Shear strengthening of reinforced concrete beams with SRG (Steel Reinforced Grout) composites: Experimental investigation and modelling

In the paper, the shear performances of reinforced concrete beams strengthened with externally bonded SRG (Steel Reinforced Grout) composites were analyzed experimentally, analytically and numerically. The aims of this study were: i) to assess the experimental behavior of the SRG shear strengthened reinforced concrete beams by the evaluation of the influence of the main mechanical and geometrical parameters such as the strengthening configuration (continuous and discontinuous U-shaped SRG strips), the distance between the U-shaped SRG strips, the number of SRG layers and, the presence/absence of anchors; ii) to evaluate the effectiveness in predicting the shear capacity of strengthened beams of an analytical model found on a new formulation of the “effective strain” determined through the results of direct shear tests and, iii) to define a numerical model found on a finite element procedure developed through commercial software to predict the whole behavior of SRG strengthened beams. Nine reinforced concrete beams, one un-strengthened and eight strengthened in shear with U-shaped SRG (Steel Reinforced Grout) strips were tested. The experimental results evidenced that in comparison with the un-strengthened beams, the shear capacity: a) increased up to 80% and 53% in beams strengthened with continuous and discontinuous U-wraps, respectively; b) increased with the number of SRG layers (19% and 80% in beams strengthened by continuous U-shaped strips with one and two layers of SRG layers, respectively; 25% and 53% in beams strengthened with discontinuous U-shaped strips with one and two SRG layers, respectively); c) decreased with the distance between the U-shaped strips and, d) increased in average of the 90% in presence of the anchors. Experimental results, those described in this paper and others available in the literature, were used to evaluate the effectiveness of both the proposed analytical and numerical models. The obtained results allow evidencing that the analytical model furnishes predictions of the shear capacity of SRG strengthened beams in good agreement with the experimental results (the average value of the predicted/experimental ratio was 0.98). A very good estimation of both the ultimate loads and corresponding deflections of strengthened beams with negligible errors (less than 5%) whit respect to experimental results was, also, obtained by the numerical model.