Influence of the joining technique on the structural behaviour of hybrid timber-steel cross-sections

Timber as construction material has a long tradition and is increasingly coming into focus as a renewable material in the planning and construction of buildings. Nevertheless, there are mechanical limitations, especially for multi-storey buildings or large spans. In order to enable large spans with small cross-sections, steel and timber can be combined in a hybrid cross-section for bending beams. In this case, the performance of the hybrid component decisively depends on the bond of the individual cross-sections. The aim of this publication is to compare and investigate different joining techniques for an efficient bond between timber and steel. Small-scale specimens were used to investigate different bonding methods: dowel-type fasteners, punched metal plate fasteners (PMPF) and adhesive bonds between timber and steel. Adhesive bonded specimens exhibited stiff but brittle behaviour. The adhesive bond remained intact in all tests, while shear failure could be detected in the timber. Adhesive bonds exhibited 93 times the stiffness of dowel fasteners and 5.5 times the stiffness of PMPF. The load carrying capacity increased by approximately 80% compared to dowel-type fasteners and 30% compared to PMPF, demonstrating the superior suitability of adhesive bonds for high performance timber-steel hybrid sections.