US2885882A

US2885882A - Prestressed concrete deck

Info

Publication number: US2885882A
Application number: US611121A
Authority: US
Inventors: Wilford C Fuller; Oliver Crawford Percy
Original assignee: NORTHERN VIRGINIA CONSTRUCTION
Current assignee: NORTHERN VIRGINIA CONSTRUCTION; NORTHERN VIRGINIA CONSTRUCTION COMPANY Inc
Priority date: 1956-09-21
Filing date: 1956-09-21
Publication date: 1959-05-12
Anticipated expiration: 1976-05-12

Description

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May 12, 1-959 w. c. FULLER ET AL PRESTRESSED CONCRETE DECK Filed Sept 21, 1956 mvEmoRs .C.FULLER ATTORNEY United States Patent cc PRESTRESSED CONCRETE DECK Wilford C. Fuller, Silver Spring, Md., and Crawford Percy Oliver, Arlington, Va., assignors, by mesne assignments, to Northern Virginia Construction Company, Incorporated, Alexandria, Va., a corporation of Virginia Application September 21, 1956, Serial No. 611,121

1 Claim. (Cl. 72-68) This invention relates to a method of concrete floor or deck construction, and to the floor or deck so constructed, for structures such as bridges and warehouses,

and more especially to floor constructions of prestressed concrete.

It has long been known that concrete floors or decks submitted to heavy loads, and to the rapidly varying loads of moving traflic, may be provided by pouring the concrete with its reinforcement in situ. Recently it has been discovered that very strong precast concrete beams can be made in which the reinforcement is prestressed, that is, the reinforcement is tensioned and the concrete poured so that the concrete, after setting, and release of the tensioning means, it under compression. The decking slab, however, has continued to be poured in situ with forms that provide narrow downwardly extending webs in the finished concrete structure to save weight in the structure and in which unstressed reinforcing metal is placed. Such a slab could not be precast as its weight would make its positioning in the structure impossible.

It is an object of the present invention, therefore, to provide a method of forming decking which incorporates the desirable features of prestressed concrete and which contemplates assemblage of light weight precast elements into a unitary slab.

It is a further object of the present invention to provide a strong and light deck slab that may be readily assembled from precast prestressed elements into a substantially integral unit.

A preferred embodiment is described below and is illustrated in the accompanying drawing in which like characters of reference refer to similar parts throughout and in which:

Fig. 1 is a fragmentary perspective view of an example of the decking formed by the method of the present invention.

Fig. 2. is a section taken on line 22 of Fig. 1.

Fig. 3 is a section taken on line 33 of Fig. 1.

Fig. 4 is a perspective view on an enlarged scale of a beam used in the decking of Fig. 1.

As seen in Fig. 1, the deck slab is formed of a plurality of beam-like elements that extend from one abutment or support 1 to a second abutment or support 2.

Beam elements 10 are shown as being in the form of a channel and include an upper horizontal flange 11, a lower horizontal flange 12 and a vertical web 13. Embedded in these flanges and in the web are prestressed steel reinforcing elements 14 that may conveniently be high tensile strength seven-wire strands or may be any conventional reinforcing material of a suit-able size. The pattern in which these reinforcing elements are placed in the beam is, of course, a matter of individual design.

At each end of the channel an end block 15 is pro- 2,885,882 Patented May 12, 1959 'vided and, at spaced intervals along the channel, diaphragm blocks 16 are provided.

Were the beam shown of 1 section, it would clearly be necessary to provide two end blocks 15, one on each side of the web, and, at each diaphragm, two diaphragm blocks 16.

These end blocks 15 and diaphragm blocks 16 are, of course, cast as an integral part of beam 10. These blocks are formed with very accurate faces exposed at the edge toward the adjacent beam and their faces are parallel to the back of web 13 so as to provide a face to face contact of the faces of the blocks against the back of the adjacent beam.

To assure such face to face contact of the blocks, the blocks may extend slightly beyond the edges of the flanges as shown in Fig. 4. This extension, however, should, preferably, be as slight as possible.

In each end block 15 and in each diaphragm block 16 there is provided at least one, but preferably two or more holes 17 extending from the face of the block to the face of the web 13. These holes are normal to the faces of the blocks and web and are at right angles to the length of the beam so that when several beams are assembled each hole aligns with the corresponding hole in all of the other beams.

As seen in Fig. 1, a plurality of beams 10 are laid side by side to span the space between abutments 1 and 2 then, as seen in Fig. 3, a reinforcing bar, rod, or cable 18 is threaded through all the beams and is tensioned. The ends of these tensioned cables 18 are anchored by any known means at 18'.

In Fig. 3 it is noted that at one end reinforcement 18 is tensioned against a stress distributing plate 19 embedded in the edge beam and at the other end the reinforcement is stressed against a metal element 20, shown here serving as a hand rail stanchion as well as for a stress distributing means. Anchor means 18 transfer the stress in cable 18 to elements 19 and 20. Clearly, both ends could be the same, and either embedded plates 19 or surface means 20 are suitable for such use. Means 20 may, of course, be a simple piece of heavy steel plate having holes to align with holes 17.

The precast beams 10 include prestressed reinforcing 12 to give the greatest strength to the light channelshaped beams. Post-stressed reinforcing 18 pulls all of the diaphragms and end blocks together to form crosswise beam structures as is apparent from comparing Fig. 3 with Fig. 2, so that a load at any point on the deck is carried not only on the one beam on which the load is located but is spread to the other beams by the poststressed beam structures. While the arrangement of beams shown in Fig. 2 is considered to be the desirable one in most instances, other arrangements or patterns could be used according to the specific need of the structure.

The above description is of a preferred form and other exemplifications of the invention and the several features of the invention may be used in other combinations and changes and modifications in design, structure, and details may be made within the scope of the appended claim without departing from the spirit of the invention.

What is claimed is:

A concrete floor construction for bridges or the like, comprising a plurality of identical precast beam elements each said beam being of flat backed channel shape including a vertical web and horizontal flanges, the exterior surface of said vertical web being entirely flat and said horizontal flanges being of uniform section, and

flanges, a plurality of spaced diaphragms between the web and flanges of each beam so positioned along the beam as to align with corresponding diaphragms of adjacent beams, said diaphragms each presenting a fiat face beyond the free edges of said flanges and parallel to the entirely flat exterior surface of said vertical web, a hole in each diaphragm near each flange and post-tensioned reinforcing means passing through said holes to draw said 'plurality of beam elements together, said flat surfaces of said diaphragms and said entirely flat exterior surfaces of said vertical webs being the only surfaces of contact ,between adjacent beam elements in said floor.

References Cited in the file of this patent UNITED STATES PATENTS Welfie June 18, 1907 Coff Mar. 25, 1952 FOREIGN PATENTS Great Britain of 1903 Sweden Apr. 14, 1905 France Dec. 10, 1925 France July 21, 1930 Great Britain Ian. 2, 1945