Tensile behaviour of FRP grid strengtheneing ECC composite under a uniaxial loading

Abstract

As the fibre reinforced polymer (FRP) sheets/textiles strengthening the inorganic cementitious materials technique was presented by some researchers, a few of potential shortcomings, such as penetrating difficultly of cementitious materials to and much brittle of FRP sheets, have been found in recent years. Therefore, a new strengthening system, which was FRP grid strengthening ECC system, in combination with the Engineered Cementitious Composites (ECC) and FRP grid was proposed by the present authors. By applying this system to reinforce the reinforced concrete (RC) beams, the dual strengthening effects can be provided and the intermediate crack-induced debonding failure can also be suppressed by externally bonded the FRP gird reinforced ECC composite layer to the tensile surface of the original RC beams. To investigate the tensile mechanical behaviour of FRP gird reinforced ECC composite layer, six non-strengthened ECC specimens and eighteen basalt fibre reinforced polymer grid (BFRP) strengthening ECC composite specimens (FRP-ECC specimens) subjected to the unidirectional axial tensile loading were conducted in this paper. Three kinds of different thickness BFRP grid were applied to investigate their reinforcement effects. The test results showed that there was no slip at the interface of BFRP grid and ECC substrate significantly. The failure modes were the internal PVA fibers ruptured or pulled out from ECC substrate for the non-strengthened ECC specimens and the rupture of BFRP reinforcements of grid for the strengthened FRP-ECC specimens. The axial stiffness of FRP-ECC specimens and the ultimate tensile stress and strain were obviously increased after the ECC substrate cracked, which indicated the contribution of the internal BFRP grid reinforcements. Moreover, an analytical model was also presented to predict the stress-strain relationship and the tensile strength of the FRP-ECC specimens and validated through comparison with the rest results.

Comparison of calculation models for flexural capacity of RC beams strengthened with TRC in China and Germany

“…The strength of textile reinforcement is determined by tensile experiments on textile rovings. In addition, some authors in China, 14,19,20 use a bilinear curve to describe the tensile behavior of the textile concrete layer instead of only textile rovings (Figure 3B). It is mainly used when the textile reinforcement is combined with high ductile concrete, such as engineered cementitious composite (ECC) and ultra‐high toughness cementitious composite (UHTCC).…”

“…3.2 | Model based on the German literature 27,28 In the following example, the effect of pre-loading is considered according to Reference 27. The strain distribution of the cross-section before strengthening is determined iteratively from the given values in Table 2 by using the Equations ( 16)- (20). The iterative steps and the used equations are listed in Table 4.…”

Investigation of the Performance of Rc Beams Reinforced With FRP and Ecc Materials

“…Zheng et al proposed a new strengthening method for RC beams by combining basalt FRP grid and ECC materials as a composite reinforcement layer (CRL). The proposed technique is effective for suppressing the debonding of externally bonded materials and fully utilizing the strength of the material (Zheng & Wang, 2015;Zheng et al, 2016Zheng et al, , 2018.…”