Institute for Transportation

Experimental shear strength research conducted
cooperatively with the USDA Forest Service, Forest
Products Laboratoy; Washington State University,
and the Federal Highway Administration on solidsawn
beams is summarized in this paper. Douglas
Fir, Engelmann Spruce, and Southern Pine specimens
were tested in a green condition to determine shear
strength in members without checks and splits. Sizes
tested ranged from nominal 51 by 102 mm to 102 by
256 mm. Additional tests were conducted on air-dried
solid-sawn Douglas Fir and Southern Pine specimens.
A three-point loading setup investigated the effect of
splits and checks on shear strength, and a five-point
loading setup investigated drying effect on beam
shear. Based on the experimental tests, the following
are concluded: (1) shear strength of green solid-sawn
without splits varies with size and may be
characterized using a shear area or volume
parameter; (2) air-dried Southern Pine shear strength
free of splits is equivalent to that for Southern Pine
glued-laminated timber; (3) tests on seasoned
Douglas Fir and Southern Pine gave mixed results on
the effect of splits and checks; and (4) fracture
mechanics predictions of the shear strength of
artificially split Southern Pine were conservative.