Study on Joining and Anchoring Mechanism of Various PC Tendons by Using Highly Expansive Material

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Joining and anchoring mechanism of ordinary PC tendons as well as FRP tendons by using Highly Expansive Material( HEM) were investigated experimentally and analytically. CFRP strand (φ12.5), PC steel strand (φ12.7) and PC steel bar (φ13) were examined as PC tendons. Main results of this research are summarized below.l. From the pull-out tests, it was found that the sleeve length of 30 cm and the amount of the expansive pressure more than 50 Mpa is satisfactory to hold firmly various PC tendons and HEM anchorage is also useful for practical applications.2. The mechanism which the softening zone of HEM in layer progresses gradually from loaded end to the free end according to the increment of the load, is almost the same regardless of the kinds of PC tendons.3. HEM thin layer considered as shear transfer layer is modified as shear spring. The characteristics of the shear spring depends on the amount of expansive pressure and the bond characteristics between PC tendons and HEM.4. The analytical results calculated by the FEM model, in which the shear spring considered the softening is used, were simulated well with the experimental results.5. From the long-term tensioning tests, the loss of prestressing is negligibly small in practice because the loss of prestressing becomes within 1.5% when the length of CFRP tendon is 10 m.