US2185749A - Means of reinforcing concrete - Google Patents

Description

Jan. 2, 1940. R g KENNEDY 2,185,749

MEANS OF REINFORCING CONCRETE Filed Jan. 29, 1937 INVENTOR Patented Jan. 2, 1940 UNITED STATES PATENTgOFFICE:If

1 3- i Q .1 2,185,749 v MEANS OF nnmroncmc coNcnE'm Robert Charles Kennedy, Oakland, Calif. Application January 29, 1937, Serial No. 123,001

1 Claim. (01. 72-71) on the rods is for, the purpose of decreasingthe This invention relates to a method of combining metal and concrete to form the walls of pressure vessels such as tanks and pipes, or other I concrete structures, in such manner as to prevent 5 cracks developing in the concrete and to fully utilize the strength of the metal.

It-is common experience in building concrete vessels reinforced with steel rods simply embedded g in the concrete, that the concrete, being low in tensile strength, will develop cracks before the jsteel has assumed its proper working stress. 3 Such cracks also result from the natural tendency of concrete to shrink as it sets. Such tendency, being resisted by the rigid steel bars, causes racks to develop. Cracks result in leakage, and {the weakening of the concrete wall for taking o'mpressive and shearing stresses which it may ,also at times be required to withstand. Other esults are corrosion of the steel bars and progres- 't-sive disintegration of the concrete.

A method has heretofore been utilized for prew the cracking of concrete pressure vessels y fineans of steel bands equipped with turnbuckles, placed around the previously constructed con'erete walls and tightened to such degree by :'means' of the turnbuckles that the concrete is 'g'placed in compression. By adjusting the stress inthe steel and concrete to proper degree in this manner before pressure is placed in the vessel, it possible to prevent any tension in the concrete hriiunder pressure, and thereby cracks are iavoided. However, since it is noteconomically easible to construct the concrete walls to a per- ;jT-fectly cylindrical shape, the rods tend to bear 35 ong solated points around the circumference instead of securing uniform bearing throughout their length. As a result, a crushing of the concrete takes place at these high points. Also with thisfmethod, advantage cannot be taken of the A0 economy high-strength steels, since higher qstressed rods would out still deeper into the con crete. In order to provide the additional bearingfrequired even for ordinary soft steels, it has customary to apply a layer of concrete out- 45 side jof the steel rods, somepart of which flows into the spaces between the rods and the concrete.

The. additional concrete layer also protects the rods from corrosion and provides architectural advantages.

50 second method for overcoming the cracldng of greinforced concrete pressure vesselsis to coat the' adjustable rods with asphalt or other plastic material and then pour the entire thickness of concrete wall at one time, except for recesses for 56 operating the turnbuckles. The plastic coating bond with the concrete, so that the rods can be tightened withthe turnbuckles. One difllculty with this method is that it is not possible to sumciently prevent bonding between the steel rods and the concrete by such plastic coatings as to permit of uniform stressing of the rods, unless the turnbuckles are placed at such short intervals as to be uneconomical. Another difliculty is that the economy of the higher strength steels cannot be secured, due to greater tendency of the smaller bars to cut through the plastic material along the curve and thus still further increase frictional resistance to proper tightening.

The purpose of my invention is to overcome the above mentioned disadvantages of existing types of construction and to provide a structure that will render equal or better service, and at the same time be less expensive to build.

My invention covers the reinforcing of concrete by means of adjustable metal rods which have been placed in tubes. of metal or other material, such rods fitting loosely within the tubes so as to permit of free longitudinal movement of the rods. Grease or other lubricant may be enclosed in the tubes with the rods to facilitate movement and to act as a preservative. The entire thickness of tank wall is poured at one time, leaving recesses at proper intervals for the turnbuckles. After the concrete has set for the proper period, the rods are tightened by means of the turnbuckles to a predetermined stress. The recesses may either be filled with concrete after the adjustment is complete or left accessible for further adjustment if required.

Referring to Figures 1 and 2, the metal band is marked I. This band is made up of one or more units, depending upon the size of the structure. ,Each unit is provided with threaded ends and coupled to the adjacent units by means of threaded turnbuckles 2, or is provided with other adjustable means for tightening. The bands are enclosed in tubes or sheaths 3 in which they are free to slide, except that the portions within the recesses are not so enclosed. These tubes may be bent around the rods by drawing the rods through a properly shaped orifice togeth with strips of sheet metal, or by spirally wrap ng the strips around the rods or by inserting the rods in tubes previously formed, or by any other suitable method. A lubricant may be added either during or after the placing of the tubes around the rods. The rods and tubes are then bent to the required curve and secured in place by a suitable means, and the concrete forms are erected in the usual manner, but with provisionfor forming recesses 4 at the turnbuckles. The distance between recesses should preferably be one-half the length of the rod units, as shown in g Figure 1, so that the turnbuckles may be staggered, and so that the rods may be vibrated, mechanically or otherwise at points midway between turnbuckles to facilitate movement during tightening. The concrete wall I is then poured, 10 to the full thickness and after a suillcient period of time for proper setting, the forms are removed. The turnbuckles are then tightened to a predetermined stress. The recesses may be filled with concrete or may be left accessible for 1' future inspection and adjustment of the turnbuckles.

Advantages of my invention when used for cylindrical vessels such as tanks or pipes, are as follows:

a (1) It makes possible the pouring of the full thickness of wall at one time, and saves the cost of additional concrete or mortar applied after the steel rods are adjusted.

(2) The tension in the adjustable rods is made 35 approximately uniform throughout their length because of the low frictionalresistance to movement of metal on metal.

(3) It makes possible uniform and adequate bearing for theadjustable rods throughout the a) length thereof.

(4) The saving in material cost through the use of high-strength metals is made possible because of the ilrm bearing secured between the metal tubes and the adjustable rods.

(5) The concrete wall may be made thinner I because the use of small, high strength rods and turnbuckles is possible.

(6) It makes possible the further adjustment of the rods after the structure has been in service. 10

A similar method of permitting adjustment of metal reinforcing rods may be used for tanks or vessels having straight walls, or for beams. All of the advantages enumerated herein for cylindrical vessels when my method of reinforcing is used, apply also tothe latter structures.

I claim as my invention:

Reinforcement for a curved concrete wall, consisting of metal rods placed loosely within tubes m encased in the concrete and made continuous around the wall by means of adjustable threaded connections on said rods for placing the same in tension so as to exert a radial pressure on the concrete, said tube enclosures having their ends 25 clear of the abutments on the rods so that none of the rod tension will be absorbed directly by axial compression in the enclosing tubes.

ROBERT CHARLES KENNEDY. so

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