This study addresses the critical issue of assessing failure pressure in pressurized pipelines subjected to complex loads, such as bending moments and axial forces. Current research primarily focuses on the buckling performance of pipelines under bending loads or axial compression, with some studies also examining the failure pressure of corroded pipelines. However, there is a lack of limit state models for pipelines with both bending moments and axial forces. The study proposes a limit state equation for steel pipes under various loads, based on the unified yield criterion (UYC). This equation is derived from a three-dimensional pipeline stress model that accounts for complex load coupling. The equation is validated using full-scale burst tests and finite element (FE) simulations. The results show that the von Mises yield criterion is the most adaptable and accurate among the tested criteria, followed by the ASSY yield criterion. The study also investigates the failure mechanisms of pipelines under complex loads through experimental and numerical analyses. The experimental setup includes a full-scale burst test with axial force and internal pressure, while the FE model is used to validate the developed calculation equation. The results demonstrate the effectiveness of the proposed limit state equation in predicting failure pressure under complex loads. The study concludes that the proposed limit state equation can accurately assess the failure pressure of intact pipelines under multiple or individual external loads, such as bending moment, axial compressive force, axial tensile force, and internal pressure. The equation is particularly useful for selecting appropriate yield criteria based on load condition differences.This study addresses the critical issue of assessing failure pressure in pressurized pipelines subjected to complex loads, such as bending moments and axial forces. Current research primarily focuses on the buckling performance of pipelines under bending loads or axial compression, with some studies also examining the failure pressure of corroded pipelines. However, there is a lack of limit state models for pipelines with both bending moments and axial forces. The study proposes a limit state equation for steel pipes under various loads, based on the unified yield criterion (UYC). This equation is derived from a three-dimensional pipeline stress model that accounts for complex load coupling. The equation is validated using full-scale burst tests and finite element (FE) simulations. The results show that the von Mises yield criterion is the most adaptable and accurate among the tested criteria, followed by the ASSY yield criterion. The study also investigates the failure mechanisms of pipelines under complex loads through experimental and numerical analyses. The experimental setup includes a full-scale burst test with axial force and internal pressure, while the FE model is used to validate the developed calculation equation. The results demonstrate the effectiveness of the proposed limit state equation in predicting failure pressure under complex loads. The study concludes that the proposed limit state equation can accurately assess the failure pressure of intact pipelines under multiple or individual external loads, such as bending moment, axial compressive force, axial tensile force, and internal pressure. The equation is particularly useful for selecting appropriate yield criteria based on load condition differences.