US2375744A - Half-tubular reinforced concrete beam for use in building construction - Google Patents

Description

M y 1945- P. w. ABELES 2,375,744

HALF-TUBULAR REINFORCED CONCRETE BEAM FOR USE IN BUILDING CONSTRUCTION Filed May 1, 1941 INVENTOR PAULWILLIAM ABELES P MiMMu Patented May 15, 1945 HALF-TUBULAR REINFORCED CONCRETE BEAM BUILDING CONSTRUC- TION 1 rainy/imam Alleles, London, England ApplicationMay 1, 1941, Serial No. 391,358 In Great Britain March 13, 1940 t v a Claims;

This invention relates to improvements in half-* tubular reinforced concrete beams for use in building'construction, more particularly in floor and ceiling constructions, and provides new and advantageous forms ofsuch beams which combins great strength and carrying capacity witha relatively small weight and a reduction in the amounts of reinforcement and concrete hitherto considered necessary.

According to the invention, areinforced concrete beam for building constructions 1" is formed by centrifugal mouldin into half-tubular form with a substantially semi-cylindrical cavity, the external cross-section of the beamincluding one Or more substantially straight lines, and transverse reinforcement members are fixed in predetermined positions within the beamby the engagoment thereofwith the longitudinalreinforcement members usually provided in i such beams, such transverse members being subjected auto matically to an initial tension due to the centriiugal method of casting the beam, thus in creasing the carrying capacity of the beam due to the consequent reduction in the principal stresse thereof, and rendering it possible toem ploy reinforcement members of less weight than hitherto normally employed, and further to construct beams with walls of a thickness which is relatively small in comparison with the thickness of walls of previous beams. These reductionsin the amounts of reinforcement and concrete af; fordedr by the beams of the present invention are permissible in view of the added compactness and density which is known to result together with increased compressive and tensile strength concrete structure formed by centrifugal moulding, combined withuthe results of theiinitial tensionto which the transverse reinforcement members are automatically subjected by such centrifugal formation. The transverse members being engaged with the normal longitudinal reinforcemerit, forces are set up in the concrete opposite 3 to the strainsto which the beam are subjected in use, and the principal stresses to which the beamis subjected in use are considerably reduced.

According to the invention, such above deaddltion in situ of a concrete or similar filling in the cavity, or may be laid with the cavity upwards the cavity thereafter being filled with concrete or similar filling, or provided with reinforcing concrete ribs. The said beams may also be employedas shuttering, in which case concrete is poured into the cavity in situ to form a girder, or they may advantageously be similarly employed as purlins, beams or the like.

The semi-tubular beams of centrifugally moulded reinforced concrete inaccordance with the invention may be laidfside by side in the construction of a floor or of a ceiling, or may be laid spaced apart, such spaces being bridged byslabs of concrete, brickwork or other suitable material.

By reasonof the centrifugal method of manufacture of beams in accordance with this invention, and the consequent automatic application to the transverse reinforcement members thereof of an initial tension, it is possible to employ beams with relatively thin walls without reducing. the carrying capacity required of beams having walls of normal thickness, and without incurring the risks of the developmentof cracks during transport or erection, or while in service.

Consequent upon the added strength. of beams in accordance with the invention rendering possible the employment of beams with relatively thin walls and reduced weight, the further; ad-

vantage is obtained that when a floor structure scribed half-tubular beams are provided withshoulders and/or recesses in the external perimetersthereoffand if desired also in the cavities thereof, for purposes hereinafter more fully disclosed.

'Such semi-tubular reinforced concrete beams may be used in, the construction of floors laid with the cavity downwards, with or without the is construetedwith the improved beams, a :relatively very small average floor thickness can be obtained compared with normal concrete floor structures, with the advantages of savingin space between floors and in the weight not only of the floor itself, but also of the load carried by the walls of the building or the supporting columns or standards, and thus eventuallyin the iload actingupon the foundation of thebuilding. 3A

saving in the costs of building is thus. rendered possible, sincethe dimensions of the foundations and the supporting members can be reduced to correspond with the reduced load which has to be maintained; t

A further advantage of beams according to the invention when employedwith the cavities1there-- of upwardly disposed, e. g. when used, a shut tering, lies in that the increased resistance to the formation of cracks in the concrete under load makesit possible to reducethe number of, or entirely to dispense with, theusual intermediate propsor supporting-members between the walls or main support or columns;

The invention will now be described with reference to the accompanying drawing, in which Figure 1 shows a section of a centrifugally moulded semi-tubular reinforced concrete beam in accordance with the invention,

Figure 2 is a section, through a flooring made from beams in accordance with the invention showing severaltdifferent methods of completion thereof.

Figure 3 is a section through an alternative form of flooring constructed with beams made in accordance with the invention; and:

Figures 4 and 5 are sectional1views showing:the manner in which such concrete beams may .be used as shuttering for girders, 7

Figures 6 and 7 are detail viewsshowing'means of providing anchorage for attachingisl'abs: on plates to a beam, and V Figures 8 and 9 are sectional views howing the manner in which beams in accordance with the invention are: used: as purlins; or flooring: members,

As shown in the drawing, a flooring; and ceiling or roofingmay'be formed; by a numberof. reinforced concretebeams of; substantially semicylindrical shape aaeither laid side by side :as shown in Figure; 2, or spaced apart from each other as. shown: in- Figure- 3, with the cavities. thereof downwardly disposed. Such beamsa-re formed by centrifugal. moulding in theknown manner, with. shouldersic, f, and g thereon. upon which may be securediceiling or flooring slabs of concrete, brickwork or other suitable materials as hereinafter more fully described, and with lateral externally-projecting flanges or extensions e.

The said'beams a may be provided with the following reinforcements: a main longitudinal tension reinforcement 5 a secondary longitudinal reinforcement'b' a transverse reinforcement 6 whichmay be in the form of a 'numberof single links; and if desiredwith a further transverse reinforcement; which may comprise ties D which may be combined-with the links b Alternatively the two, transverse reinforcements may be combined in'a continuous spiral, the parts 'of. which extendingacrossthecavityserving'as the ties b and the parts thereofembedded in the concrete servin as the links b Where"a'transversereingitudinal membersso as to determine accurately their distance from the exteriorof-the wall of the beam; i i

Longitudinal: reinforcementmembers-may project from :the; endstofzthewbeam ifdesired-in: the knownmanner irr order: to provide means for connecting the beams to cross beams; girders, spreader .beams,,-or,other structural elements; and ensuring,atrigidgconnection therewith.v a

. When beams according; to. the. invention .are used in theconstruction of .floorings, they may, be"

laid sideiby side, as shown in Figure 2, and; connected, by; cement or; other. mortar. m, eitherzsin.

the:- form of spaced ribs or extending-1., along the entire lengthuof, the adiacent, beams, Alterna tively, as also shownuinsFigurezgthespace be- The necessary-fixing of the-positions tween two beams may be filled with a light concrete or other filling p. The adjacent beams thus act together and a uniform deflection is ensured.

Where a wooden floor surface is desired, joists n for boards 0 may be supported on the cement filling m, which is here preferably provided in the form of spaced ribs; the remaining spaces between the beams being further provided with filling or not, as desired.

Where a plain concrete floor surface is required, this may be provided by the upper flat faces a of the inverted. beams together with either the uppenfiush surfaceiof a filling such. as p, or by the provision ofi'c'oncrete flooring slabs q, su ported on the shoulders 9'.

Theceiling formed by the undersurface of such flooring constructions using beams in accordance with theinvention maybe left with the cavities of the beams visible, or a plane surface therefor may be provided, either or concrete, brickwork or other desired material, For this purpose, recesses havingy shoulders c are formed ill-13116811618 of the cavities of thebeams, and slabs-or plates d of. concrete or brickwork are secured in position. against such shoulders cin any convenient manrier. For example, the ends of: link members. 11 i may be arranged to, project laterally from the external walls of. the beam tov provide anchoragesupon which such slabs or plates- 11 may be secured, or members suchas -fiat metal strips or .bars Z (Figure. 6), or. wires, o1: cylindrical rods, or

latlris. or, dowels countersunk longitudinally or transversely inthe beams may be provided.

As shown in Figure 6, the fiat metal strips 2 may be passed around the reinforcement members b in the formation of the beam a, the ends thereoff projecting from the inner face of the beam into" itscavity, or" as shown in Figure 7, where no shoulders: care provided in the beam, the strips Z passing round the reinforcement n'iei'ii; bers' b project downwardly and are then bent l as shown to lie transverselyacross the cavity in. the beam. In'either case, such projectingparts Z serve to' form an anchorage to which may besecured'slabsor plates d ofcdncret'; cement or the-like. V

In "constructing such a con'crete surfaced ceil-- ing' ,the concrete slabs-orplates d maybe secured. in position by pressure mouldin'g the same upon; theshoulders a before the beams a're 'placetl position; acorebeing insertedfinto the cavity-"of" e'a'chbeam- (thecavity; being uppermost: durin moulding) and removedafter iriolding haseffected; i I

When a flooring is fcrmed rbyb'eams l-accor'dinglf: to the'invention spaced apart onefrcmi the other}. as shown in Figure 3, ceiling slabs-lr o f :con'creteor other desired materialiare:securedlfintposition by' the engagement or projecting; parts thereof withiithe shoulders fpreviously-referred to The beams: of thiswinvention' are also read-ily applicable: t'OLti'OOf constructions; and for 'useas== arezadvantageously formedwith a greater'height than, width,.- whereas when gemployed for fiooring constructions,-. the :beams are preferably formed with. the width .-thereofgreater than-theheight,

orwith; a-somewhat flattenedarch,,;thusreducing;

the 'total amount of concrete per square'yard offloor normally necessarywith beams of greater height; a $.b-W iw t 2,375,744 I tudinal reinforcement b 'is situatedin the top of the arch, and a secondary longitudinal reinforcement b is advantageously provided to ensurean anchorage at or adjacent the ends of the semicylindrical walls, serving; to provide an anchorage:-

for transverse reinforcement members b Lat:

eral extensions e of the beam serve as enlargesimilarly project into the space 12 as shown in Figure 4, and if desired, an additional longitudinal reinforcement t with transverse reinforcing membersu may be provided in such cavity 10 as shown in Figure 5, so as to provide a suitable tensile reinforcement for a concrete girder formed by pouring concrete into the space 12 the beams a then acting as shuttering. I In flooring construction employing beams a with, their cavities upwardly disposed, lateral shuttering above the beams may be provided by the use of suitably shaped slabs kof concrete or the like as shown inFiguresl and 5. Ceiling slabs W may be securedto the upper parts of the beams 01. below the flooring beams V as shown in Figure 5. j

Figures 8 and 9 show beams a laid with their cavities upwardly disposed as for use in-flooring or as purlins, roofing tiles, slabs or the like 7' being supported thereon when used as purlins, with concrete ribs h at intervals along the cavities thereof, such ribs h preferably being provided with reinforcement tie member's. As shown in Figure 9, flooring slabs qare supported on shoulders 0 formed in lateral extensions erof the beams, the cavities of the beams being filled with concrete or other suitablefilling, as shown. Instead of filling such cavities with concrete or the like, flooring or roofing slabs may be secured upon shoulders formed inthe insides of the cavicavity thereof. Such unitary structural elements havebeen found to be conveniently handled and transported and enable flooring and roofing constructions to be built in situ with a considerable saving of labour and inconvenience on the site.

Having now particularly described and ascertained the nature of mysaid invention and in What manner the same is to be performed, I declare that What I claim is: l

1. A reinforced concrete beam for building construction, formed of concrete centrifugally moulded into half-tubular form comprising a plurality of longitudinally disposed reinforcement members within the concrete, and a plurality of transverse reinforcement members within the concrete, which transverse members en gage said longitudinal members, and are under tension applied by the centrifugal motion that moulds the beam, which tension is maintained in said transverse members by the hardening of the concrete and wherein an additional reinforcement member of. steel engages a pair of the lonties, for example as shown in Figure 2 with reference to the ceiling slabs d.

According to a modification of the invention,

unitary structural elements for use in building may be formed by I beams as hereinabove described, having slabs or plates of concrete, ce-

'gitudinal reinforcement members and extends across the cavity of the half-tubular beam.

2. In a concrete beam for building construction, made centrifugally into half-tubular form with longitudinally disposed reinforcement bars of steel, the improvement comprising a transverse reinforcement member of steel wire under tension which is impressed by the. centrifugal force used informing the beam and which tension is maintained by the hardening of the concrete, such wire member being in the form a loop which engages a plurality of longitudinal reinforcement members, a section ofwhich'loop is within theconcrete of the beam anda section of which extends across the cavity thereof.

3. In a concrete beam for building construction, made centrifugallyinto half-tubular form with longitudinally disposed reinforcement bars of steel, the improvement comprising a transverse reinforcement member of steel wire, under tension which is impressed by the centrifugal force used in forming the beam and which tension is maintained by the hardening of the concrete, such wire member being in the form a

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