Uzun ve kısa çelik lif takviyeli tam ölçekli kirişlerin aderans dayanımı

Bu çalışmada, tek ve karma lif takviyesinin aderans dayanımına etkisini incelemek için altı adet tam ölçekli 200x300x2000 mm boyutlarında betonarme kiriş numunesi dört noktalı eğilme altında test edilmiştir. Bu amaçla, betonarme kiriş numuneleri lif takviyesiz, tek lif (%1 makro çelik lif) ve karma lif (%0.8 makro ve %0.2 mikro çelik lif) takviyeli olarak döküldü. Her bir kiriş numunesi, çekme bölgesinde iki adet donatı çeliğinin açıklık ortasında bindirmeli ekli olarak tasarlanmıştır. Bindirme boyu donatının akma dayanımına ulaşmadan önce bindirme bölgesinde beton örtüsünün yarılmasıyla aderans göçmesi gösterecek şekilde seçilmiştir. Deneysel çalışmada, donatı çapı, bindirme boyu ve donatı detayları sabit tutulurken, lif tip ve kombinasyonları değişken olarak belirlenmiştir. Sonuç olarak, lif takviyeli tüm betonarme kiriş numunelerinin beton ve çelik donatı arasındaki aderans dayanımı, lif takviyesiz kiriş numunelerine göre artış gösterirken, karma lif takviyeli kiriş numunelerinin aderans dayanımı ise en yüksek bulunmuştur. Karma lif takviyeli kiriş numunelerinde sünek göçme gözlemlenmiş ve çoklu çatlak davranışı sonucu genişliği daha az fakat daha fazla sayıda çatlak oluştuğu belirlenmiştir. Ayrıca, lif takviyeli kiriş numunelerinden elde edilen aderans dayanımına ait deneysel verilerin, analitik bulgularla çok iyi bir uyum içinde olduğu bulunmuştur.

Anahtar Kelimeler:

Aderans dayanımı, Bindirme boyu, Karma lif takviyeli beton, Tam ölçekli betonarme kiriş, Lif kombinasyonu

Bond strength of full-scale beams with blended short and long steel fiber

In this study, six reinforced concrete (RC) beams with the sizes of 200x300x2000 mm were tested under four-point bending to investigate the effect of single and hybrid fiber reinforced on the bond strength of reinforcing bar. For this purpose, the reinforced beams were cast as no fiber, single fiber (1% macro steel fiber) and hybrid fiber (0.8% macro and 0.2% micro steel fiber) reinforced. Each beam was designed to include two bars in tension, spliced at the center of the span. The splice length was selected so that bars would fail in bond, splitting the concrete cover in the splice region, before reaching the yield point. In experimental work, the diameter of bars, splice length and bar details was selected as constant while the fiber type and combination was variable. Finally, it was found that all beams with steel fiber reinforced had higher bond strength between concrete and steel bar than the beams without steel fiber while the beams with hybrid steel fiber reinforced had highest bond strength. A ductile failure was observed in the hybrid fiber reinforced beam specimens and it was determined that the result of multiple-crack behavior less crack width but more numbers cracked. Moreover, experimental data related to the bond strength obtained from RC beams with steel fiber were in very good agreement with analytical results.

Keywords:

Bond strength, Splice length, Hybrid-Fiber reinforced concrete, Full-Scale RC beams, Fiber combination,

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