US2298102A - Reinforced concrete - Google Patents

Description

, Oct. 6, 1942. K. P. BILLNER REINFORCED CONCRETE 2 Sheets-Sheet 1 Filed 0.013. 15, 1941 Filed Oct. 15, 1941 2 Sheets -Sheet 2 versely of their axes.

Patented o r, 6, 1942 REINFORCED CONCRETE Karl P. Billner, Philadelphia, Pa.', assignor to Vacuum Concrete l nc., a corporation of Pennsylvania Application. October 15, 1941, Serial No. 415,128 I 15 Claims.

This invention relates to reinforced concrete members such as beams and slabs which are primarily designed to withstand loads applied trans- It has long been the dream of concrete engineers to design reinforced. concrete structural members which will approach the strength and weight of steel. The patented art is replete with disclosures seeking to fulfill that dream, but the various forms and arrangements of reinforcing elements directed towards thi end. have fallen short of the degree of success achieved by the present invention.

Reinforced concrete beams and slabs conforming to present practice are in general, extremely vulnerable to impact and they also lack any de-- gree of resiliency even remotely approaching that of steel. These were the factors that limited the value of the concrete ships constructed during the emergency period of 1918. In accordance with this invention, larger and better concrete ships than heretofore believed to be feasible, can be constructed with'sufllcient speed to serve in the present crisis. And by virtue of this invention, not only are th impact and resiliency characteristics of reinforced concrete vastly improved, but many other properties of the material are enhanced, outstanding among which are the almost incredible inreases achieved in the compressive unit stresse in the concrete, commonly represented by the symbol fc.

Among the many shapes assigned to reinforcing elements in the development of this art is the helix which, together with other reinforcing stitutes the basis of the improvements proposed herein. The use of helical reinforcing elements elements arranged in a particular manner, confor concrete is in itself not new, since this expedient has been known and used for years in connectionwith compression members such as columns- An early example of such construction appears in the .patent to Considere, No. 752,523, dated February 16, 1904, and along somewhat similar lines.are the disclosures of Swenssom-No. 871,076, dated November 12, 1907,

and Maney, No. 2,035,662, dated March 31, 1936.

one side only of the neutral axis ofthe beam or slab and because of the relative positions of his other reinforcing elements, Hartman, like other prior inventors, has failed to disclose any structure which would even approach the character-.

istics which are inherent to the instant invention.

Inaccordance with the present invention, a reinforced concrete member such as a beam, slab, or wall, primarily designed to withstand loads between its supports, contains a plurality of interlocked helices each of which has its axis extending substantially parallel to an axis of the member, and each of the helices has opposed portions of its periphery substantially adjacent opposite surfaces of the member. Tension means preferably extend through certain of the helices in a position adjacent to at least one sur-. face of the reinforced concrete member, and preferably at a surface or surfaces designed to withstand tension. In the case of a wall such as that constituting a portion of a ships hull where a reversal ofstresses may be expected, tension rods .may be arranged within som or all of the helices adjacent to both surface of the member. Whereas theconcrete alone may perform the keying or interlocking function, one desirable procedure for maintaining the adjacent helices in interlocked relationship is to position themwith their turns interlocking or overlapping to form eyes and then insert a keying rod through the eyes thus formed. These keying rods will ordinarily assume positions near the ing from impact and it is proposed for some applications that they be spaced more widely than Individual helices have likewise, been proposed as reinforcing elements for'concrete beams in the patent to Swensson, No; 871,075, dated November 12, 1907, and that to Keogan, No. 1,465,307, dated August 21,1923. And helical interlocked rein forcing elements for beams and slabs have been proposed in the patent to Hartman, No. 1,233,053,

dated July 10, 1917-. But since the helices'lie on the tension rods and if desired, alternately arranged on opposite sides of the keying rods.

While. adjacent helices may bearr'anged so that their convolutions merelyoverlap, it is proposed as an alternative that they be threaded together so that their individual convolutions become interlocked. a

A further modification involves the introduction of additional helices having their axes disposed transversely with respect to the axes of the tially the same 'plane, or at least so that each helix willextend on opposite sides of the neutral axis of th member. Other reinforcing elements are contemplated for incorporation in this arrangement as well. And in cases where it may be desired to partially prefabricate the reinforcing matrix, some or all of the reinforcing elements may be assembled as a unit by suitable welding or other fastening means.

Whereas it is important that the peripheries of the helices assume positions substantially adjacent to thesurfaces of the reinforced concrete members, it is likewise important, in some applications more than others, that all metal reinforcing members be protected from the elements.

For this purpose primarily it is proposed that the helices and other reinforcing elements be entirely covered by a suflicient depth of concrete to serve this function.

By virtue of the constructions proposed herein, 2

compressive unit stresses in the concrete of the order of 12,000 lbs. per square inch and higher have been developed in beams tested only four daysafter they were poured. And beams tested at a similar age have displayed unusually high resiliency and resistance to impact. Thus, the

customary thickness or depth of concrete structures can be materially reduced with a corresponding saving in weight, adapting the invention for use in constructing ships, bridge decks, 3

and innumerable other applications.

Added advantages are recognized when the products of the present invention are prepared in accordance with the vacuum processes set forth in the prior patents of the present inventor num- 3 bered 2,046,867 and 2,116,557, dated July 7, 1936,- and May 10, 1938, respectively, and it is preferable, although not obligatory that the vacuum treatment be employed.

In fabricating a structural member of the type contemplated herein, 'the reinforcing elements will be assembled and maintained in their respective positions, whereupon the concrete will be poured into suitable forms enclosing the reinforcing elements.' In this manner, the voids 4 section and partly diagrammatic, of a structural member embodying the present invention;

Fig. 2 is a diagrammatic fragmentary longitudinal elevation along line 22 of Fig. 1; Fig. 3 is a diagrammatic end elevation showing a modification;

Fig. 4 is an elevation similar to Fig. 2 taken along line 44 of Fig. 3;

Fig. 5 is a diagrammatic end elevation of another modification;

Fig. 6-is an elevation similar to Figs. 2 and 4 taken along line 6-8'of Fig. 5;

' Figs. 7 and.8 are diagrammatic elevationsat right angles to'o'ne another illustrating a modification; and

Fig. 9 is a'sectional elevation illustrating the invention as applied to the construction of awall forming a portion of a ships hull.

The reinforced concrete member iii in the form 1 of. a beam or slab depicted in Figs. 1 and 2 of the drawings comprises a body of concrete ll (indicated in part by brokenlines) embedding a plurality of helices 20. Adjacent helices are shown as arranged in merely overlappin relationship to define a row of eyes 22, adapted to receive a keying rod or shear bar 24 threaded through each row to interlock the helices. Within each of the helices of these figures, and adjacent the lower or tension surface 26 of the reinforced concrete beam, slab or other member, are located tension bars 28. It will be noted that the peripheries of the helices, while not exposed, extend to positions substantially adiacent to the surfaces of the member l6. It is for the purpose of protecting the metal reinforcing elements that the concrete portion of the member completely overlies the metal in addition to filling the voids between the various reinforcing elements and embedding them.

Figs. 3 and 4 of the drawings show a modification which is similar to that of Figs. 1 and 2, but show in addition the use of tension rods 28 adjacent to both surfaces of the beam, slab or wall, an arrangement of particular importance in applications where there is a reversal of stress resulting in tension at both surfaces of the struc tural member.

The modification in Figs. 5 and 6 adds to the construction of Figs. 3 and 4, a mutually interlocked arrangement of the individual convolutions of adjacent helices, achieved by threading them together, combined with transverse reinforcing rods "32 crossing the axes of the spirals or helices 20 and intended primarily to distribute impact forces to which the structural member may be subjected. As indicated in Fig. 6, these transverse rods need not be arranged as closely together as are the tension rods and they may be supported in staggered relationship on opposite sides of the keying rods 24.

In Figs. '1 and 8 of the drawings, the overlapping or interlocking helices 20 constituting a first group have been shown as mutually interlocked with a plurality of overlapping or interlocking helices 30 constituting a second group extending transversely of the first group and wound therethrough in such a way that the axes of all of the helices will lie in substantially the same plane, or at least, each of the helices will extend on both sides of the neutral axis of the structural member. The tension rods 28 to be arranged within the helices adjacent to the surfaces or surfaces under tension have been illustrated as extendins through both groups of the helices. It will be In Fig. 9 the invention has been shown in its application to ship construction wherein the wall '34 represents aportion of a ship's hull and wherein the helices and other reinforcing elements are arranged in the manner appearing in Fig. 5. In such a case, it is quite important that the reinforcing metal including the helices be protected from the elements and this is accomplished by providing a wall thickness slightly exceeding the external diameter of thehelices.

As alr ady noted, one of the greatest deficicncieslof the concrete ships constructed in the .1918 period was their vulnerability to impact and their low resiliency. By way of contrast to those old constructions, a beam designed in' accordance with the present invention has been tested by the'application of repeated blows of a 500 lb. weight dropped from heights beginning from one outside of the helices.

.,Age of specimen: '4 days.

foot and increasing by one foot increments until the height reached seven feet, by which time an ordinary beam similarly treated had completely failed while the beam of the present invention displayed only a slight amount of spalling The beam embodying the present invention was then subjected to two additional blows with a weight of 2350 lbs. dropped from heights of three and four feet respectively.

Then the beam was tested for leakage under a head of 16 feet of water with the result that only one-half pint per minute penetrated for each square foot of surface'area. And this beam had been poured only four days previously, although it (as well as the beam reinforced in the conventional manner) had the benefit of the vacuum process of the prior patents referred to hereinbefore.

.L=90 in. b=13.5 in. (1:2.75 in.

Helices: 6; diameter 3% in.; pitch 1 in.; stock diameter 3% in.

-Keying rods: 5; diameter A in.

Tension rods: 6; diameter in. (100,000 Y. P.).

Concrete mix: 1:1:2 /8 max.). 5 gallons per bag. 4 in. slump. High early strength cement.

n=10 (assumed).

The results were as follows:

It'will be understood that while true helices appear tube circular in cross-section, other sectional shapes may be substituted without departing from the present'concept and it is intended that the term helices" be construed to include such, equivalent elements of other cross-sectional are not used, the overlapping helices may be retained in their relative positions in any other suitable manner. In accordance with a modification already discussed, the overlapping helices extending in one direction may be interlocked by winding transversely extending helices therethrough in such a manner as to become interlocked therewith and with one another. And in some cases it may be preferred to mutually thread adjacent helices together. Another procedure is to rely upon the hardened concrete alone to maintain the overlapping helices in their interlocked relationship.

The scopeof the invention is not to be restricted to the specific forms described and shown for purposes of illustration, beyond the limitations of the following claims.

I claim:

l. A reinforced concrete member primarily designed to withstand loads applied transversely of its neutral axis comprising a plurality of interlocked helices each having its axis extending substantially parallel to the axis of said member and having opposed portions of its periphery substantially adjacent opposite surfaces of said member.

2. A reinforced concrete member primarily designed to withstand loads applied transversely of its neutral axis comprising a plurality of interlocked helices each having its axis extending substantially parallel to the axis of said'member and having opposed portions of its periphery substantially adjacent opposite surfaces of said member, and tensile reinforcement extending through certain of saidvhelices. 3. A- reinforced concrete member primarily de- Si ned to withstand loads applied transversely of its neutral axis comprising a plurality of interlocked helices each having its axis extending substantially parallel to the' axis of said member 0 and having opposed portions of its periphery configuration. Since the invention is equally applicable to rectilinear or curved beams, slabs and walls, rather than phrase the claims in the alternative, a number of them have been worded to set forth a member primarily designed to are to be used, through the eyes, inserting reinforcing elements through those helices designed to receive them, maintaining the parts thus assembled in their proper relative positions and surrounding them and filling their voids with concrete. A supplemental step greatly enhancing the value of the method thus far set forth involves the application of vacuum in accordance with the Billner patents cited herein, to remove substantially adjacent opposite surfaces of said member, and tensile reinforcement extending through certain of said helices adjacent ,to at least one surface of said member.

4. A reinforced concrete member primarily de-.

signed to withstand loads applied transverselyof its neutral axis comprising a plurality of interlocked helices each having its axis extending substantially parallel to the axis of said member and having opposed portions of its periphery substantially adjacent opposite surfaces of said member, and tensile reinforcement extending through certain of said helices adjacent opposite surfaces of said member.

5. A reinforced concrete member primarily designed to withstand loads appliedtransversely of its neutral axis comprising a plurality of interlocked helices each having its axis extending substantially parallel to the axis of said member and having opposed portions'of its periphery substantially adjacent opposite surfaces of said member, adjacent helices having their turns in overlapping relationship defining eyes, and keying means extending through said eyes.

6. IA reinforced concrete member primarily designed to withstand loads applied transversely of its neutral axis comprising a plurality of interlocked helices each having its axis extending substantially parallel to the axis of said member and having opposed portions of its periphery substantially adjacent opposite surfaces of said member, adjacent helices having their turns in overlapping relationship defining eyes, and shear rods extending through said eyes keying said water from the concrete. Where keying rods 16 helices together.

7. A reinforced concrete member primarily designed to withstand loads applied transversely of its neutral axis comprising a plurality of interlocked helices each having its axis extending substantially parallel to the'axis of said member and having opposed portions of its periphery substantially adjacent opposite surfaces of said member, and reinforcing means extending transversely of the axes of said helices.

8. A reinforced concrete member primarily designed to withstand loads applied transversely of its neutral axis comprising a plurality of interlocked helices each having its axis extending substantially parallel to the axis of said member and having opposed portions of its periphery substantially adjacent opposite surfaces of said member, spaced reinforcing elements extending substantially parallel to the axes of said helices,

and reinforcing rods differently spaced than said surfaces and additional reinforcing elements extending through portions of said helices more remote from said surfaces.

12. A reinforced concrete slab comprising a row of interlocked helices arranged substantially throughout the width of said slab, each helix extending substantially parallel to the neutral axis designed to withstand loads applied,transversely of its neutral axis comprising interlocked helices extending transversely with respect to one another and having their axes in substantially the of said slab and having opposed portions of its periphery substantially adjacent opposite sur: faces of said member, reinforcing elements extending through portions of said helices adjacent to said surfaces andadditional reinforcing elements extending through portions of said helices more remote from said surfaces.

13. A reinforced concrete wall comprising a plurality of interlocked helices each having its axis extending substantially parallel to the surfaces of said wall and having opposed portions of its periphery substantially adjacent to said surfaces, and reinforcing rods cooperating with said helices.

14. A reinforced concrete wall defining a portion of a ship's hull comprising a body of concrete embedding a plurality of helices each having its axis extending substantially parallel to the neutral axis of said wall and having opposed portions of its periphery adjacent to but entirely covered by opposite surfaces of said wall, adjacent helices having their turns overlapping to form a row of eyes, a keying rod projecting through said row of eyes, and reinforcing ele- 1 ments received within certain of 'said helices arranged near the surfaces of said wall designed to

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