US871075A - Reinforced steel beam. - Google Patents

Description

No. 871,075. PATENTED NOV. 12, 1907.

' E. SWENSSON.

REINFORCED STEEL BEAM.

APPLIOATION FILED JUNE 17, 1907.

lERIC SWENSSON, OF MINNEAPOLIS, MINNESOTA, ASSIGNOR TO MINNEAPOLIS STEEL &

MACHINERY COMPANY, OF MINNEAPOLIS, MINNESOTA, A CORPORATION.

REINFORCED STEEL BEAM.

Specification of Letters Patent.

Patented Nov. 12, 1907.

Application filed June 17| 1907. Serial No. 379.362.

To all whoml it may concern.;

A Be it known that I, ERIC SWENssoN, a citizen of the United States, i residing at Minneapolis, Hennepin county, Minnesota,` have invented certain Improvements in Reinforced Steel Beams, of which the following is a specification.

The object of this invention is to provide a steel beam, reinforced by concrete, which Atwo materials in combination make a beam strong enough to carry theentire dead and live loads upon said beam, whichis to be an integral part of any structure suitable for this kind oi construction. Said combination of two materials, steel and concrete, is intended to provide a maximum of strength together with a minimum of material, Awith certainty, ease and facility of erection, and also intended to constitute an improved fire proof construction.' l

To this end the invention consists in the constructions and combinations hereinafter described, and particularly pointedout in the claims.

In the accompanying drawing, forming part of this specification: `Figure 1 is an elevation, partly broken away, of-a beam embodying my invention andshowing in general its arrangement and details. Fig. 2 is a transverse vertical section of the same beam. Fig. 3 is also an elevation of a modied beam embodying my invention. Fig. 4 is atransverse vertical section of the beam shown in Fig. 3.

1n carrying out this invention, I provide an I-section formed, preferably, of the upper and lower angle'- irons, one pair l and one pair 2 laced together by the diagonal bars 3. A single system of these bars may be employed, as shown in Fig. 1 or a double system as shown in Fig. 3. In any case, this web lacingis to be suiiicient to provide for any web stresses in the beam,

and concretev further on mentioned, to provide for possible web stresses when the beam is in full action under total dead and live loads.

-I make thel steel section at the top of the beam much smaller than the steel section at the bottom of the beam, because the concrete will resist most of the compression at the top, while the concrete, being Weak in tension, cannot resist the tension at the bottom of the beam, which tension therefore has to be resisted almost entirely yby the steel reinforcement. To providel this difference between the sectional area of the steel at the top of the beam, and the sectional area of the steel at the bottomof thebeam I can make the sectional area of the angle-irons at the bottom of the beam larger than the sectional area of the angle-irons at the top of the beam. But s. better construction admitting of closer adherence to requirements found by theoretical investigations, and in general admitting of greater' variation and. ease of construction, is to insert at the bottom of the beam, in addition to the angles 2. of the same sectional area as the angles 1, the rods 4. These rods 4, besides giving facilities for obtaining the exact cross sectional area of the steel required atthe bottom of the beam, also admit of increased economy, because by varying the lengths of these rods I can provide a steel section at the bottom of the beam more closely corresponding to the requirements of the pending moment under which the beam is acting, than otherwise would be possible. These rods 4, preferably will be bent up at ends and fastened rigidly to the lower angle-irons.

Outside the I-section and at a small distance from the face of the concrete, as shown in Figs. 2 and 4, I provide a strong steel Wiring 5. This Wiringis Wound the Whole length of the beam with either a constant or a varying pitch. This Wiring to be held in place .to its proper pitch by suitably arranged longitudinal spacing bars, rodsor Wires 6. The purpose of this wiring is to increase' the compressive resistance of the concrete, and to prevent the concrete from disintegrating or flaking ofi the steel during stress. My experiments have shown that if this wiring is rightly proportioned, as to size and pitch, the concretewill adhere to the steel and take its proper share of the stresses engendered by the loads under which the beam is acting, even when these loads will rupture thesteel framing. This the concrete otherwise will not do. But also, in addition to thus greatly increasing the strength of the beam this wiring also greatly increases the fireproof qualities of the construction,

vbecause even under most severe fire the concrete will crack off only until the Wiring is reached and no furY ther, thus leaving the strength of .the beam nearly unimpaired. In fact, this Wired concrete will have the same fire resistance relative to the plain concrete as Wire glass has to plain glass.

Thus it is to be clearly understood that this reinforced steel construction of beams here shown and described has for its object not only the use of concrete as a necessary reprooiing, but also its use as a large and important factor contributing to the carrying capacity of the beam, the wiring greatly augmenting the strength of the concrete; said Wiring also making the concrete act conjointly and lharmoniously with the steel framing, thus enabling me to attain the same simultaneous factor of safety in both materials, all which full size tests made by me has shown to be true.

I do not limit myself to the details of the construction, as these maybe varied in many particulars withoutI departing from my. invention, the accompanying drawings, together with above description being intended vto show only fundamental essentials.

I claim as my invention:

1. A reinforced steel beam comprising, in combination, an I-section formed of upper and lower' angle-irons laced together, a. steel wiring surrounding said I-section, and a concrete filling, substantially as, described.

2. A reinforced steel beam comprising, in combination, an Ilsection formed of upper and lower yangle-irons laced together, a steelwiring of varying pitch surrounding said I-section, and a concrete lling, substantially as detogether, the angle-irons at the top of the-beam being smallerthan those at the bottom of the beam, a steel wiring surrounding said I-section and a concrete filling,

substantially las described. f

5. .A reinforced steel beam comprising, in combination,v an I-section formed of upper and lower angle-irons laced together, the angle-irons at the top` of the beam'being smaller than those at the bottom of the beam, a steel 'combination wiring surrounding said I-section said steel wiring being held to its proper pitch and place by longitudinal spacing bars, rods, or wires, and a concrete filling, substantially as described. r

6. A reinforced steel beam ycomprising in combination an I-section formed of upper and lower angle-irons laced together, a system of'rods parallel to and near to the lower-angle-irons, a steel wiring surrounding said I-section, said wiring being held in place by longitudinal spacings,r bars, rods, or Wires, and a concrete llingg substantially as described.

7. A reinforced steel beam comprising, in combination, an I-section fprmedof` upper and lower angle-irons, one pair above, one pair below, diagonal lacing straps con-v nectiiig said pairs of angle-irons, a system .of rods parallel to and near`to the lower angleirons, said rods being otA 'different lengths asrequired by the bending moment under which the beam is calculated to act, .said rods also being rigidly fastened to the lower angleirons, a steel wiring surrounding said I-section and said rods, saidsteel wiring being held to its proper pitch and place byrlonigtudinal spacing bars, rods, or wires, and a 'concrete Iilling,'sub stantially as described.

Inwitness whereof,

I have hereunto set my hand this 7th day of June 1907,.

ERIC SWENSSON.

Witnesses VJ. B. EVA,

J. H. BALDwiN.

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