Determination of the GFRP Reinforcement-Concrete Bond Strength from Pull-Out Tests Resulting in the Debonding Failure

Öz

Fiber reinforced polymer (FRP) bars have begun to be used as an alternative to conventional steel reinforcing bars in reinforced concrete structures, especially due to their high resistance to corrosion and high tensile strength. However, their bond behavior with concrete is different than steel because of their different mechanical and physical properties compared to steel reinforcing bars. The bond behavior of FRP bars with concrete depends on many parameters such as concrete compressive strength, clear cover, embedment length, bar diameter, location of the bar, bar surface properties. Different international FRP-reinforced concrete codes recommended various equations for estimating the FRP-concrete bond strength. These equations were established using experimental results that resulted in splitting concrete failure. However, the maximum bond strength cannot be determined from the loss of bond strength due to the fracture of concrete and the parameters affecting the bond strength cannot be fully determined from the specimens failed in splitting. For this reason, the validity of the equations originating from the experiments ended up in the splitting failure must be discussed. The present study aimed at developing a bond strength equation between concrete and glass reinforced polymer (GFRP) by using multiple linear regression analysis on a total of 243 pull-out experiments from the literature that resulted in pullout failure. The proposed bond strength equation was observed to yield to more consistent values with the experimental results compared to the respective values from the international code equations.

Anahtar Kelimeler

• GFRP rebar,bond strength,glass fiber reinforced polymer rebar

GFRP DONATI-BETON ARASINDAKİ ADERANS GERİLMESİNİN SIYRILMA GÖÇME TİPİ İLE SONUÇLANAN ÇEKİP ÇIKARMA DENEYLERİ İLE TESPİTİ

Öz

Lif takviyeli polimer donatılar (FRP) özellikle korozyona uğramama ve yüksek çekme dayanımları nedeniyle betonarme yapılarda çelik donatıya alternatif olarak kullanılmaya başlanmıştır. Ancak, mekanik ve fiziksel özelliklerinin çelik donatıya göre farklı olmasından dolayı, FRP donatıların beton ile olan aderans davranışları çelikten farklıdır. FRP donatının beton ile olan aderans davranışı, beton basınç dayanımına, pas payına, donatı gömülme boyuna, donatı çapına, donatının konumuna ve donatı yüzey özelliği gibi daha birçok değişkene bağlıdır. Farklı uluslararası FRP donatılı beton yönetmelikleri, donatı aderansının tahmininde kullanılacak çeşitli bağıntılar önermişlerdir. Bu bağıntılar, donatının betondan ayrışması ile sonuçlanan deneylerin sonuçları kullanılarak oluşturulmuştur. Ancak, ayrışma ile sonuçlanan numunelerde, betonun çatlamasından doğan aderans kaybı neticesinde maksimum aderans belirlenemeyeceği için aderansı etkileyen değişkenler tam olarak tespit edilemez. Bu nedenle ayrışma göçme tipi ile sonuçlanan deneyler ile ortaya konan bağıntıların geçerliliği tartışmalıdır. Bu çalışmada, literatürde mevcut donatı sıyrılması ile sonuçlanan 243 adet çekip çıkarma deneyinden yararlanılarak,  çoklu doğrusal regresyon analizi ile cam takviyeli polimer donatıların (GFRP) beton ile aralarındaki aderans bağıntısının tespit edilmesi amaçlanmıştır. Çalışma sonucunda önerilen bağıntı kullanılarak tahmin edilen aderans gerilmesi değerlerinin, uluslararası yönetmeliklerde geçen bağıntılar ile elde edilen değerlerden daha tutarlı sonuçlar verdiği görülmüştür.

Anahtar Kelimeler

• GFRP donatı,donatı aderansı,cam takviyeli polimer donatı

Kaynakça

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