In recent years, there has been a concerning increase in road collapses triggered by failures in urban drainage systems. Concrete pipes, commonly uesd in urban drainage pipelines, endure prolonged cyclic loading from traffic above. However, the mechanisms governing the long-term performance and fatigue damage remain unclear. Through conducting fatigue model box tests on concrete pipes, the effects of different fatigue loading cycles on the circumferential strain of concrete pipes were investigated. A fatigue life prediction equation for concrete pipes was proposed, and the crack propagation under various fatigue loading cycles was observed. Additionally, corresponding 3D FE models of concrete pipe-soil interaction with bell-and-spigot joints and gaskets were constructed. These models were used to explore the vertical displacements, circumferential bending moments, and circumferential stresses of the concrete pipes under different fatigue loading cycles, the damage and failure mechanisms of the concrete pipes under fatigue loading were revealed. The results indicate that the potential failure location of concrete pipes is within the inner crown of the bell under the fatigue traffic loads. The circumferential strains and crack propagation exhibiting a three-stage evolution pattern under fatigue loads. The proposed fatigue life prediction equation accurately predicts the remaining life of concrete pipes. Upon reaching 21.89 million loading cycles, the strain at the inner crown of the bell reaches 575.0 mu epsilon, resulting in complete failure. Cracks on the inner crown of the bell extend inward and to the right from the middle of the joint, forming a channel for crack propagation. The vertical displacements at the crown and the circumferential bending moments of the bell and spigot exhibit rapid increases, stabilization, and subsequent declines with the increasing loading cycles. When concrete pipes undergo fatigue fracture, the maximum vertical displacement and circumferential bending moment at the bell are measured as 2.26 mm and 17.82 kN & sdot;m/m, respectively. Stress concentration at the bell and spigot during fatigue loading leads to crack propagation and convergence, causing redistribution of stress fields characterized by an initial increase followed by a decrease in the inner crown and invert of the bell.

Reinforced concrete pipes (RCP) are the mainstay of urban water transmission networks. Urban development entails increased potential for blasting activities (such as subway tunneling, excavation, and demolition) as well as the risk of accidental explosions. This paper provides a detailed description of the damage evolution and deformation process of RCP under explosive loads using validated numerical simulation methods. A concise phenomenon-based method is introduced for RCP damage grading. Furthermore, a comparative analysis is conducted on the damage and deformation of RCP resulting from explosions at different locations and with varying weights. At last, this paper especially investigates and explains the impact of four commonly used joint types on the RCP's response to explosions. The research results help to enhance the understanding of damage evolution and deformation behavior of RCP (or similar structures) induced by explosion, and are also references for protection, repairing and failure identification of segmented structures subjected to explosion.