Load Duration and Seasoning Effects on Mortise & Tennon Joinery

digits. This drop of moisture content can have the obvious effect of shrinkage. The
effects on joint strength <strong>and</strong> stiffness are investigated in this research.
The investigation included three different load levels <strong>and</strong> four different species of
wood. The load levels were zero load for the control group, <strong>and</strong> 1000 lb <strong>and</strong> 2000 lb.
The magnitude of the long-term load was determined by the strength of the short-term
tests conducted in this research <strong>and</strong> by Schmidt <strong>and</strong> Daniels (1999). The joints were not
kept in a special conditioning chamber, but rather they were allowed to season in an
environment in which both the temperature <strong>and</strong> humidity were subject to variation.
Short-term joint tests to failure were conducted on all of the joints after the interval of
sustained load <strong>and</strong> seasoning was concluded. A short-term test procedure similar to that
of the eastern white pine joint tests was used.
4.1.1. Test Frame Set-up
To test the effects of load duration on mortise <strong>and</strong> tenon joints, a long-term load test
frame was designed. A test frame was constructed to utilize a coil spring that could be
adjusted to maintain a desired load. The load frame held two joints at the same time,
each joint pulling against the other. Figure 4-1 shows the test frame with two joint
specimens. Two-inch diameter schedule 40 pipe was used to hold the two joints apart.
The pipes were connected to the joints with floor flanges that were bolted to the ends of
the mortise member.
The spring was contained within a piece of four-inch square tubing, three inches long.
Side plates were welded to the sides of the square tubing. The side plates had a dual
purpose. The first was structural <strong>and</strong> allowed connection to the tenon of one of the test
joints. The second purpose was to serve as a surface for calibration markings. Locations
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