Out-of-plane strengthening of masonry walls with reinforced composites

This paper presents an investigation into the effectiveness of using fiber-reinforced composite overlays to strengthen existing unreinforced masonry walls to resist out-of-plane static loads. A total of fifteen wall panels [1,200 x 1,800 x 200 mm, (4 ft x 6 ft x 8 in.)] were tested. Twelve panels were assembled with fiber-reinforcing systems attached to the tension side, and the remaining three control walls were left without any external reinforcement. Two configurations of external reinforcement were evaluated. The first reinforcement configuration consisted of two layers of fiber-reinforced plastic webbing and the second consisted of vertical and horizontal bands of undirectional fiber composites. The three wall specimens without external reinforcement were tested to evaluate the change in the system strength and behavior with application of the external reinforcing systems. In addition to the two fiber configurations, the testing program also evaluated two methods of surface preparation of the walls, sand blasting, and wire brush. All specimens were thoroughly washed by water jet, 48 hours prior to application of the fiber-reinforcing systems. Three specimens were tested for each variable. A uniformly distributed lateral load was applied to each panel using the procedures described in the ASTM Standard E-72 Test Method (airbag). Failure loads, strains in the external reinforcement (FRP), out-of-plane deformations, and failure modes were recorded. Recommendations on the usefulness of the proposed technique as a means of strengthening masonry walls for out-of-plane loads are presented. In general, flexural strength of masonry walls can be increased if the shear failure is controlled.