The quality of steel used for reinforcing concrete should be carefully specified because of the possibility of the substitution of inferior material. The specifications for “Billet Steel Concrete Reinforcement Bars,” of the American Society for Testing Materials[[63]] are the standard for engineering practice, or the following specifications may be used:
All reinforcement shall be free from excessive rust, scale, paint, or coatings of any character which will tend to destroy the bond. The bars shall be rolled from new billets. No rerolled material will be accepted. All reinforcement bars shall develop an ultimate tensile strength of not less than 70,000 pounds per square inch. The test specimen shall bend cold around a pin, whose diameter is two times the thickness of the bar, 180 degrees without cracking on the outside portion. The reinforcing bars shall in all respects fulfill the requirements of the standard specifications of the American Society for Testing Materials for Billet Steel Concrete Reinforcing Bars serial designation A 15–14.
The steel used in pipe should be a soft, open-hearth steel with an ultimate tensile strength of 60,000 pounds per square inch, an elastic limit of 30,000 pounds per square inch, an elongation in 8 inches before fracture between 22 and 25 per cent, and a reduction in area before fracture of 50 per cent. The working strength of the steel is taken at 16,000 to 20,000 pounds per square inch in tension, 10,000 to 12,000 pounds per square inch in shear, and 20,000 to 24,000 pounds per square inch in bearing. A liberal allowance should be made for corrosion. The standard specifications for Open-Hearth Boiler Plate and Rivet Steel of the American Society for Testing Materials, Aug. 16, 1919, include “flange steel,” which is suitable for the manufacture of plates, and extra soft steel which is suitable for rivets.
Steel pipe should be coated both inside and out to protect it against corrosion. The various proprietary coatings are mainly coal tar pitches, or mixtures of coal tar pitch and asphalt. A coal tar pitch is a distillate of coal tar from which the naphtha has been removed and to which about one per cent of heavy linseed oil has been added. The coating is applied to the pipe at a temperature of about 300 degrees Fahrenheit, by dipping hot pipe in the heated coating material. The pipe should be carefully cleaned and all rust and scale removed before it is dipped. In some cases the steel is pickled before dipping. This consists in rolling the cold plates to a short radius to loosen the scale, heating them to about 125 degrees, and dipping them in a warm 5 per cent acid solution for about 3 minutes, and finally rinsing in a weakly basic wash water.
The woods commonly used for the manufacture of wood pipe are spruce, Oregon fir, Douglas fir, and California redwood. Wood pipe lines have been constructed of other kinds of lumber but only in more or less unusual conditions. The following has been abstracted from the specifications for California redwood given by J. F. Partridge.[[64]]
The staves shall be of clear, air-dried, California redwood, seasoned at least one year in the open air, and shall be free from knots (except small knots appearing on one face only), sap, dry rot, wind shakes, pitch, pitch seams, pitch pockets, or other defects which would materially impair their strength or durability. The sides of the staves shall be milled to conform to the inside and outside radii of the pipe; and the edges shall be beveled to true radial planes. The staves shall be milled from stock sizes of lumber, the net finished thickness of the stave, for the various diameters of pipe, shall be as given in Table 40. The ends shall be cut square and slotted to receive the metallic tongues which form the butt joints. The slots shall appear in the same position on each stave, and shall be cut to make a tight fit with the tongues in all directions. The staves shall have an average length of at least 15 ft. 6 in. and not more than one per cent shall have a length of less than 9 ft. 6 in. Staves shorter than 8 ft. will not be accepted.
The bands shall be spaced on the pipe with a factor of safety of at least four, and shall consist of round, mild steel rods, connected with malleable iron shoes. Either open-hearth or Bessemer steel may be used.... The ultimate strength shall be from 55,000 to 65,000 lb. per sq. in.
The original reference should be consulted for complete details and for specifications for various kinds of wood and classes of pipe. The discussion following the specifications is of value.
Machine-made wood pipe is superior to stave pipe put together in the field. It is seldom manufactured in sizes large enough for use in sewers, which results in the almost exclusive use of field constructed stave pipe. The steel bands used to hold the staves together should be coated similarly to steel plates. All lumber, except California redwood should receive a preservative coating of creosote[[65]] or other material. One of the best methods of preserving the wood is to keep it submerged and to maintain the pipe under internal pressure.
| TABLE 40 | |||||
|---|---|---|---|---|---|
| Details of Design for Continuous Stave Wood Pipe | |||||
| Classes A, B, and C | |||||
| (By J. F. Partridge, Trans. A. S. C. E., Vol. 82, page 461) | |||||
| Diameter, Inches | Stave Thickness, Standard, Inches | Stock Size of Lumber, Inches | Size of Band, Inches | Top Width of Staves, Standard, Inches | Spacing of Bands for 100 Feet Head |
| 12 | 1⅜ | 2 × 4 | ⅜ | 3.56 | 6.38 |
| 18 | 1–7 16 | 2 × 4 | 7 16 | 3.66 | 5.76 |
| 24 | 1–7 16 | 2 × 4 | 7 16 | 3.70 | 4.34 |
| 30 | 1½ | 2 × 6 | ½ | 5.48 | 4.53 |
| 36 | 1–9 16 | 2 × 6 | ½ | 5.62 | 3.77 |
| 42 | 1⅝ | 2 × 6 | ½ | 5.51 | 3.23 |
| 48 | 1⅝ | 2 × 6 | ½ or ⅝ | 5.60 | 2.84 or 4.41 |
| 60 | 2½ | 3 × 6 | ⅝ | 5.56 | 3.54 |
| 72 | 3½ | 4 × 6 | ⅝ or ¾ | 5.69 | 2.95 or 4.24 |
| 84 | 3½ | 4 × 6 | ¾ | 5.65 | 3.63 |
| 120 | 3⅝ | 4 × 6 | ¾ | 5.68 | 2.54 |
| 144 | 3⅝ | 4 × 6 | ¾ or ⅞ | 5.64 | 2.12 or 2.89 |