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    THE BEHAVIOR OF INFILLED STEEL FRAMES UNDER REVERSE CYCLIC LOADING
    (HONG KONG INST STEEL CONSTRUCTION, 2014) Kaltakci, M. Yasar; Koken, Ali
    The objective of this study was to make an experimental investigation on the behavior of nine steel frames with various infill characteristics under reverse cyclic loading. The test specimens, which were one-story steel frames, had the frame length/height ratios (1/h) of 1, 1/2, and 2. The infill characteristics of the specimens were assigned as i) no infill, ii) brick wall infill, iii) brick wall+plaster infill. The specimens were tested under reverse cyclic loading representing the seismic loading in the horizontal direction, and the displacement values obtained during the tests were measured and recorded in a digital manner. At the end of the tests, the infilled frames were evaluated in terms of failure types, strength envelopes, energy consumption characteristics, and stiffness decreases by comparing the test results.
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    Evaluation of fire performance of prefabricated concrete buildings in Turkey
    (ICE PUBLISHING, 2017) Arslan, Musa Hakan; Erkan, Brahim Hakki; Erdogan, Ozgur; dogan, Gamze; Koken, Ali
    Two different large-scale industrial structures that were destroyed by fires in 2011 and 2012 in Turkey were examined. The structural framework in the first structure was constructed as prefabricated concrete, while a prefabricated concrete-steel (hybrid) was the structural framework in the second. The post-fire performance of the structures was evaluated according to the structural system properties of the buildings and tests on concrete core and steel reinforcement samples obtained from the structures. Since the fire durations of the two buildings examined were slightly different, in addition to the structural framework differences, material test results were comparatively interpreted for the two structures. The concrete used in the building exposed to the longer fire duration suffered a substantial loss in mechanical properties, the concrete cover in the reinforced concrete elements failed completely, and there was a significant loss in the yield strength of the steel reinforcement. In the second structure, which experienced a fire of shorter duration, although the concrete cover had failed similarly to the first case, there was not a substantial loss in the mechanical properties of the reinforcement and concrete. It was observed that damage to the steel structural framework in the second structure (a prefabricated concrete-steel hybrid) triggered damage in the prefabricated concrete system. The precautions that need to be taken in terms of fire, especially in industrial structures, were evaluated based on either the load-carrying system or the section, and suggestions for improvements are made.
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    Experimental Study on Beam-to-Column Connections of Steel Frame Structures with Steel Slit Dampers
    (ASCE-AMER SOC CIVIL ENGINEERS, 2015) Koken, Ali; Koroglu, Mehmet Alpaslan
    After the Northridge and Kobe earthquakes important experimental programs on beam-to-column connections were developed because of brittle fractures at welded beam-to-column connections. A number of studies are being carried out on a variety of materials and systems that dissipate the seismic loading effects in order to improve the seismic performance of steel frames. In the research reported in this paper, a slit steel damper system was developed to prevent the damage formation of standard columns and beams by dissipating lateral loads at the beam-to-column connections of steel frames. Therefore, the columns and beams of steel frames will not be damaged after a heavy earthquake, and the structures might be put into the service again simply by replacing the dampers at the connection sites. The seismic performance of the studied connection was verified through cyclic tests of two full-scale steel frames that had slit dampers and of one specimen that had a conventional extended end-plate connection. Test results indicated that the proposed connection showed a good hysteretic behavior, a good energy dissipation capacity, and good rigidity. However, plastic deformation is limited to the slit dampers, while the inelastic behavior of the beams and columns is prevented. (C) 2014 American Society of Civil Engineers.
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    INVESTIGATION OF THE BEHAVIOR OF WEAKENED AND STRENGTHENED STEEL COLUMN-BEAM CONNECTIONS UNDER SEISMIC EFFECTS
    (HONG KONG INST STEEL CONSTRUCTION, 2014) Koken, Ali; Hatipoglu, E. Tuba
    Newly developed solution techniques were used for the beam to column connections of the steel structures after the 1994 Northridge and 1995 Kobe earthquakes. Two significant methods, the use of reduced beam sections and strengthened beam to column connections, are the methods most frequently studied in recent years. In this study, an experimental procedure was performed to prevent the damages occurring at the beam to column connections of the buildings during an earthquake. For this purpose, four test specimens of beam to column connections were produced. While the first specimen was a strengthened beam to column connection, the second and third were weakened specimens with 40% and 45% ratios, respectively. Additionally, an extra reference specimen (the fourth) was produced to compare the test results. Additionally, a calculation of the analytical force and moment capacities of the test specimens, and the experimental and analytical results were evaluated. The use of reduced beam sections and strengthened beam to column connections favorably affected the behavior of the frame system in a manner that the failure formation occurred not at the connection members but at the end-sections of the beams.
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    PHOTOGRAMMETRIC APPROACH IN DETERMINING BEAM-COLUMN CONNECTION DEFORMATIONS
    (UNIV FEDERAL PARANA, CENTRO POLITECNICO, 2014) Koken, Ali; Koroglu, Mehmet Alpaslan; Karabork, Hakan; Ceylan, Ayhan
    In accordance with the advances in technology, displacement calculation techniques are ever developing. Photogrammetry has become preferable in some new disciplines with the advances in the image processing methods. In this study, the authors have used two different measurement techniques to determine the angles of rotation in beam-column connections that are subjected to reversible cyclic loading. The first of these is the method that is widely used, the conventional method in structural mechanics experiments, where Linear Variable Differential Transformers (LVDTs) are utilized; and the second is the photogrammetric measurement technique. The rotation angles were determined using these techniques in a total of ten steel beam-column connection experiments. After discussing the test procedures of the aforementioned methods, the results were presented. It was observed that the rotation angles measured by each method were very close to each other. It was concluded that the photogrammetric measurement technique could be used as an alternative to conventional methods, where electronic LVDTs are used.
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    USE OF DIFFERENT SHAPED STEEL SLIT DAMPERS IN BEAM TO COLUMN CONNECTIONS OF STEEL FRAMES UNDER CYCLING LOADING
    (HONG KONG INST STEEL CONSTRUCTION, 2018) Koroglu, Mehmet Alpaslan; Koken, Ali; Dere, Yunus
    Following the Northridge and Kobe earthquakes, extensive research was conducted on the use of various materials and systems that will absorb the earthquake effects within the structure itself in order to improve the behavior of the steel structures under seismic effects. In this study, the use of seismic dampers at beam-column joints of steel-framed structures to prevent damage to the structural members by absorbing the energy of the lateral loads was investigated. Thus, it will be possible for the steel-framed structures to be put into service right after a damaging earthquake by only replacing the dampers attached to the joints as no damage will occur to the beams and columns. For this purpose, as a first step, dampers with ductile behavior were chosen through preliminary tests. Consistent with the results of the preliminary tests, a total of six full-scale corner beam-column joint test specimens were produced. Five specimens were attached various types of dampers m different sizes and one reference specimen was designed with regular end-plate connection. After the evaluation of the test results, valuable data on the load carrying and energy consumption capacities, stiffness characteristics and the general behavior of the specimens were obtained. In the analytical part of the study, analyses of the selected specimens were performed through ANSYS finite elements software package. The analytical and experimental results were compared and have been found very consistent with each other.