Effect of strengthening by carbon fiber reinforced polymer sheets on the flexural behavior of reinforced self-compacting concrete beams under repeated loads

This study investigates the effect of strengthening self-compacted concrete (SCC) beams using CFRP sheets on flexural behaviour subjected to repeated loads. During the experiment, six rectangular reinforced SCC beams were evaluated; two were reference beams without strengthening, while the remaining four were strengthened with CFRP sheets. The beam’s length, depth, and width are 2100 mm, 300 mm, and 200 mm, respectively. A monotonic load was applied to one of the reference beams, while repeated loads were applied to the remaining (compression cyclic loads). The main parameters studied in this experimental work were the type of loading (monotonic and repeated), the positions of strengthening and the dimensions of CFRP sheets. The flexural behaviour of these beams was investigated through experimental examination by recording the ultimate load and maximum deflection. Meanwhile, the cracks’ pattern and failure modes were observed. The findings of the present study demonstrated that the limited cycles of repeated loads have marginal effect on the flexural behaviour of the beams. This results in an ultimate load reduction of no more than 11%. It was also noted that SCC beams strengthened using CFRP sheets subjected to repeated loads significantly affected the flexural behaviour of these beams. Consequently, the ultimate load of the strengthened beams was improved by up to 18%. Besides, the maximum deflection of the strengthened SCC beams was reduced by 45% compared to those without strengthening. Using strengthening throughout the beams’ entire width and length that are subjected to repeated loads improved their ultimate load to surpass that of non-strengthened beams under monotonic loads by as much as 7%.