## 3 Experiments  
Eleven specimens were fabricated for the load-transfer test in accordance with both the anchorage supplier's design and EAD 160004-00-0301 [22], all of which were made using the same concrete mixture. All specimens had square sections (\(c\times c\)) and lengths that were twice the sectional dimension (\(h=2c\)). Cylindrical specimens 100 mm in diameter and 200 mm in height were made based on ASTM C31 [26] and cured under the same conditions as the anchorage zone specimens. The average concrete strength, based on ASTM C39 [27], was 32.6 MPa on the day of the test. The average yield strength of the rebar was 455 MPa, and the average yield and tensile strength of the cast iron in the anchorage bearing plate were 184 and 288 MPa, respectively. The diameter of the anchor head and the diameter of the hole on the top surface of the anchorage bearing plate were 199 and 125 mm, respectively, as shown in Figure 2a. Details of the specimens are given in Table 1 and Figure 3. Identical anchorage devices were used in the test, each of which accommodated 12 strands and had a square bearing plate and a horizontal rib at the center of the anchorage in the longitudinal direction, as shown in Figure 3. The specimens were placed on the strong bed of a 10 MN universal testing machine (UTM) and subjected to cyclic loading from 12% to 80% of the tendon strength (\(F_{pk}\)) 10 times, followed by a continuous load increase up to fracture, as shown in Figure 4. Compressive test specimens are very sensitive to accidental eccentricity and surface contact conditions between the specimen bottom and UTM bed. An effort was made to increase precision during the fabrication process by using steel formwork and additional support for the sidewall of the formwork. If an unexpected surface flatness error occurred, a thin shim steel plate was used to fill the small gap that formed between the bottom surface of the specimen and the UTM bed. The load was applied to the anchor head on top of the anchorage device, as shown in Figure 4, to simulate the loading condition in a complete anchorage. Sensors in the UTM were used to measure load and displacement. Figure 2: Lateral confinement: (**a**) anchorage device, duct, and confinement by rebar; (**b**) confinement by spiral and stirrup rebar; (**c**) confinement by spiral rebar; (**d**) confinement by the surrounding concrete. The basic model, A12H-1, was determined on the basis of the details provided by an anchorage supplier. The anchorage bearing strength exceeds the acceptance criteria, and the model satisfies the requirements of EAD 160004-00-0301 [22]. The first group of specimens from A12H-1 to 5 was made to investigate the effect of \(A/A_{S}\) in the range from 1.82 to 9.52 under identical spiral conditions and to reinvestigate the numerical results of Cervenka and Ganz [8]. Figure 3a,b illustrate specimens with identical spirals but different \(A/A_{S}\) values. Considering stress transfer from a smaller bearing plate to a larger concrete section, the stress dispersion ratio, \(m\):\(n\) in Figure 1, can range from approximately 0.5:1 to 3:1, depending on the interaction between the two parts. Even though the bearing strength is not proportional to the dispersion ratio, a higher strength might be expected with higher \(A/A_{S}\).