Hybrid adhesively bonded timber-concrete-composite floors

Timber-concrete-composites (TCC) are structural elements in which a timber component is connected to a concrete layer such to form a composite. The advantageous properties of both materials are exploited and favourable structural and building physics floor performance is achieved, if compared to timber floors. Usually, the two TCC components are connected with mechanical fasteners where some degree of relative slip cannot be prevented. Alternatively, an almost perfectly rigid connection can be created using adhesives to bond the concrete layer to the timber. The combination of the aforementioned jointing techniques is referred to as hybrid. In this combination, the mechanical fasteners can also be considered as a back-up system for the potentially failing adhesive layer; this fail-safe option provides the incentive designers need to overcome their reluctance towards structural bonding. In the research presented herein, hybrid TCC floors combining self-tapping screws with an adhesive layer with were investigated at hand of 36 small-scale connection tests and two full-scale floor bending and vibration tests. Additionally to the initial quasi-static tests, two hybrid TCC floor segments were exposed to serviceability loads for approximately 2.5 years, with bending and vibration test performed afterwards. The long-term loading did not cause significant structural degradation, effective bending stiffness decreased by less than 10%, and vibration performance was not negatively impacted.