Finite Element Modelling of CLT-Concrete Composite Sections Utilizing Wood Screws as Shear Connectors

Mass timber buildings such as those made of glued-laminated timber (glulam) framing systems supporting cross-laminated timber (CLT) floor slabs can be designed to successfully achieve the limit state design requirements for both strength and serviceability. Floor systems in such buildings can even be made more robust and span longer distances by adding a top concrete layer to allow the formation of timber-concrete composite (TCC) floor systems when adequate shear connections are utilized. The primary technique for shear connections in TCC systems is a wide variety of metal connectors, with the self-tapping screws being one of the most used shear connectors. The numerical study presented in this paper aimed to investigate the shear characteristics of CLT-concrete composite sections that utilized wood screws as shear connectors. Three-dimensional finite element (FE) models for CLT-concrete composite sections have been developed using the commercial FE programme ABAQUS. The FE models were validated against the experimental results from a prior related study on TCC sections with concrete age of 28 days. Test specimens had 600 mm x 1000 mm shear interface between the CLT panel and concrete layer, and were experimentally examined under direct shear forces until failure. Details of the constitutive laws adopted for simulating timber and concrete in such TCC sections are addressed. The competency of the damage model implemented to capture the bi-axial stress state of wood material is also discussed. The FE models have an acceptable correlation with the experimental results, with the capability of simulating the slip behaviour between the timber panel and concrete layer.