## 1 Introduction
[PERSON] and [PERSON] (2014) tested the physical response of a 140-D type reinforced concrete pipe with an inner diameter of 600 mm when buried directly under single-axle loading was measured at nominal and full factored highway design loads to examine the possible limit states of the pipe [8]. Furthermore, [PERSON] et al. (2008) pointed out that the most important variables affecting the evaluation of characteristic values of crack opening in reinforced concrete pipes are useful height, concrete compressive strength, and pipe wall thickness [9]. Studies by [PERSON] and [PERSON] (1986) have shown that unreinforced concrete pipelines can basically fail in two modes: beam failure and ring failure. According to the existing test data, the nominal stress at beam failure is much lower  
Figure 1: Pavement collapse and pipe burst caused by cracks in concrete pipes. than that at ring failure. In addition, the nominal stress in either of failure modes decreases as the diameter or thickness of the pipe rises [10]. [PERSON] et al. (2016) modeled buried prestressed concrete cylinder pipes (PCCP), considered the interaction between the modeled pipes at the joints, simulated pipe-soil interactions and internal and external loads, and assessed the extent of PCCP damage [11]. [PERSON] et al. (2000) also evaluated the structural response of small-diameter buried pipes through experiments [12]. [PERSON], et al. (2012) utilized the concrete damage plasticity (CDP) model to simulate the ultimate strength of steel-fiber-reinforced concrete pipes. The parameters of their model were estimated by uniaxial stretching, compression, and four-point bending tests [13]. In another work, [PERSON] and [PERSON] (2012) analyzed the load bearing capacity and failure mode of PCCP using the overload damage test. The PCCP was subjected to external loading until the damage was divided into four stages: 1) elastic stage; 2) concrete cracking stage; 3) steel wire yielding stage; and 4) failure stage [14]. [PERSON] et al. (2010) also studied the damage of the prestressed concrete cylinder tubes with pre-existing cracks and investigated the influence of pre-existing cracks on the ultimate strength of the pipes in the presence of external pressure through a full-scale test and numerical simulation [15]. [PERSON] et al. (2005) analyzed the causes, mechanisms, and prevention measures of pipe cracks according to the concrete cracking mechanism. They showed that dry shrinkage deformation, temperature deformation, structural stress, etc. are the main causes of pipeline cracks [16]. [PERSON] and [PERSON] (2018) conducted a 1/10-size external pressure failure test on a steel sleeve concrete pipe and analyzed the bearing resistance of external pressure, the deformation characteristics of the inner and outer steel cylinders of the pipe, and the development of cracks in the core concrete [17]. The experiments of [PERSON] and [PERSON] (2012) on the longitudinal wall of a pipe using a longitudinally cracked PCCP revealed that the longitudinal crack of the outer wall of the core did not significantly reduce the bearing capacity of the PCCP so the partially cracked concrete pipe could be used further [18]. [PERSON] and [PERSON] (2018) conducted a study on the bearing capacity of buried pipes with corrosion defects by developing three-dimensional numerical simulation and performing experiments [19]. [PERSON] et al. (2018) also conducted an external compressive load test on a prestressed concrete cylinder pipe and studied its structural deformation law [20]. [PERSON] (2001) experimented on the corrosion damage of a prestressed concrete cylinder pipe and revealed the shallow cracks and corrosion areas expected during the stress corrosion cracking process through the bending and tensile tests of the material samples [21]. Most studies have focused on the problem of cracks in intact concrete pipes under external pressure. However, the purpose of the present work is to study the bearing capacity and mechanical properties of concrete pipes with pre-existing cracks.