Strengthening and Rehabilitation of Reinforced Concrete Slabs with Carbon‐Fiber Reinforced Polymers Using a Refined Bond Model

Abstract

Abstract: Slabs are one of the main load‐bearing elements in nearly every structure. Because of additional live loads or modifications of the building structure these slabs often have to be strengthened. Using externally bonded carbon‐fiber reinforced polymer (CFRP) strips to strengthen existing concrete structures has become common practice. One of the main failure modes is the loss of the composite action between the concrete and the CFRP strip making the bond force transfer very important. This bond force transfer depends on many parameters including the concrete strength, the ratio between shear force, and bending moment. A new parameter recently discovered by the Technische Universität München (TUM) is the deflection of the structural elements themselves. Because of this deflection self‐inducted contact pressure occurs. This contact pressure affects a higher bond transfer. The lower effective depth of slabs compared to beams causes higher deflections. In this article, first a few principles on the strengthening with adhesive‐bonded CFRP strips and the characteristics of the bond are explained. Then, the basics of the bond force transfer, at the end anchorage and in the rest of the element, are summarized. Based on these essentials, as well as numerous experiments, the change in the bond force transfer at the structural element caused by the curvature is then derived. With these findings, a complete verification concept is presented, which is ideal for computerized calculations. This verification concept is finally compared to several full‐scale test results presented in pertinent literature.