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Concrete In Australia : March 2013
34 Concrete in Australia Vol 39 No 1 FEATURE: ANCHORING & PRECAST similar average value to the PCI 5th Edition equation, but with a smaller standard deviation. is is since the model of the four-sided pyramid that forms a slope of 35° with the horizontal surface better simulates the failure surface and therefore failure load when compared with the PCI (5th edition) 45° model. It should be noted that in all of these pull-out tests, edge effects were not a factor in the failure. ese test results align with previously published data 5, 6, 7. e edge-lift anchor test data was compared with the predicted capacity as determined using the ACI 318-08M average capacity formula as a mechanism of comparison to the well-established relationship for foot anchors presented in literature and verified in the tests of Series 7. e ratio of the test failure load and the predicted load as per ACI 318-08M is shown in Table 5 and Figures 6 (a) through (e) for each series of panel tests with edge lift anchors. e ratio of test failure load to predicted failure load is plotted against the square root of the concrete compressive strength since the predicted strength is a function of and directly proportional to the square root of compressive strength. For the two series of panels with edge-lift anchors and no central mesh reinforcement in the panels; Series 1 and Series 2, the following observations were made. e addition of shear and perimeter bars (Series 2) resulted in a slightly increased absolute failure load for comparable tests and is indicated by a slightly higher average ratio of test/ predicted compared to Series 1. Since the manufacture of panels without central mesh is impractical, the number of tests conducted was small; however, the test results are valuable as an indicator that the provision of the perimeter bars is likely to be beneficial to the capacity of the anchor. us this detail (N16 perimeter bar) along with central panel mesh of SL82 was subsequently used in Series 3, 4 and 5. For the three series of panels with central mesh reinforcement and N16 perimeter bar in the panels; Series 3, Series 4 and Series 5, the following observations were made. Series 3, the edge-lift anchors with no additional N12 or N16 shear bar reinforcement, has a significantly higher capacity than the unreinforced panels as indicated by the value of test/predicted ratio average of almost 2.5. e two series with additional shear bar of either N12 or N16 had similar average and range of test/predicted apparently less than the panels without shear bars; however, Series 3 had more tests conducted at lower concrete strengths and it is these test results which appear to magnify the average ratio and the standard deviation of the data for Series 3. Further analysis of the data for trends is being undertaken. Additionally, it should be noted that the anchors were tested in tension only and at this stage of the research program, shear tests and combined tension/ shear tests have not been completed. Analysis of the impact or potential benefit (or otherwise) of the shear bars can only be made after further testing in shear and combined loading has been finalised. ese tests will simulate the anchor loading as the panels are tilted from the horizontal position to the vertical position where the anchor is engaged in tension. 4.0 CONCLUSION is paper is an evaluation of pull-out test data for edge- Figure 5. Panel of Series 7 with failed footed anchor. Table 4. Assessment of tensile strength due to concrete formula of PCI 5th Edition 13 and ACI 318-08M 2 for tests that failed in the concrete. (Series 7). Table 5. Assessment of tensile strength due to concrete formula of ACI 318-08M 2 for panel tests conducted with edge-lift anchors. Series N, number of Tests Test / Predicted Range Average Test/ Predicted Standard Deviation Test/ Predicted Series 1: No reinforcement 5 .76 -- 1.09 0.87 0.16 Series 2: N16 shear bar, N16 perimeter bar 6 .87 -- 1.21 0.98 0.13 Series 3: SL82 mesh, N16 perimeter bar 77 1.52 -- 2.99 2.09 0.30 Series 4: N16 shear bar, SL82 mesh, N16 perimeter bar 29 1.53 -- 2.19 1.92 0.18 Series 5: N12 shear bar, SL82 mesh, N16 perimeter bar 37 1.46 -- 1.92 1.69 0.12 Concrete Capacity Formula -- Footed Anchors Test / Predicted Number of tests ACI 318-08 Average concrete capacity .55 - 1.65 60 PCI 5th Edition concrete formula .62 - 2.2 60 ACI 318-08 5% fractile, concrete formula .63 - 2.1 60