Short-time procedure for fatigue assessment of beech wood and adhesively bonded beech wood joints

Timber as a structural material has experienced a revival for aspects related to sustainability, positive effect on interior building and increased architectural possibilities. To overcome a series of limitations related to partly obsolete traditional techniques, timber engineering sets high expectations on adhesive bonding as a joining method. Research on adhesively bonded timber joints has proven their superiority over mechanical fasteners in terms of strength and stiffness. Research on methods to design adhesively bonded timber joints under static loads is currently ongoing and significant progress has already been achieved. The topic of fatigue behaviour, however, has only been addressed very rarely, largely because “classical” methods for fatigue assessment based on Woehler curves, is extremely time-consuming. This paper aims to fill this gap by describing and validating an advanced time- and cost-efficient approach to quantify the behaviour of bonded timber joints under fatigue. Therefore the fatigue behaviour of beech wood as base material and adhesively bonded beech wood joints as structural elements were investigated by means of a short-time procedure. In this approach, cyclic tests with a stepwise increase of the stress amplitude were performed while the plastic strain amplitude was measured. The plastic strain amplitude gives reliable signals for an estimation of the fatigue strength. This is validated by traditional cyclic tests with constant stress amplitudes. It could be shown that the testing approach provides reliable results and has a high potential in time and cost savings for wood and adhesively bonded wood joints.