Frictional behaviour of timber-concrete contact pairs

While friction plays an important role in many timber-concrete composite structures, it has been studied only to a limited extent and current knowledge is not comprehensive enough for rigorous modelling of e.g. timber-concrete connections. The purpose of this study is to fill part of this gap by investigating timber to concrete friction under cyclic loading experimentally. The tests were conducted with small-scale double-sided shear specimens. The materials included surface treated and untreated edge-faces of coniferous laminated veneer lumber and birch plywood combined with high-strength concrete grout that was cast directly on the timber parts. The initial shear strengths are evaluated by the Mohr-Coulomb criterion, and the static and kinetic friction coefficients are determined for each load cycle. Based on the results, influence of the cumulative displacement, the wood product, the grain orientations and the surface treatment on the initial shear strength and the friction coefficients are analysed. The tests also showed interlocking that is likely related to the matching surfaces created by prior de-bonding. As this interlocking affects the results, it was also investigated.