## 3 Result Analysis
### Failure Mode
Three split cracks with smaller widths and shorter lengths appeared simultaneously on the concrete surface in the impact area. U\(-\)shaped steel plate hoops peeled away from concrete in the area where they were bonded. U\(-\)shaped steel plate hoops, however, provided greater protection against oblique cracks due to their shearing impact, as demonstrated primarily by the reduction in the number of bending-shear oblique cracks and the reduction in the width of the bending-shear oblique cracks. When U\(-\)shaped steel plate hoops were installed, the overall damage to the superimposed beam was significantly reduced. The presence of U\(-\)shaped steel plate hoops prevented the development of bending and oblique cracks, and the crack width decreased as compared to test beams B3 and B1. The failure forms on the beam side were quite different, and the B3 test beam had peeling damage at the interface between the U\(-\)shaped steel plate hoops and the concrete. With the installation of the U\(-\)shaped steel plate hoops, the local damage was slightly slowed down, and a small number of concrete samples fell off both sides of the contact area. The number of split cracks increased; however, the width decreased significantly and there was no fracturing or crushing of large\(-\)area concrete samples. Comparing the number and width of cracks in different parts of the test beam, the crack width gradually increased from top to bottom, and there was no bending crack with a large width within 30 cm of the middle span of the test beam with reinforcement. However, due to the cable\(-\)stayed failure caused by the peeling of the steel plate, more significant cable\(-\)stayed cracks were generated. There were many dense microcracks at the top of the beam, and the crack width was the narrowest but accompanied by the collapse of the concrete cover. The cracks in the web of the beam were mainly composed of oblique flexural shear cracks generated by the web and flexural cracks extending from the bottom of the beam, and the crack width was wider than that of the top of the beam. There were not many cracks at the splicing points on either side of the mid\(-\)span, and their width matched that of the top of the mid\(-\)span beam. Based on the aforementioned experimental phenomena, it can be concluded that in the unreinforced beams, their lower flexural stiffness resulted in a higher susceptibility to crack extension and concrete spalling in the case of bending-shear damage. However, for the test beams reinforced with steel plates at the bottom, this approach significantly increased the tensile capacity and stiffness of the beams in the face of bending-shear damage. This effectively reduced the tensile stresses at the bottom of the beams induced by the impact loads, thus slowing down the formation of the cracks. Meanwhile, the application of viscous steel reinforcement also effectively prevented the crack extension and further reduced the stress concentration around the crack. In addition, in the case where U\(-\)hoops were applied to the test beams, the presence of the U\(-\)hoops resulted in a certain degree of suppression of crack development at the bottom and sides of the beams when flexural\(-\)shear damage occurred. This effectively slowed down the cohesive damage and spalling of the concrete and helped to maintain the structural integrity of the beam. In summary, steel plate reinforcement at the bottom and the installation of U\(-\)hoops had significant effects in enhancing the tensile capacity and stiffness of the beams, as well as preventing the extension of cracks under bending-shear damage scenarios. These reinforcements can better protect the integrity and performance of the beams under impact loading.