Assessing the Efficiency of CFRP Discrete Confinement Systems for Concrete Cylinders

Abstract

Concrete columns requiring strengthening intervention always contain a certain percentage of steel hoops. Applying strips of wet lay-up carbon fiber reinforced polymer (CFRP) sheets in-between the existent steel hoops might, therefore, be an appropriate confinement technique with both technical and economic advantages, when full wrapping of a concrete column is taken as a basis of comparison. To assess the effectiveness of this discrete confinement strategy, circular cross section concrete elements confined by distinct arrangements of strips of CFRP sheet are submitted to a direct compression load up to the failure point. The influence of the width of the strip, distance between strips, number of CFRP layers per strip, CFRP stiffness and concrete strength class on the increase of the load carrying capacity and ductility of concrete columns, isevaluated.An analytical model is developed to predict the compressive stress-strain relationship of concrete columns confined by discrete and continuous CFRP arrangements. The main results of the experimental program are presented and analyzed and used to assess the model performance.

Premature Failure and its Prevention in Flexural Beams Retroftted by GFRP Fibers

“…These tests were performed for CFRP bars. Results of this study show that despite the low impact of the interrupted braids in increasing freight, the effect of the braids in the form of samples is very significant [1]. In this study, to increase bending and freight capacity in easier and more efficient way to use in out of laboratory environment.…”

“…In this study, he concluded: modification of epoxy resin with CNTs did not change the crack patterns and failure mode of retrofitted beams but delayed the propagation of carbon fiber sheet debonding and modification of epoxy resin with CNTs (B-CNT specimens) slightly improved the beams ultimate load by 5%, but significantly enhanced its stiffness and toughness by 35% and 28%, respectively, compared to B-NE specimens. [4] In order to compare the effects of wrapping as complete or interrupted wrapping with various intervals, carried out tests on samples with a diameter of 150 mm and a height of 300 mm cylindrical [1]. These tests were performed for CFRP bars.…”

Behavior in compression of concrete cylinders externally wrapped with basalt fibers

“…Similarly, some other specimens, for comparison, are wrapped with one or three sheets of carbon fibers, realizing a full wrapping. As a matter of fact, in the existing technical literature, other authors conducted researches on the efficiency of discrete and continuous confinement systems mainly concerning CFRP wrapping [38]. The experimental results carried out by Barros and Ferreira [38] showed that, as compared to the full-wrapping confinement arrangement, partial confinement arrangements were not as effective in terms of load carrying capacity, but provided a significant increase of the load carrying capacity, assured a high level of deformability at the specimen failure, were easier and faster to apply, and consumed less CFRP and epoxy adhesive materials.…”

Advancements in Retrofitting Reinforced Concrete Structures by the Use of CFRP Materials

“…The EBR technique has been used, mainly to increase the axial load carrying capacity, the ductility and the shear resistance of RC columns of circular or rectangular cross section of edges of similar dimensions, by applying a FRp jacket around the column [15][16][17]. The EBR technique is also used to avoid buckling of longitudinal steel bars and to enhance the bond behaviour of the starter bars in the lap splice zones.…”

“…However, taking into account that existing steel hoops assure certain concrete confinement, the effectiveness of discrete confinement arrangements, consisting on applying strips of FRp wet lay-up sheets in between existing steel hoops, can still be significant in terms of load carrying and energy dissipation requirements, and in terms of economy of FRp materials [17]. As verified in previous section, the NSM technique is quite effective for the flexural strengthening of RC slabs, but it is not effective in terms of enhancing the energy dissipation capacity of RC columns.…”