2019 Volume 44 Issue 3 Pages 109-113
This paper proposes a numerical method for estimating the ultimate clamp force of lag screw timber joints with steel side plates based on the pull-out strength and thread friction coefficient of the lag screw. Lag screw tightening tests and pull-out tests were performed using timber samples from three different wood species, for three different screw insertion angles with respect to the annual ring, to evaluate how well the predictions matched the observed empirical data. Ratios of observed to estimated ultimate clamp force ranged from 0.9 to 1.3, suggesting the proposed method well approximated the empirical trend. However, it was found that the proposed method was overestimated depending on the degree of female thread formation in the wood, so it was indicated that the reduction coefficient should be taken into consideration.