Strengthening Reinforced Concrete Beams with Carbon Fiber Laminate Mounted in a U-Shape for Static and Vibration Purposes

In the present work, a quasi-static loading experimental campaign is aimed at assessing improvements in loading capacity and dynamic properties for strengthening concrete through the use of carbon fiber-reinforced polymers (CFRP), particularly when the strengthening is confectioned in a U-shape by introducing its lateral parts in grooves made in the covering of the concrete. Based on the experimental investigation, the flexural stiffness, deformation regime and parameters related to vibration analysis were assessed after applying the strengthening. Therefore, it was possible to obtain the moment-curvature relationship, the deflection of the central line of the beam using the Runge-Kutta method, and the stiffness and frequencies of the strengthened parts. A 12% increase in the loading capacity compared to traditional bonding was noted, as well as an increase of 127% for pieces without strengthening. The stiffness was elevated by 84% in relation to pieces without strengthening and 4% when compared to those with traditional strengthening while the frequencies increased by 36 and 2%, respectively, but without incorporating mass into the system. Although the attachment process was not capable of avoiding the debonding process, it is possible to conclude that U-Shaped CFRP strengthening is a feasible solution for stiffening civil structures, in applications of a static or dynamic nature.