Reliability of corroded thin walled pipes repaired with composite overwrap

Abstract

Current design codes provide two design methods: allowable stress/strain design and limit state design. Design in the current pipework composite repair codes is based on the allowable design method and only two safety factors are applied to the ultimate strain of the composite layer and to the yield stress of steel. On the other hand, safety factors are applied to each of the load and resistance parameters in the limit state design method. The limit state design method is probabilistic based in which the safety factors are calibrated based on a target reliability index. In this study, an investigation into the reliability of rehabilitated pipelines is conducted. The limit state function is defined based on ASME PCC-2, and reliability analysis is conducted using the AFOSM method. Results show that ASME PCC-2 generally provides adequate safety although the level of safety is not uniform for different percentages of corrosion. Comparing the achieved results and the ISO 2394 target reliability indices, some resistance factors are proposed.