Welded and necked-out tees are frequently used in pressure vessel and piping design. Standard calculations based on the Kellog method are merely applicable for pressure loading. Supplementary forces and moments are excluded in this case. The application of numerical methods of structural analysis is extremely helpful in this situation. However, detailed modelling of the geometry is quite complicated and standard models of the cylinder-cylinder inter section type cannot be used. Special models of the welded and necked-out design variants have to be generated and parametrized in order to be applicable for different nominal sizes. Tees as structural components have to be considered under various aspects with respect to their mechanical behaviour. The following investigation proposes methods for design under static and cyclic loading conditions based on detailed FE analyses. The results reveal a considerable potential of tees which has to be proved by analysis.