## 4 Conclusions  
To further ensure the safety and dependability of the PC composite beams under impact loads, it is necessary to research the strengthening effect, structural toughness, and damage mode of PC composite beams reinforced with bonded steel. In this paper, one partially precast concrete beam without strengthening and three partially precast concrete beams strengthened with bonded steel plates underwent drop weight impact tests and residual flexural bearing capacity testing. The failure mode, impact force and support reaction time history curve, displacement-time history curve, overall energy dissipation, strain-time history curve, and residual flexural bearing capacity of the test beams under different strengthening degrees were compared and analyzed, and the following conclusions were drawn:  
1. The test beams all experienced bending-shear failures when subjected to impact stress, with the bottom of the beam showing the widest fracture width. The splicing part had small cracks that were both large and numerous. When the beam was strengthened with the steel plate and U-shaped steel plate hoops, the overall damage alleviated. After the steel plate was added, the local damage worsened; after the U-shaped steel plate hoops were added, the local damage improved. 2. The peak support reaction force decreased from 800 to 575 kN as the thickness of the bonded steel plate increased, while the position of the U-shaped steel hoop had no effect on the response of the support reaction force. In addition, the highest total energy release capacity of the test beams was observed when the thickness of the bonded steel plate was 2 mm. 3. The peak mid -span displacement reduced from 33.6 to 31.4 mm and the residual mid -span displacement decreased from 29.8 to 21.0 mm with an increase in the bonded steel plate thickness, considerably reducing the damage to the test beams from the impact force. The addition of U-shaped steel plate reinforcement also increased the test beams' remaining flexural strength, which was superior to the steel plate thickness. As a result, the test beams suffered significantly less damage from the impact force since the peak mid -span displacement reduced from 32.6 to 31.7 mm and the residual mid -span displacement from 21.0 to 20.3 mm. Therefore, the combination of U-shaped steel plates and steel plate reinforcement can better improve the impact resistance of PC beams, which is a guide for their design and construction in the future. 4. The failure process of the PC beams strengthened using bonded steel plates subjected to impact loading can be divided into three stages. The local impact damage stage was one of them, and it was mostly caused by the major wave peak of the impact force. Because the displacement and support response forces had not yet begun, this step had little bearing on the overall response of the test beam. Fully developed beam web oblique cracks and beam bottom bending cracks were the main outcomes of the overall impact failure stage. In addition, the concrete in the contact area spalled and the bottom steel plate came off, which caused the concrete cover to peel off and the test beam to deflect more intensely. During the elastic rebound stage, the elastic deformation of the test beam was restored and bending cracks close to the bottom of the beam were compressed. 5. The number of test beams was restricted due to cost constraints and other issues, and the features of impact loading may have caused random inaccuracies. In subsequent investigations, the number of samples should be increased to reduce the impact of chance errors. Additionally, tests in real -world - use situations should be taken into \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**ID** & **A1** & **B1** & **B2** & **B3** \\ \hline Residual flexural bearing capacity (kN\(\cdot\)m) & 166.9 & 204.0 & 212.8 & 222.6 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Residual flexural bearing capacity of the specimen.