# Design Procedure of a Mono-Anchor Head for 2360 MPa High-Strength Steel Strand
## 1 Introduction  
Concrete is vulnerable to tensile stress, and prestressing is therefore utilized to prevent the cracking of concrete structures under a service load. Therefore, the construction of PSC structures capable of increased serviceability and durability is increasing, and in the United States, more than 45% of bridges designed and constructed after 2010 are built with PSC [1]. Prestressing methods are classified as the post-tension method in which prestressed steel is anchored on hardened concrete, and the pre-tension method in which tensioning of the prestressing steel is applied before the concrete is cast on prestressed steel. Both methods require anchoring to transmit tensioning forces to the concrete. The steel used for prestressing is 1720-2360 MPa, which is a higher level than other structural steel materials, but the ultimate strength of individual anchoring device is only 500 MPa. The stress resisting at the initial stage of anchoring is 80% of the ultimate strength, and 95% of the yield strength of the prestressing steel [2]. When a prestressing anchoring system fails, it is expected to cause enormous damage to structures, with a huge release of energy of prestressing tendons. Therefore, it is very important to find and solve the factors that threaten the safety of the anchor system. In prior studies, the safety of individual components is important to improve the performance of anchorage systems under sustained loads. Accordingly, many researchers have pursued improvement of the anchorage systemby considering the load pattern applied to the anchorage system, the shape of the anchorage device, the friction between parts, and the eccentricity according to the arrangement and shape of the wedge hole [3; 4; 5; 6; 7; 8; 9]. The main concern in these studies is fracture due to local stress concentration in the strand, which is the main cause of breakage in the anchoring system, and the purpose is to control the failure of the strand. These studies are limited to anchorage systems dealing with 1860 MPa prestressing steel. Previously, 1860 MPa class strands were used as the main member for prestressing, but with the launch of 2360 MPa class strands, a smaller number of strands can efficiently transmit prestressing force to concrete [10]. As the tensile capacity of the individual strands increases, the serviceability of anchorage devices that need to resist higher loads should be considered. [PERSON] et al. [4] applied the newly developed 2200 MPa and 2400 MPa single strands and performed tensile tests according to the combination of the components of the anchorage device of various specifications. They discussed the stress concentration of the strand by the anchorage device, and mentioned that a previously used anchorage device could be used to anchor the 2400 MPa grade strands. On the other hand, PTI [11] presents performance standards so that the anchor head can have a margin for safety. However, [PERSON] et al. [4] did not consider the evaluation of the mechanical damage of the anchor head during the tensile test. Therefore, when anchoring high-strength strands, the anchor head must be improved to satisfy the PTI performance criteria for anchoring devices. Anchorage devices used on construction sites must be approved for conformity based on proof tests [12]. To this end, newly designed products are accompanied by a static load test to determine suitability. However, the static load test, which has been mainly used in the past, takes a lot of time and money, so it is difficult to perform it every time depending on the design parameters to be determined. Therefore, many studies are optimizing based on numerical analysis and minimizing experiments to solve these problems [7; 10; 13]. On the other hand, structural analysis of anchorage devices has difficulty in reflecting actual behavior due to complex mechanical interactions.