Behaviour of screw and notch shear connections in timber-low strength lightweight concrete composite (TLCC)

Abstract

In timber constructions, mortar screed is often used to increase the floor's structural mass and to mitigate thermal, acoustic and vibration problems. As an alternative to solve this structural need, the use of low strength lightweight concrete is proposed in this contribution to further exploit composite behaviour between timber and concrete. A performant shear connector is required to achieve an efficient composite behaviour. For this reason, an experimental study was conducted to investigate with push-out tests with three different mechanical configurations. The tested configurations are i) perpendicular application of the screws; ii) use of 100 x 100 mm notches and iii) 100 x 100 mm notches in combination with screws. The results show that the use of low strength lightweight concrete leads to an efficient composite action of TLCC. Use of only screws in the system leads to a flexible behaviour though, with relatively low load-carrying capacity. Use of a notch, however, leads to a significant increase in load-carrying capacity but very brittle failure was observed. As the full-scale behaviour and composite behaviour of the system depends on the slip modulus (stiffness) of the connector, by adding notches, the stiffness of the shear connection is increased. With the use of low strength lightweight concrete, structural integrity is satisfied with lower added weight to the system in comparison with normal weight concrete.