This paper presents the structural analysis and probabilistic assessment of the buckling of a pipe under external pressure. The study was conducted to improve safety of a Nuclear Power station where several hundred such pipes are used which couldbe subjected to an external pressure of uncertain magnitude under some fault conditions.A finite element model was developed to predict the failure mode of a pipe under external pressure and the mathematical model was validated by test workSensitivity studies were performed to examine the effects of varying geometric and material properties on the strength of the pipe. These studies looked at the changes in strength of the pipe due to varying pipe bore, wall thickness, initial ovality,Young's modulus, yield stress and work hardening. A sensitivity study also looked at the effect of introducing a stiffener at the mid section of the model to determine the effect this would have on the critical buckling pressure of the pipe.The model was also used to understand the post collapse behaviour of the pipe in case of a need to repair any collapsed pipe.Based on the estimate of the strength for the pipe and allowing for the variation in geometry and material properties which might reasonably be expected, a probabilistic assessment was carried out to establish a relationship between the mean pressure andthe probability of failure. This relationship was then used to set a limit on the mean value of the external pressure such that the probability of failure of any pipe remains less than 1%. Design modifications were then made to ensure that the meanexternal pressure stays within the specified limit.
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