US2558946A

US2558946A - Reinforced cast structure

Info

Publication number: US2558946A
Application number: US517402A
Authority: US
Inventors: Fromson Bertram William
Original assignee: Individual
Current assignee: Individual
Priority date: 1943-11-19
Filing date: 1944-01-07
Publication date: 1951-07-03
Anticipated expiration: 1968-07-03

Description

y 3, 1951 B. w. FROMSON 2,558,946

REINFORCED CAST STRUCTURE Filed Jan. 7, 1944 2 Sheets-Sheet 1 y 1951 B. w. FROMSON 2,558,946

REINFORCED CAST STRUCTURE Filed Jan. 7, 1944 2 Sheets-Sheet 2 l atentecl july 3, 195i REINFORCED CAST STRUCTURE.

Bertram William Fromson, Weybridge, Surrey, England Application January '7, 1944, Serial No. 517,402

' In Great Britain November 19, 1943 Claims. (Cl. 72-40) This invention relates to the casting in-situ or precast work in concrete, or similar material, including a metal or like tension member.

Hitherto, in concrete construction, whether cast in-situ or precast, the tension member has been wholly embedded as reinforcement in the concrete. For example, in the casting in-situ and the precasting of beams, slabs, floors and the like in concrete or similar material, the usual practice is to arrange the concrete so that it not only forms the compression member of the structure but extends through the neutral axis, usually in web form, to constitute an essential part of the structure.

A function of the concrete or like material as a part of the structure is to secure and locate the reinforcement and to provide rigidity for such part of the structure, the tension reinforcement being required substantially to act only as tension members. Another and secondary function of the concrete or like material is to protect the reinforcement from corrosion. In consequence of its first named function the covering of concrete must be of sufficient thickness around the reinforcement of the web and tension members at least to provide a complete cover. In consequence, and for other reasons such as simplicity of manufacture, it is usual for the concrete of the web and tension areas to be of the same width and therefore of substantially rectangular cross section.

As the engineering principle involved provides that the relative efficiency of the fibres in tension or compression in any section of a beam or slab varies as the square of the distance of the relative 3 tension and compression fibres from the neutral axis it is clear that a beam or slab of rectangular section is most ineificient as a supporting medium because the greater "part of material comprising this medium is relatively near the'neutral axis and therefore does not act proportionately as a supporting factor.

It is even more apparent in the case of members of concrete or similar material which has practically no value in tension. As an example, in a rectangular concrete beam 20" deep by wide, the upper 2" of section across the 10" width will offer sufficient compressive restraint at 750 lbs. per square inch to support a given load, provided adequate tensional restraint is also offered in the lower part of the section. The 90% bal ance of concrete in thisbeam is of no further ciency relative to the neutral'axis. The weight 2 of the redundant 90% of concrete is relatively dead weight and requires additional tension metal and compressive values for its support, thereby increasing the section, both of the compression areas and tension members required.

Parallel conditions apply to floor and roof slab and retaining walls.

The invention comprises a structure which may be formed by casting in-situ, or precasting, beams, floors, slabs, walls and the like, in concrete or similar material, wherein a compression member formed of such material is cast onto an open-trussed arrangement of web and tension members of metal or other suitable material or bar-like form so that a part of said arrangement is embedded and a stressed part of the web and tension member arrangement is relatively exposed and outstanding from the said cast compression member. The expression bar-like form is used hereafter to include rod of round, square or any other suitable cross section such as I shape or other small girder section. The said web and tension member arrangement is of sufficient strength to support its own Weight and for the application of the superimposed cast-in-situ material. Also, the compression member may be cast onto the top of the web whilst supported by shutter-like means, which latter may be assembled and united with the web and tension members as a prefabricated unit before the compression member is cast onto the top of the web.

The object of the invention'is to provide a pro-fabricated combined reinforcement and shutter unit for concrete and like structures in which the reinforcements comprise an assembly of open web and tension members of bar-like form.

According to a preferred embodiment of the present invention, it is proposed to use prefabricated tension and web members of bar-like form preferably of metal, although they may be made of any other suitable material, the webs of said members being of open construction and arranged in such a manner that when the members are in position, concrete, or similar material, poured on them will bind around the top it is poured.

The combined tension and web members may be made prefabricated in standard lengths with flanges or plates at each end securely fixed by welding, or other means to the cranked tension bar or rod and parallel thereto but near the top of the web member to which it will also be securely fastened, the object being to have standard lengths of combined tension and web members with cantilever ends which may be reduced in length if found necessary to .suit any normal requirement, without resort to modification in the main combined tension and web structure.

In the case of a precast beam or slab this 'pre-fabricated tension and web member may be inserted into the form containing the wet concrete, until the concrete has set so that the combined tension and web member and the concrete will form a complete supporting unit. As the required concrete in a beam of this type is necessarily small in section, additional light reinforcement for the concrete may be included to offer greater strength in shipment and handling.

When in the construction of pre-fabricated combined tension and web members as described the webs are made with open spaces such as in a truss, these openings will be found extremely advantageous for the passage of pipes, conduits, ducts and the like, usually required in building work and such pipes, conduits, ducts and the like may be concealed without resort to an additional suspended ceiling, as for example by the provision of a false ceiling which may be attached directly to the tension chord of the complete unit. This false ceiling may be in fibre board, or the like, or in concrete, gypsum, or similar material plastered on metal lath attached to the lower tension chords, thereby rendering the otherwise exposed metal work proof against fire and minimising corrosional effect.

In the case of the precast unit, the concrete may be made sufficiently Wide across the top to form a complete floor or roof by placing these units adjacent to one another. Alternatively, the concrete may be made in comparatively narrow sections so that these units are placed at intervals with spaces in between, additional concrete may be added to fill the open spaces to form a complete slab, securely bonding in to the concrete top chord.

In the accompanying drawings:

Fig. 1 is a cross sectional view of part of a cast in-situ floor made in accordance with one example of the invention.

' Fig. 2 is a perspective showing one endof the pre-fabricated metal reinforcement of Fig. 1.

Fig. 3 is a perspective of one end of a spacing member shown in Fig. 1.

Fig. 4 is a detail perspective of a locking plate suitable for use in the construction shown in Fi 2.

Fig. 5 shows one end of an alternative construction of a pre-fabricated metal reinforcement according to the invention.

' Figs. 6 and 7 show further alternative constructions.

Fig.8 shows one end of one example of a precast reinforced concrete beam made in accordance with this invention.

Fig. 9 shows one end of another example of a pre-cast reinforced concrete beam made in accordance with the invention.

, Figs. 10 and 11 are diagrammatic compositeillustrations of floors constructed with pre-cast reinforced concrete beam made in accordance with the invention.

Fig. 10a is a detailed view of a fireproof unit.

As shown in Figs. 1, 2 and 3, the concrete of a floor is cast in-situ onto an arrangement of a web member 2| and tension members 22a and 22b Whilst supportedby shutter-like means comprising metal channels 23 secured to the web and tension members, and intermediate shutter channels 24. The web member 2| is of zig-zag shape, the upper ends of Which extend through slots in the channel 23 so that they are embedded in the concrete where they are secured by any suitable means, such as a slotted plate 25 (see Fig. 4)

which can be slid into position either above or within the channel and fastened by welding. The lower ends of the web members are located between and welded to the tension members. The intermediate shutters 24 are held in-situ by suitable pins or wedges 240. located in registering slots 23!) and 24b in the

channels

23 and 24 respectively. The ends of the channels 23 are strengthened :by end pieces 23a of heavier gauge for the better resistance of shear stress and the ends of the web and tension members are welded thereto. The channel 23 and end pieces 23a will hereinafter be termed the shutter plate. The girder members, each formed by a web 21 and two tension members 22a and 22b and the shutter-like channel 23, are pre-fabricated and may be placed in position, with or without intermediate shutter channels 24, and each suchchannel constitutes a compression member of suincientstrength to support the weight and operation of laying the concrete thereon, such concrete when set being keyed to the beam and itself 7 then forming a compression member. A ceiling 26 is shown, located against the web and tension members.

As shown in Fig. 5, the pre-fabricated beam member comprises a zigzag web member 21, a pair of tension members 28a and 281), a shutterlike channel member 2 9 and an end piece '3!) thereforof inverted T section, to which the ends; of the web and tension members are secured. The upper ends of the web member are secured to the channel as by plates 25 as shown in Figp l, whilst the lower ends are located between and welded to the tension members.

As shown in Fig. 6, the pre-fabricated irder member comprises two parallel web members 3! and '32 respectively, of zig-zag form, welded to tension members 33a, 33b and 34a, 34b respectively, and a single channel 35. Cross bracin 3B is provided for the tension members.

As shown in Fig. '7, there is a single web member 31 of zig-zag form, the alternate upper ends ofwhich are relatively off-set to each side of a single channel 38, whilst the lower ends are located between and welded to tension members 39a. and. 39b in the same way as in the examples previously described.

As shown in Fig. 8, a pre-cast concrete beam comprises a concrete compression member 40, cast onto a zig-zag web member 4! and a pair of tension members 42a. and 421), the ends of which have 'beenpreviou'sly welded to channelshaped end pieces 43. Such end pieces and the ends of the web and tension members are left projecting as shown beyond the concrete, which ends may be burnt off to any required overall length of beam. The upper loop ends of the-web member 4'! are embedded in the concrete while the lower loop ends are welded to the tension members.

As shown in Fig. 9, a :pre-cast concrete beam' comprises a concrete compression member 44, a

pair of parallel zig-zag "

web members

45 and 45 and pairs of tension members 41a and -'41b and 48a and 48b respectively. Located in the end of the concrete are metal sockets 49 adapted to As in the previously described examples, the upper loop ends of the web members45 and 4B are embedded in the'concrete while the lower loop ends are located between and welded to their respective tension members.

In use, as shown inFig. 10, a floor 5| is cast onto the top of a pre-laid assembly of pre-cast reinforced concrete beams, having concrete compression head members 52, web members 53 and a pair of tension members 54, the head members of which are reinforced laterally by stirrup members 55, shown dotted, and which head members support intermediate shutter plates 56. The two left-hand beams shown in this figure are similar in construction to that shown in Fig. 8. At the right hand side is shown a pre-cast beam of similar construction to that shown in Fig. 9, with a concrete top member 51, with a pair of web members 58 and tension members 59. As shown also in Fig. 10, the web and tension members may be protected from flre by terra-cotta or like baked members Bl] as shown in Fig. a, a pair of which are shown part assembled to the beam.

As shown in Fig. 11, a floor is composed entirely of pre-cast concrete beams, the concrete compression heads 6|, of which are reinforced laterally by metal stirrups 62, arranged in known manner. Such beams have web members 63 or pairs of web members 64 and

tension members

65 or 66. The joints between the beams will be grouted or flashed in the usual manner for floor construction using pre-cast units.

The invention is obviously not limited to all the details of construction of the examples above described, some of which may be modified without departing from the nature of the invention. For example, the truss-like arrangement of the web and/or tension members may be of different section in the length of the girder for the variation of the stresses therein.

What I claim is:

1. A concrete reinforcing and supporting structure comprising a plurality of spaced units, each unit having an upper shutter plate provided with spaced slots and having depending side flanges, a zigzag web member with the upper apices extending through said slots and secured therein, the lower apices of said web being secured between a pair of tension chord members, said zigzag web member being extended and secured to the undersurface of the ends of said shutter plate, the ends of said tension chord members being inclined upwardly and secured to the under surface of the ends of said shutter plate adjacent to said depending side flanges, and an intermediate shutter provided with depending flanges extending between the shutter plates of a pair of spaced units with the flanges of said shutter connected to the flanges of said shutter plate flanges to close the space therebetween.

2. A concrete reinforcing and supporting structure comprising a plurality of spaced units, each unit having an upper shutter plate provided with spaced slots and having depending side flanges, a zigzag web member with the upper apices extending throughgsaid slots and secured therein, the lower apices of said web being secured between a pair of tension chord members, said zigzag web member being extended and secured to the undersurface of the ends of said shutter plate, the ends of said tension chord members being inclined upwardly and secured to the under surface of the ends of said shutter plate adjacent to said depending side flanges, and an intermediate shutter provided with depending flanges extending between the shutter plates of a pair of spaced units with the flanges of said shutter connected to' the flanges of said shutter plate flanges to close the space therebetween, said depending sides of said shutter plate and intermediate shutter ,having corresponding openings and means passing through said openings for securing said sides together.

3. A concrete reinforcing and supporting structure comprising a plurality of spaced units, each unit having an upper shutter plate provided with spaced slots and having depending side flanges, a zigzag web. member with the upper apices extending through said slots and secured therein, the lower apices of said web being secured between a pair of tension chord members, said zigzig web member being extended and secured to the undersurface of the ends of said shutter plate, the ends of said tension chord members being inclined upwardly and secured to the under surface of the ends of said shutter plate adjacent to said depending side flanges, and an intermediate shutter provided with depending flanges extending between the shutter plates of a pair of spaced units with the flanges of said shutter connected to the flanges of said shutter plate flanges to close the space therebetween, a plate having slots open on one side, said slotted plate embracing the upper apices of said web and covering said slot in said shutter plate.

4. A concrete reinforcing and supporting structure comprising a plurality of spaced units, each unit having an upper shutter plate provided with spaced slots and having depending side flanges, a zigzag web member with the upper apices extending through said slots and secured therein, the lower apices of said web being secured between a pair of tension chord members, said zigzag web member being extended and secured to the undersurface of the ends of said shutter plate, the ends of said tension chord members being inclined upwardly and secured to the under surface of the ends of said shutter plate adjacent to said depending side flanges, and an intermediate shutter provided with depending flanges extending between the shutter plates of a pair of spaced units with the flanges of said shutter connected to the flanges of said shutter plate flanges to close the space therebetween, the depending side flanges of said shutter plate flaring inwardly and forming an acute angle with said plate, and the depending side flanges of said intermediate shutter flaring outwardly and forming an obtuse angle with said intermediate shutter.

5. A concrete reinforcing and supporting structure comprising a plurality of spaced units, each unit having an upper shutter plate provided with spaced slots and having depending side flanges, a zigzag web member with the upper apices extending through said slots and secured therein, the lower apices of said web being secured to a tension chord member, said zigzag web member being extended and secured to the undersurface of the ends of said shutter plate, the ends of said tension chord members being inclined upwardly and secured to a surface of the ends of said shutter plate adjacent to said depending side flanges, and an intermediate shutter provided with depending flanges extending between the shutter plates of a pair of spaced units with the flanges of said shutter connected to the flanges of said shutter plate flanges to close the space therebetween.

BERTRAM WILLIAM FROMSON.

(References on following page) REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Schulz July 25, 1905 Yeager Aug. 20,1929 Lucy Feb. 3, 1931 Tashjian May 5, 1931 Sealey Oct. 20, 1931 Schaab Oct. 4, 1932 Gentz 1 May 9, 1933 Number Number Name Date Young Nov. 21, 1933 Sahlberg Nov. 6, 1934 Kahn Mar. 26, I935 Fromson July 9, 1946 FOREIGN PATENTS Country Date Great Britain Dec. 5, 1905 Great Britain Feb. 13, 1919 Great Britain Dec. 30, 1926 Italy L. Feb. 22, 1939 Great Britain 1944