İnşaat Mühendisliği Bölümü Yayın Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/395
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Article Simulation-based microwave imaging of plain and reinforced concrete for nondestructive evaluation(2012) Güneş, Oğuz; Büyüköztürk, OralThe focus of this paper is the implementation of a backpropagation algorithm as a potential solution for the inverse source problem for microwave imaging of plain and reinforced concrete targets. The data used in imaging was obtained from numerical simulation of far-field microwave scattering by concrete targets using typical frequency bandwidth of commercially available radar systems. A finite difference-time domain (FD-TD) technique was used for the simulations. Electromagnetic (EM) properties of concrete for various moisture conditions were obtained from a previous study. A total of four simulations were performed using a Gaussian pulse wave excitation for dry and moisture saturated concrete cylinders with and without a rebar at the center. The reflected and transmitted fields were recorded along two measurement lines. Images reconstructed using the backpropagation algorithm showed the potential of the method for concrete non destructive testing (NDT) while drawing attention to its limitations mainly due to the linearizing assumptions made in the algorithm's formulation.Book The IAEE at fifty : a brief history of the international association for earthquake engineering.(International Association for Earthquake Engineering, 2012) Gülkan, PolatArticle Orthonormal decomposition of symmetric second rank tensors(2010) Dinçkal, ÇiğdemIn this paper, a new orthonormal decomposition method for symmetric second rank tensors namely as, orthonormal tensor basis is presented. Complex variable representation method is developed by using the existing theories in literature. For comparison purposes, a brief review of the spectral method is given. It is shown that stress tensor, as an example to symmetric second rank tensors, is decomposed into six orthonormal parts by orthonormal tensor basis and complex variable representation methods. The matrix forms of these decomposed parts are given. This is the first time in literature that physical meanings of each six decomposed parts which are obtained from the orthonormal decomposition of stress tensor by orthonormal tensor basis and complex variable representation methods, different from the traditionally form, are emphasized. Illustrative applications on orthonormal tensor basis and complex variable representation decomposition methods are given. Finally, it is proved that the spectral method is a non-linear decomposition method which yields three non-linear orthonormal decomposed parts. This case is a significant innovation in decomposition procedures for symmetric second rank tensors in literature.Article Norm, norm ratio calculations and anisotropy degree(2011) Dinçkal, ÇiğdemIn this paper, for elastic constant tensor, the norm concept, norm ratio and anisotropy degree are described. The norm of a tensor is used as a criterion for comparing the overall effect of the properties of anisotropic materials and norm ratios are used as a criterion to represent the anisotropy degree of the properties of these materials. Norm and norm ratios as well as the measure of "nearness" to the nearest isotropic tensor are computed for several examples from various anisotropic materials possessing elastic symmetries such as cubic, transversely isotropic, tetragonal, trigonal and orthorhombic. These computations are used to compare and assess the anisotropy in various anisotropic materials by means of strength or magnitude and also determine the "nearness" of the nearest isotropic tensor for the materials with lower symmetry types.Article Studies on the Optimum Mechanical Response of Anısotropıc Materials Related to Elastıc Constants(2011) Dinçkal, ÇiğdemIn this paper, mechanical and elastic behaviour of anisotropic materials are investigated in order to understand the optimum mechanical behaviour of them in selected directions. For an anisotropic material with known elastic constants, it is possible to choose the best set of elastic constants (effective elastic constants) which determine the optimum mechanical and elastic properties of it. For this reason, bounds on the anisotropic elastic constants have been constructed symbollicaly for all anisotropic elastic symmetries. As illustrative examples, materials from different symmetries are selected and their elastic constants are used to compute bounds on the anisotropic elastic constants. Finally, by examining numerical results of bounds given in tables, it is seen that the materials selected from the same symmetry type which have larger interval between the bounds, are more anisotropic, whereas some materials which have smaller interval between the bounds, are closer to isotropy. The construction of bounds on anisotropic elastic constants is a significant and critical case in design of any engineering and structural materials.Article Structural health monitoring and damage assessment Part II: Application of the damage locating vector (DLV) method to the ASCE benchmark structure experimental data(2012) Gunes, Burcu; Gunes, OguzThis paper builds on the review of structural health monitoring (SHM) and damage assessment approaches provided in a companion paper by presenting an application of the damage locating vector (DLV) approach to the experimental (Phase II) data obtained from the experimental benchmark structure of the IASC-ASCE task group on SHM, which is a laboratory (scaled) size steel frame. Different damage conditions were simulated in the frame for braced and unbraced configurations, and the DLV technique was used to detect and localize damage. The damage identification results were presented and the successes and limitations of the DLV method in detecting and locating the simulated damages were discussed.Conference Object Vulnerability assessment of two instrumented masonry buildings in Antakya(2012) Genes, M.C.; Erberik, A.M.; Abrahamczyk, L.; Gülkan, Polat; Bikce, M.; Kacin, S.; Yakut, A.; Schwarz, J.Conference Object The Fatih Project: A Pilot Seismic Assessment of the Architectural Heritage in the Historic Peninsula of Istanbul(2011) Gülkan, Polat; Sozen, M.A.; Yakut, A.; Celep, Z.; Güler, K.; Kubin, J.; Kubin, D.; Eroğlu, E.; İrfanoğlu, A.; Ahunbay, Z.Conference Object Seismic behavior of a four-legged masonry minaret(2012) Kazaz, İ.; Akansel, V.; Gülkan, Polat; Kazaz, E.The four-legged Minaret of Sheikh Mutahhar Mosque has been constructed in the early 16th century during the Aq Qoyunlu Period in Diyarbakır, Turkey, which is located in the second most hazardous zone of the Turkish Seismic Zones Map. This is a special structure, because the minaret body has been placed on four cylindrical stone columns. Therefore, this minaret is seemingly vulnerable though it has survived for five centuries. We use the square cross sectioned minaret as a possible large-scale seismograph to examine the possible limits of ground motion that must have affected it without causing its collapse. In order to investigate the likely seismic performance and strength of the four-legged minaret, a model, which is very close to real structure, was generated with explicit dynamic code LS-DYNA. The developed model takes into account the material nonlinearities and the interface friction and contact behavior between the masonry units. It was displayed that the amplitude of the ground motion in Diyarbakır could not be 0.15g.