**4. Reliability Verification of the Loading System**

*4.1. Test of Loading System with a Single Set of Pulley Group*

To verify the reliability and mechanical efficiency of the loading device, the loading system with a single set of pulley group was selected for the staged loading test, as shown in Figure 10.

In this system, the horizontal beam of the portal frame is used as a substitute for the main arch ring. Gradual loading is achieved by placing 40 cm × 40 cm × 2 cm steel plates in the counterweight box. During the test, the loading was divided into four stages, with each stage having loads of 0.2 t, 0.4 t, 0.6 t, and 0.8 t, respectively. After the loading was completed, the total mass of the counterweight box was 2.0 t. By reading real-time data from the load cell, the actual amplification factor of the pulley-group loading system can be obtained. The results are shown in Figure 11.

As shown in Figure 11, after each loading is completed, the load magnification factor of the single-pulley-group loading device requires approximately 10 min to reach a stable state. This is because the steel wire rope needs to overcome the resistance at the pulley to transmit the tension of the outermost steel wire rope layer by layer to the innermost steel wire rope. This process is referred to as the hysteresis effect. It is this effect that causes the load magnification factor to suddenly drop during each loading, as indicated by points A, B, C, and D in the figure. Moreover, after the completion of each loading level, the load magnification factor remains relatively stable around 6.6 times, indicating that the mechanical efficiency of the single-pulley-group loading system is approximately 94.29%, meeting the test requirements. Additionally, the influence of friction loss on the loading value can be eliminated based on the specific readings of the tension sensor.

**Figure 10.** Test of loading system with a single set of pulley group. (**a**) Loading system with a single pulley set under viewpoint 1; (**b**) Loading system with a single pulley set under viewpoint 2.

**Figure 11.** Time load curve of the loading test.
