An Assessment of the Behaviour of Ceiling Beams of Different Structure

The article focuses on floor composite beams used in buildings. Within the scope of the conducted analytical and numerical studies, the authors compared the typical solution—namely, the T-shaped reinforced concrete beam—with various types of composite beams, the height of which could not exceed the predetermined usable depth of the beam cross-section. The analyses focused on traditional steel–concrete composite beams, which are widely used in civil engineering, as well as modern solutions, such as timber–timber and steel–timber composite beams. A new type of a steel–timber composite beam with a cold-formed girder made of two channels was presented in this study. Due to the flexibility of the connections, the timber–timber and steel–timber composite beams were examined under three different connection conditions: full composite action, partial composite action, and no composite action (friction only). Composite beams with timber slabs are consistent with the principles of sustainable construction, which makes their comparison with conventional solutions particularly relevant. The load-deflection curves and the bending resistance of the analysed elements were obtained using numerical simulations. In the numerical analyses, advanced material models were used. Composite beams with timber elements had lower stiffness than the steel–concrete composite beam. For this reason, meeting the serviceability limit state can be more challenging for such structures. Furthermore, the degree of shear connection in the composite beams with timber elements had a strong impact on their load-bearing capacity and end-slip. The steel–timber composite beam with a cold-formed girder had the most favourable resistance-to-mass ratio. The analytical results, and especially the numerical findings, provide a foundation for future experimental investigations.