THE MECHANICAL PROPERTIES OF WOOD INCLUDING A DISCUSSION OF THE FACTORS AFFECTING THE MECHANICAL PROPERTIES, AND METHODS OF TIMBER TESTING
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portion was formed early in the season, when growth was comparatively rapid and is known as _early wood_ (also spring wood); the outer portion is the _late wood_, being produced in the
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d substance than the spring wood composed of wide vessels. Therefore, rapid-growing specimens with wide rings have more wood substance than slow-growing trees with narrow rings. Since t
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en the boiling temperature. Mould fungus has been observed to develop rapidly at 130°F. in a dry kiln in moist air, a condition under which an animal cannot live more than a few minutes
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ending the handling of the timber after it is felled. Wood dries more rapidly in summer than in winter, not because there is less moisture at one time than another, but because of the h
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he diagram where the square of the deflection begins to increase more rapidly than the height of drop. The difference between the datum line and the final resting point after each drop
|-----------------+----------+-------+-------+--------+--------+---------+--------+--------+-------+ ------+---------+-------+-------+----------|
| | | | | | 1,000 | | | | | | | | | |
| | Inches | | | Lbs. | lbs. | Lbs. | Inches | Inches | | | Lbs. | | | Lbs. |
| | | | | | | | | | | | | | | |
| Longleaf pine | 4 by 5 | 46 | 26.3 | 3,480 | | 4,800 | 4 by 5 | 4 | 22 | 25.1 | 572 | 52 | 20.2 | 984 |
| Douglas fir | 6 by 6 | 259 | 20.3 | 3,271 | 1,038 | 4,258 | 4 by 8 | 16 | 44 | 20.8 | 732 | 465 | 22.1 | 822 |
| | 2 by 2 | 247 | 18.7 | 3,842 | 1,084 | 5,002 | 4 by 8 | 10 | 32 | 18.1 | 584 | | | |
| | | | | | | | 4 by 4 | 8 | 51 | 20.2 | 638 | | | |
| | | | | | | | 4 by 4 | 6 | 49 | 24.0 | 613 | | | |
| | | | | | | | 4 by 4 | 4 | 29 | 24.8 | 603 | | | |
| Shortleaf pine | 6 by 6 | 29 | 15.7 | 4,070 | 1,951 | 6,030 | 8 by 5 | 16 | 4 | 17.8 | 725 | 85 | | 1,135 |
| | 2 by 2 | 57 | 14.2 | | | 6,380 | 8 by 5 | 14 | 3 | 16.3 | 757 | | | |
| | | | | | | | 8 by 5 | 12 | 5 | 15.1 | 730 | | | |
| | | | | | | | 5 by 5 | 8 | 6 | 13.0 | 918 | | | |
| | | | | | | | 2 by 2 | 2 | 57 | 13.9 | 926 | | | |
| Western larch | 6 by 6 | 112 | 16.0 | | | 5,445 | 8 by 6 | 16 | 17 | 18.8 | 491 | 193 | 15.0 | 905 |
| | 4 by 4 | 81 | 14.7 | | | 6,161 | 8 by 6 | 12 | 18 | 17.6 | 526 | | | |
| | 2 by 2 | 270 | 14.8 | | | 5,934 | 5 by 4 | 8 | 22 | 13.3 | 735 | | | |
| Loblolly pine | 6 by 6 | 23 | | 3,357 | 1,693 | 5,005 | 8 by 5 | 16 | 12 | 19.8 | 602 | 156 | 11.3 | 1,115 |
| | 5 by 5 | 10 | 22.4 | 2,217 | 545 | 2,950 | 8 by 5 | 8 | 7 | 22.9 | 679 | | | |
| | 4 by 8 | 8 | 19.4 | 3,010 | 633 | 3,920 | 4 by 5 | 8 | 8 | 19.5 | 715 | | | |
| | 2 by 2 | 69 | | | | 5,547 | | | | | | | | |
| Tamarack | 6 by 7 | 3 | 15.7 | 2,257 | 1,042 | 3,323 | 2 by 2 | 2 | 57 | 16.2 | 697 | 60 | 14.0 | 879 |
| | 4 by 7 | 3 | 13.6 | 3,780 | 1,301 | 4,823 | | | | | | | | |
| | 4 by 4 | 57 | 14.9 | 3,386 | 1,353 | 4,346 | | | | | | | | |
| | 2 by 2 | 66 | 14.6 | | | 4,790 | | | | | | | | |
| Western hemlock | 6 by 6 | 102 | 18.6 | 4,840 | 2,140 | 5,814 | 7 by 6 | 15 | 25 | 18.2 | 514 | 131 | 17.7 | 924 |
| | 2 by 2 | 463 | 17.0 | 4,560 | 1,923 | 5,403 | 6 by 6 | 6 | 26 | 16.8 | 431 | | | |
| | | | | | | | 4 by 4 | 4 | 6 | 15.9 | 488 | | | |
| Redwood | 6 by 6 | 18 | 16.9 | | | 4,276 | 8 by 6 | 16 | 5 | 25.4 | 548 | 95 | 12.4 | 671 |
| | 2 by 2 | 115 | 14.6 | | | 5,119 | 6 by 6 | 12 | 6 | 14.7 | 610 | | | |
| | | | | | | | 7 by 6 | 9 | 5 | 14.8 | 500 | | | |
| | | | | | | | 3 by 6 | 14 | 2 | 12.6 | 470 | | | |
| | | | | | | | 2 by 6 | 12 | 2 | 16.2 | 498 | | | |
| | | | | | | | 2 by 6 | 10 | 4 | 14.3 | 511 | | | |
| | | | | | | | 2 by 6 | 8 | 2 | 13.2 | 429 | | | |
| | | | | | | | 2 by 2 | 2 | 145 | 13.8 | 564 | | | |
| Norway pine | 6 by 7 | 4 | 15.2 | 2,670 | 1,182 | 4,212 | 2 by 2 | 2 | 36 | 10.0 | 924 | 44 | 11.9 | 1,145 |
| | 4 by 7 | 2 | 22.2 | 3,275 | 1,724 | 4,575 | | | | | | | | |
| | 4 by 4 | 55 | 16.6 | 3,048 | 1,367 | 4,217 | | | | | | | | |
| | 2 by 2 | 44 | 11.2 | | | 7,550 | | | | | | | | |
|-----------------------------------------------------------------------------------------------------------------------------------------------|
| _Note.--Following is an explanation of the abbreviations used in the foregoing tables:_ |
| F.S. at E.L. = Fiber stress at elastic limit. |
| M. of E. = Modulus of elasticity. |
| M. of R. = Modulus of rupture. |
| Cr. str. at E.L. = Crushing strength at elastic limit. |
| Cr. str. at max. ld. = Crushing strength at maximum load. |
|-----------------------------------------------------------------------------------------------------------------------------------------------|
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| TABLE XXII TABLE XXII |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| [b]WORKING UNIT-STRESSES FOR STRUCTURAL TIMBER[c] |
| EXPRESSED IN POUNDS PER SQUARE INCH |
| (From Manual of the American Railway Engineering Assn., 1911, p. 153) |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| NOTE.--The working unit-stresses given in the table are intended for railroad bridges and trestles. For highway bridges and trestles the unit-stresses may be increased |
| twenty-five (25) per cent. For buildings and similar structures, in which the timber is protected from the weather and practically free from impact, the unit-stresses may be |
| increased fifty (50) per cent. To compute the deflection of a beam under long-continued loading instead of that when the load is first applied, only fifty (50) per cent of the |
| corresponding modulus of elasticity given in the table is to be employed. |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| | BENDING | SHEARING | COMPRESSION | |
| |---------------------------------+-----------------------------------------+-------------------------------------------------------------------------| Ratio |
| | Extreme | Modulus of | Parallel to | Longitudinal | Perpendicular | Parallel to | For | Formulæ for | of |
| | fibre | elasticity | the grain | shear in | to the grain | the grain | columns | working stress in | length |
| KIND OF | stress | | | beams | | | under 15 | long columns over | of |
| TIMBER |--------------------+------------+--------------------+--------------------+--------------------+--------------------| diameters | 15 diameters | stringer |
| | Average | Working | | Average | Working | Elastic | Working | Elastic | Working | Average | Working | working | | to |
| | ultimate | stress | Average | ultimate | stress | limit | stress | limit | stress | ultimate | stress | stress | | depth |
|-----------------+----------+---------+------------+----------+---------+----------+---------+----------+---------+----------+---------+-----------+-------------------+----------|
| Douglas fir | 6100 | 1200 | 1,510,000 | 690 | 170 | 270 | 110 | 630 | 310 | 3600 | 1200 | 900 | 1200(1-_l_/60_d_) | 10 |
|-----------------+----------+---------+------------+----------+---------+----------+---------+----------+---------+----------+---------+-----------+-------------------+----------|
| Longleaf pine | 6500 | 1300 | 1,610,000 | 720 | 180 | 300 | 120 | 520 | 260 | 3800 | 1300 | 980 | 1300(1-_l_/60_d_) | 10 |
|-----------------+----------+---------+------------+----------+---------+----------+---------+----------+---------+----------+---------+-----------+-------------------+----------|
| Shortleaf pine | 5600 | 1100 | 1,480,000 | 710 | 170 | 330 | 130 | 340 | 170 | 3400 | 1100 | 830 | 1100(1-_l_/60_d_) | 10 |
|-----------------+----------+---------+------------+----------+---------+----------+---------+----------+---------+----------+---------+-----------+-------------------+----------|
| White pine | 4400 | 900 | 1,130,000 | 400 | 100 | 180 | 70 | 290 | 150 | 3000 | 1000 | 750 | 1000(1-_l_/60_d_) | 10 |
|-----------------+----------+---------+------------+----------+---------+----------+---------+----------+---------+----------+---------+-----------+-------------------+----------|
| Spruce | 4800 | 1000 | 1,310,000 | 600 | 150 | 170 | 70 | 370 | 180 | 3200 | 1100 | 830 | 1100(1-_l_/60_d_) | |
|-----------------+----------+---------+------------+----------+---------+----------+---------+----------+---------+----------+---------+-----------+-------------------+----------|
| Norway pine | 4200 | 800 | 1,190,000 | 590[d] | 130 | 250 | 100 | | 150 | 2600[d] | 800 | 600 | 800(1-_l_/60_d_) | |
|-----------------+----------+---------+------------+----------+---------+----------+---------+----------+---------+----------+---------+-----------+-------------------+----------|
| Tamarack | 4600 | 900 | 1,220,000 | 670 | 170 | 260 | 100 | | 220 | 3200[d] | 1000 | 750 | 1000(1-_l_/60_d_) | |
|-----------------+----------+---------+------------+----------+---------+----------+---------+----------+---------+----------+---------+-----------+-------------------+----------|
| Western hemlock | 5800 | 1100 | 1,480,000 | 630 | 160 | 270[d] | 100 | 440 | 220 | 3500 | 1200 | 900 | 1200(1-_l_/60_d_) | |
|-----------------+----------+---------+------------+----------+---------+----------+---------+----------+---------+----------+---------+-----------+-------------------+----------|
| Redwood | 5000 | 900 | 800,000 | 300 | 80 | | | 400 | 150 | 3300 | 900 | 680 | 900(1-_l_/60_d_) | |
|-----------------+----------+---------+------------+----------+---------+----------+---------+----------+---------+----------+---------+-----------+-------------------+----------|
| Bald cypress | 4800 | 900 | 1,150,000 | 500 | 120 | | | 340 | 170 | 3900 | 1100 | 830 | 1100(1-_l_/60_d_) | |
|-----------------+----------+---------+------------+----------+---------+----------+---------+----------+---------+----------+---------+-----------+-------------------+----------|
| Red cedar | 4200 | 800 | 800,000 | | | | | 470 | 230 | 2800 | 900 | 680 | 900(1-_l_/60_d_) | |
|-----------------+----------+---------+------------+----------+---------+----------+---------+----------+---------+----------+---------+-----------+-------------------+----------|
| White oak | 5700 | 1100 | 1,150,000 | 840 | 210 | 270 | 110 | 920 | 450 | 3500 | 1300 | 980 | 1300(1-_l_/60_d_) | 12 |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| These unit-stresses are for a green condition of timber and are _l_ = Length in inches. |
| to be used without increasing the live load stresses for impact. _d_ = Least side in inches. |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
|[Footnote b: Adopted, Vol. 1909, pp. 537, 564, 609-611.] |
|[Footnote c: Green timber in exposed work.] |
|[Footnote d: Partially air-dry] |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
BIBLIOGRAPHY
Part I: Some general works on mechanics, materials of
construction, and testing of materials.
Part II: Publications and articles on the mechanical properties
of wood, and timber testing.
Part III: Publications of the U.S. Government on the mechanical
properties of wood, and timber testing.
PART 1. SOME GENERAL WORKS ON MECHANICS, MATERIALS OF
CONSTRUCTION, AND TESTING OF MATERIALS
ALLAN, WILLIAM: Strength of beams under transverse loads. New
York, 1893.
ANDERSON, SIR JOHN: The strength of materials and structures.
London, 1902.
BARLOW, PETER: Strength of materials, 1st ed. 1817; rev. 1867.
BURR, WILLIAM H.: The elasticity and resistance of the materials
of engineering. New York, 1911.
CHURCH, IRVING P.: Mechanics of engineering. New York, 1911.
HATFIELD, R.G.: Theory of transverse strain. 1877.
HATT, W.K., and SCOFIELD, H.H.: Laboratory manual of testing
materials. New York, 1913.
JAMESON, J.M.: Exercises in mechanics. (Wiley technical series.)
New York, 1913.
JAMIESON, ANDREW: Strength of materials. (Applied mechanics and
mechanical engineering, Vol. II.) London, 1911.
JOHNSON, J.B.: The materials of construction. New York, 1910.
KENT, WILLIAM: The strength of materials. New York, 1890.
KOTTCAMP, J.P.: Exercises for the applied mechanics laboratory.
(Wiley technical series.) New York, 1913.
LANZA, GAETANO: Applied mechanics. New York, 1901.
MERRIMAN, MANSFIELD: Mechanics of materials. New York, 1912.
MURDOCK, H.E.: Strength of materials. New York, 1911.
RANKINE, WILLIAM J.M.: A manual of applied mechanics. London,
1901.
THIL, A.: Conclusion de l'étude présentée à la Commission des
méthodes d'essai des matériaux de construction. Paris, 1900.
THURSTON, ROBERT H.: A treatise on non-metallic materials of
engineering: stone, timber, fuel, lubricants, etc. (Materials of
engineering, Part I.) New York, 1899.
UNWIN, WILLIAM C.: The testing of materials of construction.
London, 1899.
WATERBURY, L.A.: Laboratory manual for testing materials of
construction. New York, 1912.
WOOD, DEVOLSON: A treatise on the resistance of materials. New
York, 1897.
PART II. PUBLICATIONS AND ARTICLES ON THE MECHANICAL PROPERTIES
OF WOOD, AND TIMBER TESTING
ABBOT, ARTHUR V.: Testing machines, their history, construction
and use. Van Nostrand's Eng. Mag., Vol. XXX, 1884, pp. 204-214;
325-344; 382-397; 477-490.
ADAMS, E.E.: Tests to determine the strength of bolted timber
joints. Cal. Jour, of Technology, Sept., 1904.
ALVAREZ, ARTHUR C.: The strength of long seasoned Douglas fir
and redwood. Univ. of Cal. Pub. in Eng., Vol. I, No. 2,
Berkeley, 1913, pp. 11-20.
BARLOW, PETER: An essay on the strength and stress of timber.
London, 1817; 3d ed., 1826.
----: Experiments on the strength of different kinds of wood
made in the carriage department, Royal Arsenal, Woolwich. Jour.
Franklin Inst., Vol. X, 1832, pp. 49-52. Reprinted from
Philosophical Mag. and Annals of Philos., No. 63, Mch., 1832.
BATES, ONWARD: Pine stringers and floorbeams for bridges. Trans.
Am. Soc. C.E., Vol. XXIII.
BAUSCHINGER, JOHANN: Untersuchungen über die Elasticität und
Festigkeit von Fichten- und Kiefernbauhölzern. Mitt. a. d.
mech.-tech. Laboratorium d. k. techn. Hochschule in München, 9.
Hft., München, 1883.
----: Verhandlungen der Münchener Conferenz und der von ihr
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The Mechanical Properties of Wood Including a Discussion of the Factors Affecting the Mechanical Properties, and Methods of Timber Testing
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