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-------------------------| | 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 | |-----------------------------------------------------------
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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. The fibres (tracheids in conifers) act as hollow tubes bound closely together, and in giving way they either (1) buckle, or (2) bend.[5]
[Footnote 5: See Bulletin 70, op. cit., p. 129.]
