This section is from the "Architectural Iron And Steel, And Its Application In The Construction Of Buildings" book, by WM. H. Birkmire.. Also see Amazon: Architectural Iron And Steel, And Its Application In The Construction Of Buildings.
In all buildings hereafter erected or altered, where any iron or steel column or columns are used to support a wall or part thereof, whether the same be an exterior or interior wall, excepting a wall fronting on a street, and columns located below the level of the sidewalk, which are used to support exterior walls or arches over vaults, the said column or columns either constructed double, that is, an outer and inner column, the inner column alone to be of sufficient strength to sustain safely the weight to be imposed thereon; or such other iron or steel column of sufficient strength and so constructed as to secure resistance to fire, may be used as approved by the superintendent of buildings. Iron posts in front of party walls shall be filled up solid with masonry and made perfectly tight between the posts and walls, to effectually prevent the passage of smoke or fire. Cast-iron posts or columns which are to be used for the support of wooden or iron girders or brick walls, not cast with one open side or back, before being set up in place, shall have a three-eighths of an inch hole drilled in the shaft of each post or column, by the manufacturer or contractor furnishing the same, to exhibit the thickness of the castings, and any other similar-sized hole or holes which the superintendent of buildings, or his duly authorized representative, may require, shall be drilled in the said posts or columns by the said manufacturer or contractor at his own expense. Iron posts or columns cast with one or more open sides and backs shall have solid iron plates on top of each to prevent the passage of smoke or fire through them from one story to another, excepting where pierced for the passage of pipes, and at the bottoms and tops of all iron posts and columns, caps and bases shall be made true.
The iron arches, or the usual light castings connecting the columns of an iron front of a building, shall be filled in from the soffits to the sills on each upper story with brickwork not less than eight inches thick, or hollow fire-proof blocks not less than eight inches thick, and carried through on the same upper level, the brickwork or blocks to rest on the plates within the columns.
No cast-iron posts or columns shall be used in any building of a less average thickness of shaft than three quarters of an inch, nor shall have an unsupported length of more than twenty times its least lateral dimension or diameter, nor have a thickness of metal less than three quarters of an inch. No wrought-iron or rolled-steel column shall have an unsupported length of more than thirty times its least lateral dimension or diameter, nor shall its metal be less than one fourth of an inch in thickness. All cast-iron, wrought-iron, and steel columns shall have their bearings faced smooth, and at right angles to the axis of the column; and when one column rests upon another column, they shall be securely bolted together.
Where columns are used to support iron or steel girders carrying curtain walls, the said columns shall be of cast iron, wrought iron or rolled steel, and on their exposed surfaces be constructed to resist fire, by having an outer shell of iron, with an air space between, or by having a casing of brickwork or burnt-clay blocks, not less than four inches in thickness and bonded into the brickwork of the curtain walls; and the exposed sides of the iron or steel girders shall also be similarly covered in, and tied and bonded.
The factors of safety shall be as one to four for all beams, girders and other pieces subject to a transverse strain; and as one to five for all posts, columns and other vertical supports subject to a compressive strain; and as one to six for tie rods, tie beams and other pieces subject to a tensile strain.
Rolled iron or steel beam girders, or riveted iron or steel plate girders, used as lintels, or as girders, carrying a wall or floor, or both, shall be so proportioned that the loads which may come upon them shall not produce strains in tension or compression upon the flanges of more than twelve thousand pounds for iron nor more than fifteen thousand pounds for steel per square inch of the cross-section of each of such flanges, nor a shearing strain upon the web plate of more than six thousand pounds per square inch of section of such web plate, if of iron, nor more than seven thousand pounds if of steel; but no web plate shall be less than one quarter of an inch in thickness. Rivets in plate girders shall not be less than five eighths of an inch in diameter, and shall not be spaced more than six inches apart in any case. They shall be so spaced that their shearing strains shall not exceed nine thousand pounds per square inch of section, nor their bearing exceed fifteen thousand pounds per square inch on their diameter, multiplied by the thickness of the plates through which they pass. The riveted plate girders shall be proportioned upon the supposition that the bending or chord strains are resisted entirely by the upper and lower flanges, and that the shearing strains are resisted entirely by the web plate. No part of the web shall be estimated as flange area, nor more than one half of that portion of the angle iron which rests against the web. The distance between the centres of gravity of the flange areas will be considered as the effective depth of the girder.