Stiffness of Steel-Timber Dowel Connections – Experimental and Numerical Research

The interaction of the non-linear behaviour ofthe timber and the fastener is challenging, whenpredicting the load-displacement behaviour ofdowel connections. In chap. 4, the most importantinfluencing factors on the connection stiffness weresummarized, considering the experimental, numericaland analytical results, and recommendationswere given for consideration in the design. Theestablishment and evaluation of a comprehensivedatabase is seen as the key for the revision of thevalues for Kser given in EN 1995-1-1 (2004) as well asfor the specification of minimum, mean and maximumvalues. In addition to the numerous tests on steel-timber dowel connections carried out at the Instituteof Structural Design at the University of Stuttgart,further results from other research projects shouldalso be included to be able to realistically assessthe large scattering of stiffness values. However,important adjustments could already be made in thecontext of the next generation of Euro-code 5. Forexample, a 50 % reduction of the initial stiffness fora load perpendicular to the grain direction comparedto a load parallel to grain direction could easily beincluded. A reduced stiffness for α = 90° is alreadyconsidered in the Swiss timber standard SIA 265(2012) and has already been published several timesin various re-search projects and therefore may beregarded to be state of the art. The reduction of thestiffness per fastener for fastener groups has also beenknown for a long time (BRÜHL (2020), JORISSEN (1998),SANDHAAS (2012)) and could be considered as a firstapproach using a general reduction factor (e.g. 0.8).The influence of the diameter is also underestimatedaccording to the results of this research project andshould therefore be further evaluated in comparisonwith other research results. In addition to therespective research reports, a further summary ofthe overall results is currently being prepared (GAUß(2022)).