US1720693A - Precast-concrete-beam construction - Google Patents

Description

July 16, l929 vR. sAHLBx-:RG 1,720,693'

PRECAST CONCRETE BEAM CONSTRUCTION Filed Aug. 25, 1927 7e3 l J2 J3,

INVENTOR A zy .M443

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'13 ATTORNEY:

Patented July 16, 1929.

UNITED STATES PATENT OFFICE.

ROLF SAHLBERG, OF NEW YORK, N. Y., ASSTGNOR TO THE AEROCRETE CORPORATION OF AMERICA, OF NEW .YORK, N. Y., A CORPORATION OF DELAWARE.

PRECAST-CONCRETE-BEAM CONSTRUCTION.

Application filed August 26, 1927. Serial No. 215,569.

This invention relates to beams and particularly to beams which are of precast concrete construction. More especially, the invention relates to beams adapted to form a floor when laid side by side.

Concrete buildings have been constructed for many years by building forms or molds on the site where the building was to be erected, and pouring these forms with concrete mixtures which were also prepared on the site. This method of constructing concrete buildings, however, has a number of disadvantages, among which are the necessity of building entirely new forms for each job, a comparatively large amount of time required in mixing and pouring the concrete,'the time necessary for the concrete to set before continuing other parts of the building construction. the difliculty in properly supervising the mixing of the concrete so as to secure the required strength, and the comparatively large expense in finishing the poured concrete surfaces, which because of the rough character of the forms or molds used, is apt to be unsightly.

These disadvantages are to a large extent overcome by constructing a concrete building trom precast concrete elements, which can be carefully manufactured under factory conditions where the concrete mix is carefully watched in order to give the desired strength, and where nicely made molds can be used with economy, thus giving a comparatively good finish to the molded surfaces. The term precasting"7 therefore means the casting of the concrete building elements from suitable moldable materials priorto the construction of the building in which the elements are to be used. lVhen the elements are made in this way it is convenient to allow the full time required for the concrete to set before placing the elements in the building, and in this way buildings can be put up 'comparaH tively quickly.

Accordingly, the general object of the present invention is the provision of a particular building element of this type, namely a beam or floor member which is capable of being precast, and which, because of its particular construction, can be assembled in the building 'with great facility.

The invention involves especially the constriuei'iimi of haar element mf 'hema merle of a combination of materials, one relatively stronger than the other, in such manner that the stronger material is rendered capable of withstanding the greater part of the bending stress produced by the load carried upon the iioor or beam, and the weaker material is so associated with the stronger material that the load upon the weaker is transferred to the stronger.

Another object of my invention is the provision of a reinforced beam which will be of relatively light weight compared with the load which the beam is capable of carrying.

The invention will be better understood -by vreferring to the accompanying drawings,

which illustrate by way of example one einbodiment of the invention. In these drawrugs:

Fig. 1 is a somewhat enlarged plan View of my improved precast beam or floor member;

Fig. 2 is a cross sectional View taken on line 22 of Fig. 1 through the intermediate portion of the beam;

Fig. 3 is an end view of the beam;

Fig. 4l is a section taken on line 4-4 of Fig. 1, showing the transverse reinforcement;

Figs. 5 and 6 are respectively a side view and a plan on a reduced scale of a plurality of the beams shown in Fig. 1 assembled both side by side and end to cnd to form a portion of a floor, the supports for these beams being indicated diagrammatically; i

Fig. 7 is a fragmentary sectional viewtaken on line 7 7 of Fig. 6 showing the manner in which the upper corners of the beams are joined in order to form a continuous smooth floor surface Y Fig. 8 is a fragmentary section taken on line 8 8 of Fig. 6, showing the construction of longitudinally spaced keys which serve to y lock adjacent beams together;

Figs. 9 and 10 are detailed views of the reinforcing bars used in each beam;

Fig. 11 is a detailed view of the tie bar orrod which is employed for locking the beams'togcther end to end;

Fig. 12 is a greatly magnified section similar to Fig. 2 showing how the strength-giving sections and the floor-area-malring sections of the beam are interlocked with one another; and

Fig. 13 is an end view of a modification.

Referring new te the. acompa dra-ivm ings and particularly to Figs. 1, 2 and 3, the improved beam is composed principally ot moldable material 2() which is relatively light in weight and I prefer to employ for this purpose a material which has now come to be known as light weigl'it concrete or expanded co creto or cellular, vesiculated orvporous concrete. Concrete of this character may be produced in a number ot dil'lerent ways, but the most satisfactory light weight concrete of which I am aware is made by mixing finely powlered aluminum with the other materials entering the concrete mix. The powdered aluminum reacts with the lime, or other alkaline constituents ot thc mixture in the presence of water to form hydrogen. rlhe mixture ot thc concrete is so manipulated that the generation of this gas takes place to a large extent after the concrete has been poured, so that the gas causes the concrete to rise in somewhat the same manner as yeastI causes dough to rise, the bubbles of gas thereby forming 'innumerable voids or spaces evenly distributed throughout the concrete mix. Light weight or expanded concrete made in this manner is described in Patent No. 1,087,098, granted to J. W. Aylsworth and Frank Il. Dyer on February 17, 1914.-.

As was stated above, the relatively light material constitutes the principal portion of the beam. A section 21 is provided, however, to supplement the strength ot the material 20 so as to give the beam sufficient strength to support the load which it is intended to carry. This strength-giving section 21 is composed of any suitable moldable material, such for example, as ordinary concrete, that is, dense concrete, which has not been expanded or aerated by means of gas as referred to above, or section 21 may be of metal, such as steel, of particular torni, as will later appear. The section 21 is intended primarily for the purpose ol giving strength to the beam and lor this reason it extends substantially throughout the depth ot the beam, and is relatively narrow compared with its depth. Section 21 is provided at its upper part, however, with a transversely extending portion 22 lor the purpose of strengthening the beam sidewise. Although the material 2O possesses a remarkably high degree of strength 'for its weight, the principal purpose which is served by this material is that of providing surface area for the beam. The material 2O constitutes therefore the areaA making portion of the beam. The expanded or aerate-d concrete referred to above is well adapted for use in molding the area-making section 20 because it possesses a remarkable strength for its weight, and is especially well adapted in making beams that are intended to serve vas lloor elements inasmuch as this material is highly resistant to abrasion and wear,l and to the transmission of heat and sound. The strength-giving section 21 may be placed either centrally of the area-making portion 2() as illust-rated in Figs. 2 and 3, or at one side thereof, it' desired.

The improved beam illustrated in the accompanying drawings is reinforced by steel rods 23 ol the general shape shown in Fig. 9

.running longitudinally of the beam, and also by other steelrods 24 shaped as shown in Fig. 10. T he rods 24 are placed in thc area-making section shown in Fig. 2, and rods 23 in the dense concrete section. Transversely positioned steel rods 25 are provided at spaced intervals throughout the length out the beam as indicated generally in Fig. 5.

rllowards cach end of the beam the strengtlu giving section 21 is increased in width as may be seen in Figs. 1 and 3, both at its web portion 26, and at its upper transverse por tion 27. Also a lower transverse portion 28 is provided at these same regions, so that at each end of the beam the strength-giving section 21 is o't general Ibeam shape, as may be seen in Fig. 3. rlhe purpose of this change in, 'torn'iation of the strength-giving section 21 is to provide increased strength at cach 'end olf the beam near the supports.

Reference should be made to Figs. 5 and G in connection with the previous iigures lior an understanding of the remaining` details of the improved beam construction. Figs. 5 and 6 illustrate two beams laid side by side, and two similar beams also laid side by side and placed at the ends of the first two beams, thus forming a small section of floor. In securing the beams together at their ends a channel 29 is provided in the upper transverse part 27 ot the strength-giving section 21, and when these channels 29 in two beams placed end to end are aligned, a reinforcing rod 30 (see Figs. 3, 5, 6 and 11) is laid in the channel, and dense concrete poured around it. In this way each beam is individually locked at its ends to the next beam beyond it.

The beams are provided at their corners with shallow grooves 31 running longitudinally throughout the lengtli ol the beams, and when two beams are placed side by side these grooves form a channel 32 (see Figs. 6 and 7 At intervals the grooves 31 `are deepened to a point near the bottom ot the beams as shown in Fig. 8.' These deepened channels olf adjacent beams form pockets and the walls of these pockets are made oi bulging formation having sides sloping gently from the top away from the vertical, and then at a point toward the bottoni quickly sloping back as indicated at 311 to the side of the beam.

The channel 32 and the pockets 33 are filled with a dense concrete mixture or cement after the beams have been finally placed in position, and the cement in the channels 32 serves to connect the floor elements making a smooth continuous lloor and doing Cil away with cracks. The cement in the spaced pockets 33 serves to key the adjacent beams together. That is, because of the bulging side walls of the pockets 33 whenever a greater load is placed upon one beam than its neighbor, any consequent defiection in that beam is transferred from one beam to the other through thel shearing stress of the cement keys.

In manufacturing my improved precast beam a suitable mold is prepared having the appropriate conformation to form the grooves 31, and their deepened portions corresponding to the pockets 33, and then the strength-giving section 21 of relatively dense material, and the area-making portion 20 of relatively light material are poured in any suitable manner.

The modified form of beam or floor element shown in Fig. 13 is provided with a strength-giving section of metal, such as steel, instead of the strength-giving section 21 of dense concrete. The web 26 of this steel section is, however, of uniform and relatively narrow width throughout the length of the beam, and is not widened at the ends as is the web 26 shown in Fig. 3. Also the upper transverse portion 27 is of uniform width throughout the length of the beam, whereas it has already been seen in Figs. 1 and 3 that the corresponding portion of the concrete strength-giving section 21 is widcned at the ends. The transverse portion 28 of the steel reinforcement is, however, of the same general shape as the portion 2S of the concrete strength-giving section. As in the case of the all-concrete floor member or beam, the floor element shown in Fig. 13 is constructed principally of light weight concrete 20, which is preferably the same kind of concrete as the material 20 which has been previously described. Channels 29 are provided in the metal strength-giving section of the modified beams similar to the channels 29 in the all-concrete bea-m.

By referring to Fig. 12, the interlocking of the two sections 2O and 21 when section 21 is of concrete will be understood. The relatively large pores in the expanded concrete 2() form numerous pockets of relatively large size into which the particles of the denser concrete 21 readily penetrate so that after the pouring of the two sections of the beam is completed they are both firmly and inseparably bound together.

It will be understood that any suitable aggregate material may be used both in the preparation of the relatively dense concrete forming the strength-giving section 21, and also in the preparation of the light Weight concrete forming the section 20. For example, ordinary crushed stone might be used as aggregate in the mix for the relatively dense concrete, and porous slag having extremely light weight, such, for example, as

described in the pending application of Emrik Ivar Lindman, filed November 21, 192V, Serial No. 70,695 might be used as aggregate in the mix for the light weight concrete 20.

That I claim as my invention and desire to secure by Letters Patent of the United States is:

1. As an article of manufacture, a beam having a strength-giving section of relatively strong material, and an area-making portion of relatively light material, the strengthgiving section being relatively narrow and extending substantially throughout the length and depth of the member, and the areamaking portion being relatively wide and secured to said strength-giving section throughout the depth and length of the member.

2. As an article of manufacture, a beam of molded material having a strength-giving sect-ion of relatively strong material, and an area-making portion of relatively light material, the strength-giving section being relatively narrow and extending substantially throughout the length and depth of the member, and the area-making portion being relatively wide and secured to said strength-giving section throughout the depth and length of the member.

3. As an article of manufacture, a beam composed principally of light weight concrete and having a section of dense concrete extending substantially throughout the length and depth of said member, the said light weight concrete and dense concrete sections being inter-locked with one another throughout their entire contacting surfaces so as to aid the light weight concrete to transfer its load to the dense concrete.

el. As an article of manufacture, a beam having a strength-giving section of dense concrete, and an area-making portion of light weight concrete, the strength-giving section being relatively narrow and extending substantially throughout the length and depth of the member, and the area-making portion being relatively wide and secured to said strength-giving section throughout the depth and length of the member.

5. As an article of manufacture, a beam having a strength-giving section of dense concrete, and an area-making portion of light weight concrete, said strength-giving section having a vertical web and a transverse portion, and extending substantially throughout the length and depth of the member.

6. As an article of manufacture, a. beam having a strength-giving section of dense concrete, and an area-making portion of light weight concrete, said strength-giving scction having a vertical web and a transverse portion extending substantially throughout the length and depth of the member, and said strength-giving section being wider at each end of the beam than at the central portion concrete and dense concrete Sections being thereof. nterlocked With one another throughout 10 7. As an article of manufacture, a beam their entire contact-ing' surfaces so as to aid comprising a plurality of sections of light the light Weight concrete to transfer its load 5 Weight concrete and a section of dense conto the dense concrete.

crete, the Said dense concrete Section extend- In testimony whereof I affix my signature.

ing substantially throughout the length and v depth' of said beam, and the said light Weight ROLF SAHLBERGr.V

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