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Wall thinning caused by flow accelerated corrosion is one of the major degradations for piping systems in power plants. Collapse bending moments for pipes with local wall thinning under torsion moments were analysed by finite element modelling at the presence of internal pressure. The wall thinning shapes used in the analyses are two types, rectangular and round in shapes. Plastic deformation behaviours of pipes with these wall thinning were found to be different. Equivalent collapse moments defined as the root of the sum of the squares of the torsion and bending moments at collapse are also different between the rectangular and round shape wall thinning. In case of rectangular shape wall thinning, plastic collapse bending moment decreased rapidly with increasing torsion moment. The equivalent collapse moment is not equal to pure bending collapse moments. On the other hand, the equivalent collapse moment becomes almost constant for the round shape wall thinning if the torsion moment is within the actual plant range. Combined torsion and bending moment at collapse can be estimated by pure bending collapse moment of a pipe with round shape wall thinning.