Experimental and FE study on RC one-way slabs upgraded with FRP composites

The use of externally bonded Fiber Reinforced Polymer (FRP) composites as a means of upgrading the flexural capacity of Reinforced Concrete (RC) one-way slabs is experimentally and numerically investigated in this study. A total of four groups of eight slabs were tested under four-point bending. The two slabs of the first group were left unstrengthened to be used as control specimens. The two slabs of the second group were externally strengthened with adhesively bonded pultruded, pre-cured CFRP plates. The four slabs of the last two groups were externally upgraded with unidirectional carbon (or E-glass) fiber fabric impregnated with an epoxy resin. In addition to the experimental program, a numerical investigation utilizing nonlinear Finite Element (FE) analysis was conducted using LS-DYNA software. Besides the eight slabs tested in this study, another eleven slabs were collected from the literature for the purpose of finite element validation. A comparison was made between the experimental and numerical results and good agreement was achieved. Based on FE validation, the numerical analysis was extended to include additional cases to study the effect of axial FRP stiffness and FRP-to-concrete width ratio on the flexural performance of upgraded slabs. As a result of the numerical study, new stiffness and reinforcement parameters were introduced in this research. These parameters were employed in the development of two new formulas for predicting the FRP debonding strain and percent gain in flexural capacity of FRP-strengthened slabs.