Load Duration and Seasoning Effects on Mortise & Tennon Joinery

the joint deflection prior to any adjustment. The load was then adjusted by compressing
the spring to the calibration mark by tightening the nut down further on the length of allthread
rod. The joint deflection was then recorded again. This adjustment procedure is
visible as a jump in deflection on the time deflection graphs that follow.
4.2. Douglas Fir
Long-term seasoning <strong>and</strong> creep tests were conducted on twelve Douglas fir joints. Six
joints were loaded, while the control group was composed of the remaining six joints.
Six joints were drawbored in an effort to investigate benefits or possible drawbacks to
drawboring. The drawbored joints were divided equally between the loaded <strong>and</strong> control
groups of joints. Detailing requirements made by Schmidt <strong>and</strong> Daniels were followed:
2.5D edge distance, 2.0D end distance <strong>and</strong> 2.5D spacing. All of the Douglas fir joints
were connected with 1” diameter white oak pegs.
4.2.1. <strong>Load</strong>ing <strong>and</strong> <strong>Load</strong> <strong>Duration</strong>
The load group of six joints was loaded for 348 days at 2000 lb. This long-term load
is 35% of the average yield load reported by Schmidt <strong>and</strong> Daniels (1999) from testing of
recycled Douglas fir joints with 1” diameter pegs. Note that the joints used in the longterm
load test were fabricated from green material, not recycled. The characteristics of
the individual joints are given in Table 4-1. The time-deflection curves of each loaded
joint are shown in Figure 4-2.
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