Yazar "Koksal, H. Orhun" 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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    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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    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.