Flexural behaviour of reinforced concrete beams strengthened with a composite reinforcement layer: BFRP grid and ECC

In this paper, a new strengthening technique for reinforced concrete (RC) beams is proposed by combining Basalt fiber Reinforced Polymer (BFRP) grid and Engineered Cementitious Composites (ECC) as a composite reinforcement layer (CRL). Five RC beams externally bonded with the CRL at the soffit and one control RC beam were tested to investigate their flexural behaviour. The thickness of BFRP grids (i.e. 1 mm, 3 mm and 5 mm) and the bonded length of CRL (i.e. 400 mm, 450 mm and 500 mm) were selected as two main parameters in the test program, while the width and thickness of CRL were fixed approximately at 200 mm and 30 mm, respectively. The test results showed that there is no clear CRL debonding in the strengthened beams. The two final failure modes were concrete crushing or rupture of the BFRP grids, indicating that the proposed technique is effective in suppressing the debonding of externally bonded materials and fully utilizing the material strengths. An analytical model is also presented to predict the load-deflection responses of the strengthened beams, which was validated through comparisons with the test results.