## 2 Experimental Study
### Damage Processes  
The loading process was divided into a trial loading stage and a formal loading stage. Specifically, the displacement control method was adopted in the trial loading stage, and the distance increment was 2 mm. The trial loading process was repeated for three times in order to not only check and debug the equipment, but also eliminate the gap between the loading device and the specimen through preloading. The vertical load was not applied in the trial loading stage. In the formal loading process, the steel plate did not have significant deformation in the first four cycles. Due to the convex and concave defects of the steel plate, the steel plate had crisp sound during the conversion process of positive loading and negative loading. In the fifth cycle (the first cycle of 5 mm), a tension strip appeared above the main diagonal line of the steel plate under the action of the tensile force. After the second cycle of 5 mm, the tension strip moved down to the main diagonal. When the displacement reached 11 mm, an obvious convex stripe was formed along the main diagonal direction of the steel plate with the increase of the load, as shown in Figure 7a. When the displacement returned to 0 in each cycle, the steel plate had a great sound which was slightly greater  
Figure 5: Displacement Meter Layout. Figure 6: Strain Gauges Layout. than the sound in preceding cycles, and such sound volume increase was caused by the convex position alternation on the main diagonal direction. The deformation of steel plate could be obviously observed that convex and concave orderly form from top to bottom, then from bottom to top. Subsequently, with the increase of the peak displacement of cycle, the tension stripe generated along the two diagonal directions becomes more obvious in the positive loading and negative loading process. The degree of concavity and convexity of the tension strips reached the maximum when the positive and negative peaks were reached. The tension stripe formed by the convex firstly appears at the main diagonal line (see Figure 7b). When the displacement reached 14 mm, a secondary diagonal tension stripe (see Figure 7d) gradually appeared at the upper and lower 1/3 positions of steel plate. When the displacement reached 20 mm, the paint coating of web of frame beam bugled slightly. This indicated that the web of the frame beam began to buckle. In the 17 th cycle (the first cycle of 23 mm), the frame beam had a small out-of-plane displacement. The maximum out-of-plane displacement appeared at the middle of the beam, and the displacement was not more than 3 mm. The paint coating of web of frame beam cracked and transverse cracks appeared at the concrete in the middle of the column, as shown in Figure 7e. In the 20 th cycle (the second cycle of 26 mm), the stress showed that the steel plate stress reached the yield strength of the steel, and the out-of-plane deformation of the beam was slightly changed due to the yield of the infill steel plate. During the period from the 17 th cycle to the 21 st cycle, the infill steel plate continuously suffered tension and compression deformation at the peak displacement of +23\(\rightarrow\)+29 mm, and the residual strain was gradually accumulated to wrinkle at the crossing position of the diagonal lines to form folding damage. In the 22 nd cycle, the laceration formed by the folding damage of the diagonal lines was continuously promoted at the peak of +29 mm to cause more obvious damage and gradually formed four significant folding damages. In the 24 th cycle (the second cycle of 32 mm), the concrete near the actuator in PEC column had 3-5 slight cracks, a large out-of-plane displacement appeared as shown in Figure 7f. In the 25 th cycle, the framed beam and the upper and lower flanges of the beam end (near the actuator) were broken, as shown in Figure 8i. In consideration of the significant damage of the specimen, the test was terminated.