The flooring system with its connections to the supporting column significantly influences the technical quality and performance of the steel-concrete composite design and the overall economic viability of the construction. Expectations of technical and economic flexibility and cost-effectiveness that alternative feasible solutions may offer motivate research and development in this field. This study focuses on the behaviour of beam-column connections in a building frame consisting of slim floor beams. The principal purpose was to gain a better understanding of the engineering features of semi-continuous composite joints and to apply this knowledge in the design of structures frequently used in Finland.A new advanced structural design connecting a slim floor beam to a tubular steel column section filled with concrete was designed using an application of the semi-continuous concept. The design was implemented and the construction tested in a thorough empirical study. Experimental work included two tests on bare steel connections and four tests on composite connections with full-scale specimens. The two tests on the bare steel connections demonstrated the joint behaviour during the erection and concreting work of the floor. Four specimens of composite connections were then tested in order to learn the influence of the slab characteristics on the connection behaviour in terms of the amount of reinforcement used in the slab, the shear-to-moment ratio, and the concrete strength.A mathematical model for predicting the moment-rotation characteristics of the joint response was formulated based on the geometrical and mechanical joint properties and findings from the empirical study. In the model formulation the basic mechanism of force transfer within the components of a composite connection was applied. Derived from the model and validated by the experimental results simple and robust methods that can be used by the designers are proposed.
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