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    Behavior and strength of hidden Rc beams embedded in slabs
    (ELSEVIER, 2020) Ozbek, Eray; Aykac, Bengi; Bocek, Meryem; Yilmaz, Mahmut Cem; Mohammed, A. B. Khadeeja; Er, Sule Bakirci; Aykac, Sabahattin
    Reinforced concrete (RC) beams protrude from the ceiling, unless there is an infill wall beneath. Sometimes the construction of these beams is avoided due to aesthetic concerns, and instead a reinforcement arrangement with an equivalent bending moment capacity in the slab is made; this is named as a hidden beam. However, since such a design based only on strength can change the behavior to a great extent, the drawbacks of hidden beams were experimentally investigated. A total of fourteen half-scale specimens, including conventional T-beams and slabs with identical flexural capacities (hidden beams), were tested to failure under four-point loading. Reinforcement ratio and slab thickness were adopted as test parameters. The results indicated that hidden beams were able to achieve reference strengths after excessive (up to eight times larger) deformations, or they occasionally could never achieve these capacities. Experimental data were also compared with analytical deflection approaches.
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    Behavior of Postfabricated RC Beams under Monotonic Transverse Loading
    (Asce-Amer Soc Civil Engineers, 2019) Aykac, Sabahattin; Jamal, Rohullah; Ozbek, Eray; Kalkan, Ilker; Aykac, Bengi
    Postfabricated beams, that is, newly constructed beams in an existing structural system, provide an effective remedial solution to the serviceability and strength problems in an existing floor system and the discontinuities and irregularities in the seismic-force-resisting system of a structure, mostly caused by design and construction errors or intended omissions of certain members. The purpose of this study is to develop new techniques for postfabrication of these beams and connecting the postfabricated beams to the existing columns and slab. In this respect, an experimental study was planned and a total of 16half-scale specimens, including 3 monolithic (slab, columns, and beams cast monolithically) specimens and 13 specimens with postfabricated beams, were tested under monotonic vertical loads. The longitudinal reinforcement ratio of the postfabricated beam and the connection techniques of the postfabricated beam to the surrounding columns and slab constituted the test parameters. The tests indicated that the specimens with postfabricated beams were able to reach the strength and behavior of the monolithic specimens.
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    Discussion on "Seismic capacity of masonry infilled RC frame strengthening with expanded metal ferrocement" by A. Leeanansaksiri, P. Panyakapo, A. Ruangrassamee [Eng. Struct. 159 (2018) 110-127]
    (Elsevier Sci Ltd, 2018) Aykac, Sabahattin; Ozbek, Eray; Kalkan, Ilker; Aykac, Bengi
    A discussion on the paper by Leeanansaksiri et al. (2018) is presented. In the paper, strengthening of the masonry infill walls using ferrocement reinforced with standard expanded steel plates (EMS) was investigated experimentally. A bare frame without infill wall, a frame with a plain (unstrengthened) infill wall and a frame with a strengthened infill wall were tested under reversed cyclic lateral loading. The type of EMS to be used for strengthening was decided based on compressive strength tests on plain (unstrengthened) and strengthened masonry prisms and monotonic diagonal loading tests on wall panels. The results of the prism and panel tests were also used to determine the parameters of the analytical hysteric models, which closely estimated the experimental results of the frame tests. While the paper reached important conclusions related to the proposed strengthening technique, the authors of this discussion felt obliged to present their significant findings on the issues, raised in the paper for further research to increase the efficiency of the proposed technique. Furthermore, this discussion summarizes the findings of the authors on the strategies to investigate the efficiency of an infill wall strengthening technique.
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    Flexural Behavior and Strength of Reinforced Concrete Beams with Multiple Transverse Openings
    (Amer Concrete Inst, 2014) Aykac, Bengi; Aykac, Sabahattin; Kalkan, Ilker; Dundar, Berk; Can, Husnu
    Reported are the results of experiments on 10 rectangular reinforced concrete (RC) beams with and without multiple web openings. The effects of opening geometry, the-use of longitudinal stirrups in the posts between the openings, the use of diagonal reinforcement around openings, and the longitudinal reinforcement ratio on the flexural behavior of RC beams with openings were investigated. The stirrups in the posts were shown to have a significant contribution to the ductility of an RC beam with openings if no diagonal reinforcement is used. For the same reinforcement details, RC beams with circular openings were found to have higher load capacities and ductilities than beams with rectangular openings. The experiments indicated that the posts between the openings need to be prevented from undergoing shear failure to avoid Vierendeel truss action and allow a beam to develop its ductility and bending capacity.
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    Flexural behavior of RC beams with regular square or circular web openings
    (Elsevier Sci Ltd, 2013) Aykac, Bengi; Kalkan, Ilker; Aykac, Sabahattin; Egriboz, Yusuf Emre
    This paper presents a study aimed at investigating the influence of multiple web openings along the length of an RC beam on its flexural behavior. A total of nine rectangular beams were tested. Diagonal reinforcement around openings effectively prevented premature failure of some specimens due to Vierendeel action, the expected failure mode according to bending moment-axial force interaction diagrams. Longitudinal rebars and full-depth stirrups adjacent to openings and short stirrups in the chords prevented beam-type and frame-type shear failures. The length of the plastic failure mechanism increased in the presence of multiple openings compared to beams with a single opening. (C) 2013 Elsevier Ltd. All rights reserved.
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    Strengthening and Repair of Reinforced Concrete Beams Using External Steel Plates
    (Asce-Amer Soc Civil Engineers, 2013) Aykac, Sabahattin; Kalkan, Ilker; Aykac, Bengi; Karahan, Servet; Kayar, Sinan
    The study presents the results of an experimental program aimed at investigating the flexural behavior of externally plated RC beams. A total of 13 full-scale rectangular RC beams were tested. The effects on the behavior of the plate thickness, the anchorage of the plate to the beam through anchor bolts or side plates (collars), and the use of perforated plates instead of solid ones were investigated. The experiments indicated that the beam ductility increases as the plate thickness decreases, and the anchorage of the plate to the beam through bolts or collars proves to be an efficient method for preventing the premature plate peeling failure and achieving sufficient ductility in beams strengthened with thick solid plates. Anchor bolts had adverse effects on the ductilities of the beams with thin plates, and the use of perforated steel plates was found to be an efficient method for increasing the ductility of a strengthened beam. The beams repaired with perforated plates anchored to the beam with collars had load-carrying capacities close to those of the undamaged beams. (C) 2013 American Society of Civil Engineers.
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    Strengthening of RC T-beams with perforated steel plates
    (Ice Publishing, 2013) Aykac, Sabahattin; Kalkan, Ilker; Aykac, Bengi; Ozbek, Eray
    The study investigates the flexural behaviour and ductilities of reinforced concrete (RC) T-beams strengthened with perforated steel plates. A total of eight full-scale RC T-beams were tested. Three strengthened beams and a reference unplated beam were reinforced with closely spaced stirrups, while the remaining plated beams and reference beam did not have adequate amounts of shear reinforcement (shear deficient). Shear strengthening with post-tensioned anchors was found to shift the failure mode of a shear-deficient beam from shear to flexure. The post-tensioning forces in the anchors were established to be kept at an optimum level to provide adequate shear strength to the beam and to prevent overstraining of the soffit plate between the shear anchor locations. The perforations increased the ductilities, energy absorption capacities and permanent deformations of the specimens. The use of compression plate in addition to the tension (soffit) plate greatly contributed to the ductilities of specimens with adequate and inadequate shear strength.