Nonlinear Analysis of Concrete Strength and CFRP Strengthening on RC Deep Beams

This study examines the influence of concrete compressive strength and Carbon Fiber Reinforced Polymer (CFRP) strengthening methods on the shear strength, load-carrying capacity, and failure modes of reinforced concrete deep beams. The objective was to evaluate how varying concrete compressive strengths (40 MPa, 45 MPa, and 50 MPa) impact the structural performance of unstrengthened and CFRP-strengthened beams. Two configurations of Carbon Fiber Reinforced Polymer—side-bonded and U-wrapped—were analyzed using finite element models, which were validated against experimental data. The results showed that higher concrete compressive strength improved the load-carrying capacity and delayed cracking, but the increase from 45 MPa to 50 MPa was minimal. CFRP strengthening, particularly the U-wrapped configuration, provided significant improvements in shear strength, crack control, and deflection, especially for beams with lower concrete strengths. Side-bonded CFRP also enhanced performance, but it was more effective in beams with higher concrete compressive strengths. The findings indicate that the U-wrapped CFRP configuration is more suitable for beams with lower compressive strengths, offering superior crack control and shear resistance, while side-bonded CFRP is more beneficial for higher-strength concrete beams. This study provides valuable insights for the design and strengthening of reinforced concrete deep beams in structural applications.