Oguz C. Celik

Monotonic and Cyclic Bond Behavior of Deformed CFRP Bars in High Strength Concrete

Composite reinforcing bars (rebars) that are used in concrete members with high performance (strength and durability) properties could have beneficial effects on the behavior of these members. This is especially vital when a building is constructed in an aggressive environment, for instance a corrosive environment. Although tension capacity/weight (or volume) ratios in composite rebars (carbon fiber reinforced polymer (CFRP), glass fiber reinforced polymer (GFRP), etc.) are very high when compared to steel rebars, major weaknesses in concrete members reinforced with these composite rebars may be the potential consequences of relatively poor bonding capacity. This may even be more crucial when the member is subjected to cyclic loading. Although monotonic bond tests are available in the literature, only limited experimental studies exist on bond characteristics under cyclic loading conditions. In order to fill this gap and propose preliminary design recommendations, 10 specimens of 10-mm-diameter ribbed CFRP rebars embedded in specially designed high strength concrete (f’c = 70 MPa) blocks were subjected to monotonic and cyclic pullout tests. The experimental results showed that cyclically loaded CFRP rebars had less bond strength than those companion specimens loaded monotonically.

Importance of Wood and Iron Tension Members on Seismic Performance of Historic Masonry Buildings: Three Case Studies from Turkey

Wood and/or iron tension members in the form of either tie bars (both wood and iron) in historic masonry arches or externally applied tension rings (iron) of masonry domes have been used in historic buildings especially in the areas that are vulnerable to severe earthquake excitations. Earthquake reconnaissance investigations revealed that masonry arches and domes with tension members showed satisfactory behavior under earthquake loading. To investigate their effectiveness on behavior, three case studies are analyzed from Turkey. The first one is a 16 th century mosque having major structural cracks on its 25m-diameter brick masonry dome. Combined steel and CFRP sheets as tension members at several dome levels are proposed as a seismic retrofit measure. Significant improvement is obtained in response, leading to maximum 60% reduction in stresses. The second case study is a stone masonry vault having damaged wooden tie bars. Similarly, numerical results show that stresses as well as deformations can be reduced up to 50% by replacing the old ties with the new wooden tie bars. The third one is a 508year-old tomb having a nearly collapsed brick masonry dome. At the support level of the dome, externally applied steel rings were used as tension members to limit stresses and deformations. Similar amounts of reductions in stresses are obtained. This study also shows that both traditional and contemporary retrofit strategies can be used in the same project when required.

Çelik Çekirdekli Burkulması Önlenmiş Çaprazların (BÖÇ) Tasarımı, Üretimi ve Deneysel İncelenmesi

Bir tur metalik sonumleyiciler olarak kabul edilen Burkulmasi onlenmis Caprazlar (BOC) onemli depremlerde cekme ve basincta akarak dengeli bir histeretik davranis gosterirler. Bu calismada farkli celik uc detayi malzemesine sahip BOC’lerin yon degistiren tekrarli yukler altindaki histeretik davranisina iliskin deneysel bulgu ve degerlendirmeleri verilmektir. Denenen BOC’ler icin kuvvet-yerdegistirme histeretik egrileri, histeretik enerji yutma miktarlari ve etkili sonum oranlari hesaplanarak karsilastirmalar yapilmistir. Ozgun detaylar ile uretilen ve denenen BOC’lerin yeterli bir performans gosterdigi ve bu performansinin ileride yapilabilecek calismalarla iyilestirilebilecegi sonucuna varilmistir.