18, U.S.Division of Forestry: Progress in timber physics, pp.

13-18; also Bulletin 70, U.S.
Forest Service: Effect of moisture on the strength and stiffness of wood, pp.

42, 89-90.] |-------------------------------------------------------------------------------| | TABLE V | |-------------------------------------------------------------------------------| | RELATION OF FIBRE STRESS AT ELASTIC LIMIT (r) IN BENDING TO THE CRUSHING | | STRENGTH (C) OF BLOCKS CUT THEREFROM, IN POUNDS PER SQUARE INCH | | (Forest Service Bul.

70, p.

90) | |-------------------------------------------------------------------------------| | LONGLEAF PINE | |-------------------------------------------------------------------------------| | | Soaked | Green | 14 | 11.5 | 9.5 | Kiln-dry | | MOISTURE CONDITION | 50 per | 23 per | per | per | per | 6.2 per | | | cent | cent | cent | cent | cent | cent | | -- -----------------------+--------+--------+-------+-------+-------+----------| | Number of tests averaged | 5 | 5 | 5 | 5 | 4 | 5 | | _r_ in bending | 4,920 | 5,944 | 6,924 | 7,852 | 9,280 | 11,550 | | _C_ in compression | 4,668 | 5,100 | 6,466 | 7,466 | 8,985 | 10,910 | | Per cent _r_ is in | | | | | | | | excess of _C_ | 5.5 | 16.5 | 7.1 | 5.2 | 3.3 | 5.9 | |-------------------------------------------------------------------------------| | SPRUCE | |-------------------------------------------------------------------------------| | | Soaked | Green | 10 | 8.1 | Kiln-dry | | MOISTURE CONDITION | 30 per | 30 per | per | per | 3.9 per | | | cent | cent | cent | cent | cent | |----------------------------------+--------+--------+-------+-------+----------| | Number of tests averaged | 5 | 4 | 5 | 3 | 4 | | _r_ in bending | 3,002 | 3,362 | 6,458 | 8,400 | 10,170 | | _C_ in compression | 2,680 | 3,025 | 6,120 | 7,610 | 9,335 | | Per cent _r_ | | | | | | | is in excess of _C_ | 12.0 | 11.1 | 5.5 | 10.4 | 9.0 | |-------------------------------------------------------------------------------| When a short column is compressed until it breaks, the manner of failure depends partly upon the anatomical structure and partly upon the degree of humidity of the wood.