Numerical simulation of the shear behaviour of reinforced concrete rectangular beam specimens with or without FRP-strip shear reinforcement
The successful validation of a numerical model is presented that can realistically approximate the shear behaviour of reinforced concrete (R/C) rectangular beams strengthened against shear with externally applied open hoop fibre reinforcing polymer (FRP) strips. For this purpose, the measured load-deformation response of ten (10) full-scale R/C beam specimens is utilised. These specimens were loaded monotonically in a four-point bending arrangement up to failure. Open hoop FRP strip shear reinforcement was applied externally to upgrade the shear capacity of eight (8) R/C beam specimens. Four of these specimens had these FRP strips without anchorage, whereas for the other four the FRP strips were attached together with novel anchoring devices. This successful numerical simulation predicts with a very good degree of approximation the observed load-deformation behaviour and the ultimate shear capacity of all these specimens as well as the observed modes of failure including diagonal concrete cracking, debonding of the FRP strips in the case of no anchoring, or the plastification of parts of the anchoring devices plus the adjacent crushing of the concrete.
EXPERIMENTAL MEASUREMENTS AND NUMERICAL SIMUATION OF NOVEL ANCHORING DEVICES FOR OPEN HOOP FIBER REINFORCING POLYMER STRIPS USED IN THE SHEAR UPGRADE OF R/C T-BEAMS
Shear strengthening of reinforced concrete (R/C) T-Beams can be achieved by open hoop FRP strips applied externally as transverse reinforcement. Unless these FRP strips are anchored the transfer of tensile forces developing in these strips relies solely on the interface between the FRP sheet and the concrete contact surface. In this case, the delamination (debonding) mode of failure of these FRP strips is very likely to occur, disrupting the effectiveness of such a shear strengthening scheme. Consequently, there is need to study both this debonding mode of failure as well as various forms of effective anchoring. For this purpose a number of special unit T-Beam R/C specimens were fabricated employing open hoop FRP strips with or without anchoring. One type of anchoring that was tested is based on a novel anchoring device. It was demonstrated that an anchoring scheme devised by the authors can provide the necessary satisfactory transfer of forces between the FRP strip and the concrete volume of the R/C T-Beam. This used testing arrangement was also numerically simulated employing the exact properties of the materials which were used in the experimental sequence. Two different types of numerical models were studied. The first was without any anchoring device whereas the second the novel anchoring device that was employed during testing was simulated in detail. It can be demonstrated that the used numerical simulation predicts in a satisfactory way both the bearing capacity as well as the mode of failure that was observed in the test specimens with or without the anchoring device. 120 Available online at www.eccomasproceedia.org Eccomas Proceedia COMPDYN (2017) 120-141 © 2017 The Authors. Published by Eccomas Proceedia. Peer-review under responsibility of the organizing committee of COMPDYN 2017. doi: 10.7712/120117.5412.16891
Shear Strengthening of Continuous Reinforced Concrete Beams Using Externally Bonded Carbon Fiber Reinforced Polymer Sheets
This paper presents the results of an experimental investigation on the response of continuous reinforced concrete (RC) beams with shear deficiencies, strengthened with externally bonded carbon fiber reinforced polymer (CFRP) sheets. The experimental program consisted of nine full-scale, two-span, continuous beams with rectangular cross section. The tested beams were grouped into three series. Three beams, one from each series, were not strengthened and taken as reference beams, whereas, six beams were strengthened using different schemes. The variables investigated in this study included the amount of steel shear reinforcement, amount of CFRP, wrapping schemes, and ply combination. The experimental results indicated that the contribution of externally bonded CFRP to the shear capacity of continuous RC beams is significant and is dependent on the tested variables. In addition, the test results were used to validate shear design algorithms. The proposed algorithms show good correlation with the test results and provided conservative estimates.