Knot dinteraction in wood poles

Summary Superposition of the longitudinal stress distributions associated with neighboring knots was used to determine the interaction distances between different knot sizes. The interaction between two knots was considered significant when the superposition of the stress distribution caused an increase in the longitudinal stress level of ten percent or more. Out of 4,374 knots measured in 44 Douglas-fir poles only 55 knots showed significant interactions with adjacent knots. However, in more than half of the poles at least one interacting knot pairs existed. Therefore, it has been concluded that stress interaction between knots could play a major role in controlling the failure of poles in bending.