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Concrete In Australia : March 2011
Concrete in Australia Vol 37 No 1 29 4.2 Experimental setup e near end supported (NES) single pull test configuration was adopted for direct shear testing of each anchorage specimen. A test rig was constructed to ensure each specimen was able to be securely fixed to a Baldwin Universal testing machine which clamped the specimen into place. e rig was carefully designed to eliminate any forward movement of the concrete specimens that may occur during loading. e final testing configuration is presented in Figure 5. 4.3 Test preparation and material properties Two alternative concrete prism dimensions suitable for each anchorage type were utilised in the experimental program. Type A reinforced concrete blocks of dimension 250 mm x 300 mm x 600 mm (Figure 4a, 4b, 4d, 4e) were utilised for anchorage types 0, 2 and 4. Anchorage types 3, 5 and 6 utilised two (type B) reinforced concrete blocks of dimension 200 mm x 400 mm x 600 mm with a curved end recessed from the base of the prism (Figure 4f, 4g, 4h). Blocks were reinforced nominally with 4 x 16 mm diameter bars at 200 mm centres each face to replicate the existing reinforcement present in the box girder webs. e reinforcement cover used was 30 mm. All specimens consisted of a single laminate strip bonded to the surface of the concrete block with a bond length of 500 mm for concrete block type A and 425 mm for block type B. Table 1 summarises the material properties used in the specimen construction as per manufacturer's specifications. 4.4 Instrumentation and loading procedures e specimens were loaded under displacement control at a load rate of 1 mm/min. Strain and load results were obtained from surface mounted strain gauges and a 3D non-contact measuring technique based on image correlation photogrammetry (GOM mbH, 2005). e 3D photogrammetry measurements were taken using a pair of high resolution, digital CCD (charged couple device) cameras. rough sophisticated processing of image pixel displacements during loading, stress and strain values could be calculated at any location within the imaging zone for direct comparison with strain gauge measurements. A series of strain gauges were placed on the FRP laminate in the locations shown in Figure 5. Gauges G1 and G2 were installed at the front and back of the laminate to monitor any bending in the FRP plate during testing indicating the presence of tilting. G1 was placed at the back of the laminate and G2 at the front at the same location. e remaining gauges were used to monitor strain levels along the length of the laminates and in the direction of bidirectional fibres. 4.5 Experimental results A total of six concrete cylinders were tested to assess the concrete properties, which exhibited an average compressive strength of 62 MPa after 53 days curing at room temperature. Pull-off tests conducted in accordance with (I.S. EN 1542 1999) verified a bond interface failure that occurred within the concrete at a bond pressure of 3.6 MPa. is suggested complete bonding between laminate strip and concrete Type Ref Pmax Max laminate strain (µε) Max strain in FRP ±45° fabric (SG) Max strain in FRP ±45° fabric (AR) Max bond stress (Zone: 0--175mm from edge) Failure mode SG/AR (kN) SG (με) AR (με) LS (με) RS (με) LS (με) RS (με) SG (MPa) AR (MPa) 0 WG9 99.6 2535 2706 -- -- -- -- 5.2 5.1 CSF 1 WG1 194.4 4640 4434 -- -- -- -- 11.3 11.0 CSF/ ASF WG2 198.5 4881 4733 -- -- -- -- 17.5 10.9 CSF/ ASF 2 WG3 138.2 3242 3212 -- -- -- -- 9.57 8.73 CSF WG4 142 3142 3235 -- -- -- -- 4.35 4.11 CSF/ ASF WG5 156.5 3470 3607 -- -- -- -- 4.59 5.14 CSF/ ASF 3 WG6 146 3239 3488 -- -- -- -- 5.34 5.22 CSF/ ASF WG7 145.3 3245 3204 -- -- -- -- 6.16 7.71 CSF/ ASF 4 WG12 218.3 5800 4867 12896 13632 13136 -- -- -- CSF/PLR/PFR 5 WG10 213 4900 5261 5228 5225 3982 -- -- -- CSF WG11 236.9 5300 -- 7433 12834 -- -- -- -- CSF 6 WG8 261.4 7500 7589 4177 4372 4054 -- -- -- PASF/LR Note: CFS (Cover separation failure); ASF (Adhesive separation failure); PASF (Partial Adhesive Separation Failure); LR (Laminate Rupture); FR (Fabric Rupture); LS (fabric left ride of laminate); RS (fabric right side of laminate) Table 2. Maximum FRP elongations and corresponding effective FRP strains and utilisation percentiles.