The Mechanical Properties of Wood: Including a Discussion of the Factors Affecting the Mechanical Properties, and Methods of Timber Testing

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J. Wiley & Sons, Incorporated, 1914 - Forests and forestry - 165 pages
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Page 131 - One of each pair of specimens from the same stick shall be tested in radial shear (surface of failure radial) and the other in tangential shear...
Page 87 - Ibid., p. 21. See also Cir. 108, p. 19, table 5. depends upon the method of treatment than upon the preservatives used. Thus preliminary steaming at too high pressure or for too long a period will materially weaken the wood. (See Temperature, supra.) The presence of zinc chloride does not weaken wood under static loading, although the indications are that the wood becomes brittle under impact. If the solution is too strong it will decompose the wood. Soaking in creosote oil causes wood to swell,...
Page 86 - A high degree of steaming is injurious to wood in strength and spike-holding power. The degree of steaming at which pronounced harm results will depend upon the quality of the wood and its degree of seasoning, and upon the pressure (temperature) of steam and the duration of its application. For loblolly pine the limit of safety is 30 Ibs.
Page 160 - Old yellow pine posts from Boston Fire Brick Co. building, No. 394 Federal St., Boston, Mass., pp. 451-473. House Doc. No. 143, 55th Cong., 3d sess., 1899. Fire-proofed wood (endwise and transverse tests), pp. 676-681. House Doc. No. 190, 56th Cong., 2d sess., 1901. Cypress wood for United States Engineer Corps; compression and transverse tests, pp. 1121-1126. Old white pine and red oak from roof trusses of Old South Church, Boston, Mass., pp. 1127-1130. Compression of rubber, balata, and wood buffers,...
Page 33 - Later the top layer of fibres on the upper or compression side fail, and on the load increasing, the next layer of fibres fail, and so on, even though this failure may not be visible. As a result the shortenings on the upper side of the beam become considerably greater than the elongations on the lower side. The neutral plane must be presumed to sink gradually toward the tension side...
Page 144 - The working unit-stresses given in this table are intended for railroad bridges and trestles. For highway bridges and trestles the unit-stresses may be increased twenty-five (25) per cent.
Page 144 - For highway bridges and trestles the unit stresses may be increased 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 50 per cent.
Page 109 - ... radial. In designing a shearing specimen it is necessary to take into consideration the proportions of the area of shear, since, if the length of the portion to be sheared off is too great in the direction of the shearing face, failure would occur by compression before the piece would shear. Inasmuch as the endwise compressive strength is sometimes not more than five times the shearing strength, the shearing surface should, in general, be less than five times the surface to which the load is...
Page 5 - Elastic limit, as measured in tests and used in design, may also be defined as that unit stress at which the deformation begins to increase in a faster ratio than the applied load.
Page 144 - To compute the deflection of a beam under long-continued loading instead of that when the load is first applied, only fifty (50) per c-nt of the corresponding modulus of elasticity given in the table is to be employed.

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