Simplified nonlinear model for timber-concrete composite beams

Abstract

Timber-concrete composite (TCC) structures have been emerging in several industrial applications due to potential to simultaneously optimize their structural stiffness, dynamic vibration and ecological imprint. However, when one considers nonlinear behaviour of timber-to-concrete connections and the cracking of the concrete slab, the structural analysis of the composite system becomes quite complex. The scope of this article is to provide a powerful one-dimensional model accounting for the nonlinear behaviour of steel dowel connections and cracking of the concrete slab for better understanding the structural behaviour of TCC structures. First, we extended the existing Winkler model of a beam on an elastic foundation for calculating the load-slip deformation of a steel dowel connecting concrete to timber. Then, we extended the composite beam theory with the secant stiffness approach to account for the nonlinear behaviour of the connection and the cracking of concrete in a TCC beam. An original 4-level model for predicting the structural behaviour of a TCC beam starting from the behaviour of the steel dowel connection is developed by combining three upscaling models. The model has been implemented in a Finite Element Method and has been validated with experimental tests available in literature. An in-depth discussion of the results shows the usefulness of such simplified engineering model to better understand the structural behaviour of TCC beams in terms of the composite action, cracking distribution and structural ductility.