Presented herein is a procedure and numerical results for flexural rigidity characterization of Fiber Reinforced Polymer (FRP) plates retrofitted with various types of fabrics. The FRP plates were retrofitted with Kevlar® 49 (Aramid), Carbon Fiber (Harness-Satin H5), and Unidirectional Carbon Fiber (T700 Aerospace Grade) fabrics, respectively. The FRP plate flexural rigidity values were calculated with a central finitedifference iterative scheme while utilizing the experimental load-deflection relations based on bending tests. The tests were performed on each plate by applying a concentrated load at the center. A fourth-order partial differential equation of plate equilibrium was adopted to estimate the plate flexural rigidities and ultimately obtain the theoretical load-deflection relations. The results were verified with Navier\u27s solution for the same type of loading. Excellent agreement was found between the two approaches. The flexural rigidity estimation procedure can be used for more complex retrofitted plates while utilizing homogenous plate deflection equations. The FRP plates showed a significant increase in flexural rigidity, with the Aerospace Grade Carbon fiber fabric providing the most significant increase
