resistant Slightly or nonresistant Baldcypress (old growth)* Catalpa Cedars Cherry, black Chestnut Cypress, Arizona Junipers Locust, black Mesquite Mulbery, red Oak: Bur Chesnut Gambel Orgeon white Post White Osage orange Redwood Sassafras Walnut, black Yew, Pacific Baldcypress (young growth)* Douglas fir Honeylocust Larch, western Oak, swamp chestnut Pine, eastern white* Souther pine: Longleaf* Slash* Tamarack Alder Ashes Aspens Basswood Beech Birches Buckeye Butternut Cottonwood Elms Hackberry Hemlocks Hickories Magnolia Maples Oak (red and black species) Pines (other than longleaf, slash, and eastern white) Poplars Spruces Sweetgum True firs (western and eastern) Willows Yellow poplar * The southern and eastern pines and baldcypress are now largely second growth with a large proportion of sapwood. Consequently, substantial quantities of heartwood lumber of these species are not available. These woods have exceptionally high decay resistance. From U.S. Forest Products Laboratory. The most commonly employed water-soluble salts are acid copper chromate, chromated copper arsenate and arsenite, fluor chrome arsenate phenol, chromated zinc chloride, and other materials that are often sold under various proprietary names. The principal solvent-soluble organic materials are chlorinated phenols, such as pentachlorphenol, and copper naphthenate. Preservatives may be applied in a variety of ways, including brushing and dipping, but for maximum treatment, pressure is required to provide deep side-grain penetration. Butts of poles and other parts are sometimes placed in a hot boiling creosote or salt solution, and after the water in the wood has been converted to steam, they are quickly transferred to a cold vat of the same preservative. As the steam condenses, it produces a partial vacuum, which draws the preservative fairly deeply into the surface. Pressure treatments may be classified as full-cell and empty-cell. In the full-cell treatment, a partial vacuum is first drawn in the pressure-treating tank to withdraw most of the air in the cells of the wood. The preservative is then let in without breaking the vacuum, after which pressure is applied to the hot solution. After treatment is completed, the individual cells are presumably filled with preservative. In the empty-cell method, no initial vacuum is drawn, but the preservative is pumped in under pressure against the back pressure of the compressed air in the wood. When the pressure is released, the air in the wood expands and forces out excess preservative, leaving only a coating of preservative on the cell walls. Retentions of preservative depend on the application. For teredo-infestation, fullcell creosote treatment to refusal may be specified, ranging from 16 to 20 lb per cubic foot of wood. For ordinary decay conditions and resistance to termites and other destroyers of a similar nature, the empty-cell method may be employed with retentions in the vicinity of 6 to 8 lb of creosote per cubic foot of wood. Salt retentions generally range in the vicinity of 11/2 to 3 lb of dry salt retained per cubic food of wood. Solvent-soluble organic materials, such as pentachlorphenol, are commonly employed for the treatment of sash and door parts to impart greater resistance to decay. This is commonly done by simply dipping the parts in the solution and then allowing them to dry. As the organic solvent evaporates, it leaves the water-insoluble preservative behind in the wood. These organic materials are also employed for general preservative treatment, including fence posts and structural lumber. The water-soluble salts and solventsoluble organic architects leave the wood clean and paintable. Creosote in general cannot be painted over, although partial success can be achieved with top-quality aluminum-flake pigment paints. Treatment against fire consists generally of applying salts containing ammonium and phosphates, of which monoammonium phosphate and diammonium phosphate are widely employed. At retentions of 3 to 5 lb of dry salt per cubic foot, the wood does not support its own combustion, and the afterglow when fire is removed is short. A variety of surface treatments is also available, most of which depend on the formation of a blanket of inert-gas bubbles over the surface of the wood in the presence of flame or other sources of heat. The blanket of bubbles insulates the wood beneath and retards combustion. See also Art. 10.6. A variety of adhesives is now available for use with wood, depending on the final application. The older adhesives include animal glue, casein glue, and a variety of vegetable glues, of which soybean is today the most important. Animal glues provide strong, tough, easily made joints, which, however, are not moisture-resistant. Casein mixed with cold water, when properly formulated, provides highly moistureresistant glue joints, although they cannot be called waterproof. The vegetable glues have good dry strength but are not moisture-resistant. The principal high-strength glues today are synthetic resins, of which phenol formaldehyde, urea formaldehyde, resorcinol formaldehyde, melamine formaldehyde, and epoxy are the most important. Phenol, resorcinol, and melamine provide glue joints that are completely waterproof and will not separate when properly made even on boiling. Urea formaldehyde provides a glue joint of high moisture resistance, although not quite so good as the other three. Phenol and melamine require application of heat, as well as pressure, to cure the adhesive. Urea and resorcinol, however, can be formulated to be mixed with water at ordinary temperatures and hardened without application of heat above room temperature. Waterproof plywood is commonly made in hot-plate presses with phenolic or melamine adhesive. Re- sorcinol is employed where heat cannot be applied, as in a variety of assembly operations and the manufacture of laminated parts like ships keels, which must have the maximum in waterproof qualities. Epoxide resins provide strong joints. Adhesives containing an elastomeric material, such as natural or synthetic rubber, may be classified as contact or mastic. The former, applied to both mating surfaces and allowed to partly dry, permit adhesion on contact. Mastics are very viscous and applied with a trowel or putty knife. They may be used to set wood-block flooring. An emulsion of polyvinyl acetate serves as a general-purpose adhesive, for general assembly operations where maximum strength and heat or moisture resistance are not required. This emulsion is merely applied to the surfaces to be bonded, after which they are pressed together and the adhesive is allowed to harden. As ordinarily made, plywood consists of thin sheets, or veneers, of wood glued together. The grain is oriented at right angles in adjacent plies. To obtain plywood with balancethat is, which will not warp, shrink, or twist undulythe plies must be carefully selected and arranged to be mirror images of each other with respect to the central plane. The outside plies or faces are parallel to each other and are of species that have the same shrinkage characteristics. The same holds true of the cross bands. As a consequence, plywood has an odd number of plies, the minimum

The tension force on the net section should not exceed Pa, kips, calculated from Eq. (8.43). P
P / (8.43) a n t P
A F (8.44) n n t where t
safety factor for tension on net section
2.22 for single shear
2.00 for double shear An
area of net section of thinnest sheet, in2 The nominal limiting tension stress Ft , kips, is given by F
(1  0.9r  3rd/ s)F  F (8.45) t uu where s
bolt spacing, in, measured normal to line of stress
width of sheet for a single bolt in the net section Fu
tensile strength, ksi, of connected part d
nominal diameter, in, of bolt r
ratio of force transmitted by the bolts at the section to the tension force in the member at that section (if r  0.2, it may be taken equal to zero) When washers are not provided under the bolt head and nut, see AISI specification. 8.18.3 Bearing Stresses and Bolt Tension The bearing force should not exceed Pa, kips, calculated from Eq. (8.46). P
P / (8.46) a n b P
F dt (8.47) n p where b
safety factor for bearing
2.22 Fp
nominal bearing stress, ksi, in connected part d
nominal diameter of bolt, in t
thickness, in, of thinnest connected part Table 8.9 lists nominal bearing stresses for bolted connections. Table 8.10 lists nominal shear and tension stresses for various grades of bolts. The bolt force resulting in shear, tension, or combinations of shear and tension should not exceed the allowable force Pa, kips, calculated from Eq. (8.48). P
A F/ (8.48) a b where Ab
gross cross-sectional area of bolt, in2 F
nominal stress, ksi, Fnv, Fnt, or Fnt in Tables 8.10 and 8.11 Safety factors given in Tables 8.10 and 8.11 may be used with Eq. (8.48) to compute allowable loads on bolted joints. Table 8.11 lists nominal tension stresses for bolts subjected to a combination of

4.11.3 Hardness Coarse-aggregate hardness is measured by the Los Angeles Abrasion Test, ASTM C131 or C595. These tests break the aggregate down by impacting it with steel balls in a steel tumbler. The resulting breakdown is not directly related to the abrasion an aggregate receives in service, but the results can be empirically related to concretes exhibiting service lives. 4.11.4 Soundness Aggregate soundness is measured by ASTM C88, Test Method for Soundness of Aggregates by Use of Sodium Sulfate or Magneisum Sulfate. This test measures the amount of aggregate degradation when exposed to alternating cycles of wetting and drying in a sulfate solution. 4.11.5 Particle Shape Natural sand and gravel have a round, smooth particle shape. Crushed aggregate (coarse and fine) may have shapes that are flat and elongated, angular, cubical, disk, or rodlike. These shapes result from the crushing equipment employed and the aggregate mineralogy. Extreme angularity and elongation increase the amount of cement required to give strength, difficulty in finishing, and effort required to pump the concrete. Flat and elongated particles also increase the amount of required