US2495724A - Elevated tank - Google Patents

Description

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ELEVATED TANK Film Jan. 24, 1945 2 sheets-sheet 1 G. T. HORTON ELEVATED TANK Hmm EL W@ 2 Sheets-Sheet 2 Filed Jan. 24, 1945 Patented nJan. 3l, i950 Ni GEFICE ELEVATED TANK George T. Horton, Chicago, Ill., assignor to Chicago Bridge & Iron Company Application January 24, 1945, Serial No. 574,402

This invention relates to elevated tanks for the storage of water or other liquids.

Elevated storage tanks for liquids have been widely used for the storage of water and the like. These tanks were for many years made in the shape of a cylinder with a substantially flat bottom supported by beams or other rigid supports. in these tanks of the old type having lat bottoms, it was discovered that the bending moments set up in these bottoms required an excessive thickness of steel in order to resist this bending. These excessive thicknesses added to the cost of the tanks and made them quite heavy.

have discovered how elevated tanks may be built so that bending moments are substantially eliminated and the only stresses on the steel are those of tension. This enables tanks to be built with thinner shells for any given capacity as now there is only need to provide resistance to tension and not resistance to both tension and bending as was true of the old hat bottom tanks. The new elevated tanks are thus considerably lighter in weight and substantially cheaper to build.

The invention will be described as related to the embodiments set out in the accompanying drawings. Of the drawings, Figure 1 is an elevation, partially in a cross-section, of an elevated tank made according to -this invention; Figure 2 is an elevation, partially in cross-section, of an alternate embodiment of the invention; and, Figure 3 is a sectional elevation showing the region of intersection of the toroidal sections of the tank bottom.

In the embodiment shown in Figure 1 there is provided an elevated tank I including an arched roof portion Ii, side portions I2 and a bottom I3 comprising concentric toroidal sheet metal sections. These toroidal sections include the outer section It joined to the side portion I2 and inner toroidal section I5 joined to the outer section I4. The two toroidal sections make up the bottom of the tank and are concentric to each other. At the center ci the section i5 there is positioned a vertical riser pipe it that is normally filled with water. This riser pipe I6 serves to support the central portion oi the tank. The entire tank is supported at its outer edge, where the outer toroidal section ifi joins the side portion I 2, by means o a circular girder il. This circular girder is supported upon a series of vertical posts l2 arranged around the girder. The tivo sheet metai toroidal sections, It, l5, are supported at their line intersection i@ by means of a second cii'cinn girder Zai. This second circular girder is supported on top oi a vertically arranged cylin- 2 Claims. (Cl. 220-1) drical shell 2l. The cylindrical shell 2| has attached to it, as by welding, vertical reinforcements 22 at spaced intervals in order that the shell 2I can resist bending when under full load. in the tank described herein, the bottom toroidal sections may be made much thinner than would ordinarily be used as the tank bottom is designed for tensional stress only. Because of -this design there is an absence of any substantial bending stress as the bottom is not flat but is in the shape of intersecting toroidal sections. These tanks may be made of two toroidal sections, or, where tanks of larger capacity are constructed, may have more than two of these sections.

The embodiment of invention shown in Figure 2.is quite similar to that of Figure 1. In this second tank, however, the toroidal sections have relatively short radii of curvature. The tank, which is the second embodiment of this invention, comprises a roof portion 23, a side portion 24 and intersecting toroidal bottom sections 25, As in the rst tank these toroidal sections are concentric to 'each other and intersect at a substantially circular line of intersection 2l'. The outer circumference of the tank is supported by a circular beam 28, Whichv in turn is supported by a numberof vertical 'posts 29. The .twotor'oidal sections, 25, 26 are supported at their'line .of intersection 21 by means of a circular. I-beam girder 3a, which is secured to the linel orintefr- Section as by'welding 35. The girder 34 is supported at the top of a vertically arranged cylindrical shell 39. This shell has longitudinal reinforcements 3l fastened thereto, as by welding, in order to assist in resisting bending. The central section of the tank is supported by vertical riser pipe 32, which joins the inner toroidal section 25 at its inner circumference. Further support for the structure is provided by a plurality of lateral reinforcing bars 33 extending from the riser pipe 32 to the cylindrical shell 36. Those reinforcing bars are spaced at intervals Within the structure.

In building tanks of the type here under discussion it is important that the stresses in the various sections of the tank be substantially equalized. This is a matter of ordinary engineering skill and is used universally in order to provide stresses that will, in the main, neutralize each other. Thus it is advisable that the horizontal components of the tension in the two toroidal sections, 25, 26, be equal in magnitude and opposite in direction at the line of intersection 27 of these sections. These horizontal components of forces in the tensional members 25 and 26 will substantially neutralize each other if there is a proper selection of the radii of the curvature of members 25 and 26 and a selection of the line of intersection. When stated in mathematical terms it may be set out that the horizontal component of the force on each toroidal section at its line of intersection with the other section is equal to the load vertically above such section and in cluded between the line of intersection and the lowest level of the toroidal section multiplied by the cotangent of the angle formed between two lines lying in a plane normal to such connection, one such line being horizontal and the other line being tangent to the section at the line of connection thereof to the other toroidal section. The mathematical analysis of the structure is shown in Figure 3. In this figure, line A extends vertically from the lowest level of the inner toroidal section 26. Line B extends vertically from the point of intersection of the two members 25 and 26. Line C extends vertically from the lowest level of the member 25. The weight of water W between lines A and B exerts a tensional force on member 26. The weight of water W between B and C exerts tensional force on member 25. In order to get the horizontal components of the` forces, W and W', horizontal lines band b are drawn at the point of intersection 2'! of the two members. Line a is drawn tangent to the member 2B at the point of intersecting, and line a' is drawn tangent to the member 25 at the point of intersection. Line a and line b dene the angle 0, while lines a and b define the angle 0. It is then obvious from simple engineering mathematics that in order to have a balanced structure where the horizontal components of force W and W are equal, thatW cotangent 6=W' cotangent 0. Where these horizontal components of the forces are equal, the loads balance each other and the only tensional force in member 26 is caused by weight W while the only tensional force in member 25 is caused by weight W'.

Although the above discussion has been applied to the structure shown in Figure 2, it also applies to the structure of Figure 1 or to any other structure hof this same general type wherein it is desired to have truly balanced stresses.

Having described my invention in detail as related to vaiious embodiments of the same, it is my intention that the invention be not limited by these details, unless otherwise specied, but rather be construed broadly Within its spirit and scope as set out in the accompanying claims.

I claim:

l. A sheet metal tank comprising side, bottom, and top walls with the bottom portion including at least two toroidal shells located in concentric relationship with the adjacent edges of two such shells attached to each other and support means located substantially beneath and supporting said adjacent edges, said shells being so formed that the load vertically above the first such shell and included between the lines of attachment of said edges and the lowest level of the nrst such shell multiplied by the co-tangent of the angle formed between two lines lying in a plane normal to such attachment, one such line being horizontal and the other being tangent to said shell at the line of attachment thereof to the adjacent shell is substantially equal to the product of the corresponding vertical load and the corresponding cotangent for the attachment of the second shell on the other side of said line of attachment. c

2. An elevated tank comprising, a sheet metal upwardly extending portion, an'arched roof portion and a composite bottom portion, said bottom portion being formed of a plurality of concentric toroidal shells, the outer of such shells being attached to said upwardly extending portion, and circular support means located sul,- stantially beneath and supporting adjacent edges of the toroidal shells with said adjacent being secured in fluid tight relationship, said toroidal shells having different radii of curvature f and being so positioned with reference to each REFERENCES CITED The following references are of record in the file of this patent:

Name Date Jackson May 16, 1944 Number

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