Influence of Stirrups and Concrete Strength on Behavior of RC Beams Strengthened in Shear with CFRP–Strips

Abstract

This paper presents the results of an experimental investigation conducted on rectangular RC beams strengthened externally in shear with CFRP-U strips. The main objective of this research was to evaluate experimentally and analytically the influence of the following parameters on the shear performance of such beams; amount of internal shear reinforcement with and without (stirrups), amount of longitudinal steel, and concrete compressive strength (normal and high strength). Test results indicated that the contribution of CFRP strips to the shear capacity of beams is strongly influenced by the studied parameters. CFRP strips are less effective when beams are heavily reinforced with stirrups. The gain in shear capacity increases as amount of longitudinal steel and/or concrete compressive strength increases. After analyzing the experimental results, the empirical model previously proposed by the author, to predict the contribution of CFRP-U strips, was modified to take the effect of the studied parameters into consideration. The modified model can predict the experimental results with acceptable accuracy, while ACI code guidelines fail to capture the influence of the studied parameters. At the end, recommendations for further work have been given.