Shear capacity investigation of RC concrete beams using self-prestressing Fe-based shape memory alloys strips

Shear failure is a sudden and brittle failure, which causes human and economic losses. Hence, enhancement of shear capacity is critical for shear-deficient members of existing structures. In this study, the effectiveness of using Shape Memory Alloy 'SMA' strips on the shear capacity of reinforced concrete (RC) beams was investigated in a series of experiments. The experimental work included the study of six RC beams with a 200 x 300 mm cross-section considering shear parameters such as transverse shear reinforcement and the effect of prestressing. Beams were strengthened in U configuration using Fe-SMA strips 30 mm wide and anchored by one expansion anchor (M10-Hilti). The testing was performed in a simply supported condition where each beam was tested twice. The purpose of testing specimens twice was to confirm the results. The activation of the strips was ach-ieved by heating the strips using a custom-made heater up to 200 degrees. The method was proven effective, with an increase in shear capacity of up to 32-45% and 24-25% for specimens strengthened with passive strengthening (non-activated strips) and specimens strengthened by activated SMA strips, respectively. However, the active strengthening improved serviceability conditions by delaying the appearance of cracks and reducing the crack width. The occurrence of the main crack was delayed by 12.5-19.2%, the width of the crack was reduced by more than 65% compared to the reference beam, and the angle of the main crack increased compared to the reference beam as a result of activation. Beams containing internal transverse reinforcement performed better than the beams without shear reinforcement.