Shear strengthening performance of fiber reinforced lightweight SCC beams

Abstract

In recent years, the demand for fiber reinforced lightweight concrete (FLWC) has increased rapidly to make high-strength, durable and lightweight structures. The strengthening behaviour of FLWC has never been studied in the literature and currently there are no standard guidelines for strengthened FLWC beams. Therefore, the main aim and objective of the current experimental study is to investigate the shear behaviour of fiber reinforced lightweight self-compacting concrete (FLWSCC) beams externally strengthened with CFRP strips. Six full-scale reinforced concrete (RC) beams were tested under four-point bending with varying CFRP strip spacing, number of layers, and configuration. One additional beam served as the control specimen to compare the performance of the strengthened specimens. The experimental results indicated that the external CFRP strips enhanced the strength and stiffness of the strengthened FLWSCC specimens. The strength enhancement ranged from 12% to 91% and pull out of steel fiber and debonding of CFRP strips was the predominant mode of failure in the control and strengthened specimens. The presence of steel fibers in the concrete has increased the shear strength of concrete and limits the external contribution of CFRP strips. Furthermore, all the experimental results were compared with theoretically predicted shear capacities using various FRP design standards for external strengthening. All the design standards have overestimated the shear capacity of FLWSCC specimens and CNR-DT (2013) design standard was found to be the most conservative as compared to other design standards. In addition, a lightweight modification factor has been recommended for strengthened FLWSCC beams