BOND OF FRP TO CONCRETE IN REINFORCEMENT RODS WITH AXISYMMETRIC DEFORMATIONS

摘要

The direct pull-out test was used to study the FRP/concrete bond behavior for machined glass/vinylester, carbon/vinylester, and carbon/epoxy FRP reinforcement rods with axisymmetric lugs. This test method allows for the measurement of the loaded- and free-end slips of the FRP rod and the placement of a strain probe inside the rod to monitor internal strain distribution (axial and hoop directions) without affecting the FRP/concrete interface. Glass/vinylester rods with five and ten lugs, and different lug widths and heights were studied. Increasing the embedment length did not increase the pull-out load linearly due to the progressive nature of failure of the lugs. Provided that enough confinement is used, concrete splitting did not occur. Bond between the machined FRP rods and concrete is controlled by failure of either the concrete or the lugs by shear near the interface between FRP and concrete. The internal strain probe was found to slightly reduce the pullout load, but did not affect the shape of the load-slip behavior or the bond mechanism.