Penggunaan bar Polimer Bertetulang Gentian (FRP) sebagai alternatif kepada tetulang
keluli tradisional dapat membantu mengatasi masalah ketahanlasakan dalam struktur
konkrit bertetulang. Kelakuan struktur FRP-RC adalah memuaskan pada suhu yang
rendah sahaja, oleh itu, penggunaan bahan-bahan FRP mudah terbakar dalam
perdagangan, industri dan bangunan kediaman, di mana kemungkinan berlakunya
kebakaran adalah agak tinggi, boleh menjadi berbahaya. Penyelidikan lanjut
diperlukan untuk menilai dan meningkatkan prestasi struktur FRP-RC di bawah
keadaan kebakaran. Dalam kajian ini, kesan suhu yang tinggi ke atas sifat mekanik bar
FRP / Keluli, tingkah laku ikatan antara bar-bar FRP / keluli dan konkrit, dan tindak
balas lenturan rasuk konkrit dengan pelbagai jenis bar tetulang FRP telah disiasat
secara mendalam. Teknik tetopi-hujung keluli baru telah dicadangkan bertujuan untuk
memperbaiki tambatan bar FRP yang tertanam dalam konkrit. Untuk itu, sampel dalam
bentuk bar FRP / keluli, konkrit biasa, sampel tarik keluar dan rasuk (dengan dan tanpa
tetopi-hujung keluli) telah disediakan dan kemudian diawet selama 28 hari serta
seterusnya diuji sebelum dan selepas didedahkan kepada suhu tinggi sehingga 500°C.
Konkrit dan FRP bar mengalami pengurangan ketara dalam sifat-sifat mekanikal
mereka disebabkan oleh pendedahan kepada suhu yang tinggi. Kekuatan ikatan antara
bar-bar FRP dan konkrit telah berkurangan apabila terdedah kepada suhu dalam julat
125-325°C, dengan pengurangan mencapai sehingga 85%. Pengurangan ini telah
dipaparkan secara negatif dalam tingkah laku rasuk konkrit bertetulang FRP yang
dipanaskan, di mana beban retak, kapasiti beban muktamad, kekakuan dan jumlah
tenaga diserap telah berkurang sehingga 89%, 81%, 79%, dan 70%, masing-masing
manakala pesongan pertengahan rentang dan indeks kemuluran telah meningkat
dengan ketara sehingga masing-masing setinggi 50% dan 94%. Memasang tetopi
hujung keluli di hujung bar FRP telah meningkatkan kekuatan ikatan mereka dengan
konkrit sebelum dan selepas terdedah kepada suhu yang tinggi sehingga 325°C. Oleh
itu, prestasi lenturan rasuk konkrit bertetulang FRP dengan tambatan tetopi hujung
telah meningkat; beban retak, kapasiti beban muktamad, kekukuhan, pesongan pada
beban muktamad, jumlah tenaga terserap dan indeks kemuluran masing-masing telah
meningkat sehingga kira-kira (124%, 208%, 225%, 196%, and 453%) and (33%,
123%, 58%, 216% and 215%) sebelum dan selepas pemanasan sehingga 500 ° C,
berbanding dengan rasuk kawalan tanpa tetopi-hujung keluli. Berdasarkan keputusan
eksperimen, model analisis telah dicadangkan untuk meramalkan tingkah laku
bahagian menaik hubungan ikatan-gelinciran antara bar FRP yang berbeza dan konkrit
di bawah suhu yang tinggi. Satu kaedah teori juga tealah dicadangkan untuk
meramalkan keupayaan beban muktamad teori rasuk konkrit bertetulang FRP.
Ramalan kedua-dua model itu adalah bersetujuan dengan yang sangat baik dengan
keputusan eksperimen.
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The use of Fiber Reinforced Polymer (FRP) bars as an alternative to traditional steel
reinforcement helps overcoming durability problems in reinforced concrete structures.
The behavior of FRP-RC structures is satisfactory at only low temperatures, hence the
application of combustible FRP materials in commercial, industrial and residential
buildings, where the possibility of fire occurrence is relatively high, can be dangerous.
Further research to evaluate and enhance the performance of FRP-RC structures under
fire conditions is required. In this study, the effect of high temperatures on the
mechanical properties of FRP/Steel bars, bond behavior between FRP/Steel bars and
concrete, and the flexural response of concrete beams with different types of FRP bar
reinforcement was investigated in much details. A new steel-end-caps technique was
proposed aiming to improve anchorage of embedded FRP bars in concrete. For that
FRP/Steel bars, plain concrete, pullout and beam specimens (with and without steel
end caps) were prepared and then cured for 28 days and later tested before and after
subjected to elevated temperatures of up to 500°C. Concrete and FRP bars suffered
significant reductions in their mechanical properties due to exposure to high
temperatures. Bond strength between FRP bars and concrete had decreased upon
exposure to temperature in the range of 125 to 325°C, with the reduction reaching as
high as 85%. These reductions were reflected negatively in the behavior of heated
FRP-RC beams hence cracking load, ultimate load capacity, stiffness and total
absorbed energy were reduced by as high as 89%, 81%, 79%, and 70%, respectively
whereas mid-span deflections and ductility indices were increased noticeably by as
high as 50% and 94%, respectively. Attaching steel end caps to the ends of FRP bars
had improved their bond strength with concrete before and after exposure to high
temperatures of up to 325oC. Consequently, the flexural performance of FRP-RC
beams with end-cap anchorage was improved where the cracking load, ultimate load
capacity, stiffness, deflection at ultimate load, and total absorbed energy were
increased to reach as high as (124%, 208%, 225%, 196%, and 453%) and (33%, 123%,
58%, 216% and 215%) before and after heating up to 500°C, respectively, compared
with that of control beams without end anchorage. Based on the experimental results,
an analytical model was proposed to predict the behavior of the ascending part of bondslip
relation between the different FRP bars and concrete under high temperatures.
Another theoretical method was also proposed to predict the theoretical ultimate load
capacity of FRP-RC beams. The predictions of the two models were in an excellent
agreement with the experimental results.
Efficiency of using steel end caps in improving the post-fire flexural behavior of frp reinforced concrete beams_Rami J. A. Hamad_A9_2017_MYMY