Introducing Perfobond connectors in timber-concrete composite floor elements

Abstract

Shear connections have crucial importance in assuring the composite behaviour between the timber and the concrete in timber-concrete composites (TCC). Perfobond connectors were originally developed for steel-concrete composite structures to increase beam lengths by using their strong and stiff behaviour. Given the demonstrated efficiency of this type of connectors in these beams, its application to realize TCC floor elements is here proposed. In this paper symmetric push-outs tests are reported. Each specimen consists of a central timber element and two concrete layers connected by Perfobond connectors glued to the timber element. The testing variable analysed is the concrete type, namely: i) normal weight concrete and ii) lightweight concrete. As a result of this experimental work, the specimens with the use of normal weight concrete had a failure in the timber under shear stresses in the connection zone adjacent to the glued layer. With the use of lightweight concrete, however, two types of modes were observed: i) concrete dowel failure and ii) shear failure of timber. Specimens with normal weight concrete had a higher strength when compared to the specimens with lightweight concrete. In terms of stiffness, specimens with normal weight concrete lead to a slightly better performance, however, the use of lightweight concrete lead to a better performance in terms of deformation capacity. The results of this experimental work showed that Perfobond connectors are a promising solution to be used in TCC, especially when comparing with other shear connections. However, it is clear that within the range of the tested specimens, ductility is not provided, as the failure is governed by brittle failure modes. Further improvements are still necessary to optimize the connection in order to reach a ductile behaviour.