US2569669A

US2569669A - Beam connection for precast concrete members

Info

Publication number: US2569669A
Application number: US650495A
Authority: US
Inventors: Henderson Albert
Original assignee: Peoples First Nat Bank & Trust
Current assignee: Peoples First Nat Bank & Trust; Peoples First National Bank & Trust Co
Priority date: 1946-02-27
Filing date: 1946-02-27
Publication date: 1951-10-02
Anticipated expiration: 1968-10-02

Description

Oct. 2, 1951 A. HENDERSON BEAM CONNECTION FOR PR-ECAST CONCRETE MEMBERS Filed Feb. 27, 1946 Patented Oct. 2, 1951 UNITED ST TES PATENT OFFICE V 2,569,669 I r. i BEAM CONNECTION FOR PRECAST CONCRETE MEMBERS Albert Henderson, Pittsburgh, Pa., assignor, by mesne assignments, to Peoples First National Bank & Trust Compan y, Pittsburgh, Pa... a national banking association Application February 27, 1946,- Serial No. 650,495

This invention relates to a building construction composed of precast reinforced concrete members and, in' particular, to a connection between a, beam thereof and a supporting member such as a column.

In building structures composed of precast concrete members, it isfrequently necessary to provide a supporting member, such as-a column, with a'bracket secured thereto for supporting a, beam or girder. If the beam or girder simply rests on the upper face of the bracket, it develops a tension in the upper portion of the bracket'tending to pull it away from the supporting column. The bracket must, therefore, be specially reinforced and secured to the column by a connection of exceedingly great strength. I have-invented a novel form of. connection between a beam or girder, the bracket which supports it and the column to which the bracket is secured, whereby the aforementioned force is eliminated'and a compression force is developed instead, tending to hold the upper portion of the bracket in abut- 1 Claim. (01. 72108) ment with the supporting column. In a preferred embodiment of the invention, I provide a precast reinforced concrete beam or girder having upper and lower longitudinal bars embedded therein. A securing member such as a length of angle bar is disposed transversely at the ends of the girder and is welded to the upper reinforcing bars thereof. The angle bar is secured to the reinforcing bars embedded in the column. The column has a bracket secured thereto on which the girder rests. A connection is provided between the girder and bracket which tends to develop compression in the bracket on deflection of the girder under load.

A complete understanding of the invention may be obtained from the'following detailed description which refers to the accompanying drawings illustrating a preferred embodiment and modifications thereof. In the drawings,

Figure 1 is a partial, side elevation of acolumn having a bracket secured thereto and a girder mounted thereon and attached to the column and bracket;

Figure 2 is a: similar view showing a modified form of construction; and

Figure 3 is a similar view showing a further modified form.

Referring in detail to the drawings, a precast reinforced concrete column I 0 has longitudinal reinforcing bars ll embedded therein connected by transverse reinforcing rods l2 welded thereto. The column is preferably rectangular in section and the bars H are located adjacent the corners thereof. The rods l2 extend around the bars H. A precast reinforced concrete bracket I3 is secured to one side of the column. The bracket has reinforcing bars I 4 embedded therein, the ends .of which ar welded to pipe lengths I5 also embedded in the bracket and extending through the full thickness thereof. The pipe lengths l5 accommodate securing bolts [8 extending therethrough; "The heads of the bolts are provided with protective concrete covers H. The bolts l6 are threaded into nuts I8 embedded'in the column In. The nuts [8 are of extra length and are partly threaded on anchor bars l9 embedded in the column. Short anchor bars lBa embedded in thecolumn are welded to the nuts. These bars resist the shear stress applied to the nuts by the bond between the bars and the concrete of the column.

A precast reinforced concrete girder 20 has upper and lower reinforcing bars 2| and 22 embedded therein connected by stirrups 23 extending around the bars and Welded thereto. Alength of angle bar 24 is disposed transversely of the girder at each end and is welded to the ends of the upper reinforcing bars 2|. A notch 25 is formed in the upper face ofthe girder adjacent each end to permit the "insertion of bolts 26 through holes drilled in the vertical flange of the angle bar 24. The bolts '26 are' threaded into nuts 21 similar to the nuts l8. As in the case of the latter, the nuts 2'! are partly threaded on anchor bars 28 and are welded to short anchor bars 21a embedded in the column. As shown in the drawing, there is clearance between the angle bar 24 and the side of the column to permit the bolts 26 to be turned home so-as to tension the upper bars 2| of the girder. Strutsv 29 in the form of short bars are welded to the angle bar 24 and the ends of thelower bars 22 of the girders. The notch "25 may be filled with concrete after the girder has been placed on the bracket and secured thereto.

Pipe lengths 30 are embedded in the' girder adjacent the ends thereof and are welded to the re inforcing bars 2| and 22. Bolts 3| inserted through the pipe lengths 30 are threaded into nuts 32 embedded in the bracket l3 and welded to the pipe lengths I 5 thereof.

' By reason of the-means provided for securing the upper portion of the end of the girder 22 to the column, 1. e., the anchor bar 24 and bolts 26, nuts 21 and bars 21a, deflection of the girder under load will develop a horizontal compression in the upper portion of the bracket [3. That is to say, as the girder is loaded, the end shown the column. The bracket, furthermore, share the shear load on the girder with the bolts 26.

Figure 2 illustrates a modified form of column 35 having a bracket 36 cast integral therewith.

The column has longitudinal reinforcing bars 31 and transverse reinforcing" rods 39 similar to those of the column l0. concrete girder 39 rests on the bracket 35.. The girder has upper and lower reinforcing bars 49 and 6 I, the ends of which project beyond the end of the girder and are threaded. The column has nuts 42' weldedto the bars 31' thereof. Studs fi'ii'are threaded into the; nuts; The: studs pref erably have left-hand threads on their protruding ends whereby the bars may be secured thereto by nuts 44. When the girder has been secured to thecolumn, the space between them may be filled with concrete.

The bracket S'Bhas reinforcing bars 45 embedded therein; pipe lengths 46 are also embedded in the bracket and'are welded to the bars 45. Bolts 41 inserted through the pipe lengths 46 are threaded into nuts 48 embedded in the girder and welded tothe lower reinforcing bars 4! thereof.

It will be apparent that the construction shown in. Figure 2 serves inthe manner already explained in connection with Figure l to develop horizontal compression in the bracket on de flection of the girder under load. In Figure 2 this compression is applied partly to the lower studs 43, the tension beingcarriedby the upper studs.

Figure 3 shows a construction generally similar to that of Figure 2 with slight-modification. The bars 40' and 4! of. the girder 39- have their protruding ends welded to the endsoif anchor bars 50 embedded in the column 35". Sleeves of thermal insulating material, such as asbestos, are disposed about the ends of the bars 40, M and 59- to prevent cracking of the concrete of the girder and column on. heating of the bars incident to welding. The upper corner of the bracket 36' of the column 35' is beveled as at 52 for engagement by a shoulder 53 formed on the lower face of the girder 49' adjacent the end thereof. This shoulder transmits to the bracket a portion of the compression developed on loading the girder, the remainder of. the compression being transmitted from the lower bars 4| to the lower anchor bars 50, the tension being sustained by the upper anchor bars 50.

It will be apparent from the foregoing description and explanation that the construction of my invention has many advantages over the previous practice according to which the bracket securing means was relied on exclusively to with! stand the tension resulting from the. loading of the girder. The invention permits the bracket A precast reinforced securing means to be designed principally from the standpoint of carrying the shear load since there is no tension in the upper portion of the bracket but actually a heavy compression tending to hold it against the column. The upper portion of the end of the girder maybe readily secured to the column in' any one of several different ways, as shown in the drawings and fully described above.

Inthe-case of the separately formed brackets shown in Figure 1, the construction of my invention tends to increase the friction between the abutting faces of the bracket of the column. In thecase of the integral brackets, the construction avoids the tendency toward splitting of the bracket under the load of the girder. In all cases the construction provides a rigid connection between the column, girder and bracket. The bars of the girder are placed under tension in all cases; in Figure 1 by turning up the bolts; in Figure i! by' turning. up the nuts; and in Figure 3 by the shrinkage of the weldv or cooling. This tension gives continuous beamv action in stead of simple beam action. The tension existing in the bars of the girder, furthermore, tends to force the bracket against the column.

Although I have illustrated several. forms in which the invention may be provided, it will be understood that changes in the details of the construction may be made without departing from the spirit of the inventionv or the scopeot the appended claim.

I claim:

A building construction comprising a plurality of precast concrete members including a sup port member and a bracket member and a beam member resting on the bracket member, two hollow metal members embedded in the bracket member, a tie projecting from the support member entering one of the metal members and a tie projecting from the beam member entering the second. metal member, the two hollow metal members being connectedv together.

ALBERT HENDERSON.

REFERENCES CITED The following references are of record inthe file of this patent:

UNITED STATES PATENTS OTHER REFERENCES Cementstone Precast Concrete Column Load Tables, The Cementstone (20-. Pittsburgh, Pa. July 1942. 72-I:I en. Dig.