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Analysis methods for the fracture mechanics assessment of asurface defect in a bi-metallic weld have been investigated and verifiedduring a three-year European research programme BIMET. Two large-scale4-point bend tests on a piping assembly containing a ferritic to stainlesssteel weld with a notch at the interface between the ferritic steel and thebuttering layer were carried out. The paper reports on an engineeringassement and results of finite element analyses performed at GKSSaccounting for the material gradients in the weldment. A CTOD criterion isapplied to predict crack initiation and growth. It appears to be better suitedfor welded structures than J as CTOD is a near-field quantity which doesnot suffer from problems like path dependence, material gradients etc.CTOD based resistance curves can be easily determined experimentallyeven for welded structures.