FRP donatı-beton aderansı deney yöntemlerinin aderansı etkileyen parametrelere göre karşılaştırılması

FRP donatı-beton aderansını belirlemek için uluslararası deney yönetmeliklerinde birçok deney yöntemi bulunmaktadır. Ancak, bu deney yöntemlerinin deney şartlarındaki farklılıklar FRP donatı-beton aderansını etkilemektedir. Dolayısıyla değişkenlerin aynı değerlerine göre yapılan deneylerde bile deneysel farklılıklardan ötürü farklı aderans gerilmesi değerleri oluşmaktadır. Bu çalışmada, gauss süreci regresyonu (GPR) kullanılarak FRP donatı-beton aderansını etkileyen faktörler aderans deney yöntemlerine (mafsallı kiriş, kiriş ucundan çekip çıkarma, bindirme eki boyu ve çekip çıkarma deneyi) göre ayrı ayrı belirlenmiştir. Çalışmada, donatı çapı, donatı lif türü, donatı yüzey özelliği, donatı gömülme boyu, donatının beton içindeki konumu, pas payı, beton basınç dayanımı ve enine donatı etkisi gibi sekiz değişken göz önüne alınmıştır. Bu sayede hem FRP donatı-beton aderansını etkileyen her bir değişkenin deneysel yöntemlerden ne kadar etkilendiği araştırılmış hem de aderans deney yöntemlerinin aderansı etkileyen parametrelere göre karşılaştırılması yapılmıştır. Dört aderans deney yönteminin aynı deney değişkenlerine göre yapılan analizleri, deney yöntemlerine göre aderans gerilmesi değerleri arasında neredeyse dört kata varan farklar olduğunu göstermiştir. Mafsallı kiriş deneylerinden elde edilen ortalama aderans gerilmesi değerleri, çekip çıkarma deneylerinden elde edilen ilgili değerlerden % 31, kiriş ucundan çekip çıkarma değerlerinden % 3 ve bindirme eki boyu deney değerlerinden % 146 yüksek çıkmıştır. Aynı zamanda aderansı etkileyen faktörlerin deneysel yöntemlere göre aderans gerilmesine etki oranlarının değiştiği ve hatta aynı değişkenin farklı deneysel yöntemlerde zıt etkilere neden olabileceği gözlemlenmiştir.

Anahtar Kelimeler:

Aderans deneyleri, FRP donatı aderansı, Lif takviyeli polimer donatı, FRP donatılı beton, Mekanik kenetlenme, , Aderans sıyrılması

Comparison of different FRP reinforcement-concrete bond test methods according to parameters affecting this bond

There are many test methods in the international testing standards for the evaluation of FRP reinforcement-concrete bond. However, differences in test conditions of these methods affect FRP reinforcement-concrete bond. Therefore, even in the tests with identical test parameters, different bond strength values are attained due to experimental differences. In this study, the factors affecting FRP reinforcement-concrete bond were determined individually for four different test methods (hinged beam, beam-end, spliced beam and pullout tests) by using the gauss process regression (GPR) method. Accordingly, eight parameters affecting the bond strength, namely the diameter, fiber type, surface texture, embedment length, location in concrete and clear cover of reinforcement, the concrete compressive strength and the presence and degree of confining by means of transverse reinforcement were adopted as test parameters. In this way, the effects of each variable on bond strength were investigated for each test method and the methods were compared in terms of each parameter. The analyses on the four methods for identical test parameters depicted that there were differences in bond strength values as great as four times from one test parameter to another. The average bond strength values from the hinged beam tests were about 31, 3 and 146 % higher than the respective values from the pullout tests, beam-end tests and spliced beam tests, respectively. The degree of influence of each parameter on bond strength was established to depend on the test method and the same parameter was found to even have opposite effects on bond strength in different test methods.

Keywords:

Bond test methods, FRP reinforcement bond, fiber reinforced polymer reinforcement, FRP reinforced concrete, Mechanical interlocking,

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