US3256786A - Concrete joint and loading transfer device - Google Patents

Description

June 21, 1966 w. F. MIDDLESTADT CONCRETE JOINT AND LOADING TRANSFER DEVICE Filed June 11, 1962 2 Sheets-Sheet 1 INV EN TOR 444/17 rr-Mxoazaszvog' ATTORNEYS June 1966 w. F. MIDDLESTADT 3,

CONCRETE JOINT AND LOADING TRANSFER DEVICE Filed June 11, 1962 2 Sheets-Sheet 2 INVENTOR MAL/WM F". m/opwwoa' ORNEY5 United States Patent 3,256,786 CONCRETE JOINT AND LOADING TRANSFER DEVICE William F. Middlestadt, Severna Park, Md. (Rte. 2, Box 330, Arnold, Md.) Filed June 11, I962, Ser. No. 201,437 3 Claims. (CI. 94-18) This invention relates to a combined concrete joint and load transfer device. The present specification is a continuation-in-part of my prior application Serial No. 740,858, filed June 9, 1958, for Concrete Joint now Patent No. 3,038,395, issued June 12, 1962.

In the aforesaid patent application there is disclosed a method of forming a concrete joint wherein a substantially tubular shaped member is forced downwardly into plastic concrete until the upper surface of the member is substantially flush with the upper surface of the concrete. The concrete is then cured and, following curing, the upper surface of the member is depressed or deformed to provide a space above the member and sealing compound is filled into this space above the insert member. The insert member is adapted to form a weakened plane so that when the concrete contracts the crack will be formed beneath the insert. The side walls of the insert member are secure with the adjacent concrete so that when the concrete contracts the side walls of the member move apart. Similarly, when the concrete expands the side walls of the member will move together.

This method has many advantages over prior art methods for forming joints. There is no possibility of infiltration of foreign material prior to sealing as the filler piece completely fills the formed joint when initially inserted in the plastic concrete thereby maintaining a smooth even surface with the rest of the pavement. The curing of the concrete need not be disturbed by persons walking on the surface and a uniform curing operation is assured. Since the filler piece occupies the major portion of the joint, a minimum of sealing compound is required. The approximately square cross-section of scaled slot above the filler piece results in minimum sealer movement during summer winter cycles resulting in maximum life of the sealed joint. The most important advantages of this method of joint formation from a commercial standpoint are that the cost of join-ts is not affected by hardness of aggregate, concrete cracking is controlled and a smooth riding surface is maintained.

There is, however, another problem in connection with the proper maintenance of a concrete road. It can be appreciated that, as vehicles travel from one concrete block over a joint to the adjacent concrete block, there must be some vertical shifting of the blocks as the load is transferred unless adequate provision is made therefor by means of load transfer devices. Such devices normally take the form of metal bars which are embedded in the concrete and extend across the joint. Such bars do provide means for transferring the load between adjacent blocks but these devices are difficult to install, are costly and sometimes prevent proper functioning of the concrete joints during expansion and contraction of the concrete.

Other means has been proposed for providing for load transfer between adjacent concrete blocks. This means may comprise a lateral projection on one concrete block extending into a recess in an adjacent concrete block. This projection permits load .on one block to be transferred to the adjacent block. Such a means also permits "ice direction provides a weakened vertical plane at a point at which the joint is to be formed.

Furthermore, according to prior art teachings such projections are rectangular and the particular size and location of the projections are not specified.

The present invention incorporates load transfer means with the joint forming member. The joint forming member may be generally similar to the joint forming member disclosed in my above referred to patent. The load transfer means comprises a plurality of cups or dowel forming members which extend alternately in opposite directions .so as to form projecting rods or dowels of concrete which extend across the joint from one concrete block into cooperating recesses in an adjacent block. Since the projections are spaced from each other and extend alternately in opposite directions, there is no secondary plane of weakness formed by this load transfer means. Furthermore, it has been found that the size, shape and specific location of the projections is critical to the successful operation of the load transfer means. This is due to the load bearing characteristics of concrete as will be explained more fully hereinafter. The projections are made substantially cylindrical in shape, are of a diameter approximately one half the thickness of the slab and are located at approximately the center of the slab.

The present invention thus combines two functions in a single element by providing a joint forming member which incorporates load transfer means. There is no need for the separate insertion of bars to perform load transfer functions and a considerable savings in time and money results.

An object of the present invention is to provide an in sert member for forming joints in concrete which also serves as a load transfer device.

Another object of the present invention is to provide a combined concrete joint and load transfer means wherein means is provided for forming substantially cylindrical concrete projections on one concrete block which fits within recesses in an adjacent concrete block.

I Still another object of the present invention is to provide load transfer means for concrete comprising substantially cylindrical concrete projections having a diameter approximately one half the thickness of the concrete slab and being centrally located with respect to the upper and lower surfaces of the concrete.

Other objects and many of the attendant advantages of the present invention will become more fully apparent upon consideration of the following detailed specification in connection with the accompanying drawings wherein:

FIG. 1 is a plan view of an insert member made in accordance with one embodiment of the present invention,

FIG. 2 is an elevational view thereof,

FIG. 3 is a sectional view showing the insert member when initially placed in the plastic concrete,

- FIG. 4 is a similar sectional view of the insert member after the concrete has hardened,

FIG. 5 is a sectional view of a modified form of insert member when initially placed in the plastic concrete,

FIG. 6 is a similar sectional view of the insert member shown in FIG. 5 after the concrete has hardened and,

FIG. 7 is an elevational view of the embodiment shown in FIGS. 5 and 6.

Referring now to the drawings there is shown an insert member 1 having an upper surface 2 which is substantially fiat with the exception of a groove 3 disposed therein for a purpose which will become more fully apparent hereinafter. Depending from the upper wall 2 are side walls 4 and 5. These walls extend substantially perpendicularly with respect to the top wall 2 so as to form a hollow upper end portion 6. The side walls 4 and 5 are bent inwardly so that they extend in adjacency as shown at 7. At the lower edges thereof the side wall 4 is provided with an angular flange 8 and the side wall 5 is provided with an angular flange 9. These flanges extend along the entire length of the insert member.

There are provided punched out holes 13 extending through the side walls 4 and 5 so that the pressed out metal in one side wall engages the other sidewall which serves to maintain the sidewalls temporarily in engagement with each other. However, upon any substantial outward pressure being applied to the sidewalls, the sidewalls will pull apart.

The insert member is provided with laterally projecting portions in the side walls which serve as load transfer devices. These projections comprise circular pressed out cup shaped portions such as shown at 10, 11 and 12. It will be noted that these cups are pressed out alternately in opposite directions and that both sidewalls are pressed together in the same direction as is clearly shown in FIGS. 3 and 4. The projections are formed by clamping the metal immediately surrounding the projection and pressing the metal inwardly so that no metal is drawn into the projections from the flat portions. This method of forming the projections is significant in that the parallel alignment of the projections is maintained and there is no distortion of the insert member along the length thereof.

The presently disclosed insert for forming joints functions in the following manner. The insert member is pressed into plastic concrete at the point where the joint is to be formed so that the top is substantially level with the upper surface of the concrete as shown in FIG. 3. After the concrete has cured a deforming or depressing tool is engaged with the upper surface of the insert so as to force the upper surface downwardly into the slot formed by the member until it forms a substan tially bellows shape configuration. A sealer such as shown at 21 is filled in abovethe member.

It will be noted that the concrete fills the pressed out -portions 10, 11, and 12 forming laterally extending cup tween the insert and the concrete to prevent the insert from separating from the concrete slab adjacent thereto. The parts are shown in FIG. 4 with the concrete in a contracted state. The projections pressed in sidewall 5 have moved with respect to the projection in side wall 4 but it will be noted that the concrete on the left slab as viewed in FIG. 4 is supported by the concrete in the right slab .as viewed in FIG. 4. The projections on both sides of the projection along the length of the insert member provide columns of concrete in the right hand slab which are supported in the left hand slab. Thus, the load from a heavy weight disposed on a single concrete block will be transmitted to adjacent blocks so as to prevent slipping of one block along a vertical plane with respect to an adjacent block. A lubricant may be provided between the interengaging faces of the sidewalls to facilitate the telescopic movement of the sidewalls.

It can be appreciated that the presently disclosed device is inexpensive to install and eliminates the need for locating rods and the like within the concrete forms prior to pouring the concrete in order to provide for load transfer at the concrete joint.

In FIGS. 5 to 7 ther is disclosed another embodiment As the of the invention wherein the insert member comprises a joint forming member 14 and a load transfer device 15. It will be noted that the insert member 14 has outwardly extending flanges 16 and 17 along the lower edges of the sidewalls. The load transfer device 15 has upwardly extending wall portions 18 which extend between the sidewalls of the joint forming member. The load transfer device is provided with cup shaped projections 19' which function in a manner identical to that described with ref erence to FIGS. 1 to 4. There are provided punched out holes 20 which serve to maintain the sidewalls of the load transfer device 15 in engagement until the device is inserted in the concrete and a pressure is exerted by the contracting concrete. The device according to this embodiment may be more readily manufactured than that shown in FIGS. 1 to 4.

The size, shape and location of the projecting concrete elements forming the load transfer means are critical to the proper functioning of the system. It is well recognized that concrete possesses far greater strength in compression than in flexure. Thus, the concrete will break along an angular line, approximately 60 with respect to a horizontal plane. In the event that rectangular projections are used, a corner breakingoff along the length of the projection will permit vertical displacement of the concrete slabs. This breaking off" of a right angular corner may occur relatively easily since fracture along a straight line is involved. However, in the case of substantially cylindrical projections a cresent shaped piece of the projection would have to be broken off in order to permit vertical displacement of the concrete slabs. There is considerably less likelihood that a fracture, if occurring, would under dynamic loading elongate into such a configuration. The cylindrical shaped lprojections provide for equal resistance to a load applied in any direction. The subsoil beneath the concrete may become washed away beneath a joint and the lower surface of the projections then become load bearing areas. The cylindrical projections are advantageous in that no sharp corners are provided which would create difiiculties in filling with concrete and there are no areas of high stress concentration.

The size of the projections relative to the thickness of the concrete slab is critic-a1. By using projections having a diameter of 4.5 inches on 6-inch centers in a concrete slab of 9-inch thickness load at failure reached 4950 pounds which gives a safety factor of approximately 5 over the normal requirements. Projections having a diameter smaller than 4.5 inches did not provide nearly as great resistance to load. Furthermore, projections having a diameter greater than 4.5 inches did not provide suflicient concrete above and below the projection in the female concrete slab so that the projections broke out the surface of the concrete. Further experiments have shown .that cylindrical projections having a diameter substantially one-half the thickness of the concrete slab provide optimal strength characteristics.

It is essential that the projections be located substantially centrally of the concrete slab. There must be sufiicient concrete both above and below the concrete projections to prevent the projections from breaking out to disrupt the upper surface or the lower surface should the subsoil become displaced. The staggering of the projections prevents the formation of a secondary continuous weakened line which would permit simultaneous fracture of all of the projections.

Obviously, many modifications and variations of the present invention are possible in light of the above teachings. What is claimed as new and desired to be secured by Letters Patent is:

1. A concrete joint and load transfer device adapted to be inserted in a slab of concrete comprising a pair of opposing walls, load transfer means formed in said opposing walls, said load transfer means comprising cylindrical shaped projections in said opposing walls, each pro- 4 jection comprising a cylindrical side wall and an enclosing end wall, said projections providing deformations in both said opposing walls to extend alternately along the length of the device to opposite sides of the center line -extending between said opposing walls, said cylindrical shaped projections having a diameter substantially one half of the thickness of a concrete slab into which the device is adapted to be inserted, the load transfer means adapted to form cylindrical concrete projections in a concrete slab, the projections extending alternately along the length of the joint from one side of the joint to the other side of the joint.

2. A concrete joint and load transfer device adapted to be inserted vertically into a slab of concrete compris-' ing a member having a pair of opposing Walls, an upper wall interconnecting said opposing walls, said opposing walls being shaped to form a hollow upper end portion, and load transfer means formed by the lower portions of said opposing walls, said load transfer means comprising cylindrical shaped projections in said opposing walls, each projection comprising a cylindrical side wall and an enclosing end wall, said projections providing deformations in both said opposing walls to extend along the length of the device to opposite sides of the center line extending between said opposing walls, said cylindrical shaped proje-ctions having a diameter substantially one half of the thickness of a concrete slab into which the device is adapted to be inserted, the load transfer means adapted to form cylindrical concrete projections in a concrete slab, the concrete projections extending alternately along the length of the joint from one side 'of the joint to the other side of the joint.

3. A concrete joint and load transfer device adapted to be inserted in a slab of concrete comprsing a member having a pair of opposing walls, an upper wall interconnecting said opposing walls, the portions of said opposing 3 walls adjacent the upper wall being shaped to form a hollow upper end, load transfer means formed by the lower portions of said opposing walls, said load transfer means comprising spaced cylindrical shaped projections in said opposing walls, each projection comprising a cylindrical side wall and an enclosing end wall, the spacing between the projections being approximately one-third the diameter of the projections, said projections providing deformations in both said opposing walls to extend towards opposite sides of the center line extending between the opposing walls alternately along the length of the device, said cylindrical shaped projections having a diameter substantially one half of the thickness of a concrete slab into which the device is adapted to be inserted, the load transfer means adapted to form cylindrical concrete projections in a concrete slab, the concrete projections extending alternately along the length of the joint from one side of the joint to the other side of the joint.

References Cited by the Examiner UNITED STATES PATENTS 1,586,326 5/1926 Older 94-18 1,604,991 11/1926 Gregg 94-18 1,755,480 4/1930 Kramer 94-17 1,806,275 5/1931 Adler 94-18 2,005,301 6/1935 Rafter -440 X 2,085,168 6/1937 Payne 94-18 X 2,101,154 12/1937 Older 94-18 2,118,340 5/1938 Burgess 94-18 2,133,387 10/1938 Heltzel 94-18 2,291,109 7/1942 Sensibar 94-18 2,301,137 11/1942 Musall 94-18 2,311,286 2/1943 Tufts 94-17 2,632,367 3/1953 Martin 94-18 CHARLES E. OCONNELL, Primary Examiner.

JACOB L. NACKENOFF, Examiner.

N. C. BYERS, Assistant Examiner.

Claims (1)

1. A CONCRETE JOINT AND LOAD TRANSFER DEVICE ADAPTED TO BE INSERTED IN A SLAB OF CONCRETE COMPRISING A PAIR OF OPPOSING WALLS, LOAD TRANSFER MEANS NFORMED IN SAID OPPOSING WALLS, SAID LOAD TRANSFER MEANS COMPRISING CYLINDRICAL SHAPED PROJECTIONS IN SAID OPPOSING WALLS, EACH PROJECTION COMPRISING A CYLINDRICAL SIDE WALL AND AN ENCLOSING END WALL, SAID PROJECTIONS PROVIDING DEFORMATIONS IN BOTH SAID OPPOSING WALLS TO EXTEND ALTERNATELY ALONG THE LENGTH OF THE DEVICE TO OPPOSITE SIDES OF THE CENTER LINE EXTENDING BETWEEN SAID OPPOSING WALLS, SAID CYLINDRICAL

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