Sürdürülebilir Kalkınma Amaçları
Yazarlar
- Çavdar, Ahmet(5)
- Çullu, Mustafa(3)
- Akpinar, Salih(2)
- Arslan, Metin(2)
- Aydin, Murat Demir(2)
- Bayraktar, Alemdar(2)
- Cakir, Tufan(2)
- Tonkaz, Duygu Erkal(2)
- Tonkaz, Mehmet(2)
- Topal, Umut(2)
- Yetgin, Şükrü(2)
- Özel, Adnan(2)
- Adanur, Süleyman(1)
- Akay, Seref(1)
- Akdeniz, Cemre(1)
- Akdeniz-Leblecicier, Merve(1)
- Akpinar, Adem(1)
- Alemdar, Alkan(1)
- Altunişik, Ahmet Can(1)
- Alwasel, Saleh H.(1)
- Anik, Ihsan(1)
- Aydemir, Sezgin(1)
- Azadi, Hossein(1)
- Benli, Tolga(1)
- Bingol, Zeynebe(1)
- Bolat, Hakan(1)
- Can, G.(1)
- Can, Ömer(1)
- Ceylan, Savas(1)
- Coskun, Eda(1)
- De Smet, Seppe(1)
- Demir, M.(1)
- Dogru, Tarik(1)
- Doru, Muhammet Onur(1)
- Durmaz, Lokman(1)
- Durmuş, Gökhan(1)
- Döner, Fatih(1)
- Emengen, Atakan(1)
- Erdogdu, Ferruh(1)
- Erol, Ismail(1)
Yayınlar
- MakaleYalnız künye2013The effects of high temperature on mechanical properties of cementitious composites reinforced with polymeric fibers
Çavdar, Ahmet
Polymeric fibers are cheap and popular materials used in the concrete industry, and they may improve the mechanical properties of cementitious composites under high temperature. In this study, three different types of polymeric fibers - Copolymer Polypropylene/polyethylene (CPP), Homopolymer Polypropylene (HPP), and Aramid (AR) - are added to cement mortars with the aim to investigate their mechanical contributions to mortars under high temperature, comparatively. These fibers are added into mortars in five different ratios (0.0%, 0.3%, 0.6%, 0.9% and 1.2%) by volume. The mortars are subjected to following temperatures: 21 °C (normal conditions), 100 °C (oven dry), 450 °C, 650 °C and 850 °C. It is concluded that polymeric fibers used in this study contribute to the flexural strength of mortars under normal dry conditions (100 °C). This effect continues clearly up to 450 °C and polymeric fibers show effects on flexural strength especially at 450 °C. Each fiber shows the best performance different addition ratio when flexural and compressive strength are taken into consideration at the same time under high temperature. The highest increase in flexural strength and the lowest decrease in compressive strength are at 0.3-0.9% fiber addition ratio for HPP, at 0.3-0.6% fiber addition ratio for CPP and at 0.9% fiber addition ratio for AR for every temperature.
- MakaleYalnız künye20133-D non-linear stress analysis on the adhesively bonded T-joints with embedded supports
Akpinar, Salih; Aydin, Murat Demir; Temiz, Şemsettin; Özel, Adnan
In the present study, it is aimed to compare mechanical behaviors of T-joint types with embedded and non-embedded supports subjected to bending moment. For this purpose, after experimental studies on the two different T-joint types were conducted, stress analyses in the T-joints were performed with a three-dimensional finite element method by considering the geometrical non-linearity and the material non-linearities of the adhesive (DP460) and adherend (AA2024-T3). Finally, stress analyses and experimental results show that the variation of the geometry of the bonding zone, e.g., embedding the supports, would change the stress distributions and strength of the joint. Additionally, it is seen that T-joints with embedded supports carry 30% more load than T-joints with non-embedded supports although their bending stiffnesses decrease.
- MakaleYalnız künye2012Fast practical analytical model for analysis of backfill-rectangular tank-fluid interaction systems
Cakir, Tufan; Livaoglu, Ramazan
The paper describes a simple, efficient and reasonably accurate analytical model for analysis of backfill-rectangular tank-fluid interaction systems. The presented model uses Housner's two-mass approximation for fluid interaction and mass-spring-dashpot system for backfill interaction and accommodates a variety of features that may affect the behavior of rectangular tanks including fluid volume, backfill geometry, soil properties and flexible/rigid wall types. Unlike the conventional finite element and the finite difference models that require considerable effort and knowledge to prepare the input data, the proposed model requires only a few pieces of data to define the problem and control the analysis. A series of finite element simulations were also fulfilled on two real rectangular tanks subjected to backfill and fluid effects. A reasonably good accord was obtained comparing the analytical predictions to results from numerical simulations. Thus, it can be stated that the model may be used effectively to perform a broad suite of parametric studies at the design stage and also as a reliable tool for estimating the system behavior. The results obtained from parametric seismic analyses indicated that backfill interaction, wall flexibility and fluid interaction considerably affect the lateral displacements. The sloshing response, however, was not practically affected by the backfill interaction and the wall flexibility.
- MakaleYalnız künye2012A study on the effects of high temperature on mechanical properties of fiber reinforced cementitious composites
Çavdar, Ahmet
The flexural strength and ductility properties of cementitious composites (mortar) under high temperature may be significantly improved by incorporating different types of fibers. In this study, four different types of fibers are added to cement mortars with the aim to investigate their mechanical contributions to mortars under high temperature, comparatively. Polypropylene (PP), carbon (CF), glass (GF) and polyvinyl alcohol (PVA) fibers are chosen for research. These fibers are added into mortars in five different ratios (0.0%, 0.5%, 1.0%, 1.50% and 2.0%) by volume. The mortars are subjected to the following temperatures: 21°C (normal conditions), 100°C (oven dry), 450°C and 650°C. The mechanical properties investigated are flexural strength, deflection and compressive strength of the cement mortars. In addition, thin sections of mortars are investigated to obtain changes in mortar because of high temperature. It is concluded that all fiber types contribute to the flexural strengths of mortars under high temperature. However, this contribution decreases with an increase in temperature. The samples with PVA show the best flexural performance (75-150%) under high temperature. CF which does not melt under high temperature also gives high flexural strength (11-85%). The compressive strengths of the mortars reduce under high temperature or with fiber addition. The highest increase in flexural strength and the lowest decrease in compressive strength is at 0.5-1.5% for CF if all temperature conditions are taken into consideration. The optimum fiber addition ratios of the samples containing PP and GF are 0.5% by volume. And for PVA, it is between 0.5% and 1.5% by volume.
- MakaleYalnız künye2011Alternative gaseous fuels in port fuel injection spark ignition engines
Sezer, I.
This paper investigates the use of alternative gaseous fuels in port fuel injection spark ignition engines via the Lotus engine simulation program. To this end, the engine model for a port fuel injection spark ignition engine was designed, and engine performance was determined separately for gasoline and alternative gaseous fuels, i.e. compressed natural gas and liquefied petroleum gas. According to the results, brake thermal efficiency increases while engine performance and fuel consumption decrease with methane and propane when compared to gasoline under the same conditions. While a slight increase in the fuel/air equivalence ratio of gaseous fuels improves the engine performance, fuel consumption remains almost stable. Another factor that enhances engine performance is the increasing compression ratio for methane and propane. In this manner, performance values that are closer/equal to gasoline are achieved. Under these conditions, fuel consumption decreases notably, while significant increases are observed in brake thermal efficiency.
- MakaleYalnız künye2011Experimental and analytical system identification of Eynel arch type steel highway bridge
Altunişik, Ahmet Can; Bayraktar, Alemdar; Sevim, Bariş; Özdemir, Hasan
This paper describes a full scale arch type steel highway bridges, its finite element modelling and Operational Modal Analysis. Eynel Highway Bridge which has arch type structural system with a total length of 336 m and located in the AyvacIk county of Samsun, Turkey is selected as a case study. The bridge connects the villages which are separated with Suat Uǧurlu Dam Lake. The three dimensional finite element model is constructed using project drawings and an analytical modal analysis is then performed to generate natural frequencies and mode shapes in the three-orthogonal directions. The ambient vibration tests on the bridge deck under natural excitation such as traffic, human walking and wind loads are conducted using Operational Modal Analysis. Sensitive seismic accelerometers are used to collect signals obtained from the experimental tests. To obtain experimental dynamic characteristics, two output-only system identification methods are employed namely, Enhanced Frequency Domain Decomposition method in the frequency domain and Stochastic Subspace Identification method in time domain. The correlation between the finite element model and experimental results is studied. Good agreement is found between dynamic characteristics in the all measurement test setups performed on the bridge deck. It is demonstrated that the ambient vibration measurements using Enhanced Frequency Domain Decomposition and Stochastic Subspace Identification methods are enough to identify the most significant modes of steel highway bridges. It is seen that there are some differences between analytical and experimental natural frequencies and experimental natural frequencies are generally bigger than the others.
- MakaleYalnız künye2010The synthesis and characterization of metal-free and metallophthalocyanine polymers by microwave irradiation containing diazadithia macrocyclic moieties
Kaya, Elif Celenk; Karadeniz, Huelya; Kantekin, Halit
A tetranitrile monomer was synthesized by nucleophilic aromatic substitution of N,N'-(2,2'-(propane-1,3-diylbis(sulfanediyl))bis(ethane-2,1-diyl))bis(4-methylbenzenesulfonamide) onto 4-nitrophthalonitrile. A metal-free phthalocyanine polymer was prepared by the reaction of the tetranitrile monomer under N-2 in the presence of 2-(dimethylamino)ethanol at 145 degrees C for 24 h. Zinc(II), copper(II), cobalt(II), nickel(II), lead (II), phthalocyanine polymers were prepared by reaction of the tetranitrile with the chlorides of zinc (II), copper (II), cobalt (II), nickel (II), lead (II), employing microwave irradiation in the presence 2-(dimethylamino)ethanol at 175 degrees C, 350 W for 10 min. The thermal stabilities of the phthalocyanine compounds were determined by thermogravimetric analysis. The new compounds were characterized by a combination of IR, H-1 NMR, C-13 NMR, UV-vis, elemental analysis and MS spectral data. (C) 2009 Elsevier Ltd. All rights reserved.
- MakaleAçık Erişim20104D cadastres: First analysis of legal, organizational, and technical impact-With a case study on utility networks
Döner, Fatih; Thompson, Rod; Stoter, Jantien; Lemmen, Christiaan; Ploeger, Hendrik; van Oosterom, Peter; Zlatanova, Sisi
The increasing complexity and flexibility of modern land use requires that cadastres need an improved capacity to manage the third dimension. As the world is per definition not static, there also will be needs in relation to the representation of the temporal (fourth) dimension either integrated with the spatial dimensions or as separate attribute(s). In this paper, registration of utility networks in cadastre are considered in this 3D. +. time (=4D) context. A number of countries in the world have developed methods to register utility networks complying with their legal, organizational, and technical structure. We researched the different approaches of three specific countries: Turkey, The Netherlands and Queensland, Australia. These are analysed to evaluate a solution that matches legal, organizational, and technical cadastral requirements in the most optimal way.
- MakaleYalnız künye2010Investigation of mechanical and mineralogical properties of mortars subjected to sulfate
Çavdar, Ahmet; Yetgin, Şükrü
The durability can be described as concrete's resistance to the destructive influences of a medium containing acid, sulfate and/or various chemicals and mechanical effects. The main objective of this study is investigation of mechanical and mineralogical properties of cement mortar with different pozzolanic compositions and subjected to sulfated medium. In the study, the mortars produced with cement samples having seven different compositions and varied with an air-entraining agent were subjected to the influence of sulfate. This study is supported by thin section and X-ray powder diffraction (XRPD) investigations, in addition to being subjected to the basic tests, such as compression and flexure. The most important findings obtained from the study are that the compact structure has more effective properties against sulfate effects for cement mortars than pozzolanic materials' effects and the highest pozzolanic material ratio is restricted about 25-30% by mass because this ratio is a boundary of mechanical properties.
- MakaleYalnız künye2010Investigation of abrasion resistance of cement mortar with different pozzolanic compositions and subjected to sulfated medium
Çavdar, Ahmet; Yetgin, Şükrü
The durability phenomenon for concrete, or cement mortar, has gained attention recently as one of the important mechanical properties. It can be described as concrete's resistance to the destructive influences of a medium containing acid, sulfate and/or various chemicals and mechanical effects, like abrasion. Most of the studies attempted to improve these individual properties in concrete. However, concrete can be subjected to two or more of these effects simultaneously. In this study, the mortars produced with cement samples having seven different compositions and varied with an air-entraining agent were subjected to the influence of sulfate and abrasive effects simultaneously. In this study, several examples were evaluated using samples cured for six different periods throughout one year. This study is supported by thin section and XRPD investigations, in addition to being subjected to the basic tests, such as compression, flexure and abrasion. If the most important findings obtained from the study are summarized, it is seen that a compact cement matrix is more effective against both sulfate and abrasive effects than mineral additives. The mortars subjected to coupled (sulfate and abrasive) effects show less durability if compared to ones cured in water and later abraded.
- MakaleYalnız künye2010Stochastic finite element analysis of a cable-stayed bridge system with varying material properties
Çavdar, Özlem; Bayraktar, Alemdar; Adanur, Süleyman
Stochastic seismic finite element analysis of a cable-stayed bridge whose material properties are described by random fields is presented in this paper. The stochastic perturbation technique and Monte Carlo simulation (MCS) method are used in the analyses. A summary of MCS and perturbation based stochastic finite element dynamic analysis formulation of structural system is given. The Jindo Bridge, constructed in South Korea, is chosen as a numerical example. The Kocaeli earthquake in 1999 is considered as a ground motion. During the stochastic analysis, displacements and internal forces of the considered bridge are obtained from perturbation based stochastic finite element method (SFEM) and MCS method by changing elastic modulus and mass density as random variable. The efficiency and accuracy of the proposed SFEM algorithm are evaluated by comparison with results of MCS method. The results imply that perturbation based SFEM method gives close results to MCS method and it can be used instead of MCS method, especially, if computational cost is taken into consideration.
- MakaleYalnız künye2009Multiobjective optimization of laminated composite cylindrical shells for maximum frequency and buckling load
Topal, Umut
This paper deals with multiobjective optimization of laminated cylindrical shells to maximize a weighted sum of the frequency and buckling load under external load. The layer fibre orientation is used as the design variable and the multiobjective optimization is formulated as the weighted combinations of the frequency and buckling under external load. The first order shear deformation theory is used for the finite element formulation of the laminated shells. Five shell configurations with eight layers are considered as candidate designs. The modified feasible direction method (MFD) is used as optimization routine. For this purpose, a program based on FORTRAN is used for the optimization of the laminated shells. Finally, the effect of different weighting ratios, shell aspect ratio, shell thickness-to-radius ratios and boundary conditions on the optimal designs is investigated and the results are compared.
- MakaleYalnız künye2009Frequency optimization of laminated general quadrilateral and trapezoidal thin plates
Topal, Umut
This paper deals with frequency optimization of symmetrically laminated angle-ply general quadrilateral and trapezoidal thin plates. The objective function is to maximize the fundamental frequency of the quadrilateral and trapezoidal laminated plates and the fibre orientation is considered as design variable. The mathematical formulation is based on the classical laminated plate theory (CLPT) for the frequency analysis. The modified feasible direction (MFD) method is used as the optimization routine. Therefore, a program based on FORTRAN is used. Finally, the significant effects of aspect ratios, boundary conditions, taper ratios and unsymmetric trapezoidal plates on the optimal results are investigated and the results are compared.
- MakaleYalnız künye2009Thermal buckling load optimization of laminated skew plates
Topal, U.; Uzman, Ü.
In this study thermal buckling load optimization of laminated skew plates subjected to uniformly distributed temperature load is investigated. All of the laminates considered are assumed to have fully clamped boundary conditions, though the general boundary conditions may also be studied without any difficulty. The objective function is to maximize the critical temperature capacity of the laminated skew plates and the fibre orientation is considered as design variable. The first-order shear deformation theory is used in the mathematical formulation. Nine-node Lagrangian rectangular plate element is used for the finite element solution of the skew laminates. The temperature field is assumed to be uniform over the plate surface and varies in the thickness direction only. Modified feasible direction method (MFD) is used for the optimization routine. A program based on FORTRAN is used for the optimization problem. Finally, the effect of number of layers, skew angles, aspect ratios, width-to-thickness ratios and antisymmetric lay-up on the optimal designs is investigated and the results are compared.
- MakaleYalnız künye2007Optimum shape design of shell structures
Uysal, Habib; Gul, Rustem; Uzman, Umit
A finite element-based shape optimization program has been developed for three-dimensional shell structures and the shape optimization of shell structures has been performed. The shape optimization program is implemented by a job control language and a reliable finite element package program, ANSYS, is used for structural analysis. To achieve the shape optimization, different principles such as structural analysis, automatic mesh generation, sensitivity analysis and mathematical programming are inter-related. The objective is to minimize the weight of the shell structure under constraints that are the maximum value of the von Mises stress in each element and the move limit for each design variable. The design sensitivities are calculated using the finite difference method. The search for the final shape of a structure is performed using the linear programming technique. Several examples are provided.
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