Refuerzo a Cortante de Estructuras de Hormigón Armado Con Laminados de Polímeros Reforzados Con Fibras (FRP) : Verificación Experimental

Download or read book Refuerzo a Cortante de Estructuras de Hormigón Armado Con Laminados de Polímeros Reforzados Con Fibras (FRP) : Verificación Experimental written by Mireia Pujol and published by . This book was released on 2018 with total page 231 pages. Available in PDF, EPUB and Kindle. Book excerpt: The use of externally bonded fibre reinforced polymers, FRP, for strengthening reinforced concrete (RC) beams or columns is an alternative to other traditional strengthening techniques due to its high strength-to-weight ratio, stiffness-to-weight ratio, and improved durability in comparison to steel. The use of FRP for shear strengthening is not as widespread as flexural strengthening or column confinement. One of the main reasons is that the shear resisting mechanisms of FRP strengthened elements are more complex. In addition, there is still no universally accepted model to evaluate the contribution of the FRP to the shear strength of the reinforced element, because this contribution is strongly related to the stress level of the external reinforcement, which is linear elastic up to failure and does not yield as conventional steel. The total shear strength of an structural element is given by several components: concrete, longitudinal and transverse steel reinforcement and external FRP reinforcement. The contribution of each part is difficult to evaluate, since there is an interaction between them. This coupling effect is not taken into account in the major part of the current models, which are additive without considering the possible modification of the shear component resisted by the concrete, Vc, and by the steel, Vs, due to the existence of the FRP, VFRP. The present thesis aims to identify and quantify the contribution of each component that contributes to resist the shear force of RC elements externally strengthened in shear by FRP, as well as the interaction between them. For this purpose, 20 shear tests of RC beams with a T-section, externally strengthened by FRP sheets have been performed. The influence on the shear strength of different FRP reinforcement ratios in a U-shaped configuration and the influence of two longitudinal steel reinforcement ratios have been analysed. The thickness of the FRP laminate has been kept constant, as well as the spacing between the sheets which is the same as the stirrups spacing. The different FRP reinforcement ratios correspond to different widths of the sheets applied to the beams (discontinuous of 50 or 100 mm wide, or continuous). In the control beams, upon a certain load level, a critical shear crack appears in the web with a certain inclination. Failure occurred when this critical shear crack propagated through the flanges with less inclination up to the load application point. In the tests with U-shaped FRP sheets, a premature debonding of the reinforcement was observed once the critical shear crack opened. Failure occurred in a similar manner when the critical shear crack propagated through the beam flanges to the load application point. In some tests, especially those with a greater longitudinal reinforcement ratio, the ultimate load was similar to that of the control beam. In order to avoid premature debonding of the reinforcement, two types of anchorage were designed and applied in some of the tests. The anchors held the transverse FRP sheets once the critical shear crack opened and propagated, delaying debonding. Failure occurred in a similar manner but for a higher ultimate load in compariston to the unanchored beams. In order to quantify the different contributions of concrete, transverse steel and FRP reinforcement to the shear strength, the beams were instrumented with strain gauges and displacement transducers. The analysis of the information provided by the instrumentation has allowed to estimate the contribution to the shear strength of the concrete web, concrete flanges, the longitudinal and transverse steel reinforcement and the FRP sheets.