Experimental Analysis of a Novel Hybrid Timber-Concrete-Steel Flooring System

This study investigates a sustainable, novel composite floor system integrating steel, concrete, and timber members in a prefabricated unit, with the aim of evaluating both structural and environmental performance. Preliminary investigations included numerical analyses, the fabrication of two mock-ups, and an experimental campaign to assess the dynamic and static behavior of a floor unit. The mock-ups differed in the timber chord configuration and the arrangement of the steel diagonals, while the geometry of the upper concrete slab remained unchanged. This paper presents only the results of the experimental static tests conducted until failure, conducted at the Laboratory of the Department of Building Technology at Linnaeus University in Växjö (Sweden). Two specimens were tested under a four-point bending test to investigate the flexural behavior and failure modes. Initially, the specimens were subjected to serviceability limit state (SLS) loading, applied in three cycles. Subsequently, three loading cycles were applied under the design ultimate limit state (ULS). Finally, each specimen was loaded under monotonic static loading until failure. Both Specimen S1 and Specimen S2 showed consistent behavior during all three SLS loading cycles. At collapse, detachment of the diagonals from the bottom chord was observed, while the steel diagonal connections to the upper concrete slab performed as intended throughout the test duration. The discussion focuses primarily on the behavior of the connections between the timber bottom chords and the thin-walled steel diagonal members, as these elements governed the global response and failure mechanisms. Based on the observed failure modes, the paper also discusses possible improvements to enhance the overall system performance.