ABSTRACT: 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 3 1,800 3 200 mm (4 ft 3 6 ft 3 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.