US2976781A - Concrete expansion joints - Google Patents

Description

Mg ch 28, 1961 J. N. HELTZEL 2,976,781

CONCRETE EXPANSION JOINTS Original Filed Sept. 7, 1944 12 20 15 //v VEN TOR 1 JOHN NICHOLAS HELTZEL, deceased,

1] BY Union Savings 8 Trust Company and Carl J. Helzel, co-execufors J BY dg ATTORNUJ CGN CRETE EXPANSION JOINTS John Nicholas Heltzel, deceased, late of Warren, Ohio,

by Union Savings and Trust Co. and Carl J. Belize], executors, both of Warren, Ohio Application .luiy 23, 1948, Ser. No. 40,328, now Patent No. 2,780,149, dated Feb. 5, 1957, which is a division of application Ser. No. 553,057, Sept. 7, 1944, now Patent No. 2,452,462, dated Oct. 26, 1948. Divided and this application Dec. 17, 1956, Ser. No. 628,898

2 Claims. (Cl. 94-18) This invention relates to dowel means for concrete expansion joints or contraction joints, and is a division of' allowed application Serial Number 40,328, filed July 23, 1948 (now Patent No. 2,780,149, dated February 5, 1957), which latter application is a division of application Ser. Number 553,057, filed September 7, 1944, on which Patent No. 2,452,462 issued on Oct. 26, 1948. Also the said application Serial Number 553,057 is a continuation in part of the application filed January 9, 1940, which matured into Patent No. 2,358,328, dated September 19, 1944.

The present invention is more particularly concerned with improved dowel means for expansion joints as provided between concrete or similar slabs or sections of roadways, floors, airfield runways, walls, and the like, for permitting relative horizontal movement of the slabs, while preventing the same from shifting laterally and vertically of their planes.

Modern trafiic conditions on highways and airfield runways have necessitated an increased use of load transfer members bridging joints, both longitudinal or transverse, between the opposed edges of adjacent concrete slabs. Experience has shown that the problem is not solved by the mere addition of load transfer dowels, such as commonly employed for the shrinkage of plastic concrete when drying sets up a frictional drag on the embedded dowel bars, with the consequent breaking of the concrete at points remote from the joints between the slabs. It has been found, also, that where dowel bars alone are depended upon, there is an inevitable warping of the concrete slabs which tends to bend the dowel bars. This bending prevents restoration of the slabs to their initial condition on the subgrade, and in addition, there is a constant breaking away of concrete or spalling off of the material at the faces of the concrete slabs in the areas surrounding and adjacent to the dowel bars.

The tendency of adjacent concrete slabs and the joints 1 Patent t between the slabs to shift under changing atmospheric conditions as well as under the incessant loads passing thereover has long been recognized, and the provision of efficient load transfer means at such joints has attracted the skill of engineers in many fields as well as steel and concrete contractors, and as a result many varieties of load transfer means in the form of dowels bridging concrete slab joints have been proposed and used.

In the use of such load transfer dowels, it is necessary, of course, that expansion and contraction of the joint be permitted, as a result of which the dowels must have relative movement to one of the slabs adjacent a joint in a direction axially of the dowels, and it is also essential that the dowels have relatively no movement transversely of their axes.

It has been found that dowels in use with concrete expansion joints should, for greatest efiiciency, be so united with at least one of the slabs as to remain rigid therewith under all conditions of use, and that such 2,976,781 Patented Mar. 28, 1961 united dowels be confined to axial movement only rela tively to another slab.

It has also been found that for maximum efiiciency the load bearing members ordowel structures should be so constructed and arranged as to be balanced on opposite sides of the joint and that the dowel portions spanning the joint should have a maximum load bearing and transferring capacity vertically through the dowel.

It is a primary object of the invention, therefore, to provide dowel means for concrete expansion joints and the like which satisfy the above noted requirements in providing load transfer connections of maximum strength and efiiciency.

An object of the present invention, therefore, is to provide improved means for producing joints in concrete roads and the like, utilizing dual dowel means in association with dual supporting shear plates, in which friction with respect to the surrounding concrete is reduced to a minimum by the novel bridging structure of balanced dowel and bearing members.

Another object is to provide, in such joints, means to eliminate tension in the concrete itself and to confinesuch tension directly and uniformly to the dowel and shear plate means constituting the load transfer elementsextending in balanced relation between the respective slabs.

A still further object is to provide a dual dowel assembly concrete slab in a joint installation for transferring vertical load strain to the dowel means at the joint by the employment of cooperating dual shear plates associated with the concrete slabs and dowels.

A further object of the invention is the provision of dowel means for concrete expansion joints including a dowel and dowel shear plate and socket arranged for rigid connection with each slab adjacent a joint therebetween with provision for each dowel to telescopically engage within a socket in the expansion and contraction of the joint.

A still further object of the invention is the provision of a dowel unit for use in concrete expansion joints comprising a pair of shear plates, each having a dowel and dowel socket rigid therewith, each shear plate having an aperture for confining the dowel of the other shear plate to axial movement in expansion or contraction of the connected concrete slabs, and each shear plate having means rigid therewith for transmitting strains remote from the joint directly to the shear plate.

A still further object of the invention is the provision of dowel means of the above noted character, wherein the shear plates are retained for contact with an expansion joint strip during pouring of concrete in the formation of slabs thereof.

A still further object of the invention is the provision of dowel means for concrete expansion joints including elements for cooperation at opposite sides of the joint and which elements are of like construction whereby manufacture and the setting up of the dowel means is simplified to a notable extent.

A still further object of the invention is the provision of dowel means for concrete expansion joints wherein the joint is greatly strengthened and balanced at each side thereof.

With the above and other objects in view, which will become more fully apparent as the nature of the invention is better understood, the same consists in the novel features of construction, combination and arrangement of parts as will be hereinafter more fully described, illustrated and claimed in the accompanying drawings.

In the drawings, wherein like characters of reference denote corresponding parts in related views:

Fig. 1 is a perspective view, partly broken and partly in section, disclosing a pair of opposed and cooperating dowel-incorporating shear plates disposed on opposite sides of a joint strip, and showing means for retaining the parts in upright assembly preparatory to the pouring of the concrete slabs;

Fig. 2 is a section on the line 22 of Fig. 1;

Fig. 3 is a view similar to Fig. 1 after the slabs have been poured and after the joint strip and shear plate retaining means has been removed; and

Fig. 4 is a section on the line t4 of Fig. 1.

Referring now in detail to the drawings, it will be understood from an inspection of Figs. 1 and 3 that there is provided a dual dowel reinforcing and load transferring structure for use at the joint 7 which separates the concrete slabs 5 and 6 and which joint space receives the joint strip 10.

As will be understood, the load transferring structure comprehends opposed shear plates 11 which are provided with upper and lower flanges 12 and 13 for anchorage in the concrete slabs 5 and 6 whereby holding the shear plates efiectively in position. Each shear plate 11 carries the functionally integral dowel bar 15 which projects from opposite faces of the plate and the rear ends of the dowel bars 15 which are embedded in the related slab are each provided with an upwardly anda downwardly deflected rear end portion, indicated at 16 and 17, respectively, for the purpose of greater anchorage in the concrete body of the slab as well as stress-relieving. The downwardly directed dowel end portions 17 have a further function which will be referred to presently.

As indicated in the drawing each shear plate 11 provides the rectangular aperture or opening 13 of a width to accommodate not only its functionally integral dowel bar 15, but also to provide for passage therethrough of the dowel bar 15 of the companion shear plate 11. Also the rear portion of each dowel bar 15, which is adjacent its shear plate 11, cooperates with a U-form sheet metal piece 19 in the formation of a socket 20 for the reception of the forwardly projecting end portion of the dowel bar 15 of the other shear plate. Thus the U-form sheet metal piece 19 is welded to the back of the related plate 11 about its opening 18 and its ends overlie and are welded to the adjacent dowel bar 15 which constitutes one side of the socket 20.

Figs. 1 and 3 show the joint strip 10 as having openings 21 which are alignable with the shear plate openings 18 for passage of dowel bars 15.

In the invention as herein illustrated, the expansion joint strip 10 is supported or held with its openings 21 in registration with the shear plate openings 18 by a removable cap strip 22 which is of inverted U-shape. This cap strip 22 as shown is provided with prongs 23 in registry with apertures 24 which are provided in the top shear plate flange 12 to enter same as indicated. This also temporarily prevents separation of the shear plates 11 from the strip 10 after setting up of the parts and during the pouring of the slabs.

Referring back to the downwardly extending dowel bar-provided end anchor portions 17, it is to be noted that they constitute supports for engagement with the sub-grade. Such anchor portions 17 are of a length to support the joint strip 10 on the sub-grade, or if desired in a suspended position thereabove. The cap strip 22 is removed while the concrete is still soft and proir to the final finishing of the concrete slabs 5 and 6 so that it can be re-used. A wire spring member 25 may extend between the anchor portion 17 provided supports and under the joint strip 10 to aid in holding the shear plates 11 against the joint strip 10. However, when the cap strip 22 is used, such spring member 25 may be omitted.

As will be appreciated, the top and bottom flanges 12, 13 of the shear plates 11 constitute top and bottom shear plate reinforcing means to resist stresses tending to bend the plates along lines extending from the top to the bottom thereof. Likewise the dowels 15 of Figs. 1

and 3 being functionally integral with the related shear plates 11 reinforce such plates at the mid-portion thereof and operate to resist distortion of same at the site of the openings or apertures 18 therein through which the dowel 15 of the companion plate 11 extends when the units are assembled.

From the foregoing it willbe apparent that effective means has been provided for preventing separation of the dowel carrying shear plates 11, 11 during pouring of concrete in the formation of slabs. It is also evident that means is present for firmly bonding from points distant from the plates or expansion joint to the plates with which the dowels are rigidly connected.

, depending cap prongs 23.

Thus, each shear plate 11 has rigidly connected therewith and' extending therethrough a bear member 15, a portion of'which provides a dowel and another and longer portion provides the aforementioned anchoring members 16 and 17 for firmly bonding the shear plates 11 with the related slab and for transmitting strains from points distant from the joint to the shear plates.

It is further to be observed that the shear plates 11, when embedded in and firmly bonded with the slabs 5, 6 as disclosed, there is no tendency or even possibility of the dowels having any movement transverse of their axes relative to the slabs 5 and 6 with which they are united. Furthermore, the novel structure is such that in use the dowels 15 cannot have lateral movement independently of each other or with the slabs 5, 6 with which they are relatively lengthwise movable. The reason that this is so is that the dowel-receiving apertures or holes 18 in the various shear plates 11 are of a vertical dimension so as to provide a close sliding fit with the upper and lower edges of the dowels 15.

Also, upon consideration of the drawing, it will be noted that each dowel 15 is rigidly supported by its shear plate 11 in one slab and is confined by the guide hole or apertures 18 in the opposed shear plate 11 to horizontal or axial movement. Thus, the two dowels 15 pro vide a rigid load transmitting truss between the opposed edges of the slabs 5, 6.

Additionally, the dowel-providing bars 15 have sub stantial vertical depth for maximum load-transmitting properties and they are disposed substantially distant from the top surface of the slabs 5, 6 so as to avoid an otherwise possibility of cracking thereof.

The structure disclosed, as will be appreciated, comprises a pair of substantially identical members 11, 15, which not only simplifies manufacture but also materially expedites assembly in that it is not necessary to select left and right members, as is the case with prior structures of this general character. Funthermore, the members 11, 15 are relatively simple in construction and can be readily formed from bar and sheet material.

The shear plate flanges 12, 13 eiiectively reinforce plates 11, and the top flanges 12 have the additional function of providing the hole-form seats 24 for the Also the removable joint stripcarried cap 22 provides a convenient re-usable means for maintaining the dowel bar-carrying plates 11 and joint strip assembled during the pouring of the concrete and until the slabs have partially set.

From the above description, it is believed that the features and advantages of the invention will be readily apparent to those skilled in the art, and it will, of course, be understood that changes in the form, proportion and minor details of construction may be resorted to without departing from the spirit of the invention and scope of the appended claims.

What is claimed is:

1. In an expansion joint structure comprising plates adapted to be embedded in opposed slab faces, a parting strip between the plates and adapted to have its upper edge lying in a plane adjacent the planes of the top surfaces of the slabs to be poured, a functionally integral dowel and socket provided by each plate, the socket of each plate slidably receiving the dowel of the other plate, rearward extensions provided by each dowel at the slab side of the related plates and having subgrade engaging portions spaced from the latter, said subgradeengaging dowel portions supporting said plates to dispose the top portions of the latter below but adjacent the plane of the top edge of said parting strip, a lateral projection functionally integral with the slab side of each plate adjacent the top edge thereof and having an upwardly opening aperture, a removable inverted U-form member seated on the upper edge of the parting strip and engaging opposite side portions of the latter, and depending rigidly carried outwardly offset pin means provided by said member at each side and engaging in said plate projection-provided apertures for holding the parting strip and adjacent plates against outward separation during the pouring of the slabs, said member being removable for re-use after slab-pouring and while the concrete is soft.

2. In an expansion joint structure for adjacent road slabs comprising plates adapted to be embedded in opposed slab faces, a parting strip between the plates and adapted to have its upper edge adjacent the planes of the top surfaces of the slabs to be poured, slidably interfitting dowel and socket means provided by said respective plates and connecting the same for adjustment toward and away from one another, horizontal rear-wardly extending reinforcing flanges adjacent the top of each plate at the slab side thereof, each of said flanges having a hole extending therethrough, an inverted U-form, oap removably seated on the upper edge of the parting strip and embracing adjacent side portions thereof, and depending rigidly carried outwardly ofiset pin means provided by said cap member at each side and engaging in said flange-provided holes for holding the parting strip in position between the plates during the pouring of the slabs While preventing outward shifting of said plates, said cap member being removable for subsequent re-use after slab pouring and while the concrete is still soft.

References Cited in the file of this patent UNITED STATES PATENTS 2,016,858 Hall Oct. 8, 1935 2,027,553 Robertson Jan. 14, 1936 2,082,978 Robertson June 8, 1937 2,138,817 Jacobson Dec. 6, 1938 2,189,156 Willard Feb. 6, 1940 2,194,718 Older Mar. 26, 1940 2,236,463 Brickman et al Mar. 25, .1941 2,240,786 Kinzer May 6, 1941 2,256,930 Willard Sept. 23, 1941 2,267,023 Godwin Dec. 23, 1941 2,780,149 Heltzel 'Feb. 5, 1957

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