[en] The fracture mechanics based stress intensity factor (K-factor) concept has obtained wide-spread acceptance as a tool for quantitative analysis of both fatigue crack growth and instable fracture. The high local stresses associated with discontinuties such as perforations (pipe plates) and cylinder-to-cylinder or cylinder-to-sphere connections enhance crack initiation and extension. Such cracks generally develop in the shape of quarter ellipses. Due to the complexity of such crack configurations a fully 3-D finite element treatment seems mandatory to obtain solutions, but the associated high computation costs makes this procedure extremely expensive for standard design procedures. By contrast, analytical approximations, allowing for the application of available analytical solutions by strongly schematizing the complex geometry and stress distribution, are cheap, but generally unreliable, unless checked with accurate experimental and/or finite element data. The present study discusses the applicability of various simple analytical approximations, some of which have been advocated in literature, and of a specially developed semi-analytical procedure, by comparing results with experimental data. (Auth.)