Yazar "Güllü, Ahmet" seçeneğine göre listele

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    Development of Finite Element Model for a Special Lead Extrusion Damper
    (2021) Güllü, Ahmet; Çalım, Furkan; Yüksel, Ercan; Soydan, Cihan
    A significant amount of seismic energy is imparted to the structures during earthquakes. Theenergy spreads within the structure and transforms in various energy forms as dissipatedthrough the structure. The conventional seismic design provides specific ductile regions,namely plastic hinges, on structural elements. Therefore, the energy dissipation capacities ofthe structural elements and the structure enhance. However, this approach accepts that thedeformations will concentrate on the plastic hinge zones and severe damage may occur onstructural elements within deformation limits that are defined by the seismic codes. The modernseismic design aims to dissipate a large portion of the seismic input energy by installing energydissipating devices (EDDs) to the structure. Thus, deformation concentrates on EDDs whichcan be replaced after an earthquake, and energy demand for structural elements is decreased.Lead extrusion damper (LED) is a passive EDD that utilizes the hysteretic behavior of lead. Inthis paper, the preliminary results of the developed three-dimensional finite element model(FEM) for a LED is presented. The results obtained from the finite element analysis (FEA) werecompared with the experimental ones in which LEDs were exposed to sinusoidal displacements.Also, the applicability of the developed FEM was checked for different component dimensionsgiven in the literature. The comparison study yielded a satisfactory consistency. Additionally,the maximum relative difference obtained for the literature devices was reduced to 12% from39% by the developed FEM.
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    Effect of building importance factor on seismic performance of rc frame type shopping malls subjected to pulse-like records
    (Elsevier Science Inc, 2021) Güllü, Ahmet; Karameşe, Genco
    Since they offer many alternatives for shopping, eating, resting, etc. many people spend a considerable time in shopping mall buildings. Therefore, this type of building is increasing rapidly. The increment rate was almost three in Turkey for the last decade. The recently released seismic code of the country has some serious alterations such as increased seismicity of some regions and reduced performance level limits of structural members. Besides, the building importance factor (I) of the shopping malls was defined clearly to be 1.2 whereas some shopping malls were designed considering I = 1.0 and constructed before 2018. Therefore, seismic performances of the shopping malls became questionable according to the code. In this study, seismic performances of two existing shopping mall buildings, which were designed and constructed by considering I = 1.0, are investigated based on the recently released seismic code and nonlinear analyses in which the utilized records were scaled considering I = 1.2. The results showed that the increased seismicity and reduced performance level limits may lead to excessive story drifts and plastic rotations for some records. However, the mean value of the analysis results satisfies the life safety (LS) performance level. Therefore, the importance factor might be suggested to be 1.0 for shopping malls close to the faults to avoid an unnecessary increment of the initial cost.
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    Evaluation of the Relation between Seismic Input Energy and Spectral Velocity
    (2020) Güllü, Ahmet
    Energy based seismic design concept is getting attention owing to its advantages over theconventional methodologies. Particularly, the consideration of duration and frequency content ofthe earthquake record are chief superiority of the concept. For this original design procedure,accurate determination of seismic input energy is crucially important. Because of solving energybalance equation is a tedious job, the seismic input energy is determined in terms of equivalentvelocity in the literature mostly. However, it was also shown that this relation is valid for onlyundamped systems. Therefore, this study aims to provide the nonsteady relation between seismicinput energy and equivalent velocity for damped systems. Intensive response history analyseswere performed by using plenty of earthquake records those were selected by considering theimpulsive characteristics (ordinary and pulse-like) and shear wave velocity. It was found that therelation given in the literature for seismic input energy and spectral velocity relation is not true fordamped systems. Dependently, it is proposed a set of coefficients considering structural dampingproperties to modify the existing relation.
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    Experimental investigation and pseudoelastic truss model for in-plane behavior of corrugated sandwich panels with polyurethane foam core
    (Elsevier Science Inc, 2021) Yüksel, Ercan; Güllü, Ahmet; Özkaynak, Hasan; Soydan, Cihan; Khajehdehi, Arastoo; Şenol, Erkan; Saghayesh, Amir Mahdi; Saruhan, Hakan
    Sandwich panels are commonly used in facades and the roofs of industrial buildings due to their well-known advantages. However, there is limited data about the in-plane behavior of the panels. Hence, this paper aimed to propose a pseudoelastic truss model to represent the effective in-plane stiffness and strength properties of the corrugated sandwich panels with a polyurethane foam core. Two separate sets of experiments (mock-up and system test) were conducted in the laboratory. The variables were the number of fasteners, sheet thickness, loading direction, and number of ribs. The number of fasteners, sheet thickness, and loading direction are the most effective parameters for the in-plane behavior. A formula was proposed to compute axial stiffness of the truss members by considering the effective parameters. Experimental results showed that the proposed robust truss model could give a good estimate of the pseudoelastic stiffness and maximum load bearing capacity of the sandwich panels.
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    Rapid and easily applicable procedure for full-scale laboratory tests of ballastless slab tracks
    (ASCE-American Society of Civil Engineers, 2021) Güllü, Ahmet; Özden, Bayezid; Ölçer, Beyazıt; Özcan, Ali İhsan; Binbir, Ergün; Durgun, Yavuz; Saruhan, Hakan; Şahin, Fatih; Şenol, Erkan; Khajehdehi, Arastoo; Noobakhtjoo, Amir; Yüksel, Ercan
    Increasing demand for high speed railway lines necessitates reducing construction and maintenance costs. Accordingly, RC slab tracks are preferred due to their advantages such as being almost maintenance free and supplying uniform support conditions. However, new testing procedures are required for the performance evaluation of the slab tracks to identify possible failure modes which may not be observed in numerical analyses. Although there are some procedures in the literature, there still is no consensus on loading intensity, shape, frequency, or number of cycles. A testing procedure that greatly decreases experimental costs was adopted for the design approval tests of precast RC slab tracks. The procedure was evaluated experimentally through full-scale laboratory tests of intact and intentionally damaged specimens. The study demonstrated that the proposed testing procedure reduces experimental costs and identifies the mechanical properties of slab tracks.
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    The efficiency of photovoltaic panels to meet energy demand of a school building in the Mesopotamia region
    (2022) Al-Rubaii, Shaimaa; Köse, Ali; Kazar, Gökhan; Güllü, Ahmet
    All kinds of energy are one of the basic requirements in life to sustain it. Therefore, the majority of research and applications have been mostly focused on self-sufficient energy or zero-energy buildings in developed countries. Most of these countries encounter energy demand and suffer from carbon dioxide emissions from existing buildings. Energy-efficient applications must be also spread across developing and undeveloped countries especially in the Mesopotamia region due to the hot climate. Hence, the efficiency of a common practice, implementation of photovoltaic panels (PVs), in Iraq is investigated in this study. PVs were designed and empirically implemented in an existing conventional primary school building in Baghdad, Iraq as a case study for the Mesopotamia region. The sustainability and energy analysis of a school building was conducted in diverse scenarios to explore the potential of energy-saving and payback period of the PVs. The slope and number of PV panels located on the school building are the parameters of the current study. Results showed that PV panels with a 30° inclination angle reduced the energy cost of the building by 50%. The payback for the implementation of PVs can be obtained approximately in 8 years. Consequently, the PVs have major potential in energy efficiency and can be implemented in governmental buildings such as public-school buildings in the Mesopotamia region. Besides, society and private institutions may become aware of the importance of sustainable energy with this study. With this case study, the importance of taking advantage of solar energy has been emphasized for undeveloped countries.