Strengthening of Ultra-high Performance Concrete Beams with CFRP Strips

Abstract This study explores the structural enhancement of ultra-high-performance concrete (UHPC) beams through the application of carbon fiber-reinforced polymer (CFRP) strips in various reinforcement configurations. The experimental program evaluated several CFRP arrangements, including full-face wrapping, U-shaped and side bond, and strips applied at different angles. These configurations were assessed to understand their influence on the beams' shear resistance and failure modes. Six samples of ultra-high-performance concrete, 2050 mm long, 200 mm wide, and 400 mm thick, were used, reinforced with five (16 mm) diameter reinforcing steel bars, distributed three at the bottom and two at the top with only two shear links (10 mm) diameter reinforcing steel bars were used to ensure the main reinforcement was distributed in the appropriate place, noting that they were placed outside the supports to ensure that they did not contribute to the shear resistance. All materials used in the research were subject to laboratory tests and are shown in detail, as will be explained later. This study presents an experimental investigation into the effectiveness of carbon fiber-reinforced polymer (CFRP) strips in enhancing the shear behavior of ultra-high-performance concrete (UHPC) beams. Various reinforcement configurations were examined to determine their impact on structural performance. Results revealed that CFRP significantly improves the shear capacity of UHPC beams, with inclined and wider sheet applications proving especially effective. The most substantial enhancement (63.288%) was achieved through complete face wrapping, while U-shaped and side-bonded configurations also yielded notable gains ranging from 44% to 60%. CFRP reinforcement not only increased load-bearing capacity but also altered failure modes, often shifting them from shear-dominated to flexure-dominated. These findings highlight the importance of CFRP configuration and orientation in optimizing UHPC structural performance under shear loading. These results highlight the importance of reinforcement configuration and orientation in optimizing the structural performance of UHPC beams using CFRP materials.