Effective design concepts for welded mixed connections in steel structuresMixed connections made of normal strength and high strength steels enable optimal material use to the forces acting on them. This leads to ecological and economic advantages through reduced material consumption and smaller weld geometries. Normative rules for butt-welded mixed connections of normal strength and high strength steels do not exist, therefore a design approach for such connections is to be developed in the research project "Effective design concepts for mixed connections in steel structures". In addition, the design concepts already developed for butt-welds and fillet-welds are being extended up to S960, in order to integrate the results into the new version of EN 1993-1-12. For this purpose, extensive experimental investigations of the load-carrying capacity are carried out by varying the base material, welding consumable, heat input, plate thickness and weld geometry. With the results obtained and further accompanying investigations, the influences of the varying parameters on the load-carrying capacity of the welded connections will be identified. First results of that project are reported in the following.

<p>High-performance materials such as high strength steels allow for resource-efficient innovative structures. Therefore, economical and user-friendly design concepts for welded connections of high strength steels are required. Current design rules had been developed mainly for mild steels, e.g. requiring an overmatching of the filler metal. It is not considered, that a soft area which may form in the heat-affected zone of welded high strength steel connections may lead to an overestimation of the load-carrying capacity. Besides, mixed connections as well as under- and overmatching filler metals are not included in the current design codes. Based on a large number of experimental and numerical investigations, a design concept has been developed which takes the characteristics of butt welded high strength steel connections into account. Additionally, experimental and numerical investigations are planned to transfer the new concept of design also to mixed connections.</p>