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BUILDING before fracture of not less than 25 per cent, in 8 inches of length, and that a piece of the material may be bent cold 180 degrees over a mandril equal to the thickness of the piece tested without fracture of the fibre on the outside of the bend. At least two pieces are taken from each melt or blow at the mill, and are stamped or marked, and all the various sections rolled from the melt or blow are required to bear a similar stamp or mark for identification. All finished material is carefully examined to see that it possesses a smooth surface, and that it is free from cracks, seams, and other defects, and that it is true to section throughout. Rivets are either of wrought iron or of extra soft steel, with an ultimate tensile strength of 55,000 Eb per square inch. The material must be sufficiently tough to bend cold 180 degrees flat on itself without sign of fracture. The greatest care is taken that no steel is left in a brittle condition by heating and cooling without proper annealing. All abutting joints in riveted work are faced to exact lengths and absolutely at right angles to the axis of the piece, and are spliced by scarf plates of proper dimensions adequately secured by rivets. The work should be so accurate that no packing pieces are necessary. If the conditions are such that a packing or filling piece must be used, the end of one piece is cut to a new and true surface, and the filling piece is planed to fill the space accurately. Where cast iron is used it must be of tough gray iron free from defects. In testing it pieces 1 inch square, 14 inches long, are cast from each heat and supported on blunt knife edges spaced 12 inches apart; under a load in the centre of the piece of 2500 lb the deflexion must not exceed of an inch. All metal should receive one coat of paint at the works before shipment. All faced and turned surfaces should receive a coat of white lead or tallow before leaving the shop, and the entire structure should receive two coats of paint after erection. As the protection from corrosion will largely depend upon the paint, the most careful inspection is employed to insure that the metal is perfectly clean from scale and thoroughly dry when painted, and that no painting is done in damp or frosty weather. The paint must be applied with an ordinary painter’s brush, and well worked in over the entire surface by hand to secure an even and perfect covering. It is valuable as a protection from corrosion in proportion to the amount of oil with which the metal can be coated by its application. The pigment itself is of small value except as a vehicle to assist in the spread of oil, and as facilitating the inspection of the work to insure that the oil has been thoroughly and evenly spread. The pigment which allows the spread of the largest percentage of oil is therefore the most valuable as a preventive of corrosion. The filling between the girders and floor beams consists of segmental arches of brick, segmental or flat arches of porous (sawdust) terra cotta, or hard-burned hollow terracotta voussoirs, or various patented forms of concrete floors containing ties or supports of steel or iron. In all cases it is customary to fill on top of the arches with a strong Portland cement concrete to a uniform level, Floors an §enera^y ^°P the deepest beam; the partitions ^00r filling is constructed and carried to this level immediately upon the completion of each tier of beams, for the purpose not only of stiffening the frame laterally, and of adding to its stability by the imposition of a static load, but also to afford constantly safe and strong working platforms at regular and convenient intervals for use throughout the entire period of the construction. In cases in which the lateral rigidity of the floors is depended upon to transfer the horizontal strains to the exterior walls which are framed to resist

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them, no form of floor construction should be used which is not laterally strong and rigid. With very rapid building, no method of construction of floors, furrings, or partitions should be adopted which will not dry out with great speed. In flat forms of masonry floor construction the level of its bottom is placed somewhat below the bottom of the “I” beams and girders, so that when it is plastered a continuous surface of at least an inch of mortar will form a fireproof protection for the lower flanges of the beams and girders. Where the width of the flange is considerable it is first covered with metal lath secured to the under side of the floor masonry. Girders projecting below the floor are usually encased in from 1 to 2 inches of fireproof material, 2 or 4 inches of which is also put on all columns. Such fireproof coverings, and also interior partitions, are composed of hollow, hard-burned terra-cotta blocks, of porous (sawdust) terra cotta, or various plastic compositions applied to metallic lath, many of which are patented both as to material and method of application. The most simple test for the value of a system of fireproof coverings, and of partitions and furrings, is to erect a large sample of the work and to subject it alternately to the continued action of an intensely hot flame which is allowed to impinge upon it, and to a stream of cold water directed upon it from the ordinary service nozzle of a steam fireengine. It is important in all fireproofing of columns and girders, and in all floor construction, furring, and partitions, that there shall be no continuous voids, either vertical or horizontal, which may possibly serve as flues for the spread of heat or flame in case of fire. All furrings and partitions must be started on the solid masonry of the floors to prevent the possible passage of fire from the room in which it may occur. The failure to make this provision has been the cause of very serious losses in buildings which were supposed to be fireproof. It is customary to lay all necessary horizontal gas pipes and electric wire conduits on the flat Portland cement concrete surface of the floors, and, where wooden floors are to be used, to lay wooden sleepers on the same surface of a uniform depth as great as the diameter of the hubs at the joints of the largest pipes. The sides of the sleepers are bevelled inwards toward their tops. The entire surface is filled to the level of the sleepers, which is the underside of the wooden floor, or to the same level if marble or tile floors are to be laid, with a very light concrete formed of screened anthracite coal cinders, or preferably locomotive screenings mixed with enough cement only to produce a hard mass. A wooden floor laid in contact with masonry needs no fireproofing; it will smoulder, but it will not burn rapidly. In some buildings the wood used for door sashes and trimming is subjected to one of the patented fireproofing processes. If such are used it is important that they should be tested to prove both that the fireproofing is permanent, and that it will not cause in the presence of water the corrosion of the steel with which it may be in contact. In some buildings doors, sashes, and window frames are covered with light metals, or are made of patented fireproof composition. If covered with metal, in order to be thoroughly efficient, the parts must be united with lock joints, not solder. In some buildings the sashes of interior partitions are glazed with wire-glass (a glass in which a mesh of fine wire is bedded in the centre of the sheet), and in some cases squares of plate-glass not more than 4 inches in diameter, united by a heavy joint of copper electrically deposited, are used for the same purpose. Both methods have proved singularly efficient in arresting the spread of fire. It is impossible to design a building which cannot be injured by fire, but the construction should be such that