An Experimental and Numerical Study on Continuous RC Deep Beams Strengthened with CFRP Strips

This paper presents the result of a research program and includes numerical analysis and experimental studies on continuous reinforced concrete deep beams and strengthening of these beams with carbon fiber reinforced polymer (CFRP) strips. Different shear span-to-overall depth ratio (a/h) between 1 and 0.33, and various reinforcing methods with CFRP strips were studied. The cracking behavior and failure modes of these beams were investigated. The experimental and numerical analysis indicated that CFRP strips significantly affect the shear capacity of continuous deep beams and their failure modes. Three experimental specimens strengthened with diagonal CFRP strips at 45 degrees angle showed a 29%, 31%, and 24% increase in the bearing capacity, in comparison to their control beams. Among different CFRP strip arrangements in beam models, diagonal reinforcement at a 45 degrees angle (SS45) was the most effective one, which increased the shear capacity up to 49%. Vertical U-wrap side arrangements (US90) showed the lowest increase in the bearing capacity for the beams. U strengthened beam models' bearing capacity increased by 16%, 15%, and 13% compared to their control beams. Experimental and numerical results showed that (a/h) ratio is a key factor affecting deformability and the ultimate strength of continuous deep beams. The ultimate strength of continuous concrete deep beams increased when the a/h ratio decreased, and the mid-span deflection decreased with decreasing the a/h ratio. Finally, the load-bearing capacities of beams were compared with the internal and external indeterminate strut-tie analysis. The results of numerical modeling and experimental studies have high compatibility with indeterminate truss analysis with a 1% difference in the final load.