Civil Engineering / İnşaat Mühendisliği
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Article Citation - WoS: 1Citation - Scopus: 1Çelik Köprü I-kirişlerine Yanal Destek Sağlayan Trapez Sac Kalıpların Mukavemeti(Turkish Chamber of Civil Engineers, 2009) Eğilmez, Oğuz Özgür; Alkan, DenizTrapez Sac Kalıplar (TSK) hem çelik bina hem de çelik köprü sektörlerinde beton döşemenin kalıp sistemi olarak sıklıkla kullanılmaktadırlar. TSK’ler her ne kadar bina inşaatlarında çelik I-kirişlere yanal destek sağlayıcı elemanlar olarak işlev görseler de, çelik köprü sektöründe trapez sac kalıplardan destek elemanları olarak yararlanılmasına izin verilmez. Ancak, önceki çalışmalar birleşim detayının geliştirilmesi durumunda TSK sisteminin kirişin yanal kararlılığına belirgin şekilde destek sağlayabildiğini göstermiştir. Bu makale halen devam etmekte olan ve TSK’lerin mukavemetinin incelendiği analitik bir çalışmanın ara sonuçlarını içermektedir. Geçmişte, TSK sistemleriyle desteklenen köprü kirişlerin genel burkulma davranışını irdeleyen basit sonlu elemanlar modelleri (SEM) kullanılmıştır. Bu çalışmada TSK’leri hem birbirlerine hem de kirişlere bağlayan vidalardaki kararlılık destek kuvvetlerini belilemek için kullanılan geliştirilmiş bir sonlu elemanlar modelinin sonuçlarına yer verilmiştir. Bu çözümleme sonuçları TSK’lerin içermesi gereken mukavemet ihtiyacını belirleyecek olan bir tasarım yönteminin geliştirilmesinde kullanılacaktır.Conference Object A Boundary Element Method for Axisymmetric Elastodynamic Analysis(John Wiley and Sons Inc., 1996) Özkan, Gonca; Mengi, YalçınA new numerical method is proposed for the boundary element analysis of axisymmetric bodies. The method is based on complex Fourier series expansion of boundary quantities in circumferential direction, which reduced the boundary element equation to an integral equation in (r-z) plane involving the Fourier coefficients of boundary quantities, where r and z are the coordinates of the r theta z cylindrical coordinate system. The kernels appearing in these integral equations can be computed effectively by discrete Fourier transform formulas together with the fast Fourier transform (FFT) algorithm, and the integral equations (r-z) plane can be solved by Gaussian quadrature, which establishes the Fourier coefficients associated with boundary quantities. The Fourier transform solution can then be inverted into r theta z space by using again discrete Fourier transform formulas together with FFT algorithm. In this paper, we present the formulation of the proposed method which is outlined above. A comparison is given between the existent methods in literature and our method, which shows that the use of FFT algorithm for the integrations in circumferential direction provides considerable saving in computer time.Conference Object Upscaling Surface Flow Equations Depending Upon Data Availability at Different Scales(Springer Verlag, 2003) Tayfur, GökmenSt. Venant equations, which are used to model sheet flows, are point-scale, depth-averaged equations, requiring data on model parameters at a very fine scale. When data are available at the scale of a hillslope transect, the point equations need to be upscaled to conserve the mass and momentum at that scale, Hillslope-scale upscaled model must be developed if data are available at that scale. The performance of the three models applied to simulate flows from non-rilled surfaces revealed that the hillslope-scale upscaled model performs as good as the point-scale model though it uses far less data. The transectionally-upscaled model slightly underestimates the observed data.Conference Object Citation - WoS: 1Effect of Water Source on Human Health: a Case Study From Biga Peninsula, Turkey(2009) Baba, Alper; Gündüz, OrhanThe concentrations of certain elements including arsenic (As), fluoride (F) and aluminum (AI) were measured in groundwater in the different part of Biga Peninsula which is located in the western parts of Turkey. The concentration values of As and AI in groundwater ranged between 10-40 ppb, 0.5-0.8 ppm and 1-11.5 ppm, respectively, in this region. Al values exceed the Turkish drinking water standard value of 0.2 ppm. Furthermore, As concentration in water from alteration zones exceed the drinking water standard value of 10 ppb. Based on this background, this study was intended to investigate the source of these heavy metals and its neurotoxin effects on human health as many people living in this region have undergone medical treatment, which are believed to be related to the quality of water resources originating from densely altered volcanic rocks.Article Citation - WoS: 53Citation - Scopus: 63Effective Stress Principle for Saturated Fractured Porous Media(Wiley-Blackwell, 1995) Tuncay, Kağan; Çorapçıoğlu, M. YavuzAn effective stress principle for saturated fractured porous media is proposed based On the double-porosity representation. Both the solid grains and the fractured porous medium are assumed to be linearly elastic materials. The derivation employs volume averaging technique to obtain macroscopic scale expressions. Two parameters, the bulk modulus of the fractured medium and bulk modulus of the porous matrix, are introduced in the formulation. The final expression reduces to the one obtained by Blot and Willis [1957], Skempton [1960], Nur and Byeerle [1971], and Verruijt [1984] when the volume fraction of the fractures vanishes, that is, for a nonfractured porous medium.Article Citation - WoS: 72Citation - Scopus: 79Artificial Neural Networks for Estimating Daily Total Suspended Sediment in Natural Streams(IWA Publishing, 2006) Tayfur, Gökmen; Güldal, VeyselEstimates of sediment loads in natural streams are required for a wide spectrum of water resources engineering problems from optimal reservoir design to water quality in lakes. Suspended sediment constitutes 75-95% of the total load. The nonlinear problem of suspended sediment estimation requires a nonlinear model. An artificial neural network (ANN) model has been developed to predict daily total suspended sediment (TSS) in rivers. The model is constructed as a three-layer feedforward network using the back-propagation algorithm as a training tool. The model predicts TSS rates using precipitation (P) data as input. For network training and testing 240 sets of data sets were used. The model successfully predicted daily TSS loads using the present and past 4 days precipitation data in the input vector with R2 = 0.91 and MAE = 34.22 mg/L. The performance of the model was also tested against the most recently developed non-linear black box model based upon two-dimensional unit sediment graph theory (2D-USGT). The comparison of results revealed that the ANN has a significantly better performance than the 2D-USGT. Investigation results revealed that the ANN model requires a period of more than 75 d of measured P-TSS data for training the model for satisfactory TSS estimation. The statistical parameter range (xmin - xmax) plays a major role for optimal partitioning of data into training and testing sets. Both sets should have comparable values for the range parameter.Article Citation - WoS: 2Citation - Scopus: 3Köprülerde Deneysel Modal Analiz Uygulamaları(TMMOB İnşaat Mühendisleri Odası, 2009) Dönmez, Cemalettin; Karakan, EyyübDeneysel modal analiz son 30 yıldır çeşitli araştırmacılar tarafından yapısal sistemlerin durum tespiti/izlemesi ve hasar tanılaması amacıyla kullanılmaktadır. Ölçüm ve analizlerin tekniğine uygun olarak tasarlanıp uygulanması durumunda bu teknik ile yapısal bir sistemin dinamik özellikleri (frekanslar, sönüm oranları ve modal şekilleri) kestirilebilmektedir. Sistemde oluşacak herhangi bir hasarın sistemin sıkılığını ve aynı zamanda dinamik özelliklerini değiştireceği gerçeğinden yola çıkılırsa, hasar öncesi ve sonrası dinamik özelliklerin izlenmesi sayesinde yapıda oluşan hasarlar tahribatsız bir biçimde tespit edilebilir. İzmir Yüksek Teknoloji Enstitüsü (İYTE), İnşaat Mühendisliği Bölümü’nde bir TÜBİTAK projesi kapsamında deneysel modal analiz tekniğinin kullanılması yönünde çalışmalar yapılmaktadır. Bu bildiri kapsamında deneysel modal analiz tekniklerinin köprülerin durum tespiti ve hasar tanılamasında ne şekilde uygulanabileceği konusunda kısa bir özet verilecek ve İYTE’de bugüne kadar öğrendiğimiz teknikleri uygulamada gösterebilmek amacı ile laboratuvarda imal, basitleştirilmiş bir köprü maketi üzerinde modal analiz teknikleri kullanılacak ve sonuçlar sergilenecektir. Ayrıca maket köprünün sonlu elemanlar modeli kurularak analiz ve deney sonuçları karşılaştırılacak ve sonuçlar irdelenecektir.Article Citation - WoS: 1Citation - Scopus: 1Kablolu Bir Köprünün Deprem Davranışının Μ-sentezli Aktif Kontrolü(TMMOB İnşaat Mühendisleri Odası, 2009) Turan, Gürsoy; Voulgaris, Petros; Bergman, Lawrence A.Bu çalışmada çeşitli kontrol algoritmalarının etkinliğini birbiriyle karşılaştırmak amacıyla oluşturulmuş bir kablolu köprü kontrol model örneği [1, 2] baz alınmıştır. Köprünün sonlu elemanlar modeli modal önem sırasına göre küçültülerek 1/6 boyutunda bir kontrol tasarım modeli elde edilmiştir. Köprünün deprem hareketi sırasındaki kritik noktaları dikkatle gözlenmiş, ve yol seviyesinde kule kesme kuvvetlerinin oluştuğu noktaların kontrolü en zor noktalar olduğunu ortaya konmuştur. Kontrol amaçlı olarak hidrolik pistonlar kullanılmıştır. Belirsizliği tolere edebilen bir tasarım önerisiyle, tasarım modeli ile değerlendirme modeli arasındaki fark sınanmıştır. Ayrıca μ-sentezi esas alınarak bir kontrol denklemi kurgulanmıştır ve bununla birlikte davranış benzetimi gerçekleştirilmiştir.Article Citation - WoS: 3Citation - Scopus: 4Cyclic Behavior of Steel I-Beams Modified by a Welded Haunch and Reinforced With Gfrp(Techno Press, 2009) Eğilmez, Oğuz Özgür; Alkan, Deniz; Özdemir, TimurFlange and web local buckling in beam plastic hinge regions of steel moment frames can prevent beam-column connections from achieving adequate plastic rotations under earthquake-induced forces. Reducing the flange-web slendemess ratios (FSR/WSR) of beams is the most effective way in mitigating local member buckling as stipulated in the latest seismic design specifications. However, existing steel moment frame buildings with beams that lack the adequate slendemess ratios set forth for new buildings are vulnerable to local member buckling and thereby system-wise instability prior to reaching the required plastic rotation capacities specified for new buildings. This paper presents results from a research study investigating the cyclic behavior of steel I-beams modified by a welded haunch at the bottom flange and reinforced with glass fiber reinforced polymers at the plastic hinge region. Cantilever I-sections with a triangular haunch at the bottom flange and flange slendemess ratios higher then those stipulated in current design specifications were analyzed under reversed cyclic loading. Beam sections with different depth/width and flange/web slendemess ratios (FSR/WSR) were considered. The effect of GFRP thickness, width, and length on stabilizing plastic local buckling was investigated. The FEA results revealed that the contribution of GFRP strips to mitigation of local buckling increases with increasing depth/width ratio and decreasing FSR and WSR. Provided that the interfacial shear strength of the steel/GFRP bond surface is at least 15 MPa, GFRP reinforcement can enable deep beams with FSR of 8-9 and WSR below - to maintain plastic rotations in the order of 0.02 radians without experiencing any local buckling.Article Citation - WoS: 277Citation - Scopus: 345Effects of Shear Mechanisms on Impact Behavior of Reinforced Concrete Beams(American Concrete Institute, 2009) Saatçi, Selçuk; Vecchio, Frank J.A well-instrumented experimental program was undertaken to contribute to our understanding of the effects of shear mechanisms on the behavior of reinforced concrete (RC) structures under impact loads and to provide data for verification of methods developed for the impact analysis of such structures. Eight RC beam specimens, four pairs, were tested under free-falling drop-weights, impacting the specimens at the midspan. All specimens had identical longitudinal reinforcement, but varying shear reinforcement ratios, intended to investigate the effects of shear capacity on the impact behavior. A total of 20 impact tests were conducted, including multiple tests on each specimen. The test program was successful in providing a substantial amount of high-quality impact test data. The test results showed that the shear characteristics of the specimens played an important role in their overall behavior. All specimens, regardless of their shear capacity, developed severe diagonal shear cracks, forming a shear-plug under the impact point. © 2009, American Concrete Institute.