Profile URL: https://hdl.handle.net/20.500.12573/2715
Job Title:Dr. Öğr. Üyesi
Email Address:cihan.ciftci@agu.edu.tr
Main Affiliation:02.03. İnşaat Mühendisliği
Status: Current Staff
ORCID:
0000-0001-9199-6437
0000-0001-9199-6437Scopus ID:
55615441700
55615441700YÖK Akademik: D096DB923A0FA882
Google Scholar:
UsLlbKMAAAAJ&hl
UsLlbKMAAAAJ&hlWeb of Science ID:
LNQ-9606-2024
LNQ-9606-2024Name Variants:
Ciftci, Cihan Cihan Çiftçi
15 results
Scholarly Output Search Results
Now showing 1 - 10 of 15
Conference Object Citation - WoS: 2Citation - Scopus: 1The Numerical Solutions for Stiff Ordinary Differential Equations by Using Interpolated Variational Iteration Method With Comparison to Exact Solutions(Amer Inst Physics, 2018) Ciftci, Cihan; Cayci, Hatice Sinem Sas; Atay, Mehmet Tarik; Toker, Batuhan; Guncan, Berkay; Yildirim, Afsin TalhaRecently proposed Interpolated Variational Iteration Method (IVIM) is used to find numerical solutions of stiff ordinary differential equations for both linear and nonlinear problems. The examples are given to illustrate the accuracy and effectiveness of IVIM method and IVIM results are compared with exact results. In recent analytical approximate methods based studies related to stiff ordinary differential equations, problems were solved by Adomian Decomposition Method and VIM and Homotopy Perturbation Method, Homotopy Analysis Method etc. In this study comparisons with exact solutions reveal that the Interpolated Variational Iteration Method (IVIM) is easy to implement. In fact, this method is promising methods for various systems of linear and nonlinear stiff ordinary differential equations as an initial value problem. Furthermore, IVIM is giving very satisfactory solutions when compared to exact solutions for nonlinear cases depending on the stiffness ratio of the stiff system to be solved.Article 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.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.Conference Object Citation - WoS: 1Citation - Scopus: 2Experimental Study on Increase of Bonding Strength of FRP Reinforcement in Concrete(Springer-Verlag Singapore Pte Ltd, 2021-11-27) Taskin, Furkan; Ciftci, CihanIn 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.Article Citation - WoS: 4Citation - Scopus: 6Experimental Investigation on the Bonding Strength of Knotted CFRP Bars in Bulk Plastics(MDPI, 2023-04-25) Ciftci, CihanImproving 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.Article Citation - WoS: 22Citation - Scopus: 28Loss in Moment Capacity of Tree Stems Induced by Decay(Springer Heidelberg, 2013-12-29) Ciftci, Cihan; Kane, Brian; Brena, Sergio F.; Arwade, Sanjay R.We model varying decay in tree cross-sections by considering bending theory to estimate moment capacity loss (MCL) for the sections. We compare MCL with experiments on selected oak trees. 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.Article Citation - WoS: 35Citation - Scopus: 41Analysis of the Probability of Failure for Open-Grown Trees During Wind Storms(Elsevier Sci Ltd, 2014-07) Ciftci, Cihan; Arwade, Sanjay R.; Kane, Brian; Brena, Sergio F.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. (C) 2014 Elsevier Ltd. All rights reserved.Article Citation - WoS: 6Citation - Scopus: 6A Rational Utilization of Reinforcement Material for Flexural Design of 3D-Printed Composite Beams(Sage Publications Ltd, 2019-08-05) Ciftci, Cihan; Sas, Hatice S.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.Conference Object Investigation of Compressive Performance of 3D Printed Carbon Fiber Reinforced Plastics(Soc. for the Advancement of Material and Process Engineering Janie@sampe.org, 2018) Eroglu, Fatih; Yildirim, Afsin Talha; Yesilyurt, Ogulcan; Sas, Hatice Sinem; Çiftçi, CihanThe 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. © 2018 Elsevier B.V., All rights reserved.Article A Methodology for Fast and Accurate Analytical Fragility Analysis of Linear Structural Systems during Wind Storms: ALFA(2023) Ciftci, CihanWind-storms are extremely destructive natural disasters that cause structural damage, and consequently severe personal injuries and casualties. To reduce these injuries and casualties, risk assessment of existing structures and improvement of building design regulations have become important. To assess the risk of structural systems during wind storms, analytical fragility analysis is a recently developed method by providing conditional failure probabilities for the structural systems. However, the analytical fragility analysis requires extensive computational time and effort which makes it infeasible for large scale structures. This proposed paper develops a new methodology (Analytical Linear Fragility Analysis: ALFA) to simplify and to expedite the analytical fragility analysis for linear structural systems without compromising accuracy. ALFA is exemplified by obtaining the fragility curves of 70 different multi-degree of freedom (MDOF) linear mass-column systems subjected to varying wind loading conditions. The fragility curves of the same mass-column systems were also obtained using Monte-Carlo (MC) based brute-force methodology, which is a commonly used computationally expensive method in literature, and results are compared. This comparison yields the conclusion that ALFA is 240 times faster than the brute-force one, without losing accuracy. Moreover, ALFA can be utilized for improvement of performance-based design specifications and for the preliminary risk assessment of nonlinear structural systems.Article Citation - WoS: 2Citation - Scopus: 1The Comparison of Fragility Curves of Moment-Resisting and Braced Frames Used in Steel Structures Under Varying Wind Load(Turkish Chamber Civil Engineers, 2025) Ozalp, Abdulkadir; Gokdemir, Hande; Ciftci, CihanIn this study, the performance of two different steel structure types (moment-resisting frame and braced frame) under wind loading was compared by addressing the fragility curves of these structure types. To perform this comparison, the dimensions of the members of these structural systems were first determined. Then, nonlinear static pushover analyses were conducted to assess the performance levels of each frame type. After applying these analyses, time-history analyses were performed with 100 different wind loads for each varying equivalent mean wind speed. Afterwards, the probability of exceeding the predetermined structural performance limits of the structure types was determined using Monte Carlo simulation method. Finally, the results of the simulation method were used to adapt the maximum likelihood estimation method to obtain the fragility curves of the structures. To conclude, it has been revealed that the material cost of the structure doubles when diagonal elements are used, but the wind speed required for a 100% collapse probability to occur in the braced frame is twice as high compared to the moment-resisting frame.