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Universal high‐performance columns made of high‐strength steels without welding In recent years, steel‐concrete composite columns made of normal‐strength steels are seldom used owing to the economic and technological advantages of precast reinforced concrete columns. Though, the use of high‐strength structural steels bears high potential for the efficient production of composite columns with excellent structural performance that are economically competitive to precast concrete columns, there are currently major obstacles to use of the ultra‐high‐strength steels (UHSS) in Germany. Hollow section composite columns with embedded high strength steel core without welded connections provide an opportunity to regain lost market share. A research project, funded by the AiF (Arbeitsgemeinschaft industrieller Forschungsvereinigungen), is intended to explore the potential of UHSS composite columns by experimental and theoretical investigations. The present paper demonstrates the concept of such composite columns with UHSS and gives first exciting insights into the research results. In addition to column tests under ambient and fire conditions, small scale tests are necessary to investigate various influencing factors and to create the basis for new and easy to use design and construction principles that allow efficient application. [ABSTRACT FROM AUTHOR]

Structural behaviour of high‐strength composite columns and material behaviour in case of fire Concrete‐filled steel tubular composite columns are increasingly used in enineering practice, as they provide competitive solutions, for buildings with high demands on the load‐bearing capacity and cross‐sectional dimensions. Additionally, composite columns are characterised by high fire resistances. The use of high‐strength materials for composite columns also facilitates the realisation of more sustainable, efficient and economical steel‐concrete composite structures and thus to maintain the long term competitiveness of steel and composite structures. The use of high‐ and ultra‐high‐strength materials for composite columns is currently still limited by the application range of Eurocode 4. The research projects of the HOCHFEST, which are strongly supported by the research association FOSTA, address exactly this limitation and are presented in this issue of Stahlbau. The HOCHFEST research network comprises a total of 15 research projects, which investigate the multiple application potential of high‐strength steels. The research projects P 1287, P 1349, P 1500, P 1501 and P 1502 address the load‐bearing behaviour of high‐performance composite columns and the material behavior of high‐strength steel at ambient temperature as well as in case of fire and under earthquake conditions. The findings of the research projects therefore are essential for the future development of design methods for high‐performance composite columns. [ABSTRACT FROM AUTHOR]