# Finite Element Analysis of the Structural Behavior of a Corroded Pipe Culvert
## 1 Introduction  
At present, culverts are widely used and studied worldwide. Research on the impact of culvert corrosion primarily focuses on understanding the mechanisms and patterns of corrosion. Culverts play a vital role in municipal infrastructure as integral components of waterways and rainwater management drainage systems. The service life of culverts varies from 30 to 100 years, depending on various factors, such as geographical location, climate, culvert structure material, construction methods, etc. [1]. Physical processes associated with environmental factors and aging can lead to deterioration in culvert-soil systems, impair their mechanical properties, and reduce their longevity. Environmental conditions contribute to the formation of erosion cavities and corrosion within the filling body. Soil degradation mechanisms are influenced by water presence, soil type, uniformity, density, and clay content, as well as by mineralogy [2, 3]. Consequently, concrete durability gradually diminishes over time [4, 5, 6].  
The degradation of the culvert system can result in life-threatening and expensive damage to both the culvert itself and its associated systems [7]. Numerous factors contribute to this deterioration, such as the presence of water and sulfate in the soil, which gradually diminish the durability of concrete over time [8, 9, 10]. Specifically, subterranean culverts near coastal areas are vulnerable to chloride attacks. Furthermore, when thereis a disparity between dry interior conditions and moist surrounding soil, environmental asymmetry induces differential shrinkage in the concrete, leading to cover cracking. This decline in durability and occurrence of cracks can expedite the corrosion of the steel bars within the concrete. Corrosion reduces both the effective cross-sectional area and the bonding performance of the steel bars. Consequently, this deterioration between steel bars and concrete significantly impacts the structural performance of reinforced concrete members [11; 12; 13].  
It is widely acknowledged that corrosion can significantly impair the structural performance of culvert components [14; 15; 16; 17; 18; 19; 20; 21; 22; 23; 24; 25; 26]. [PERSON] and [PERSON] [15; 16] conducted reverse cyclic loading tests on beam-column joints designed with self-weight load to investigate the impact of corrosion damage on their hysteretic behavior, energy dissipation, and strength degradation. Their experimental findings demonstrate that the hysteresis behavior is notably influenced by the type of corrosion (pitting or uniform corrosion), with localized corrosion damage leading to more severe strength degradation. In addition, they observed that steel bar corrosion transformed the failure mode from joint shear failure to longitudinal splitting or cracking in corroded reinforced concrete structures, emphasizing the need for immediate performance evaluation and appropriate modifications to prevent disasters. [PERSON] [22] introduced the nonlinear finite element method of degraded concrete structures, and compared the analysis results with and without considering cracking deterioration. The existing research does not consider the influence of the combination of strength reduction, thickness reduction, and corrosion at different positions of the pipe culvert. Therefore, this study integrates these three factors to perform a numerical simulation research on pipe culvert corrosion.  
In summary, the finite element numerical simulation analysis software PLAXIS 3D was used to construct the culvert model for numerical simulations in this study. By varying the thickness and stiffness of pipe culvert to simulate different degrees of corrosion, a number of experimental controls are established to analyze the structural behavior of the pipe culvert under various conditions. The impact of soil degradation-induced culvert corrosion on deformation is examined, providing valuable insights for practical project design and construction.