Duvarların püskürtme beton ile güçlendirilmesi yöntemi, ülkemizde hasarlı veya hasarsız yığma binaların güçlendirilmesi amacıyla yaygın olarak kullanılmaktadır. Bu yazıda, püskürtme beton kullanarak; ülkemizdeki betonarme yapılara yönelik uygun, etkili, kolay uygulanabilir ve ekonomik bir güçlendirme yöntemi önermek amacı ile yapılmış olan çalışmanın bir kısmı sunulacaktır. Püskürtme beton ile güçlendirme yönteminin betonarme çerçevenin yatay yük taşıma, enerji yutma kapasitesi ve rijitlik özelliklerine olan etkisi ile sistemin göçme şekli incelenmiştir. Ülkemizdeki betonarme yapıların genel özelliklerini yansıtan tek katlı ve tek açıklıklı ½ ölçekli düzlem çerçevelerin içerisine tuğla duvar yerine ıslak karışımlı püskürtme beton paneller eklenmiştir. Oluşturulan panel; dış çerçevenin kirişlerine kayma kamaları kullanılarak bağlanmış, duvar ve çerçevenin birlikte çalışması amaçlanmıştır. Panel, kolon iç yüzeyine 20 cm mesafeli olarak yerleştirilmiştir. Panel genişliğine karar verirken, çerçeve kirişinde yatay ve düşey yükler etkisinde göreli olarak daha az eğilme momenti meydana gelen bir bölgede kalınması hedeflenmiştir. Üretilen numuneler, sabit düşey yük ve tersinir tekrarlı yatay yük çevrimleri etkisinde denenmiştir. Yalın çerçeve ile püskürtme beton bölme duvarlı çerçeve davranışları karşılaştırıldığında, önerilen güçlendirme yöntemi ile sistemin yatay yük taşıma kapasitesinin yaklaşık 1.6 kat arttığı gözlenmiştir. Püskürtme beton ile oluşturulan duvarın sistem davranışına etkisi analitik olarak da incelenmiştir. Anahtar Kelimeler: Püskürtme beton, güçlendirme, betonarme çerçeve.The existence of many vulnerable reinforced concrete buildings in earthquake prone areas that were built before the current Turkish earthquake code, presents one of the most serious problems facing Turkey, especially in Istanbul today. During 1999 Kocaeli Earthquake, buildings had greater damage than expected at that magnitude of an earthquake in the city. Since then researchers have been trying to find cheap and easily applicable strengthening solutions for the reinforced concrete and masonry structures. Shotcrete is used in lieu of conventional concrete, in most instances, for reasons of cost or convenience. Properly applied shotcrete is a structurally sound and durable construction material which exhibits excellent bonding characteristics to existing concrete, rock, steel, and many other materials. It can have high strength, low absorption, good resistance to weathering and resistance to some forms of chemical attack. Shotcrete is used for repairing of bridges, buildings, marine structures; underground excavations in rock; slope and surface protection and for new structures such as building pools, tanks, walls, floors and domes. Shotcrete can be applied by two distinct application techniques; the dry-mix process and the wet-mix process. In this study wet-mix shotcrete is used. Retrofitting structures with shotcrete is commonly used for damaged and undamaged masonry structures in Turkey. The aim of this study is to adapt this retrofitting technique to find out whether it is fast, cheap and adequate method for reinforced concrete structures. To understand the effect of this retrofitting technique, experimental research has been carried out. Panels made from wet-mixed shotcrete in lieu of a traditional masonry are used to form an infill wall within a vulnerable reinforced concrete frame. The frames were chosen to represent weak column/strong beam type structures that were very common in Turkey especially for the buildings constructed before the current earthquake code. The experimental work is composed of strengthening of one undamaged and one bare frame. Nearly ½ scale one story, one bay specimens were tested under constant vertical loads acting on the columns and lateral reversed cycling loads. The panel is connected to the beam and the foundation through shear studs used at two edges of the infill wall to create strong bond between panel and reinforced concrete members of the frames. They are connected by lapping the infill reinforcement to the anchorage placed in frame members. The panel has 20 cm distance to the columns. The specimens had non-seismic details such as large spacing of hoops, no hoop in beam-column connection region and no use of 135° seismic hooks. One story, one bay reinforced concrete frames with a portion of slab on top and a foundation at the bottom have been constructed in the laboratory. The cross sectional dimensions of columns and beam of the frames are 20 cm by 25 cm and 20 cm by 32.5 cm, respectively. The height and the width of the frames are 152.5 cm and 220 cm, respectively. Main reinforcement of the frames was consisted of 16 mm steel bars (average yield stress, fy = 270 N/mm2) and the reinforcement of the panels 4.5 mm steel bars (average yield stress, fy = 320 N/mm2). The reinforcement ratio of the column and the panel are 1.6% and 0.2% respectively. A wire mesh (Q 106/106) consisting of 4.5 mm steel bars was placed in the middle of the frame. By lapping the infill reinforcement to the anchorages placed in the frame members, full contact of the panel was established. The anchorages used were 10 mm steel bars placed in the frame by epoxy resin. The length of the anchorage in the panel was 20 cm. By using wet-mixed sprayed concrete, a 5 cm-thick panel was formed. The axial load applied on each column is 132.5 kN. Lateral reversed cycling loading imposed as displacement was applied to the specimen by means of a 250 kN-capacity hydraulic MTS actuators, which were placed at the slab level. Up to 0.467 mm top displacement, the cycles were applied only once. Later target displacements were repeated three times up to 42 mm. In this study, the effect of the technique on load carrying capacity, energy dissipation, rigidity and the failure mode of the frame is investigated with experiments. The results of the experiments show that the lateral load carrying capacity of the infilled frames strengthened using this method are approximately one and a half times that of the bare one. Keywords: Shotcrete, strengthening, reinforced concrete frame
