US2075234A - Dowel for roadway expansion joints - Google Patents

Description

March 30, 1937. w. F. SCHULZ DOWEL FOR ROADWAY EXPANSION JOINTS Filed May 28, 1935 3 Sneets-Sheet 2 March 30, 1937. w. F. SCHULZ DOWEL FOR ROADWAY EXPANSION JOINTS Filed May 28, 1955 5 Sheets-Sheet 3 Patented ar. 30, 1937 UNITED STATES DOWEL FOR ROADWAY EXPANSION JOINT Walter F. Schulz, Youngstown, Ohio, assignor to Truscon Steel Company, Youngstown, Ohio, a

corporation of Ohio Application May 28, 1935,'Serial No. 23,923

8 Claims.

This invention relates to road building accessories and more especially to a novel device for interconnecting the concrete slabs, at expansion joint locations, for the purpose of permitting relative horizontal movement of the slabs and preventing heaving or lifting of one slab with reference to the other.

' To that end the invention contemplates a novel dowel plate which is disposed vertically in the roadway and connects the adjoining ends of adjacent slabs after the fashion of the vertical web of a beam, whereby, when the device is in use, the concrete of the slabs above and below the edges of the plate form in effect top and bottom chords of the beam, thus causing the joint to present great resistance or stiffness to loads imposed perpendicular to the longitudinal axis of the plate, while at the same time including provision for yieldingly permitting the plate to shorten or lengthen in the direction of its longitudinal axis to compensate for the expansion and contraction of the connected slabs of the roadway.

Accordingly, the present invention has pri- 5 marily in view novel means for permanently connecting adjacent slabs'in such a way that ample provision is made for movement of the slabs in' expanding and contracting under temperature changes, while at the same time offering maximum resistance to wheel batter as heavy rolling loads pass over the joint, for the purpose of effectively preventing sinking or lifting of the ends of the slabs and maintaining them in proper horizontal surface alignment under all conditions of use.

Another object of the invention is to provide a dowel plate having end sections of substantial area to be permanently and securely anchored in adjacent slabs and including an intermediate fiexing section disposed in the joint space between adjacent slabs so that all relative movement between the slabs is focused and confined to the expansion joint in such a way that all movement of the plate incident to the expansion 45 and contraction of the slabs is centered where it cannot damage the slab proper, namely, at the expansion joint.

A further object of the invention is to provide a dowel plate intended to be used in combination 50 with an expansion joint unit of the type including spaced yielding side walls which permits of the plate being readily assembled and set up with the unit at the time of installation in a simple and efiective manner and without requir- 55 ing the use of supports other than the unit itself, thereby effecting considerable economy of time and material in setting up the entire joint structure.

A still further object of the invention is to 50 provide a dowel plate meeting approved engineering practice and which is economical to manufacture and install, thereby materially enhancing the value of the invention from both a manufacturing and practical standpoint.-

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

A preferred and practical embodiment of the invention is shown in the accompanying drawings, in which:-

Figure 1 is a vertical cross-sectional view of an expansion joint between adjacent road slabs including the present invention.

Figure 2 is a perspective view of the novel dowel plate.

Figure 3 is a top plan view of a portion of an expansion joint showing the application ofthe dowel plates. in use.

Figure 4 is a side elevation of the construction shown in Fig. 3.

. employed are dowel bars which extend to either side of the expansion joint and into the concrete of the slab, the said bars being spaced transversely of the roadway in accordance with the desired specifications. This practice is open to numerous objections. For example, it is time consuming from the standpoint of installation due to the necessity of supporting the bars while the slabs are poured and in many cases subsequently removing the supports, but its primary objection is that it does not satisfactorily permit relative movement of the slabs under seasonal temperature variations. That is to say, where dowel bars are disposed across and through the expansion joint and have their opposite ends embedded directly in the concrete of the slab, the

surface adhesion between the bars and the concrete has frequently been found so great as to resist necessary expansion and contraction of the slabs with the result of causing the slabs to buckle at the joint or forcing undesirable cracks or fissures away from the joint location either of which conditions lead to a rapid deterioration of the road surface. While this objection has been remedied in some instances by providing the dowel bars with sleeves about which the concrete is molded and which sleeves in turn have been lubricated with respect to the bar by the use of bituminous compounds, nevertheless, this practice has also met with the disapproval of engineering practice for the reason that there is no assurance that the sleeves will function in practice as intended once that they are encased in the slab, and, moreover, this method inevitably affords undesirable play or looseness between the slabs which frequently sets up a. bending strain in the bars and leads to eventual ruptures in both the bars and the road bed.

It has also been proposed to equip expansion joints with angle members having one flange engaging the joint unit while the other is provided with a plurality of oblique fins or projections which are embedded in the slab, but the installation procedure in connection therewith is tedious and expensive and at the same time the projections or fins are subjected to shearing stresses which render their usefulness of short life under heavy rolling loads such as modern roadways are continuously subjected to under ordinary trafiic conditions. A further expedient utilizes a continuous flat strip extending horizontally to either side of the joint unit, a portion of which acts as a guard or shoe. While this construction has some meritorious features, nevertheless, it is expensive to install and moreover it is diflicult to pack the concrete beneath the shelf or ledge formed by the strip with the consequent possibility of original voids which are increased by the shrinkage of the concrete.

Accordingly, the present invention is intended to avoid the objections incident to present and prior practice and provide a device which has its ends firmly anchored and keyed in the adjoining slabs so that no movement between the slabs and the portions of the device embedded therein can take place, but the necessary movement in the device itself will be provided for directly in the joint space between the slabs where approved engineering practice dictates that all relative movement between sections of the road should occur. This advantage is supplemented by the definite factor of vertical stiffness or resistance to superimposed loads which effectively maintains connected slabs in proper horizontal alignment.

Referring to the drawings it will be observed that the present dowel plate is designated generally as A and may be used in connection with any selected type of expansion joint unit B intended to be located between adjacent road slabs C.

For the purposes of illustration the expansion joint B is shown to be of the air cushion type which includes a substantially U-shaped body having side walls l-l separated to provide a compensating space in the well known manner, and having a cap member 2 for supporting a mastic flller at the upper edge of the joint. In the illustration, the member 3 is merely an installing device which is used while the slabs are being poured and which is ultimately removed to expose the void or cavity for. receiving the hot mastic. The side walls |-l of the joint may be slotted as indicated at 4 (Fig. 4) or provided with equivalent means for receiving the dowel plates A as will presently appear. The expansion unit therefore serves as a rack or carrier for the dowel plates, and no other support is needed.

Referring to Fig. 2 it will be observed that the dowel member is in the form of a plate of sheet metal of suitable gauge or thickness and preferably made from a grade of steel having a comparatively low degree of fatigue. This plate includes the end sections 5-5 presenting anchoring flanges of relatively wide area, and an integral-intermediate flexing section 6 which is compressible and expansible under changes in the length of the slabs. The longitudinally alined end sections 55 are intended to be firmly embedded and anchored in the slabs C-C while the offset flexing section 8 is intended to be located in the joint space between the slabs, and, in the illustration shown, between the walls I-l of the expansion joint device. In practice the portions of the end sections 55 where they join the flexing sections 5 -5 are placed in the slots 4 of the expansion joint device B, as will be observed from Figs. 3 and 4. The substantially transversely disposed flexing section 6 therefore assumes the position previously referred to.

The entire plate A is thus vertically disposed in the roadway with its upper and lower edge portions respectively facing toward the top and bottom of the slab to be poured so that no air pockets or voids can be formed. For the purpose of insuring the anchoring of the end sections 55 in the slabs they may be provided with-the key openings 5 which may be formed by punching out the flanges 5 to one side of the plane of the section. In that connection however it will be understood that these flanges do not interfere with the pouring of the concrete and the presence of the key openings 5' adjacent the flanges also prevents the formation of pockets or voids between the end sections and the concrete when the latter is poured. It will also be apparent that due to the vertically edgewise disposition of the entire plate, little or no resistance is offered to the pouring of the concrete and it is readily possible to insure packing and setting of the concrete about the end sections 5 to insure flrm embedment and anchorage thereof in the slabs. The flexing section 5 ar- .ranged between the end sections 5-5 is of genan offset fold or gusset to provide the vertical compressible and expansibleflexing wings 1 connected by the tubular portion 8 which has the effect of absorbing and distributing relative compressive and tensioning movement between the wings Any desired number of dowel plates A may be used at suitably spaced intervals across the joint location as will be apparent from Figs. 3 and 4, and, it will of course be understood that the same may be used with any approved type or style of expansion joint unit or device.

A distinctive feature of the invention is that the dowel plates are vertically disposed so as to present maximum stiffness or resistance to superimposed loads. In'other words, the entire plate, including the end sections 5 and intermediate flexing section 6 possesses great vertical stiffness and therefore offers maximum resistance to loads imposed perpendicular to the longitudinal axis of the plate. Thus. adjoining slabs are held sive wheel batter as it is rapidly transferred from one slab to another under heavy rolling loads.

On the other hand, normal movement of the slabs under temperature changes will cause the plate to yield in the direction of its longitudinal axis so that rupture or cracking of the slabs is avoided due to the fact that all movement incident to expansion and contraction of the slab is focused entirely within the space between the slabs which is intended to provide a preformed joint.

A modified form of expansion dowel A is shown in Figures 5 and 6 from which it will be observed that the compensating or flexing section 6 is formed by folding the intermediate portion of the strip constituting the dowel so that the sides of the bend or fold are brought together as indicated at a: to form the junction of the wings 1. The end sections or anchoring portions 5 are formed similar to those shown in Figure 2. If desired, the folded portion a: of the compensating section 6 may be provided with spot welds y at suitable intervals as shown in Figure 6.

A further modification of the expansion dowel is shown in Figs. '7 and 8, wherein the dowel A is made from a relatively short plate section which is preliminarily bent into angular formation and the medial portion thereof cut away and deflected in the opposite direction to provide the yieldin compensating section 6 That is to say, according to this form of construction, a plate I is bent to form one of the end sections H and one of the wings I2 of the compensating section 6'; and, as will be observed from Fig. 8, the medial portion of the plate ill is cut or slitted along the lines I3-l3 throughout the length of the end section II and substantially but not entirely to the end of the wing portion I2. Thus, sufiicient metal I4 is left to provide a web and to permit of the cut or slitted intermediate portion being deflected to provide the wing l5 and opposite end sections I6. The flexible compensating section therefore, in this form of construction, consists of the wings I2 and I5 and the end sections II and 16, the latter being imbedded in adjacent road slabs while the compensating section lies within the joint space between the slabs.

Both of the foregoing modifications provide the desirable features and characteristics pointed out in connection with the construction shown in Figure 2. And, it will, of course, be understood that the same may be used in connection with any appropriate type of expansion joint or stool.

From the foregoing it will be apparent to those skilled in the art that the present invention will permanently connect adjacent slabs in accurate alignment and thus prevent heaving, while at the same time afiording an adequate easement for expansion and contraction of the slabs. It will also be understood that changes in the form, proportion and details of construction of the improved dowel plate may be resorted to within the scope of the appended claims without departing from the spirit of the invention or sacrificing any of its advantages.

I claim:

1.-Dowel means for connecting road slabs at joint locations comprising a beam plate of a depth to extend above and below the horizontal face of said slabs whereby all vertical loading stresses are imposed edgewise through the entire beam plate.

2. In a roadway, the combination with adjacent slabs, of means for rigidly holding the slabs in surface alignment, comprising, a dowel plate having only a vertically disposed bending axis perpendicular to the tramc surface of the slabs.

3. In a roadway, dowel means for rigidly holding the adjacent ends of road slabs in surface alignment while permitting relative contraction and expansion thereof, comprising, a metallic plate having a depth to extend above and below the horizontal axis of the slabs and disposed vertically of the roadway at a joint location, said plate having end portions rigidly anchored in the slabs and a medial flexible portion of substantially V-shape as viewed in top and bottom plan located in and disposed vertically of the joint space between adjacent slabs and effective to rigidly transmit vertical loading stresses from each slab to the other.

4. In a roadway, dowel means for rigidly conmeeting the adjacent ends of road slabs in surface alignment, comprising, a metallic plate having a depth to extend above and below the horizontal axis of the slabs and disposed vertically of the roadway at joint locations, said plate having end portions rigidly anchored in the slabs and a vertically rigid medial gusset section including a knuckle-like hinge portion and wings rigidly connected with the said end portions to prevent heaving of adjacent slabs and horizontally yieldable to permit movement of the slabs when expanding and contracting due to temperature changes.

5. In a roadway, the combination with theadjacent slabs, of means for rigidly holding the slabs in surface alignment while permitting relative movement in a plane parallel to the traflic surface in joint locations, comprising, a dowel plate having end portions anchored vertically edgewise in the slabs and having a folded inter-- mediate portion disposed in the joint space and providing only a bending axis vertically parallel to perpendicular loads imposed on the tramc surface.

6. Dowel means for rigidly connecting road slabs at joint locations comprising a beam plate having a depth to extend above and below the horizontal axis of the slabs and adapted to be disposed vertically in the roadway and including longitudinally aligned slab anchoring end portions and an intermediate vertically rigid horizontally flexible portion adapted to be located in the space between the slabs.

7. In a roadway, the combination with an ex pansion joint unit arranged between adjacent road-forming slabs, of dowel means having end portions anchored in the slabs and provided with an intermediate vertically rigid horizontally flexible portion located within the space between the slab ends.

8. In combination, adjacent road slabs having an expansion space between adjacent ends thereof, and a vertically disposed plate anchored at its ends in said slabs, respectively, and having an intermediate substantially V-shaped, vertically rigid, horizontally flexible portion disposed in the expansion space between said slabs, whereby the slabs are permitted freely to expand and contract horizontally and are held rigidly against vertical movements relative to each other. i

' WALTER F. SCHULZ.

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