ملخص الدراسة:

In recent years, researches have been increasing towards studying the strengthening of concrete structures using different methods. Various studies have shown that structural concrete members such as square reinforced concrete (RC) columns can experience a significant increase in the ultimate load carrying capacity and ductility when strengthened by a concrete jacket. Despite the large number of performed studies, most of them did not consider the application of fibrous ultra high performance self-compacting concrete as a jacketing material. This study aimed at investigating the effectiveness of strengthening the entire height of downscaled square RC columns by applying Forta Ferro Polypropylene Fibrous Ultra High Performance Self Compacting Concrete (Fibrous UHPSCC) as a jacketing material. The experimental work included the fabrication of three identical unjacketed reference columns (UC) having similar cross sections of 100×100mm and 300mm high. Nine monolithically cast reference columns (MC) were fabricated having three cross sections of 150×150, 160×160, 170×170 mm and 300mm high. The UC and MC reference columns were made of normal strength concrete (NSC). A total of 27 identical column cores were made of NSC having similar cross sections of 100×100mm and 300mm high. The four sides of the 27 column cores were strengthened by applying three jacketing styles with three jacket thicknesses namely; 25, 30 and 35 mm. The applied three jacketing styles in this study were; Group1 (G1) consisted of nine column cores jacketed by Fibrous UHPSCC without steel reinforcement, Group2 (G2) consisted of nine column cores jacketed by Non-Fibrous UHPSCC with steel reinforcement, and Group3 (G3) consisted of nine column cores jacketed by Fibrous UHPSCC with steel reinforcement. All the fabricated column specimens were tested under monotonic uniaxial compression loading in order to investigate the ultimate load carrying capacity, longitudinal axial strain and failure pattern. A comparative study was performed between the jacketed column specimens and the reference columns. The G1, G2 and G3 jacketed column specimens showed significant increase in the ultimate load carrying capacity higher about 4.4 times than the UC reference column, and higher about 2.1 times than the MC reference columns respectively. The measured longitudinal axial strain of G1 and G3 jacketed column specimens was higher about 2.1 and 2.3 times than that of UC and MC reference columns respectively. Whereas the longitudinal axial strain of G2 jacketed column specimens was reduced by about 27% less than that of UC and MC reference columns. The results also revealed that the failure patterns and crack formation were significantly influenced by both the jacketing thickness and the jacketing style.

توثيق المرجعي (APA)