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Concrete In Australia : March 2011
Concrete in Australia Vol 37 No 1 27 reinforcement bar was installed within a mechanical chase, which was found to later enhance the substrate properties over the length of the anchorage zone resulting in a higher FRP-to- concrete bond strength. Type 2 -- e concept was developed to address two objectives: (1) to investigate the effectiveness of unidirectional fabric to resist the tensile peeling stresses in the anchorage zone and (2) to pursue the potential for the distribution of fibre-adhesive stresses over a greater area of concrete, resulting in enhanced anchorage capacity. For this purpose, two plies of 250 mm wide unidirectional FRP fabric were applied horizontally across the end of the laminate and at the web-flange interfaces, as seen in Figure 4. e direction of fabric fibres were 90° to the direction of laminate. e first sheet of fibre overlayed the second, sandwiching the laminate strip in between. Type 3 -- In order to sufficiently enhance the anchorage capacity and to provide the continuous transfer of tensile stresses around the web-soffit joint, a scheme was devised consisting of two plies of L-shaped lengths of FRP unidirectional fabric applied to the corners of a box section. ese were appropriately lapped with a FRP laminate which was applied to the main faces of the concrete prism, as seen in Figure 4. Type 4-6 -- In order to provide a more efficient distribution of anchorage bond stresses over a larger area of concrete the use of a bidirectional fabric with ±45° fibre orientation relative to the direction of the laminate was investigated. e nature of the bidirectional fabric meant that it could also be successfully applied around the transition between the outer webs and the deck soffit of the box section. Anchorage types 4, 5 and 6 represented variations of the same concept involving the application of one ply, two plies and a combination of unidirectional and bidirectional fabrics respectively. 4.0 LABORATORY PROGRAM 4.1 Specimen design Full scale test specimens were designed with material properties extrapolated from onsite test data. Consideration was given to the following parameters: the depth of the concrete free edge dc, FRP bond length Lf and the width ratio between the FRP strip and the concrete prism bf/bc. Each of the above parameters was selected to provide the most representative distribution of bond stress within the depth, length and width of the concrete specimen. Figure 4 presents the resulting specimen geometry and material properties used throughout the laboratory program. Figure 4. Anchorage types 0 and 2-6 specimen geometry and material properties (a) type 0; (b) type 1 (WG1, WG2); (c) section 1; (d) type 2 (WG35, WG4); (e) type 3 (WG5, WG6, WG7); (f) type 4 (WG12); (g) type 5 (WG10, WG11); and (h) type 6 (WG8).