A feasibility study in which a pultruded fiber reinforced polymer (FRP) plank was used as the both formwork and the tensile reinforcement for a concrete structural member is described in this paper. The study was motivated by the desire to use the FRP plank as a stay-in-place form and reinforcement for a new bridge that is currently being designed in Wisconsin and will be constructed in early 2007. For the FRP plank and the concrete to act as a "composite" structural member a satisfactory bond at the interface between the smooth surface of the pultruded plank and the concrete must be developed. To achieve this interface, stone aggregates of different sizes were bonded to the surface of the pultruded FRP plank. Two kinds of aggregate, gravel and sand, were bonded to the pultruded FRP plank using a commercially available epoxy system. Concrete beams of different lengths were fabricated using a commercially available pultruded FRP plank. No additional flexural or shear reinforcement was provided in the beams. Two of the beams were used as control specimens. One control did not have any aggregate bonded to the FRP plank and the other control had internal steel reinforcing bars instead of the FRP plank. The beams were loaded by central patch load to their ultimate capacity. The experimental results were compared to current ACI 318 and ACI 440 code predictions. Depending on the length of the beam, shear or flexural failures occurred, which demonstrated satisfactory bond between the FRP plank and the concrete. The ultimate capacity of the aggregate coated FRP plank specimens was higher than that of the control specimens. This study demonstrates that the FRP plank has the potential to serve as formwork and as tensile reinforcement for appropriately sized concrete beams.
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