Determining End & Edge Distance Criteria for Tenon Joints in Timber Structures

Traditionally, timber-frame connections use hardwood pegs to hold the main member within the joint. Currently the end and edge distance criteria for these connections have either been established by tradition or by an equivalent steel bolt diameter approximation. The object of this research is to determine a more specific method to establish the end and edge distances for wood pegs in wood connections. This investigation entails two separate tests that were developed from the standard American Society for Testing and Materials (ASTM) testing methods for steel bolds in wood members.

End and edge distance tests were performed on ¾ inch and 1 inch diameter Red Oak and White Oak pegs. The test method simulated a tenon joint. Main member species tested were Southern Pine and Douglas Fir. These combinations of material thus generated eight sets of data depicting behavior at various edge and end distances.

Analysis of these test data resulted in recommending the following end and edge distances in order to develop the full shear strength of the peg. For 1 inch diameter pegs, the recommended edge distance is approximately 2.6 diameters from the edge. For 1 inch diameter pegs loaded in the end direction, the recommended end distance is approximately 2.8 diameters from the end. For ¾ inch diameter pegs, the recommended edge distance is approximately 3 diameters and the recommended end distance is approximately 2.5 diameters.