## 6 Elastic Ultimate Load under Medium and Low Cycle Fatigue Loads  
### Analysis of Influencing Factors  
Through the establishment of a large number of ABAQUS finite element rebar planting system models, the elastic ultimate load curve of 8 mm and 6 mm steel bars under different anchor depths and fatigue loading times was obtained, as shown in Figure 13. In this simulation, four anchor depths were set: 10d, 15d, 20d, 25d. We set the fatigue loading times to 10,000, 50,000, 75,000, 100,000, 150,000 and 200,000 for a total of six fatigue gradients, and established a set of control groups without fatigue loading.  
The analysis in Figure 13 shows that when the fatigue loading times were the same, the elastic ultimate load increased with the increase in the anchor depth. In the case of different fatigue loading times, the elastic ultimate load of the specimen increased differently with  
Figure 12: Comparison of stress distribution of steel bars between experiment and finite element simulation.  
Figure 13: The relationship between fatigue loading times and anchor depth on elastic ultimate load: (**a**) specimens of 8 mm steel bar; (**b**) specimens of 6 mm steel bar.  
the increase in the anchor depth: when the fatigue loading was of less than 10,000 times, the elastic ultimate load of the specimen was basically unchanged compared with the control specimen without fatigue loading at the same depth, and the elastic ultimate load only increased slightly with the increase in the depth. When the number of fatigue loading was of 50,000 to 75,000 times, and the depth of the planting bar was increased from 10d to 15d, the elastic ultimate load was obviously improved; with an anchor depth of greater than 15d, the increase in the anchor depth did not improve the elastic ultimate load. When the fatigue loading was of 100,000 to 200,000 times, and the depth of the planting bar was increased from 10d to 20d, this significantly increased the elastic ultimate load. If the depth of the planting bar was increased to 25d, the increment of the elastic ultimate load value was significantly reduced.  
When the anchor depth of the rebar was fixed, the elastic ultimate load of the specimen decreased with the increase in fatigue loading times. The smaller the anchor depth of the rebar, the greater the influence of the fatigue load on the elastic ultimate load of the specimen, and the more obvious the decrease in the elastic ultimate load. When the anchor depth was 10d, the decrease in the elastic ultimate load of the specimen was most obvious when the number of fatigue loads increases. After the fatigue load reached 75,000 times, the decrease in the elastic ultimate load was more significant than before. When the anchor depth was 15d, the slope of the curve of elastic ultimate load-fatigue loading times begins to converge, and no large sudden changes occurred. When the fatigue load times increased, the overall load level of the specimen was greatly improved compared with that of 10d, especially when the fatigue times were 100,000 to 200,000. When the anchor depth of the specimen was 20d to 25d, the overall load level of the curve is close, and the resistance of the specimen to fatigue load disturbance tended to be close under the anchor depth. When the depth of the planting bar reached 25d, the increase in the number of the fatigue load had the least effect on the elastic ultimate load of the specimen, but the load still exhibited a certain decrease.