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for the introduction of the smoke flues or "up-takes” from the boilers, the placing of the ash doors and the general appearance.

The ash door is shown in Fig. 22. The opening should be arched, preferably of semicircular design, as affording the most strength to sustain the great weight of brickwork over it. It should be closed with a sheet iron door. The openings for smoke flues should also be strongly arched, similar to the ash doorways. From the square portion at the base, the main shaft of the chimney is of octagonal form, as indicated in Fig. 24.

For foundations the earth should be excavated to perfectly hard ground, making a pit 28 feet square; that is, twice the depth of the foundation, assuming that in consequence of the condition of the ground it is necessary to excavate to a depth of 14 feet. In this pit should be a bed, 4 feet thick of large stones laid in strong cement mortar. Upon this should be courses about 18 inches thick and gradually drawn in at the top to 16 feet square.

By strong cement mortar we mean that containing two parts cement, one part of lime, and about three parts of clean, sharp sand. The amount of sand will vary considerably with its fineness, sharpness, and its freedom from dirt; the finer the sand the greater the quantity that must be used.

In erecting the central core and the outward supporting structure great care should be used to make all joints of uniform thickness, and to see that as the courses are laid on they are frequently leveled.

“Batter plumbs” should be used for the outside; that is, the board on which the plumb line is attached should have the batter or inclination by being made narrower at the bottom. For instance, a plumb board 4 feet long should be 6 inches wide at the top and 4 inches at the bottom (the batter being equal on both edges).

Another matter that must be scrupulously attended to is that of properly supporting the inner core. It will not do to lay bricks from wall to wall so as to tie them together, as the expansion and contraction of the inner core would soon ruin the structure.

The support is given by building up into the outer wall inwardly projecting bricks reaching half way across the space, and against these, others projecting outwardly from the inner core. These should be placed on all eight sides, in the same course, and at intervals of not over eight feet through the entire height.

The form and thickness of walls and the heights of the “breaks” are shown in Fig. 21. The central flue is formed after the model of the wellknown student lamp and forms a very effective combustion chamber for escaping smoke. It is the form adopted by a prominent engineer who built a large number of chimneys of this design which have been in successful use for many years.

The smoke flues enter the chimney below the constricted portion of the inner flue. The top caps are of cast iron and may be made in sections and bolted together, as well for convenience in erecting as for economy of pattern making

That on the inner core terminates 7 feet 2 inches below the top of the main cap. At four sides of the outer structure are openings, as shown in Fig. 21, the bottom of each opening being on a level with the top of the inner cap. By this means the current of air which always rises along any high wall is taken advantage of, as it passes up the side of the chimney, into these openings, and out the top of the chimney, and creates a partial vacuum over the top of the central flue, thus considerably increasing the draft.

Means should be provided for reaching the top of the chimney, as the iron caps will need painting, or lightning rods may have to be placed or repaired. Iron ladders up the side may be fastened to the wall, or a permanent block may be attached to the main cap and provided with a wire rope, for

this purpose.

As a matter of safety from lightning it is well to provide lightning conductors. A round copper rod of not less than 3-inch diameter, or one of equal area of cross-section, may be run up outside of the chimney, through heavy glass insulators, and terminate four feet above the main cap in four points, 16-inch diameter or equivalent area. The lower end of the rod should go into moist earth and be attached to a cast iron plate 30 inches square and {-inch thick.

It is often the case that chimneys are erected that are much higher in proportion to their width than the example here shown, and in situations where the structure is well protected from the pressure of the wind, this may be safely done. But when erected in an exposed situation it will be well to consider, as of first importance, the factor of stability.

It will not be proper or fair, however, to confound the appearance of a chimney built in the substantial form herein described, with some of the smaller and more slender structures sometimes seen, which have no central core, either because their moderate height does not render it necessary, because the temperature of the gases is not so high as to endanger a chimney of single walls, or from considerations of economy.

The chimney here shown is in every way substantial and reliable, and from the dimensions and proportions given, chimneys of any required capacity, or to suit any condition of surroundings, may be successfully designed and constructed.

CHAPTER X

CONSTRUCTION OF FOUNDATIONS

The proper bed for a foundation. Care necessary in its preparation. Sounding. The

various types of foundation. Timber support for heavy buildings on alluvial soil. Timber support for foundations. Piling support for foundations. Timber and concrete supports for foundations. Laying stone foundations. Mortar for foundation work. Foundations for machinery in general. Engine foundations. Planer foundation. Special foundation for testing lathes or other machines. Drop hammer foundations. Steam hammer foundations. Timber foundation for heavy machines on soft ground. Example in experience.

It is but quoting an old maxim to say that if we are to build a good house we must have a good foundation to build it on. And we may just as pertinently say that if we are to build a good and substantial foundation, we must have something solid to lay it upon.

Otherwise we shall be like the man who built his house upon the sands. The diversity of the ground, at the surface and down through the stratifications of material of various densities and strengths, from the solid nature of rock to the almost fluid condition of alluvial soil, must be considered. Each of these conditions requires special treatment according to its nature.

To properly secure a firm bed for the foundation of a building, we must either excavate down to firm and solid ground, technically called “hard pan," or we must by artificial means produce a substantial surface upon which to begin the masonry. It is quite impossible for the architect, the mason or the contracting builder to tell us by a superficial examination of the ground how deep we must go to reach solid ground, or “hard pan.'

To some extent this may be ascertained by “sounding”; that is, by making small excavations at various points, to obtain the necessary information upon which to determine not only the depth to which the foundation must extend, but whether the nature of the ground renders such artificial support as piles necessary

It may be found that at some points in the foundation of extensive buildings we need excavate only a few feet, while at others, very deeply; and still at other points the ground may be of such a yielding nature that piles must

be driven. Or we may find that the use of piles would be a much more economical method than very deep masonry.

But whatever the depth we may be obliged to go to, or the process by which we produce our bed for the foundation, all parts of it must be, not only firm and practically unyielding, but level. Hence, when we excavate to varying depths the earth must be “benched out,” as it is called, as shown in Fig. 31.

Great care should be taken to have all parts of the bottom of the excavation of as equal density and resisting power as possible, that they may equally support the great weight of the wall to be built. This condition becomes all the more important as the walls of the building are higher and the consequent weights and strains correspondingly increased.

It is, of course, true that no ground can be found so absolutely solid as not to yield somewhat when the weight of the building is put upon it, and therefore we must not expect to wholly prevent a certain amount of settling; but we should use all possible care to have this settling as equal as possible over the whole area of the foundation.

Having ascertained the nature of the ground as far as possible, we may determine the kind or kinds of foundation necessary. If the ground is so soft and yielding that excavation to solid earth will have to be very deep, making a stone foundation excessively expensive, piles should be driven as deep down as possible — say two feet apart from center to center — and cut off level at the top, and be down low enough to remain always wet.

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Upon these piles timbers of sufficient size are placed, being laid across each row of piles; then upon these another course of timbers, at right angles to the first. These may be laid close together or two or three inches apart, the size of the timbers being determined by the weight of the wall they are to support. For instance, for the walls of the machine shop proposed in these articles, the timbers may be 10 X 12 inches laid on edge.

Fig. 27 gives a plan view of this method and Fig. 28 shows a cross-section

of the same.

It is not always necessary to arrange the piles in three lines, with those in the center row in line with those of the two outer rows, as shown. Where the weight of the superstructure is not excessive it is often preferable to begin by setting three piles in a row, then two so they will come opposite the intervals of the first row; then the next row of three in line with the first; then another row of two piles and so on.

Where there is considerable depth from the top of the piles without side support it is necessary to drive “sheet piling." Set planks three inches thick, or thicker, with their edges close together so as to enclose the work on both sides, and afterward fill in the spaces between these planks and the solid earth with tightly rammed gravel, and if necessary fill the spaces between the piles with stones or concrete. This will give them quite sufficient support to make a very firm foundation bed and prevent any lateral movement which might result from the bending of the piles.

Timber should not be used under a foundation unless it is in a position to be kept continuously wet by the surrounding soil, for the reason that if always wet enough to exclude the air it will endure for a very long time, but if so situated as to be sometimes wet and again dry, it will soon decay.

Therefore, if the use of timber, as above described, is not feasible we must use stone and so arrange the piles, regarding the distances from center to center, as to allow the use of such stones as are available, cutting off the tops of the piles below the water line if possible, or at least so low as to have them always wet. This arrangement is shown in Fig. 29.

CONCRETE

CONCRETE

FIG. 29. — Piling and

Stone Support for
Foundation Wall.

Fig. 30. — Timber and Concrete

Support for Foundation Wall.

Sometimes fairly solid earth may be reached within a reasonable depth, but it requires digging quite a considerable depth beyond this before reaching really solid ground or “hard pan.” In such a case it may be advisable to lay down, first, a course of concrete four to six inches thick, then a layer of timber and another course of concrete, which will furnish an excellent bed for the foundation.

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