Yazar "Doran, Bilge" seçeneğine göre listele

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    AN INVESTIGATION ON THE NONLINEAR BEHAVIOR OF UNREINFORCED MASONRY WALLS
    (Yildiz Technical Univ, 2012) Jafarov, Oktay; Koksal, H. Orhun; Doran, Bilge; Karakoc, Cengiz
    Recently, numerous studies on the modeling technique for masonry structures and their structural components have been carried out, such as masonry shear walls existing in the literature. This paper is focused on nonlinear finite element modeling of masonry walls at a micro-level. For this purpose, Drucker-Prager yield criterion is employed in the elasto-plastic analyses of walls deriving the material parameters from the compressive strength of both brick and mortar. The performance of the proposed approach is verified by simulating a series of experiments reported in the literature.
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    Computational material modeling of masonry walls strengthened with fiber reinforced polymers
    (Techno-Press, 2013) Koksal, H. Orhun; Jafarov, Oktay; Doran, Bilge; Aktan, Selen; Karakoc, Cengiz
    This paper aims to develop a practical approach to modeling of fiber reinforced polymers (FRP) strengthened masonry panels. The main objective is to provide suitable relations for the material characterization of the masonry constituents so that the finite element applications of elas to-plastic theory achieves a close fit to the experimental load-displacement diagrams of the walls subjected to in-plane shear and compression. Two relations proposed for masonry columns confined with FRP are adjusted for the cohesion and the internal friction angle of both units and mortar. Relating the mechanical parameters to the uniaxial compression strength and the hydrostatic pressure acting over the wall surface, the effects of major and intermediate principal stresses sigma(1) and sigma(2) on the yielding and the shape of the deviatoric section are then reflected into the analyses. Performing nonlinear finite element analyses (NLFEA) for the three walls tested in two different studies, their stress-strain response and failure modes are eventually evaluated through the comparisons with the experimental behavior.
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    CONSTITUTIVE MODELING OF MASONRY WALLS UNDER IN-PLANE LOADINGS
    (Yildiz Technical Univ, 2016) Aktan, Selen; Doran, Bilge
    The aim of this study is to examine the behavior of the historic masonry walls by analyzing both the experimental and numerical results. In the experimental part of the study, original material parameters used in repair, strengthening and restoration of historical monuments were determined. For this purpose, in the context of the research Project numbered as 111M568; the characteristics of the original building materials for the brick and mortar specimens from two distinct historical monuments that are located in Turkey were obtained. Physical and mechanical properties of these materials were calculated and in the direction of this results, new mortars were produced. New masonry walls were constructed with the clay bricks and different types of produced mortar. The experimental walls were subjected to compression and incremental lateral loads and the results were evaluated within the load-displacement relations. Experimental walls were modelled with a new approach called 'fictitious joint material' in which the constitutive behavior of the mortar joint and the brick-mortar interface were included together. In this scope of this work, an elasto-plastic damage (EPD) approach is adapted calibrating the parameters of Oliver's damage model [1] together with the modified von-Mises yield criterion for the masonry constituents.
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    Elastoplastic Finite Element Analysis of Masonry Shear Walls
    (Korean Society Of Civil Engineers-Ksce, 2016) Koksal, H. Orhun; Doran, Bilge; Kuruscu, A. Osman; Kocak, Ali
    Masonry is the most important construction material in Turkey. It has been used for public and residential buildings in the past several thousand years. A great number of well-preserved old masonry structures still exist proving that this form of construction can successfully resist loads and environmental impact. Traditionally, most major buildings were solid walled structures with the walls bearing directly on the ground. Engineers work hard to convert the highly indeterminate, ambiguous and nonlinear behavior of historic masonry construction into something which can be understood with mathematical certainty. Therefore, practical and accurate structural analysis techniques are needed for the preserve the historical monuments as a huge cultural heritage. This paper is focused on Nonlinear Finite Element (NLFE) modeling of masonry shear walls at a macro-level taking the geometric arrangement of constituents. In this study, 3D elasto-plastic Finite Element (FE) analysis for the masonry walls that subjected to the combinations of vertical and lateral loads, are determined to find a practical method. An original meshing procedure is introduced to consider the orthotropy along the two natural directions of the masonry while the material is still assumed to be isotropic. The paper further examines parameter studies carried out to show that the relation suggested for cohesion values of mortar joint masonry can also be adopted for the masonry walls with dry joints employing compressive stresses on the top surface of the wall despite using its compressive strength. The accuracy of the proposed approach is verified by simulating a series of experiments reported in the literature. Those papers include shear tests on masonry walls with both dry and mortar joints by Raijmakers and Vermeltfoort, Oliveira and Roca. Comparisons between the predicted and measured failure loads of the walls confirm that it is possible to reproduce the fundamental features of masonry shear walls with the proposed meshing scheme. Finally, the proposed approach is shown to fit quite well the experimental load-deformation plots of masonry walls with both dry-and mortar joint under shear-compression fracture.
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    Hava Kireci Harcı Kullanılarak Üretilen Tarihi Yığma Duvarlarda Bünyesel Modelleme
    (2017) Doran, Bilge; Aktan, Selen
    Bu çalışmada, düzlem içi yükler etkisinde kalan tarihi yığma duvarların üç boyutlu doğrusal olmayan sonlu elemanlar analizi için bir bünyesel modelleme tekniği önerilmiştir. Tarihi yığma yapıların karmaşık mekanik davranışları, büyük ölçüde yapı malzemelerinin kompozit niteliğine bağlıdır. Taş veya tuğla gibi yığma birimlerden ve farklı içeriklerde harç (bağlayıcı) malzemesinden oluşan yığma duvarlarda, zayıf özellikte ve kompozit yapıda olan malzeme harçtır. Tarihi yapılarda kullanılan harcın yığma birimlere nazaran mekanik olarak zayıf olması, bu etkiyi gerektirmiştir. Bu kapsamda, modellemede derz bölgelerine yoğunlaşan bir yaklaşım olarak 'sanal birleşim bölgesi malzemesi' tanımlanmıştır. Çalışmada önerilen malzeme modeli, yığmanın gerilme birim şekil değiştirme davranışını ifade etmek üzere, geliştirilmiş von-Mises akma kriteri ile Oliver hasar modeli yaklaşımlarının, ihtiyaç duyduğu malzeme parametreleri dikkate alınarak birleştirildiği elasto-plastik hasar mekaniğinden türetilmiştir. Plastik şekil değiştirme için, kırılma yüzeyindeki çekme ve basınç gerilme değerlerini ayrı ayrı dikkate alan geliştirilmiş von-Mises plastisite modeli ile hasar mekaniğindeki şekil değiştirme artışı Oliver vd. (1990) modeli kullanılarak ifade edilmiştir. Sayısal model sonuçları ve kırılma modları deneysel verilerle karşılaştırılmıştır.
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    In-Plane Shear Behavior of Traditional Masonry Walls
    (Taylor & Francis Inc, 2017) Doran, Bilge; Koksal, H. Orhun; Aktan, Selen; Ulukaya, Serhan; Oktay, Didem; Yuzer, Nabi
    The evaluation of the material properties of masonry built with traditional lime mortar remains largely unclear to what extent the complex mechanical behavior of its constituents and sampling difficulties. This article presents the experimental results of a research project carried out on the four unreinforced masonry (URM) walls with four different types of lime mortars used in the Roman and Byzantine periods under shear-compression. Besides, an elasto-plastic damage (EPD) approach is adapted calibrating the parameters of Oliver's damage model and the modified von-Mises yield criterion for the masonry constituents. For the modeling purposes, a new fictitious joint material approach is introduced to describe the constitutive behavior of both mortar and mortar-brick interface. The proposed approach can be useful to describe the behavior of mortar and mortar-unit interface in existing masonry structures.
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    Numerical Modeling of Traditional Masonry Walls Strengthened with Grout Injection
    (Taylor & Francis Inc, 2020) Doran, Bilge; Yuzer, Nabi; Aktan, Selen; Oktay, Didem; Ulukaya, Serhan
    The main purpose of this article is to experimentally and numerically study the improvements introduced by the grout injection strengthening technique for the structural rehabilitation of traditional unreinforced masonry (URM) walls. In this context, four damaged URM walls with four different types of lime mortars under shear-compression are strengthened using grout injection method. Injection materials (Grout) which have same contents with existing mortar types are applied to all cracks in damaged walls. Besides, for the numerical simulations, a simplified micro modeling strategy is preferred combining the mortar and the mortar-unit interface behavior and then an elasto-plastic damage (EPD) approach is adopted calibrating the parameters of Oliver's damage model and the modified von-Mises yield criterion for the masonry constituents. Results show that the proposed approach can be useful to describe the behavior of mortar and mortar-unit interface in strengthened masonry structures with grout injection.
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    Strengtening R/C and masonry structures with fiber reinfirced polymers in disaster areas
    (Ios Press, 2015) Doran, Bilge; Koksal, Hasan Orhun; Akbas, Bulent
    This paper presents the use of fiber reinforced polymers (FRP) for strengthening reinforced concrete (R/C) and masonry structures in disaster areas. FRPs have gained rapid popularity in recent years as one of the strengthening techniques of structural concrete and masonry members. Although substantial experimental and analytical researches have been conducted to model and simulate the response of these members confined with FRP jackets under concentric and eccentric loading, there is still an apparent need for efficient numerical models to further understand the stress-strain behavior and failure mechanisms of the confined material. The primary aim of this paper is to introduce an effective modeling procedure for the reinforced concrete (R/C) and masonry structural members such as columns and walls under shear and/or compression.
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    Stress-strain model for fibre-reinforced polymer confined rectangular columns
    (Ice Publ, 2011) Koksal, Hasan Orhun; Doran, Bilge
    Applying fibre-reinforced polymer sheets around existing columns is an innovative technique in the field of civil engineering due to their high stiffness and strength-to-weight ratio, corrosion resistance and potentially high durability. The confinement effect of high-stiffness fibre jackets simply results in an increase in the compressive strength of columns. Various constitutive models have been constructed to predict the increase in the axial strength of concrete due to the confinement effect of fibre-reinforced polymer laminates. In this paper, a new stress-strain model is proposed for square/rectangular concrete columns confined with fibre-reinforced polymer jackets. The model is an extension of previous work on circular columns, adopting a previously proposed relation to plot the stress-strain curves. The proposed model utilises a failure criterion of concrete under triaxial compression, unlike the most existing models which rely on a previously presented general formulation. A large comparative study of 163 square/rectangular concrete specimens is performed on the basis of the prediction accuracy of existing models and the proposed approach for their ultimate strengths in compression. The recommended axial stress-strain plots are used to simulate the uniaxial compressive tests. The results confirmed that the axial stress-strain relationship evaluated by the presented technique can appropriately describe the deformation under uniaxial compressive loading.