Load Duration and Seasoning Effects on Mortise & Tennon Joinery

shear planes per peg. This type of peg failure is the most common throughout all of the
joints tested. Comparing shear stress rather than joint yield load also makes it possible to
include results for the joints that were tested with 3/4” diameter pegs. A plot of the
average shear yield stress versus base material specific gravity is shown in Figure 2-8.
2500
τ = 1617G + 1063
R2 = 0.4638
2000
Mean Shear Stress at Yield
1500
1000
500
Red Oak
Douglas Fir
Souterh Yellow Pine
Eastern White Pine
0
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
Base Material Specific Gravity
Figure 2-8 Correlation of Specific Gravity to Peg Joint Shear Stress
The base material specific gravity is related to base material strength. With a
relationship between base material specific gravity <strong>and</strong> base material strength, a
correlation between confinement strength <strong>and</strong> specific gravity is assumed. In other words
a higher base material specific gravity equates to a larger peg shear yield value <strong>and</strong>
higher joint yield strength. With increased confinement strength the peg is subjected to a
smaller shear span L (Figure 2-9) over which it can deform producing a higher joint yield
value.
21