The principles of concrete floors having been explained, and the various points to be considered and guarded against thus brought to the notice of the student, it only remains to set forth the different systems which have been invented and introduced of late years; those which conform to the principles already laid down being, of course, the best The following is a list of the chief British systems in use: -
Fswcetts System Fig. 524.
Fox and Bennetts System Fig. 525.
Dennett's, as illustrated by Fig. 523, will be seen to consist of iron girders and concrete arches of various spans, not exceeding 12 feet, and rising no less than 1 inch per foot. The matrix of the concrete is gypsum, which has been proved to retain coherence even when burnt or drenched with water, or both in succession.
Fawcett's, consisting of iron girders, 2 or 3 feet apart, the interspaces being filled in with earthenware pipes of hollow arched section laid diagonally, on which a 6-inch layer of breeze and cement concrete is laid, is illustrated by Fig.. 524.
Fox And Barrett's, as Fig.. 525 explains, consists of iron girders, spaced at intervals every 20 inches, between which wood strips are placed, and the whole covered with concrete, rising above the girders, as shown.
Hornblowtt's consists of hollow fire-clay tubes, of wedge-shaped form, springing from blocks of similar material encircling wrought iron girders bedded in concrete about 26 inches apart, as Fig. 526, the top being levelled over the same as shown.
Hornblower's Syftem Fig. 526.
Homan And Rogers' Patent, as Fig. 537, is made up of iron girders, between which are placed special bricks, which may be glazed or ornamental on soffit; and the top is filled up with concrete, the same as the other methods.
Section of bricks.
Hommn & Rodger's System.
Lindsay's Patent is of two kinds, as illustrated by Figs. 528 and 529; the former consisting of wrought-iron or steel joists, spaced 18 inches apart, and laced together, as it were, by wrought-iron rods or strips passing over and under each one alternately, as shown; the whole of the iron being then encased in what is called pumice concrete, which is really made of breeze and cement, being much lighter than the ordinary mixture.
Lindsay's system with I Girders Fig. 528.
The other method, very much used for goods-sheds, etc., as Fig. 529, will be seen to consist of wrought-iron troughs, riveted together ever the whole area, and the top spaces are filled with the usual concrete and levelled for the floor in the ordinary way; and for the purpose of covering the underside, which is very necessary to render it complete, cast blocks Lindsay's System with trough girders of breeze or pumice are bolted up to the underside, as shown on the illustration.
Measure's Patent is similar to Fox and Barrett's, with the distinction that the girders are spaced 3 or 4 feet apart, and T-irons, about 9 inches centre to centre, span them from flange to flange, and support the usual concrete.
Northrofts System Fig. 530.
Whichcords System Fig. 531.
Morelani's System consists of wrought-iron girders, supporting curved intermediate girders, at right angles to the main girders, and covered over with corrugated iron, on which the concrete is laid and levelled up as before.
Northcrqfts consists of two layers of flat arches, of special wedge-shaped bricks, resting on similar skewbacks, supported by wrought-iron joists, as Fig.. 530, the spaces above and' between the arches being filled, up with concrete.
Doulton and Peto's Fig. 532.
Whiehcord's Method consists of solid fire-clay arches springing from fire-clay springers, enclosing the wrought-iron girders as Fig. 531, and filled up with concrete.
Doulton And Peto's Variety, as Fig.. 532, consists of fireproof hollow-keyed blocks, which encircle the lower parts of the girders, as well as form a strong light floor of simple construction.
The Adamant Company's System consists of blocks of concrete and adamant cement placed from joist to joist, as Figs. 532A and 532B, and covered over and levelled with ordinary concrete suited to the locality. The girders can be placed 3 feet apart, and the blocks are cast with a wood strip on edge embedded in them, in order to be the better able to resist tension.
Banks's Patent, Fig. 532c, completely protects the steel work - which is a distinct gain; and there are other advantages, such as its ready application to existing floors and its ventilating space, which the illustration sufficiently explains.
The "Carlisle" Fireproof Floor, Fig. 532D, consists of two tubes forming an arch between the joists, which have to be bolted together to resist the thrust successfully; they are covered with concrete in the usual way, and provide in themselves a space for ventilating and other purposes.
Potter's System is somewhat similar, Fig.. 532E; but the lintels are in one piece, requiring no bolts.
Picking's, Fig. 531F, is almost a combination of the last two, as the illustration explains.