SHEAR STRENGTH OF WOOD BEAMS

Experimental shear strength research conducted cooperatively with the USDA Forest Service, Forest Products Laboratory; Washington State University; and the Federal Highway Administration on solid-sawn 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 51x102 mm (2x4 in.) to 102x256 mm (4x10 in.). 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 charaterized using a shear 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.