Browsing by Author "Yigit, ME"

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    Glass Fibre Reinforced Concrete Rebound Optimization
    Yildizel, SA; Yigit, ME; Kaplan, GK
    Glass fibre reinforced concrete placement technique generates losses due to rebound effects of the already sprayed concrete particles. Rebounded concrete amount cause a significant difference between the initial mix design and emplaced mix compositions. Apart from the structural differences, it comes with a cost increase which was resulted by the splashed concrete amount. Many factors such as viscosity and quantity of mixes dominate this rebound amount in sprayed glass fibre reinforced concrete applications depending on production technologies and processes; however, this research focuses on the spray distance and the angle of the spray gun which mainly effects the rebound amount in glass fibre reinforced concrete production. This paper aims to understand the required angle and distance for glass fibre reinforced concrete mixes having on-site plastic viscosity values. Glass fibre reinforced mixtures were also modelled with a finite element method based software and, the analysis results were compared with production line results. Results of the analysis and on-site studies showed a decisive correlation between, discharge distance, discharge angle and the viscosity of the concrete.
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    Investigation of the Seismic Performance of Historical Masonry Aqueducts with Eulerian-Lagrangian Coupled Analysis
    Yigit, ME
    Throughout history, aqueducts have been built to exceed obstacles on the waterway while preserving the energy of water. Our priceless cultural heritage, aqueducts must be protected to be passed on to future generations. Filling the channel with water can increase earthquake resistance due to the damping effect of water. Investigating of fluid and structure interaction of aqueducts through numerical analysis is crucial to understand their behavior under seismic forces. The aqueducts, for which 3D finite element models were prepared, were analyzed using the combined Eulerian-Lagrangian approach, taking into account two main scenarios: with and without fluid-structure interaction. With this approach, it's aimed to observe the damping effect of the fluid, the sloshing on its surface and possible water overflows. Using the CDP material model for masonry units, the analyzes were diversified with various ground motion records at different Peak Ground Acceleration values. The presence of water in the channel significantly reduced displacements, stresses and damage rates. In addition, it was seen that the spectral acceleration value of the earthquake record was more effective in causing damage rather than the PGA value. Graphics and contour diagrams are given to understand and compare the analysis results of aqueduct models under different conditions.
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    Comparative analysis of tripod offshore structure
    Gücüyen, E; Yigit, ME; Erdem, RT; Gökkus, U
    Marine structures are nowadays used in a variety of ways. The analysis of a tripod-type offshore structure sixty m in total height is performed in this study. In addition to operation-related loads, the structure is also under the effect of wind and wave loads. While the Eurocode velocity profile is used to calculate wind forces, the Airy wave velocity profile is utilized to determine wave forces. The model is created by a finite elements analysis program, and is composed of fluid and structural parts. The interaction of the parts is ensured by Coupled Eulerian Lagrangian (CEL) technique.
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    Damping impact with different water level on structural behaviour of elevated water towers
    Altiok, TY; Yigit, ME; Eser, CB; Demir, A
    Water towers with tall and delicate geometry are highly susceptible to seismic actions. This study aims to develop a fast, reliable and cost-effective method for examining the seismic behaviour of such structures, by taking a reinforced concrete water tower with known material parameters and dimensions as an example. The impact of water absorption on structural response under dynamic loading at empty, half full and full capacity was investigated. Ideal finite element models of the water tower were constructed using operational modal analysis. Linear time history analyses were conducted using the finite element software. The structure was modelled with the Lagrangian approach, while the fluid was modelled using the Eulerian approach in finite element analysis. The coupled Eulerian Lagrangian technique was employed for the analysis. Results obtained from the analyses indicate that an increase in tank fill level led to enhanced structural damping, resulting in reduced displacement and stress values.
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    Behaviour of Large Cylindrical Offshore Structures Subjected to Wave Loads
    Dagli, BY; Yigit, ME; Gökkus, Ü
    Spar-type and monopole substructures consisting of a large-diameter, single vertical cylinders have been used as wind turbine towers, oil storage platforms, tankers and wave energy converters at deepwater region in the sea. These towers and platforms are exposed to environmental forces such as wind, wave and current. Wave force is the most effective force in the total environmental force. The body disturbs the incident wave and Diffraction Theory is used for computing the pressure distribution for designing the structure. Therefore, this study aims to present the effect of structural design of towers on dynamic behavior due to wave actions. Two different cases of structural models are selected to employ bidirectional fluid structure interaction (FSI) analysis. Diffraction Theory is utilized to investigate wave forces. Solid and fluid domains are modeled in Abaqus finite elements program. Behaviors of various types of offshore structures are evaluated and compared according to the significant stresses and displacements. The hydrodynamic pressure on the cylindrical structure surface and the diffraction forces acting on structures are presented. Mode shapes, first three natural frequencies are comparatively given.