###### Abstract  
External load is one of the important reasons for structural damage and failure of reinforced concrete sewage pipelines, causing pipe leaks, pipe explosions, and even road collapses. In this paper, three-point loading experiments on full-size reinforced concrete pipes were carried out, and the damage state of the pipes was monitored by acoustic emission technology; the evolution trend of the mechanical properties and acoustic emission monitoring indexes under load was investigated. The experimental results showed that: (1) According to the change of acoustic emission energy and accumulated energy during loading, the mechanical response of the pipeline can be divided into an elastic compression phase, a plastic damage phase, and a residual strength phase; (2) The accumulated acoustic emission energy (E) and the maximum value of a single acoustic emission energy (Emax) can effectively characterize the different damage states of the loaded pipe; (3) A \"double-peak\" was observed in AF/RA data within the loading process. The appearance of the two peaks corresponds to the change of the loading phase of the pipeline and the occurrence of the major damage. Thus, the AF/RA index can effectively characterize the loading state and the damage degree of the pipeline. This study provides a valuable reference for pipeline health monitoring by using AE technology.  
acoustic emission; reinforced concrete sewage pipeline; structural health monitoring; mechanical loading; parameter analysis; RA/AF 2022128624. 2022128624.  
grouting connection, and analyze the AE signal characteristics under different concrete strengths, compactness, and hollow sleeve positions. The results showed that the amplitude of C30 concrete is higher than that of C40 concrete, while the amplitude of the dense grouting sleeve is higher than that of the hollow sleeve. [PERSON] et al. [7] used AE technology to detect cracks in concrete hollow slab bridges. By studying the relationship between crack propagation and AE signals, it is concluded that low-amplitude signals are generated due to the propagation of microcracks and the mutual friction of old crack fracture surfaces. The high amplitude signals are generated by the further propagation of macro cracks. [PERSON] et al. [8]. summarized seven nondestructive testing methods for reinforced concrete. They point out the application of acoustic emission technology in concrete structure damage detection, and also put forward the disadvantages of acoustic emission technology such as the existence of many sources of noise interference, the immaturity of quantitative research, and the inconsistency of structural damage evaluation indexes.  
Therefore, it is necessary to study the mechanical response characteristics of pipelines under external loads. On this basis, effective pipeline damage characterization methods and monitoring indicators are further explored. This is important because the monitoring and early warning of the concrete pipeline loading damage process is of great significance to ensuring the maintenance and safe operation of the pipeline network system [9].  
For this paper, a full-scale loading test was designed for the damage monitoring of reinforced concrete sewer pipes, analyzed by AE signals. The damage monitoring indexes for reinforced concrete pipes are proposed and expected to be used in practical projects as a more accurate method.