US2428304A - Hollow centrifugally molded beam - Google Patents

Description

Sept`. 30, 1947@ P. ABELES ET AL I 2,428,304

" HOLLOW CENTRIFUGALLY MQLDED BEAM Filed Oo. 8, 1936 2 Sheets-Sheet 1 i. f 1 v v Sept, 30, 1947. P. ABELES ET AL HOLLOW CENTRIFUGALLY MOLDED BEAM Filed oct. e, 19:56 2 sheets-sheet 2 Patented Sept. 3, 1947 UNiltT EDF STATES O 2,428,304

HOLLOW CENTRIFUftAlltll?VS Paul* Abeles, Vienna, Austriaand.'LT Er-'nst Braun-v liofck, Dugaresa, near Karlovae, Yugoslavia Application October'S, 1.936y *SerialV 104,730. In Austria October 281935 Section Si, Public Law 690; August 8; 9462l Patent expires October'ZS; 19555V 1 Claim.

In the past,l attempts have been` made to provide pre-fabricated hollow reinforced concrete beams for the construction of floors.- 'I-hese have the advantage that they do not require shutterin-g; and enable the building operation to be speeded up.k Moreover, they have great lateral stiffness andv for this reason are particularly suitable for loors.- sufficiently rigid to` exclude the possibility of oscillation. However,v on the. sides adapted to take up: compression stresses these beams. had to be made with a considerable wall thickness, whereby the weight of the beams; was made relatively great. Furthermore,` it is know-n to producemastsy and conduit pipesof reinforced concrete. by a centrifugal process, the longitudina]`X reinforcement being uniformly distributed over the: whole of the annular cross sectional area.

The invention consists in the special construction: of. ahcllow centrifugally molded beam of reinforced concrete for use in building construction especially in Hoorsisaid beam being substantially tubular in cross section, and including7 a main longitudinal reinforcement provided in the part of the tube required to endure tensile stress, g

and several longitudinalbars forminga secondary reinforcement arranged in the other parts. of the tube; said beam also having a surrounding reinforcement interconnected with both said longitudinal reinforcement t'o form a rigid framework ofthe beam, so that they act jointly.

Such a combinati'onv results in4 tubes of great carrying capacity while having comparatively thin walls and renders it generally unnecessary to increase the cross sectional area in the compression zone of the beaml rI ifhe strength. of centrifugally cast concrete being much greater than that of ordinary molded concrete, tensile stresses are set up in the surrounding reinforcement which relieve the longitudinal reinforcement to some extent. Beams constructed according to the invention are therefore lighter and much more economical, not only as compared to the known centrifugally cast concrete tubes, but also in cornparison to any reinforced concrete beams. Owing to the increased load carrying capacity it isa'of advantage to employ the hollow reinforced concrete beams as joints or sills and summers and as iioor beams. In the latter case the hollow beams may be laid as desired side by side contiguously or with spacing. The interspaces may be bridged over by reinforced concrete, concrete, light slabs or hollow bricks, Various embodiments of the invention are illustrated in the accompanying drawings showing in cross section parts of floors and beams of various forms.

Fig 1 showfs a). oor cjrsist'ing ofV a series of hC.. beams l. made` according tothe centrifugal castma process, between winch floor lling bodies fare formed', made of? any suitable material'having a. suoient load carrying capacity for exams ple,- liollow bricls or stones'` o fli'ght; concrete. The embodiment. shows hollow beams with octagonal cross section, which are particularly easy to cast oe.ritrifilsal'lfy In Fie., 1` for e2tarrliolelv two reir1 forcing members SQ are shown disposed in the lower zone,y which must be, marked. as such so as to, ensure that. the beamis built into-the wall or' @our correctly. At other parts of the tubular beam' weaker members 2t are provided, to hold the surrounding. reinforcement or rings in. position. Since these are connected to the longitudireinforcing bars at individual points, a stiff Yreinfbrcir-lg frameworkv is formed, whichl increases the carlifyifnsy Capacity of the' hollow beamcompertson to one formed by molding aindfcomnressing only. In this manner, they newbeam a combination of a tube and of usual; beams of reinforoed concrete. iiithertfal the reinforcement off the tubes was evenly distributed, whilethe usual. beams are provided with loneitudinalbars only in the Zone or"` tensile stress upwardly bent.- parts to endure the thrustl and with. ,stirrups. Accordingto the. invention, the mainlongit'ud'i'nall reinforcement is the same as in the usual beams, but. a secondary longitudinal reine forcement. is distributed over the other parts of tile cross.- sectional v4a1`"ea.andfr bothi reinforcements are' interconnected by? a surrounding reinforcenient forma rigidi frame workl so that they ,works intly.

Instead' ofthe bodies 2V, which fill up the whole space between two adjacent carrier beams l, concrete connecting arches may be constructed between the carrier beams with the aid of arched shuttering, which may be disposed at any desired level, since they do not take compression stresses. The flat lower surface may be made for example by a suspended trimming secured to wires which extend from the hollow beams.

In the embodiment according to Fig. 2 a reinforced concrete plate i is disposed between two adjacent hollow beams l flush with the lower surface thereof, whereby not only is a thorough concrete surface obtained as an underface, but erection without shuttering is made possible, since only ready made concrete parts are to be connected together. The slabs or plates 4 are held in place by wires 5, which are connected to the reinforcing wires 6 of the slabs. The ends of the wires t which extend from the slabs are bent to form eyes and the wires are secured, for example, to the hollow beams I. In the space above the slabs 4 a oor filling 'I, for example, ashes, cinders or the like is disposed. If the space is filled with concrete, it is sufficient to attach the upper ends of the wires 5 temporarily to the beams I, since after the concrete has hardened they become fixed therein.

As shown in Fig. 3, the slabs Ia may also be secured in position by a rabbet joint, the tongue 8 being formed in this case on the beams I2L and the groove 9 on the slabs, but this arrangement could of course be reversed. The tongue 8 may extend over the whole length of the beam, or it may be of short lengths distributed over the length of the beam. If a plane undersurface is not required, the slabs 4' are disposed at a higher level, as shown in Fig. 4, in order to reduce the quantity of floor filling required. Another construction of this kind is shown in Fig. 5, wherein the slabs 4 rest on ledges 2| of the beams Ib.

Fig. 6 shows an embodiment of the hollow beam, which forms a closed plane concrete underface if the beams are placed side by side. In this embodiment the width of the underface I0 is equal to the width of the beam I. This construction is suitable for centrifugally cast hollow concrete beams of light cement (pumice cement). The smaller strength of the light concrete hitherto prohibited its use for carrying bodies. However, the strength is increased by the centrifugal process and thus the above objection is eliminated. It is of advantage that by the employment of light concrete beams placed side by side as floor carriers insulation is also assured.

According to Fig. 7 the lower zone of the beam le is widened by the provision of two lateral extensions I I. In this case again a closed underface is obtained by placing the beams side by side. A saving of material is effected by providing a constriction I3 where the extensions IIe join the walls of the hollow beam.

AsV shown in Fig. 8, slabs 4f may also be employed in connection with hollow beams provided with extensions Ilf, so that the beams according to Fig. 7 may be spaced in the same manner as adhere to the lower face of the beam and form a continuous under face when the beams are placed in position side by side.

Although the employment of the centrifugal casting process generally is not essential to form thetube with greater thickness of the upper zone, such reinforcement may be employed in some cases. Fig. 9 shows such a construction with reinforced upper zone I5.

If the beam is to be utilized as a window or door joist or as a sill, any one of the cross sectional forms Ydescribed above may be employed. As summers beams of the cross section shown in Fig. 10 are particularly suitable. In this form the beam Ig is formed with ledges 2|g similar to the ledges 2l of the beams shown in Fig, 5, such ledges acting as supports for beams or the like. By the provision of projecting iron parts and subsequent trimming it is possible to connect together summers, beams and slabs to form a monolithic whole.

It will be understood that in Figs. 2-10, the

Vbeams are reinforced in the manner described and shown in Fig. 1. We claim: Y A reinforced oentrifugally molded concrete beam, said beam being substantially tubular in cross section, at least two longitudinally extending reinforcing members formed in said beam adjacent one surface only thereof, the part of the tubular wall opposite that part of the wall containing the main reinforcement being thicker than the other parts, a plurality of spaced and transversely arranged and substantially annular reinforcing members in said beam, said members being connected to said longitudinally extending reinforcing members whereby to form a stiif three-dimensional frame work for said beam.

PAUL ABELES. ERNST BRAUNBOCK.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Datel 406,209 Meyenberg Sept. 29, 1891 974,868 Ericsson Nov. 8, 1910 1,172,375 McCabe Feb. 22, 1916 FOREIGN PATENTS Number Country Date 85,684 Switzerland July 1, 1920 46,510 Denmark Nov. 21, 1932 44,329 Switzerland July 20, 1908

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