SCFs and fatigue design of multi-planar tubular DT-joints

The present paper concerns the fatigue design of multi-planar welded tubular DT (double T) steel connections. Stress Concentration Factors (SCFs) are used for the calculation of the hot-spot stress of the joint and, subsequently, to assess joint structural integrity against fatigue. Extensive numerical research has been conducted, using finite elements, to develop a large SCF data base for multi-planar DT-joints, and are compared successfully with available experimental data. Using this FE data base, a simple and efficient methodology has been developed to predict stress concentrations in DT-joints, due to axial loads and bending moments. The important phenomenon of carry-over lending is examined in detail. The proposed SCF design tools are presented in the form of parametric SCF design equations and diagrams to be used by design engineers. The design methodology is illustrated in a design example. The results of the present investigation are aimed towards a reliable tubular DT-joint design in tubular st ructures subjected to repeated loading