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Ah Sir Cho,Thomas H.-K. Kang 한국콘크리트학회 2018 International Journal of Concrete Structures and M Vol.12 No.2
ACI 318-14 and 423.7-14 require the use of encapsulation system for an unbonded single-strand tendon for the purpose of corrosion protection and enhanced durability. In this study, load-carrying performance and hydrostatic tests were conducted for a newly developed, unbonded post-tensioning (PT) anchor with encapsulation, following the guidelines put forth in KCI-PS101 and ACI 423.7-14. The static load and fatigue tests as part of this study were used to evaluate the anchorage system behavior under static and cyclic loads, respectively. The hydrostatic test was used to demonstrate that the encapsulation system withstood at least 9.3 kPa of water pressure in a 24 h period according to ACI 423.7-14, and thus has been proven to promote the durability of unbonded PT single-strand tendons. Additionally, the push-in and jacking tests were used to assess the compressive and tensile strengths of the anchor as used in the field. Although these tests were not performed to failure for safety reasons, the anchor endured at least 1.18 and 1.02 times the nominal ultimate strength of a strand in each test, respectively. The authors’ previous load transfer tests were also reported in this paper, showing that test specimens with only two horizontal backup bars were capable of resisting at least 1.7 times the nominal ultimate strength of a strand. Based on the favorable results from the loadcarrying performance and hydrostatic tests, the developed encapsulated anchor systems are being applied in actual practice as an economically feasible option in Korean PT industry and are expected to improve the corrosion resistance and durability of posttensioned structures.
Computer-based design optimization of post-tensioned anchor for single-strand
Cho, Ah Sir,Kang, Thomas H.K. Techno-Press 2021 Advances in computational design Vol.6 No.4
In Korea, a 15.2-mm diameter strand is preferred for a post-tensioning (PT) method to reduce the total tendon and anchor number. However, the anchor for the Ø15.2-mm strand is large and sometimes inefficient while the anchor using the Ø12.7 mm single-strand is common in the United States. This study developed a post-tensioned anchor for Ø15.2-mm unbonded single-strand tendons to address the existing trend in domestic PT construction. The shape of the anchor is optimized to minimize the von Mises stress through a finite element analysis by varying the shape of the tubular body, bearing plate, and gussets. In addition, the design is also determined in consideration of a jacking device, accessories, and workability. ACI 423.7-14, on the other hand, requires the use of an encapsulation system, which is highly resistant to corrosion, for elevated floors. Therefore, the encapsulated anchor was also developed to enhance the durability of PT tendons and buildings.