Study on load‐carrying capacity of MAG butt‐welded mixed connections with different steel strengths

Mixed connections of normal-strength steel and high-strength steel can enable an optimum resource-saving use of materials by adapting the material strength to the forces acting on them. But the design and calculation of butt-welded mixed connections is not clearly regulated in the currently valid standards EN 1993-1-8 and EN 1993-1-12. In the research project Effective design concepts for mixed connections in steel structures an extensive experimental program with 180 mixed connections has been conducted to investigate the load-carrying capacity and behaviour of these connections. The weld joint specimens were made with normal-strength steel S355J2+N and different high-strength steels S690QL, S700MC or S960QL. Varying parameters were also the filler metals, plate thicknesses, weld bevels and the heat input during welding. The influence of these parameters on the load-carrying capacity and the deformation behaviour of mixed connections was investigated. Moreover, high-resolution microhardness mappings (UCI) on the welded specimens were carried out to examine the formation of the soft zone in the heat-affected zone of the high-strength steels.