Evaluation of hysteretic response and strength of repaired R/C walls strengthened with FRPs

Experimental data from cyclic tests of eleven wall specimens, first tested to failure and subsequently repaired and strengthened using FRP sheets, and retested, are used to evaluate the hysteretic response characteristics of such members. Displacement ductility factors, contribution of individual deformation modes to total displacement, energy dissipation, and stiffness degradation, calculated from post-processing of experimental data, are presented. An attempt is then made to validate the currently available relationships for estimating flexural and shear strength of FRP-strengthened reinforced concrete (R/C) walls against experimentally measured values. The formulas adopted by international codes (Europe, US, Japan) and others from the literature for the estimation of shear and flexural strength were used. The analytically derived shear strengths were higher than the shear corresponding to the development of flexural strength; this was also evident from the failure modes observed during the test. Theoretically predicted flexural strength is higher than the experimental one when failure of the composite material is considered, but lower when failure of anchorage or debonding on both sides of the main flexural crack is considered.