Accurate prediction of burst pressure of line pipes is essential for the safety design and integrity assessment of transmission pipelines. Different analytical and empirical formulae for determining the limit load of defect-free pipes have been proposed, but none is widely accepted and broadly validated. The commonly used method to determine the burst pressure by code in pipeline industry is based on the hoop stress of a pipe when it reaches a critical stress, such as flow stress or ultimate tensile stress of the pipeline steel. Recent experiments have shown that the criterion by code may be too conservative for modern high strength pipeline steels. Based on the plastic instability theory and the von Mises or Tresca yield criterion, theoretical solutions to predict the burst pressure of defect-free pipes have been proposed for years. However, it can be shown that experimental data for various pipeline steels lie between the two theoretical solutions of burst pressure of pressurized defect-free pipes, and fit the average result of the two solutions. In general, the von Mises prediction is the upper bound, and the Tresca prediction is the lower bound of burst pressure. Because traditional criteria like Mises and Tresca tend to bounded experimental data, a new failure criterion referred to as Average Shear Stress criterion is proposed. A plastic collapse analysis solution is developed as the corresponding theoretical solution of pipe limit pressure at plastic collapse. The new solution is formulated as a function of pipe geometry, strain hardening exponent and ultimate tensile stress of materials. Finite element results and experimental data are then introduced to validate the proposed solution. Comparisons indicate that the present solution matches the numerical results and the average experimental data of burst pressure of defect-free pipes for various pipeline steel grades.

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