İnşaat Mühendisliği Bölümü Yayın Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12416/395

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Author: search.filters.author.Büyüköztürk, OralHas files: No

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  • Article
    Simulation-based microwave imaging of plain and reinforced concrete for nondestructive evaluation
    (2012) Güneş, Oğuz; Büyüköztürk, Oral
    The 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.
  • Article
    Citation - WoS: 49
    Citation - Scopus: 64
    Ductility of Frp-Concrete Systems: Investigations at Different Length Scales
    (Elsevier Sci Ltd, 2013) Lau, Denvid; Tuakta, Chakrapan; Bueyuekoeztuerk, Oral; Gunes, Oguz; Büyüköztürk, Oral
    Fiber reinforced polymer (FRP) materials have been increasingly used in the last two decades to improve various structural characteristics of reinforced concrete (RC) bridges, buildings and other structures. Ductility of the resulting FRP-concrete system plays an important role in structural performance, especially in certain applications such as earthquake resistant design of structures, where ductility and energy dissipation play a vital role. Wrapping RC columns with FRP has been shown to generally result in significant increase in ductility due to the confinement of concrete by the FRP. Other applications such as flexural strengthening of beams involve tradeoffs between ductility and the desired load capacity. Furthermore, environmental factors may adversely affect the FRP-concrete bond raising concerns about the ductility of the system due to possible premature failure modes. Characterization of these effects requires the use of more involved mechanics concepts other than the simple elastic or ultimate strength analyses. This paper focuses on characterizing ductility of the FRP-concrete systems at different length scales using a combined experimental/computational mechanics approach. Effects of several parameters on ductility, including constituent material properties and their interfaces, FRP reinforcement geometry at the macro- and meso-level, and atomistic structure at the molecular level are discussed. Integration of this knowledge will provide the basis for improved design strategies considering the ductility of FRP-concrete systems from a global as well as local perspective including interface bond behavior under various mechanical and environmental conditions. (C) 2012 Elsevier Ltd. All rights reserved.