US2768520A

US2768520A - Head plate for structural columns

Info

Publication number: US2768520A
Application number: US252273A
Authority: US
Inventors: George E Strehan
Original assignee: Lally Column Co
Current assignee: Lally Column Co
Priority date: 1951-10-20
Filing date: 1951-10-20
Publication date: 1956-10-30
Anticipated expiration: 1973-10-30

Description

6. E. STREHAN 2,768,520 l lEAD-PLATE FOR STRUCTURAL. COLUMNS Fil d Oct. 20, 1951 1320886202 Geoflge ES em 63 I 7% Z/imwn United States Patent 2,768,520 PLATE FOR STRUCTURAL COLUMNS George E. 'Strehan, Leonia, N. J., assignor to Lally Colulrlnn $0., Cambridge, Mass., a corporation of Massac use s Application October 20, 1951, Serial No. 252,273 1 Claim. (Cl. 72-'-159- This invention relates to improvements in head plates or frames for structural columns used in monolithic, fireresistant buildings in which a floor slab of reinforced concrete or the like is poured in place around the supporting columns.

Channel type head frames designed for this general purpose are disclosed in my Patent No. 2,033,595, dated March 10, 1936, and in the Donahue and Strehan Patent No. 2,469,455, dated May 10, 1949. In the latter patent, the head frame is rigidly secured to the top of a well known type of prefabricated structural column comprising a steel casing filled with concrete. Such framed columns are adaptable and adequate for all building conditions; they are easy to install and maintain; they present minimum obstruction to light and air and obviate bulky columns and bulging projections under the panel joints of a flat slab floor; and they afford other practical advantages which are explained in the patents just mentioned.

The principal purpose of the present invention is to provide a head frame of relatively simple and economical construction, comprising a pair of flat steel plates rigidly secured together and to the ends of upper and lower concrete-filled columns, and reinforced by shear and bond rods which are preferably welded to one of the plates and so disposed that portions of the rods may be bent to most effective position after the upper column is installed and before the concrete slab is poured.

The improved, reinforced head plate serves to transmit to the connected columns that portion of the moment of the rigid frame, based on the relative rigidity of the columns and the intersecting bands of the concrete slabs at the panel joint; and to transmit the total panel load to the column in shear, while reducing the shear in the slab to a small percentage of the ultimate compressive strength of the concrete.

A further object of the invention is to provide a reinforced head plate having projections, preferably formed by portions of the reinforcing rods, on its underside, which serve as ties to prevent cracking or spalling of the concrete in which the plate is embedded; and having rod projections above the plate, which are adequate to resist the horizontal shear in the slab in both directions, thus ensuring the rigidity of a fixed hinge and preventing diiferential movement between the column head and the floor slab.

Additional advantageous features of the improved head plate will become apparent from the following description of the recommended embodiments of this invention shown on the accompanying drawing, in which:

Fig. 1 is a fragmentary section of a floor slab at the panel joint, showing the portions of the assembled upper and lower columns, and the head plate, in elevation, and illustrating a basket arrangement of the reinforcing rods certain of which are shown in section;

Fig. 2 is a plan view of the structure shown in Fig. 1;

Figs. 3 and 4 are views similar to Figs. 1 and 2 respectively, illustrating a stirrup-like arrangement of the reinforcing rods; and

Figs. 5 and 6 are similar views, illustrating a loop ar-. rangement of the rods.

In the several optional embodiments therein illustrated, the installed column head comprises a pair of substantially square shaped, flat steel plates 11 and 12, riveted or otherwise rigidly fastened together at 13 and securely welded to the opposed ends of the lower column 14 and.

small steel shapes, and is wholly embedded and concealed within the normal thickness of the concrete floor slab 16, as indicated in Figs. 1, 3, and 5. The cross sectional area of the column head should be such that the total panel load is transmitted to the column in shear; and the lateral dimensions of the head plate should be sufiicient to reduce the shear in the slab to approximately three per cent of the ultimate compressive strength of the concrete. The section modulus of the plate should be adequate to transmit that portion of the total negative moment resisted by the columns in proportion to the relative rigidity factors of the columns. The total cross sectional area of the steel reinforcing rods, above the plate 11, should be adequate to resist the horizontal shear of the slab in both directions.

The reinforcing rods are preferably welded to the bottom plate 11 at the shop. The respective plates are welded and anchored to the respective columns, either at the shop or on the job, where the two plates are riveted or otherwise rigidly fastened together while the uppermost portions of the rods are bent outwardly, for example to the broken line positions of Figs. 1, 3 or 5. After the columns are thus rigidly connected, the rods are bent inwardly, to the full line positions of the drawing, before the concrete slab is poured in the conventional forms.

Although the plates 11 and 12 are preferably square when used as the head frames of interior columns, one or more sides of the plate 11 may be partially cut away for use on exterior columns or in corners. It will also be understood that the ultimate angular position of the inwardly bent rod portions will depend upon the requirements of the particular installation.

In the basket type reinforcement of Figs. 1 and 2, a plurality of parallel rods 17 extend in both directions under the plate 11, and are bent upwardly against the edges of the plate to which the rods are welded; the upwardly projecting end portions 18 being ultimately bent inwardly and downwardly toward the upper surface of said plate. The underlying portions of the rods are preferably spaced from the bottom surface of the plate, so that they are embedded in the floor slab 16 and tend to prevent cracking or spalling of the concrete.

In the stirrup form of Figs. 3 and 4, a reinforcing rod 19 extends under each of the four overhanging side portions of the plate 11 and projects upwardly through holes bored in the plate adjacent the corners thereof. The rods are welded in said holes, and the underlying portions thereof are spaced from the bottom surface of the plate for the purpose mentioned above. The upwardly projecting end portions 20 are ultimately bent inwardly and downwardly so that their extremities overhang plate 12 and preferably meet the casing of the upper column 15 to which they may be welded, if desired.

Patented Oct. 30, 1956 In the loop type of Figs. 5 and 6, four reinforcing rods, bent in the form of loops 21 have their crossed ends 22 welded to the upper surface of plate 11 adjacent each edge of the plate, and the upwardly projecting loop portions are ultimately bent inwardly and downwardly to the desired angular position relative to the plate, preferably overhanging plate 12, as aforesaid. In this form, studs 23 may be welded or riveted to the underside of the plate. to provide anchoring projections which tend to prevent cracking of the concrete.

A column head constructed as herein described is easy and economical to fabricate and to assemble with the concrete filled columns; it afiords adequate rigidity, strength and resistance to shear, and is firmly bonded to the floor slab; and it is compact, relatively light in weight, and convenient to install in meeting the requirements of flat slab building construction.

I claim:

A head frame assembly, adapted to be embedded in a concrete floor slab and to connect two prefabricated structural columns disposed one above the other, comprising; a flat rectangular metal head plate adapted to be attached to the lower column, having a central portion adapted to rest on the lower column, and four overhang- References Cited in the file of this patent UNITED STATES PATENTS 1,009,712 Anderson Nov. 28, 1911 1,065,322 Thomson June 17, 1913 1,248,049 Wunder Nov. 27, 1917 1,258,917 Lally Mar. 12, 1918 1,329,614 Lally Feb. 3, 1920 1,550,316 Hardison Aug. 18, 1925 1,625,899 Lally Apr. 26, 1927 FOREIGN PATENTS 59,081 Switzerland Jan. 15, 1912