## 7 Conclusions  
This study performed static loading tests on simply supported reinforced concrete beams under three different conditions. Throughout the study, we examined the acoustic emission characteristics, beam deflections, strains, and prestress variations during the entire failure process. This investigation aimed to understand the propagation of damage in reinforced concrete beams. The main conclusions of the study are as follows:  
1. The load values determined based on the acoustic emission characteristic parameters are in good agreement with the theoretical values. The load at which the top concrete of the P3 beam is crushed is determined to be 85 kN based on the acoustic emission characteristic parameters, which is within 5% of the theoretical load value of 89.92 kN. The strain variation trend of ordinary reinforced concrete beams correlates well with the acoustic emission signal characteristics. Furthermore, the strain and deflection variations of prestressed reinforced concrete beams closely align with the acoustic emission signal characteristics. This alignment provides additional validation for the accuracy of acoustic emission non-destructive testing. 2. The critical load for the prestressed reinforced concrete beam P3 is 70 kN, with an ultimate load of 85 kN. Typically, the critical load occurs at around 80% of the ultimate load during the process from intact to failure of the beam. In contrast, for the ordinary reinforced concrete beam P1, the critical load often appears at around 40% of the ultimate load. At the critical load point, significant acoustic emission signal characteristics are observed, and spectral analysis reveals a broad frequency range. Beyond this critical load, the beam experiences accelerated deterioration, indicating that it should no longer be used. 3. The ultimate load of prestressed reinforced concrete beams under cyclic loading conditions is approximately 20% lower than that under hierarchical loading conditions. Before reaching the critical load, significant acoustic emission signals are observed only during the loading process. There are no noticeable acoustic emission signals during the unloading process. However, after reaching the critical load, the unloading process continues to generate acoustic emission signals. This pattern can be utilized as a criterion for determining the critical load of prestressed beams subjected to cyclic loading. 4. During routine bridge operation and maintenance, it is advisable to use acoustic emission devices for structural damage monitoring when the maximum load on the bridge structure approaches 60% of the ultimate load. And a significant peak change in the acoustic emission signal analysis indicates proximity to the critical load. This stage suggests that the bridge structure may have developed or already experienced through-cracks, necessitating prompt reinforcement measures. 5. Further research should focus on noise signal filtering to achieve a more precise analysis of AE signal characteristics at different stages of failure. Changes in AE signals and wave velocities during the beam's failure process can cause inaccuracies in AE source localization. Therefore, there is a need to explore the propagation behavior of elastic waves in beams with variable densities, with the aim of developing more accurate AE detection techniques. This will enhance the effectiveness and application of AE technology in structural health monitoring. **Author Contributions:** Conceptualization, J.B. and J.Z. ; methodology, Z.G. and J.Z. ; software, Z.G. and J.Z. ; validation, Z.G. and J.Z. ; formal analysis, Z.G. and J.Z. ; investigation, [PERSON] and [PERSON]; resources, [PERSON]; data curation, [PERSON] and J.Z. ; writing--original draft preparation, [PERSON], [PERSON] and Y.Z. ; writing--review and editing, [PERSON] and J.Z. ; visualization, [PERSON], [PERSON] and Y.Z. ; supervision, [PERSON]; project administration, [PERSON]; funding acquisition, [PERSON] All authors have read and agreed to the published version of the manuscript.