Design of composite sway building frames for global instability

Eurocode 4 is the European design code for composite construction; in its so-called ENV version, the scope is limited to "nonsway buildings" with efficient bracing systems. Therefore, it gives mainly rules to analyze and to check structural elements like beams, columns, slabs, and joints. However, in the last years, the construction of taller buildings and larger industrial halls without wind bracing systems is susceptible to make global instability a relevant failure mode, which is not covered by Eurocode 4. For 3 years, in the framework of a European research project funded by the European Community for Steel and Coal, in which the Univ. of Liege was deeply involved, intensive experimental, numerical, and theoretical investigations have been carried out. The latter aimed at improving the knowledge in the field of sway composite frames and at developing appropriate design rules. The rotational behavior of the beam-to-column composite joints is one of the key aspects of the problem to which special attention has been paid. This paper presents the numerical and analytical studies carried out at Liege Univ., as part of above European project, with the objective to investigate the behavior of sway composite structures under static loading. Particular phenomena put into sight through different analyses are illustrated herein. The actual response of the beam-to-column composite joints may be easily integrated into the described design and analysis procedures; this specific aspect is therefore not addressed in the paper.