated. This investigation involves the effect of the matrix material with and without short-fiber reinforcements for a specified fiber placement in the beam and fiber filaments placement in compression and tension sides of the composite beam elements along with the ambient temperature change.
Experimental Investigation on the Bonding Strength of Knotted CFRP Bars in Bulk Plastics
(MDPI, 2023) Ciftci, Cihan; 0000-0001-9199-6437; AGÜ, Mühendislik Fakültesi, İnşaat Mühendisliği Bölümü; Ciftci, Cihan
Improving the interfacial bonding strength of CFRP materials is crucial for enabling the development of novel composite beam structures with higher specific bending strength demanded by the composite industry. In this research study, for reinforced bulk plastic composites, the aim is to enhance the interfacial bonding strength of CFRP bar elements in bulk plastics by on the formation of knots. In this context, firstly, the knotted CFRP bars with varying cross-sectional areas were manufactured under laboratory conditions for the experimental investigation on the effect of knots on bonding strength. Commercially available smooth-surfaced CFRP bars were also purchased to be used as the reference. Then, all these CFRP bars were subjected to pull-out tests by using in bulk plastics. According to the test results, it was observed that the interfacial bonding strength of CFRP bars in bulk plastic materials could be increased up to 233% because of the knots.
Experimental Study on Increase of Bonding Strength of FRP Reinforcement in Concrete
(SPRINGER LINK, 2022) Taskin, Furkan; Ciftci, Cihan; 0000-0001-9199-6437; AGÜ, Mühendislik Fakültesi, İnşaat Mühendisliği Bölümü; Taskin, Furkan; Ciftci, Cihan
In the last two decades, the use of fiber-reinforced polymer (FRP) bars is of great interest to reinforce concrete beam structures due to its high specific strength, effective corrosion resistance, and low cost fabrication. Therefore, the flexural performance of these reinforced concrete beams containing FRP bars has been investigated by researchers for years with great interest. According to these investigations, one of the major problems is weak bonding strength between these bars and concrete material. Since, this major problem causes low flexural capacity, high deflection, and high crack widths for the reinforced concrete beams. Hence, the use of FRP bars by engineers does not sufficiently become widespread and also the engineering applications of these useful materials are still limited today. In this study, it is aimed to present an applicable solution regarding the bonding failures of the FRP bars in structurally reinforced concrete beams. For this solution, reinforced concrete beam samples were produced by using FRP materials on which knotted structures were formed. Then these samples were tested under 3-point bending tests. Furthermore, smooth-surfaced FRP bars and traditional deformed steel rebars were also used as reinforcing materials in the concrete beam samples for the comparison of the flexural capacities of each sample in order to investigate the effects of the reinforcing materials on the bonding strength. To conclude, the knotted FRP bars provide a significant contribution on the flexural capacity due to the increase of the bonding strength between the reinforcing material and the concrete in the beams.
Investigation of compressive performance of 3D printed carbon fiber reinforced plastics
(Soc. for the Advancement of Material and Process Engineering, 2018) Eroglu, Fatih; Yildirim, Afsin Talha; Yesilyurt, Ogulcan; Sas, Hatice S.; Ciftci, Cihan; 0000-0001-9199-6437; AGÜ, Mühendislik Fakültesi, Makine Mühendisliği Bölümü; Eroglu, Fatih; Yildirim, Afsin Talha; Yesilyurt, Ogulcan; Ciftci, Cihan
The compressive performance of Carbon Fiber Reinforced Plastics (CFRP) is an extensive research area of crashworthy structures due to high Specific Energy Absorption (SEA) rates. However, the traditional composite manufacturing techniques are limiting the implementation of CFRP in crash components of automobile industry. These limitations can be minimized with 3D printing technology, which can be replaced with the traditional composite manufacturing techniques by providing flexibility especially in terms of geometric complexities. In this study, the compressive performance of 3D printed CFRP samples with square and circular cross-sections are examined with different thickness and fiber volume fraction values. SEA rates obtained from axial compressive tests are compared and compressive performance of 3D printed samples is optimized in terms of crashworthiness.
Investigation of the Mechanical Behavior of a New Generation Wind Turbine Blade Technology
(MDP, 2023) Ciftci, Cihan; Erdogan, Ayse; Genc, Mustafa Serdar; 0000-0001-9199-6437; AGÜ, Mühendislik Fakültesi, İnşaat Mühendisliği Bölümü; Ciftci, Cihan
Wind turbine blades are one of the largest parts of wind power systems. It is a handicap that these large parts of numerous wind turbines will become scrap in the near future. To prevent this handicap, newly produced blades should be recyclable. In this study, a turbine blade, known as the new generation of turbine blade, was manufactured with reinforced carbon beams and recycled, low-density polyethylene materials. The manufacturing addressed in this study reveals two novelties: (1) it produces a heterogeneous turbine blade; and (2) it produces a recyclable blade. In addition, this study also covers mechanical tests using a digital image correlation (DIC) system and modeling investigations of the new generation blade. For the mechanical tests, displacement and strain data of both new generation and conventional commercial blades were measured by the DIC method. Instead of dealing with the modeling difficulty of the new generation blade's heterogeneity we modeled the blade structural system as a whole using the moment-curvature method as part of the finite element method. Then, the behavior of both the new generation and commercial blades at varying wind speeds and different angles of attack were compared. Consequently, the data reveal that the new generation blades performed sufficiently well compared with commercial blades regarding their stiffness.
Loss in moment capacity of tree stems induced by decay
(SPRINGER HEIDELBERG, 2014) Ciftci, Cihan; Kane, Brian; Brena, Sergio F.; Arwade, Sanjay R.; 0000-0001-9199-6437; AGÜ, Mühendislik Fakültesi, İnşaat Mühendisliği Bölümü; Ciftci, Cihan
Key message We model varying decay in tree crosssections by considering bending theory to estimate moment capacity loss (MCL) for the sections. We compare MCL with experiments on selected oak trees. Abstract Tree failures can damage property and injure people, sometimes with fatal consequences. Arborists assess the likelihood of failure by examining many factors, including strength loss in the stem or branch due to decay. Current methods for assessing strength loss due to decay are limited by not accounting for offset areas of decay and assuming that the neutral axis of the cross-section corresponds to the centroidal axis. This paper considers that strength loss of a tree can be related to moment capacity loss (MCL) of the decayed tree cross-section, because tree failures are assumed to occur when induced moments exceed the moment capacity of the tree cross-section. An estimation of MCL is theoretically derived to account for offset areas of decay and for differences in properties of wood under compressive and tensile stresses. Field measurements are used to validate the theoretical approach, and predictions of loss in moment capacity are plotted for a range of scenarios of decayed stems or branches. Results show that the location and size of decay in the cross-section and relative to the direction of sway are important to determine MCL. The effect of wood properties on MCL was most evident for concentric decay and decreased as the location of decay moved to the periphery of the stem. The effect of the ratio of tensile to compressive moduli of elasticity on calculations of MCL was negligible. Practitioners are cautioned against using certain existing methods because the degree to which they over- or underestimate the likelihood of failure depended on the amount and location of decay in the cross-section.
A rational utilization of reinforcement material for flexural design of 3D-printed composite beams
(SAGE PUBLICATIONS LTD, 1 OLIVERS YARD, 55 CITY ROAD, LONDON EC1Y 1SP, ENGLAND, 2019) Ciftci, Cihan; Sas, Hatice S.; 0000-0002-5179-2509; 0000-0001-9199-6437; AGÜ, Mühendislik Fakültesi, İnşaat Mühendisliği Bölümü
Recent developments in composite industry address the adaptation of 3D printing technology to overcome the design and manufacturing challenges of the traditional composite processing techniques. This adaptation can be performed with the development of design methodologies corresponding to the type of structural load-carrying members in a structure. Considering the frequently use of beams in structures, the development of the design methodology of beams is essential for the adaptation of the additive manufacturing. Therefore, in this paper, the flexural loading concept is analytically formulated to derive moment capacity for the flexural behavior of 3D-printed composite beams. Then, the formulation is adapted to develop a design methodology of 3D-printed laminates under flexural loading. Additionally, the analytical solutions developed for the design methodology presented in this paper were verified with a good agreement with experimental studies.
Wind farm site selection using GIS-based multicriteria analysis with Life cycle assessment integration
(SPRINGER, 2024) Demir, Abdullah; Dinçer, Ali Ersin; Çiftçi, Cihan; Gülçimen, Sedat; Uzal, Nigmet; Yılmaz, Kutay; 0000-0002-6392-648X; 0000-0002-4662-894X; 0000-0001-9199-6437; 0000-0002-8967-3484; 0000-0002-0912-3459; AGÜ, Mühendislik Fakültesi, İnşaat Mühendisliği Bölümü; Demir, Abdullah; Dinçer, Ali Ersin; Çiftçi, Cihan; Gülçimen, Sedat; Uzal, Nigmet
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 Türkiye. 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 İzmir, Çanakkale, Istanbul, and Balıkesir in Türkiye can lead to a reduction in emissions. İzmir 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. Çanakkale and the northwest region of Türkiye, despite having high wind speeds, are less environmentally favorable than İzmir, Balıkesir, 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.

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