US2324916A - Reinforced structural element - Google Patents

Description

July 20, 1943- J. K. DUNCAN E TAL REINFORCED STRUCTURAL ELEMENT.

Filed May 2, 1940 plied loads directly to the building framework.

Patented July 20, 1943 REINFORCED STRUCTURAL ELEMENT James K. Duncan, Chicago, 111., and George L. Phelps, Tempe, Ariz., assignors to United States Gypsum Company, Chicago, 111., a corporation of Illinois Application May 2, 1940, Serial No. 333,006

6 Claims.

This invention relates toa structural element and more particularly to prefabricated reinforced cementitious units for use in building structures. The units for which this invention is especially adapted are tiles, slabs, and the like, substantially fiat cementitious elements having an appreciable thickness. Sheets of this type are preferably made of gypsum or othersuitable material, and are commonly used as structural floor slabs in buildi'ngs'of comparatively light loadoccupancyand are also used as roof slabs in buildings of any type. Each tile is ordinarily provided with a tongue'and groove or the like on opposite side edges and usually also with a tongue or groove on each end.

There are at present two general types of such tile in use; that is, a metal edge tile in which the slab itself is reinforced only sufficiently to hold the gypsum together and to transfer applied loads to the interlocking metal edges, which later form an I-beam, and transfer all loads to the structural framing of the building. Another type is the integrallyreinforced tile which are reinforced in both directions and transfer the ap- Slabs of the metal edge type have a serious objectionable characteristic in their inability to support appreciable loads concentrated upon the main body of the tile. Furthermore, the insulating efficiency of the metal edge tiles is low for the reason that metal extends continuously from one surface to the other and heat is,'therefore, rapidly transferred.

Tiles of the integrally reinforced type are also primarily objectionable because the edges are 'easilychipped, the finished tile is of low strength, and the. production costs are high. In order to provide a tile of even mediocre strength, it has heretofore been found necessary to .employ welded wire mesh as a reinforcing agent. This,

however, has made the cost of such tile almost prohibitive.

when the gypsum keys are severed, the expanded metal mat is free to stretch in these areas and immediate failure of thetile occurs.

The present invention overcomes the previously noted objections to reinforced tile; and it is an object to provide an inexpensive, structurally strong, cementitious building unit in the form of i a tile or the like, in which the gypsum keys formed through the mesh of expanded metal reinforcement will not shear or fracture under any ordinary loads applied to the tile.

Another object of the invention is to provide a reinforced cementitious unitfor building structures with edges and corners which are highly re sistant to chipping and abrasion.

The present invention also contemplates the production of a reinforced cementitious tile in which the reinforcement may be of expanded metal so positioned within the tile as to provide definite structural advantages and also in which the composition of the cementitious mixture is such as'to effectively prevent shearing of the keys extending through the diamonds of the expanded metal.

A further object is the provision of a reinforced cementitious building unit or tile having a rein forcingmernber such as fiat expanded metal or other suitable foraminous sheet material not under tension and in which the body of the tile is formed 0 a cementitious material such as gypsum or t e like-containing predetermined percentages of fiber, such, for instance, as ground fluff newsprint or the like.

A further" object is the provision of structural units or elements comprising an aggregatecontaining a predetermined proportion of resilient and yieldable fibrous'material whereby the elements are highly resistant to cracking strains and have other shockproof qualities which make 'them particularly desirable for use in earthquake-proof constructions and especially suitable for use in areas where earth tremors are prevalentl v Another object is to provide a new and novel process for manufacturing a highly shock and strainproof cementitious building unit of, the character described. i

Further objects will be apparent from th specification and the appended claims.

'In the drawing: I

Fig. i is a perspective sectional view of a tile or slab and illustrates oneeiribodiment ofthe invention.

Fig. 2 is an enlarged sectional elevation of an edge portion of the embodiment illustrated in Fig. 1.

Fig. 3 is a fragmentary detail sectional-view taken on a line substantially corresponding to line 8-4 of Fig, l and illustrates in section the keys which extend through the diamonds of the expanded metal'reinforcement.

Referring to the drawing in details, the embodiment illustrated comprises a cementitious tile or slab I having a tongue 2 along at least one edge and a groove 3 in the opposite edge.

The tile l is preferably formed of an aggregate comprising gypsum and a predetermined amount of fibrous material of a type and in proportions which will later be described. However, it should be understood that the tile may be formed of any cementitious material which is suitable for use in structural units and which may properly be used in connection with the fibrous material specified. Also the units may be of any desired size and shape and are not to be limited to tile.

The slab or tile element disclosed is provided with a reinforcement 4 of foraminous sheet-like material, preferably flattened expanded metal having reasonably large apertures or so-called diamonds I, as shown in Fig. 3. In actual practice, a satisfactory reinforcement for ordinary the may be made of standard flattened thirteengauge expanded metal having three-fourths inch diamonds.

The reinforcing element 4 is preferably made in the form of an elongated hollow framework such as illustrated by the dotted lines I in Fig. 1 and which is of a cross sectional contour approximating that of the finished slab but with depressed sides, as shown at 0, so that, when the complete slab is formed, the sides 6 are spaced somewhat from the fiat sides I of the tile. The

reinforcing expanded metal mat is also so formed that it is substantially at the surface of the slab adjacent the edges 8 and around the tongue 2 and all of the adjacent comers. The reinforcing mat is also formed at the opposite edge so that it is substantially at the surface of the groove 3 and the adiacent edges and corners as shown. The mat extends closely adjacent the surface of the tile for an appreciable distance along the fiat sides thereof, as indicated at I. By this means, a tile may be formed which is exceptionally resistant to chipping and abrasion of the tongue and groove and all adjacent surfaces and corners.

The exact-areas at which the reinforcing is at or near the surface may, of course, be varied,

and, in fact, the reinforcement may not be completely coextensive with the entire areas of the tongue and groove. Also the exact proximity of the reinforcing element to the surface of the tile in the vicinity of the edges and in the viclnity of the tongue and groove may be varied somewhat. For instance, in Fig. 1 the reinforcement adjacent the edges is shown just slightly under the surface of the cementitious material, and at the sides 6 it is very materially spaced from the outer surfaces I of the tile. Fig. 2 illustrates substantially thesame reinforcement. However, in Fig. 2 the reinforcement in the tongue and groove and at the edge surfaces is shown substantially fiush with the surface oi. the tile.

It will, of course,be obvious that reinforcing elements shaped in accordance with the disclosure herein may be employed in building units formedfrom any suitable cementitious material.

However, particularly desirable and unexpected characteristics are'obtained in the finished prod-.

not when the aggregate from which the tile is formed is made with certain predetermined proportions of cementitious material and fiber in combination with the specified type of reinforcement.

It is desirable not to have the main body of the reinforcing material (that is; the sides 6 thereof) too closely approach the surface at the sides of the tile or panel. By spacing the reinforcement substantially as shown,- they diamonds are engaged by well formed eflicient keys 9, as in Fig. 3, with a suitable amount of key-supporting material on each side of the expanded metal.

A satisfactory process for forming the structural unit disclosed or its equivalent consists in preparing a mold of the desired size and shape, greasing the inner surfaces of the mold, placing. therein an expanded metal reinforcing element of the formation described, that is, of a shape approximating the unit and with depressed sides as shown, then filling the mold with a cementitious slurry comprising stucco and fiber in the amount of 2 4% to 14% by weight of the dry the finished product, then the reinforcing element may be supported in the mold accordingly. If, however, it is desired that the reinforcing element should be at the surface at these points,

then it may be supported directly by the mold itself.

While the slurry composition above specified (that is, containing 2 to 14% of the fiber by weight of the dry stucco) is satisfactory under certain conditions, it has been found that, to obtain the most satisfactory results, the fiber should be in the amount of 4% to 6% of the dry It has also been found that, for the flattened expanded metal used as a reinforcing medium provides a most satisfactory product. In other words, the combination of a cementitious mixture having a relatively high fiber content with fiattened expanded metal reinforcement produces a tile with remarkably efficient and unexpected characteristics.

Heretofore it has been the practice to admix comparatively small amounts of fiber (up to 1% or 1 by weight) with the stucco in the manufacture of cementitious tile, the object being to increase the bond of the tile and reduce its density somewhat. In so far as known, however, there has never been any relationship of the proportion of fiber used to a reinforcing element of any type. In the development of the present invention it has been found that, by increasing the fiber content to from 2 to 14% by weight of the stucco, and preferably to from 4% to 6%, and using expanded metal, and particularly fiattened expanded metal, as the reinforcing agent,

it is possible to produce an excellent tile having greater load-supporting characteristics and less chipping and breaking of corners and edges than any similar tile heretofore produced.

' It has also been found that, when ordinary unfiattened expanded metal is used, a relatively high proportion of fiber must be used to produce satisfactory results. However, if flattened expanded metal reinforcement is used, satisfactory tile may be made with a somewhat lower fiber content. In other words, there in a direct relationship between the proportionate amount of fiber and the type of reinforcement used. D

I to a very marked extent.

- As previously stated, the results accomplished by the combinations used in thisinvention have been very unexpected and, although it is desired that the invention should not be limited by the following theory, it is thought that the explanation for the surprising results obtained is substantially as follows:

With ordinary unflattened expanded metal employed in a tile made from a standard mix containing substantially 1% to 1 of fiber, there is practically no give" of the stucco when the strands of the expanded metal press severely against the gypsum keys by reason of a load being applied to the tile. in that vicinity. The expanded metal, being unflattened, does not develop its full strength at the first stretch, but tends to stretch until it has been pulled into a flattened condition. The result is that, with a very heavy load concentrated on the tile, the strands of the unflattened expanded metal move suiflciently to break the nonresilient stucco keys. thereby causing complete failure of the tile. By prefiattening the expanded metal; its initial stretching in the tile is substantially eliminated, thus enabling a tile, even if made from the ordinary stucco mix, to support any load. less than that sufficient to cause movement of the strands of the flattened expanded metal. Although the flattened expanded metal, even when used with the ordinary stucco mix, yields a somewhat tronger tile than when unflattened metal is used, approximately the -ntire stress of the load is still borne by that portion of thereinforcement which is in the immediate vicinity of the point of application of'the load.,

The addition of a substantial quantity of fibers to the stucco mix conditions the mix for resilient or yielding intimate co-operation with the expanded metal so that the mix and the reinforcing metal fully co'-oper'ate to produce the most effective results. The'fibers present, particularly in the stucco keys, cause the keys to be: somewhat yielding and resilient, with the result that, when a concentrated stress is applied to the tile, the'strands of expanded metal are per- 45 mitted to move sufiiciently to enable a large portion of the strain to be transmitted to other keys and other portions of the tile, thus relieving-the gypsum keys in the immediate vicinity of the load In tests made by using a stucco mix containing the standard amount of fibers with nonflattened expanded metal reinforcement, the failure of the tile has'been due to the shearing of the gypsum the load. In tile containing substantial quantities of fiber and employing flattened expanded metal, the failure has been due to the rupture of themetal reinforcement. l

The presence of substantial quantities of fibers with expanded metal reinforcement insures a considerably improved tile, even when the reinforcing expanded metal is unflattened. However, even to obtain this improvement, a fiber content of 2 /27., to 14% by weight of the stucco its ability to support loads concentrated upon tics.

In the'manufacture of standard tile it is undesirable to have the fibers present in too large quantities for the reason that they tend to weaken the body of the tile somewhat. Therefore, in the present invention the proportion of fibers and type of reinforcement bear a definite predetermined relationship ,to each other.

tile, tile may be produced having greatly improved Y load bearing characteristics.

In addition to being anexceedingly strong structural unit which is relatively cheap to pro duce, tile made in accordance with this" invention have a number of other important characteris Tests have shown that they are not nearly as subject to fatigue as are, metal edge tile of similar dimensions. That is, when subjected to a continuous load over a long period of time, the amount of ultimate deflection is much less than that of metal edge tile .and the amount of its deflection becomes constant, considerably more quickly.

Another advantage which the tile of this invention has over metal edge tile and the like is or embodiments-disclosed herein, since many modifications may be made,-. and it is contemplated, therefore, by the appended claims to cover any such modifications as fall within the true spirit and scope of this invention.

Having thus described this invention, what is claimed and desired to be secured by Letters Patent is:

1. A load supporting reinforced building slab or tile of set ementitious material comprising stucco and fiber andan expanded metal reinforcing elernent embedded in said slab and substantially coextensive therewith, said reinforcing element being, substantially flush with the surfaces and corners at and adjacent two opkeys in the vicinity of the point of application of posed edges of said slab and spaced from the panded metal, a much greater improvement is surface throughout the of said slab.

2. A reinforced building slab or tile of set major area of both sides cementitious material comprising stucco and, flber and an expanded metal reinforcing ele.-'.

are materially spaced from the side surfaces of said slab.

observed. However, if flattened expanded metal I obtained. .It will, of course, be understood that these percentages may vary slightly. depen'ding upon the type of fiber used, the size of the mesh of the expanded m and t Gauge hereof. 75 sectional contour substantially conforming to- 3. A reinforced building slab or tile having a tongue on one edge and a groove in the opposite edge, said tile being formed of set cementitious material comprising stucco and fiber and an expanded metal reinforcing element embedded'in' said tile, said reinforcing element being of a cross the cross sectional contour of said tile and being substantially at the surface of said tile adjacent its edges including said tongue and groove, and having its sides depressed, so that major portions of said sides are spaced materially from the sides of said tile, the amount of fiber to stucco being from 2%% to 14% to provide sufflcient resilience or yieldabillty in said material to prevent shearing or fracture of said material by said expanded metal when extreme loads are localized on said tile and to transmit local-- laed stress to a comparatively large area, of the material substantially in the plane of said reinforcing element.

4. An article of manufacture comprising a reinforced cementitious tile or slab having embedded therein a reinforcing shell of flattened expanded metal preformed to a shape and dimensions closely approximating the outer contour and dimensions of said slab adjacent the edges and at the corners thereof, but with a major portion of the sides depressed to provide a relatively narrow space between said depressed portions and the adjacent sides of said slab, the body of said slab being molded of a cementitious slurry comprising stucco, and fiber in an amount of 259% to 14% by weight of the dry stucco.

5. A load supporting tongue and groove building slab or tile of set cementitious material comprising stucco and fiber, a tongue and groove reinforcing shell of flattened expanded metal of substantially the same general over-all dimensions and contour as said slab and molded therein so that-the surfaces of the tongue and groove .edges -of said shell and of said set cementitious material are substantially coplanar, the intermediate portions of said shell between said tongue and groove edges being embedded beneath the side surfaces of said slab.

6. A reinforced building slab or tile having a tongue on one edge and a groove in the opposite edge, said tile being formed of set cementitious material comprising stucco and ground fluff newsprint fiber and an expanded metal reinforcing element embedded in said tile, said reinforcing element being of a cross sectional contour substantially conforming to the cross sectional contour of said tile and being substantially at the surface of said tile adjacent its edges including said tongue and groove, and having its sides depressed, so that major portions of said sides are spaced materially from the sides of said tile, the amount of ground fluff newsprint fiber to stucco being from 2 to 14% to provide sufllcient resilience or yieldability in said material to prevent shearing or fracture of said material by said expanded metal when extreme loads are localized on said tile and to transmit localized stress to a comparatively large area of the material substantially in the plane of said reinforcing element.

JAMES K. DUNCAN.

GEORGE L. PHELPS.

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