## 3 Result Analysis
### Steel Rebar, Steel Plate, and Concrete Strain
(2) The positive bending moment region in the mid\(-\)span increases as the impact process progresses, the stress wave is transferred to both sides, and the negative bending moment region eventually shifts to the quarter point. (3) When the impact enters the decay stage, the negative bending moment area moves to the support and finally disappears, and the beam body is a positive bending moment area globally. At this time, the bending moment distribution of the test beam is the same as that under the static load condition. In addition, the residual steel rebar strain value of this segment is lower than that in the mid\(-\)span area, indicating that the damage to the quarter\(-\)point is far less severe than that of the mid\(-\)span. Figure 16c presents the overall variations in the steel rebar strain. The strain response time of the strain gauge 3 is slightly quicker than the average for each strain-time history curve, which is a reflection of the fact that the transmission of stress waves does not result in the hysteresis of the steel strain response. This is because the overall flexural deformation of the test beam is what primarily contributes to the strain response of the steel rebar. The peak tensile strain of the lower steel bar in the mid\(-\)span section is 3.5 times that of the quarter\(-\)point section, and there is also a greater residual tensile strain at the same time. The steel bar strain value of the mid\(-\)span section is much higher than that of the quarter\(-\)point section. It shows that the overall failure of the test beam and damage to the longitudinal steel rebar occur mostly below the impact point. Changes in the steel plate strain in the mid\(-\)span and quarter\(-\)point regions are shown in Figure 17a. Close to the edge of the support, region 2 is where the steel plate strain gauge is situated, and region 4 is where the steel plate and concrete are initially peeled off. Figure 17b shows the various strain fluctuations in the steel plate in the two distinct sections. Because each steel plate strain response is identical to that of the steel bar, which is mainly caused by the total deflection of the beam body, the strain response to each steel plate strain-time history curve begins almost immediately at the start of the impact. The strain of each steel plate increases rapidly after the response and soon reaches the peak tensile strain. Then, except for the strain of the steel plate strain gauge 1 close to the support, the other three strains all produce obvious oscillating segments. This is because the steel plate close to the support has not been peeled off, and the steel plate is peeled off due to the concrete cohesion phenomenon in the section where the steel plate strain gauges 3 are located, and the steel plate has a relatively complex stress value at this stage. Finally, with the end of the overall failure of the test beam, the four strains are stable and tend to zero. This shows that the elastic and recoverable deformation of the steel plate mainly occur, and the impact load affects the strain of the steel plate in the early stage. In contrast, the impact load does not cause a significant residual strain on the steel plate at the later stage and, instead, mainly impacts the concrete and steel rebar. Figure 18a depicts the variations in concrete strain in the mid\(-\)span section. The fact that the concrete strain gauges 1 at the top of the beam, 2 at the beam's end, and 3 at the beam's bottom, in that order, indicate that the stress wave moves from the top to bottom along the height of the beam. The strain of the concrete strain gauge 1 at the top of the beam increases rapidly after the response, and after reaching the peak value of the tensile strain, there is a \"cliff\(-\)jumping\" decrease and it rapidly achieves the ultimate compressive strain. The concrete in the compression zone is caused by lateral expansion and extrusion. The concrete at the top of the test beam is crushed and destroyed due to the deflection and distortion of the beam.