368 Holz Roh Werks(2008)66:363-372 4.2 Estimation of the coefficient of friction Several numerical simulations were made where between the dowel and the surrounding timber varied.In Fig.6,the results are presented together with the experimental results obtained from the ARAMIS-system The coefficients of friction (between the dowel and the surrounding timber were estimated by comparing the strain By arough estimation of the results in Fig.6was decided distribution (strain perpendicular to the grain)along a cer- to le betweenou2 joints.Using a coefficient of fric- tain path as measured by the ARAMIS-system with the dis. for On Cac ig.6.The compari her compa tion between the measured and the theoretical values can be global load-displacement resr nse of the ioints.Fis4)in found,see Figs.6b,7 and 8. volving a total load of approximately 11 kN for the group 1 In Rodd (1973)tests were made to determine the co- joints and 17kN for the group 2 joints.Three joints from erent d of the ace characte Th wel suls in that study.with dowels similar to the ones were simulatec in this study.gave that the coefficients of friction was 0.339 for the smooth dowels and 0.558 for the rough dow els.Interesting to note is that these values are close to the 241 value. bove for resp d in dy T tive group 30 xactly the Group1 Smooth surface same level as obtained in this study.One parameter can 4 12 10- 4 2 0 0 4 8 10 12 14 24士 22 Group 2.Rougth surface 201 181 4 1210 号 十 0 4 6 8 10 1214 Displacement (mm) s for all Abb.5 Ty oindungen 鱼Springer 368 Holz Roh Werkst (2008) 66: 363–372 4.2 Estimation of the coefficient of friction between the dowel and the surrounding timber The coefficients of friction (µ) between the dowel and the surrounding timber were estimated by comparing the strain￾distribution (strain perpendicular to the grain) along a cer￾tain path as measured by the ARAMIS-system with the dis￾tribution calculated by numerical simulations. The location of the path is shown in Fig. 6. The comparison of the results was made for the elastic part of the response (based on the global load-displacement response of the joints, Fig. 4), in￾volving a total load of approximately 11 kN for the group 1 joints and 17 kN for the group 2 joints. Three joints from each group were studied. For comparing the results from the ARAMIS-system with those of the numerical analyses, the same load levels were simulated. Fig. 4 Load-displacement results for all joints tested Abb. 4 Kraft-Weg-Diagramme aller untersuchten Verbindungen Several numerical simulations were made where µ was varied. In Fig. 6, the results are presented together with the experimental results obtained from the ARAMIS-system. By a rough estimation of the results in Fig. 6, µ was decided to lie between 0 and 0.3 for the group 1 joints and between 0.3 and 0.5 for the group 2 joints. Using a coefficient of fric￾tion (µ) of 0.1 for the group 1 joints and 0.4 for the group 2 joints in the numerical simulations, a rather close correla￾tion between the measured and the theoretical values can be found, see Figs. 6b, 7 and 8. In Rodd (1973) tests were made to determine the co￾efficient of friction between a dowel and the surround￾ing timber. Different dowel surface characteristics as well as different diameters of the dowel were studied. The re￾sults in that study, with dowels similar to the ones used in this study, gave that the coefficients of friction µ was 0.339 for the smooth dowels and 0.558 for the rough dow￾els. Interesting to note is that these values are close to the upper values as mentioned above for respective group of joints tested in this study. There are several reasons why the results presented in Rodd (1973) are not on exactly the same level as obtained in this study. One parameter can, Fig. 5 Typical experimental observations for each group: a picture taken before final failure, b final failure mode Abb. 5 Typische Versuchsbeobachtungen bei beiden Gruppen, a Auf￾nahme vor dem Bruch, b Bruchbild 13