US2152751A - Dowel means for expansion joints - Google Patents

Description

3 S heets-Sheet 2 w. F. scHuLZ Fiied Nov. 9, 1935 game rm ILHMH I IP HI DOWEL MEANS FOR EXPANSION JOINTS April 4, 1939.

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April 4, 1939.

W. F. SCHULZ DOWEL MEANS FOR EXPANSION JOINTS Filed Nov. 9, 1955 3 Sheets-Sheet 3 Juan/Who'l Patented Apr. 4, 1939 UNITED STATES DOWEL MEANS FOR EXPANSION JOINTS Walter F. Schulz, Youngstown, Ohio, assignor to Truscon Steel Company, Youngstown, Ohio, in. corporation of Michigan Application November 9, 1935, Serial No. 49,103

'5 Claims.

This invention relates to dowel means for expansion joints provided between the concrete or similar slabs of roadway, floors and the like, for permitting relative horizontal movement of the slabs in 'a direction parallel to the length of the dowels only while preventing the same from heaving or lifting one with respect to the other, or shifting relatively in any direction.

Many dowel structures heretofore employed are open to various objections, such for example as the cost of production; expense of installation preparatory to pouring the slab; and, also to malfunctioning in use due to improper design which causes lines of cleavage or breakage in the slabs, thereby quickly defeating the very object and purpose of the device itself. In most cases, current practice requires the relatively close spacing of dowel bars across the joint structure which is costly from the standpoint of the number of devices used, and, furthermore, various expedients must be utilized to support the dowels when the joint forming structure is first laid across the sub-grade of the prospective roadway. These supports for the dowels are for the most part located substantially at the ends of the dowel bar or rod, considerably remote from the joint forming structure, and obviously not only constitute an added expense, but also do not support or engage the dowel at the proper point, namely directly adjacent the joint forming structure itself. Therefore, when the slab is poured and the paving material is tamped close to the joint structure and about the dowels there is no support for the dowels where the greatest stress is concentrated. Consequently in use, due to heavy rolling loads, the concrete surrounding the dowel bars or rods adjacent the opposite sides of the joint structure'is subjected to great stress which results in the rapid breaking down of the concrete and the forming of bell-mouthed cavities about the dowels, the base or largest diameter portions of these cavities opening into the joint space and said cavities progressively decreasing in diameter to points eventually extending throughout the length of the end portions of the dowels embedded in each adjacent slab. Obviously, when this condition occurs, undesirable lines of cleavage are not only set up in the then unsupported ends of the slabs, resulting in cracks, but, after this condition once starts, it becomes rapidly aggravated to the point that the dowel bars become deformed or twisted so as to further increase the destructive action of the dowels on the concrete, thereby resulting in exceedingly rapid deterioration of the pavement.

Accordingly, the present invention has generally in view, the provision of novel dowel means which may be used in connection wth any type of vertical joint forming structure either of metal or other material and consisting of relatively few 5 integrated parts which may be assembled with the joint either in situ at the joint location in the roadway, or which may be pre-assembled adjacent the road building site and simply placed in position by the mere act of disposing the as- 10 sembled joint and dowel means at the predetermined joint location. In that connection, the arrangement is such that the entire structure will stand erect without the necessity of supplemental anchors, pins or other supports and pour- 1 ing the concrete may proceed in an expeditious manner. When the concrete is poured, the entire structure is so embedded in the finished pavement that all of the vertical stresses are absorbed at the proper point, namely immediately adjacent the joint structure, and, from thence are adequately distributed so as to avoid the setting up of cleavage lines and preventing disintegration of the concrete at the location of the dowel bars.

More specifically, the invention contemplates a dowel structure including a horizontally disposed dowel bar or rod which passes through themedial portion of the joint structure and'has rigidly affixed to one portion thereof, novel combined supporting, anchoring and load distributing means, while the opposite portion of the bar is intended to be slidably received in a comple-. mental or mating supporting, anchoring, and load distributing element, suitable means being provided for preventing the plastic concrete form 35 filling or otherwise interfering with the space provided in said element for the movement of the dowel. This arrangement makes it possible to fit one section of the anchoring means against one side of the joint structure and then telescopically to apply the other section of the anchoring means having a guide to the end of the dowel bar projecting through the other side 01' the joint structure, so that when both sections are completely assembled with reference to the expansion joint, the entire joint 'and dowel structure is completely self-sustaining and ready for emplacement in the roadway.

Another object of the invention is to provide a dowel structure including anchoring means having portions fitting closely adjacent the sides of the joint structure while other portions thereof are preferably disposed in a vertical plane and at an angle inclining away from the opposite faces of the joint structureto be embedded in the concrete above and below the horizontal plane of the dowel bar. Thus, the combined supports and anchors may become completely embedded in the concrete in such a way as to adequately distribute the stress of superimposed loads over a maximum area of the concrete in the adjacent end of each slab and provide increased bearing value at the point of greatest bearing load, namely, where the dowel bar emerges from opposite sides of the joint structure, thereby avoiding the concentration of shearing stresses in the slabs in the immediate vicinity of the dowel pins, and placing all of the concrete throughout the depth of the slab ends in compression instead of partly in compression and partly in tension, that is in compression above and tension below the line of the dowel pins, as occurs with structures of the objectionable type heretofore referred to.

Further objects of the invention are to provide a strong dowel structure which requires the use of the least number of units across the roadway; to provide a compact joint and dowel assembly which utilizes a dowel bar of substantially square or rectangular cross-section to obtain greater bonding area on one end of the dowel and a greater bearing area on the other; to provide dowel guiding means having maximum strength in the direction of superimposed loads; to provide dowel anchor elements which may be formed in a simple and expeditious manufacturing operation and likewise assembled with respect to the dowel bar and the dowel bar guiding means in a rigid and stable manner by welding, thereby providing a structure which in its installed condition gives maximum strength and rigidity to the ends of the paving slabs under all conditions of use.

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 in the accompanying drawings and defined in the appended claims.

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

Figure 1 is a transverse section through a joint constructed in accordance with one practical embodiment of the invention.

Figure 2 is an end view of the joint forming units.

Figure 3 is atop plan view of one of the joint forming units.

Figure 4 is a perspective view showing the interfitting elements forming the tubular structure tr; slidably receive one end portion of the dowel p n.

Figures 5, 6 and 7 are views similar to Figures 1, 2 and 3, respectively, illustrating an altemative embodiment of the invention; and

. Figure 8 is a view partly in elevation and partly in section illustrating a slightly modified form of the tubular element forming pieces.

According to the several embodiments of the invention shown in the drawings, the present novel dowel means is intended to cooperate with any selected type of joint forming structure designated generally as A disposed between the ad- .jacent end portions of adjacent concrete or similar slabs Iii-i of the roadway.. The novel dowel means is designated generally as B and includes the dowel pin or bar H used in connection with the combined supporting, anchoring and load or stress distributing elements C which have special features and characteristics to be later referred to more in detail.

As shown, the dowel pin or bar II is preferably made of rectangular cross-section thereby to provide a greater bondingsurface for the end of the dowel which is embedded in the slab than if a round section were used, and to also provide a greater bearing area in theguide or frame member l2 which forms a part of a tubular housing in which the free or unbonded end of the dowel moves or slides under expansion and contraction of the slabs l0-lll. The guide I2 is preferably of a relatively heavy gauge strip of metal of U- shaped formation, horizontally disposed, with the edges thereof disposed sidewise so that the flat sides are disposed above and below the top and bottom faces of the dowel bar, thereby affording greater strength to the housing. To complete the housing a light strip of metal III, also of U-shaped formation, is placed within the guide i2 but, as will be apparent from the drawings, the same is set at an angle of 90 with respect to the member l2. That is to say, a tubular housing structure is provided to slidably accommodate one end portion of the dowel bar or pin by interfitting the two U-shaped pieces of metal designated as l2 and i3, the piece I! including upper and lower leg portions and the piece l3 fitting between the leg portions of the piece l2 and including opposite side or leg portions closing the sides of the space between the leg portions of the piece l2. Since the piece 13 carries little or no load and its main function is simply to provide closures for the sides of the space between the legs of the piece l2, it may be formed of relatively light sheet metal. on the other hand, since the legs of the pieces I2 transmit any loads to which the slabs and the dowel pins-are subjected, said piece I! may be formed from metal amply thick and strong to carry such loads.

Regardless of the specific form of the tubular elements or structures embedded in one or the other of the slabs and each slidably accommodating one end of a related dowel pin, the means for distributing loads and stresses over large areas of the slabs in the vicinity of the dowel pins comprises for each dowel pin unit, a load or stress distributing member l4 rigid with the tubular element or structure of theunit and a similar load or stress distributing member I rigid with that end portion of the dowel pin opposite the end portion thereof which is slidably engaged in the tubular element or structure of the unit and a similar load or stress distributing member l5 rigid with that end portion of the dowel pin opposite the end portion thereof which is slidably engaged in the tubular element or structure.

The load or stress distributing members l4 and I5 preferably, but not necessarily, an duplicates of each other, and also serve as combined supporting and anchoring means for the dowel bars. As illustrated, each member is formed from a single length of rod of preferably, but not necessarily, round section and comprises a horizontally disposed bottom portion l6 and a pair of arms l1, l1 extending upwardly and inwardly from the ends of said bottom portion, respectively. The arms extend upwardly and inwardly to points where the space between them is approximately equal to the width or thickness of the dowel pin, which, as previously indicated, is preferably formed from square or rectangular stock. From these points said arms are extended upwardly parallel to each other, as indicated at l8, l8, distances approximately equal to the heighth of the dowel pin and thenare directed upwardly and outwardly, as indicated at I9, I9, and finally are directed horizontally outward short distances as indicated at 20, 20. In addition, each member I4 and I5 is bent at its portions I8, I8 so that the arms I1, I! below and above the bend are disposed in planes obtusely related to each other.

The member I4 straddles the tubular element or structure I2, I3 and is rigidly secured thereto in any suitable manner, as, for example, by being welded to either or both of the pieces I2, I3 adjacent to their inner ends. The said pieces I2, I3 extend between the arm portions I8, I8 of the member I4 and the latter is disposed relative to said pieces as viewed in side elevation so that when the latter are disposed horizontally the portions of the arms I1, I! which are disposed below said pieces extend downwardly and toward the outer ends of said pieces and the portions of said arms which are disposed above said pieces extend upwardly and toward the outer ends of said pieces.

The member I5 straddles the dowel pin II and is rigidly secured thereto by welding or in any other suitable manner, the pin extending between the arm portions I8, I8 01 the member I5 and the latter embracing and being secured to said pin at a point suitably spaced inwardly from the end portion thereof which is designed to be fixedly embedded in one of the slabs Ill. The member I 5 bears the same, or approximately the same relationship to the dowel pin II as the member I4 bears to the pieces I2, I3. In other words, the

' member I5 is disposed relative to the dowel pin as viewed in side elevation so that when the dowel pin is disposed horizontally, the portions of the arms II, II below and above the dowel pin extend downwardly and outwardly and upwardly and outwardly, respectively, toward the adjacent end of the dowel pin. I

In connection with the members I4 and I5 which are rigidly secured to the pieces I2, I3 and to the dowel pin, respectively, obviously the same provide for great facility in locating and supporting the dowel pins and joint forming structure prior to and during pouring of the slabs, inasmuch as by initially assembling each dowel unit by inserting the proper end of the dowel pin into the related tubular structure I2, I3, the two members I4, I5 cooperate to form in efl'ect a fourlegged stool for supporting the dowel and joint forming structure in the proper position.

Although any suitable means may be employed to define an expansion space between the poured slabs, such means is illustrated in the present instance as comprising a two-part sheet metal casing designated generally as gl and including slab end defining walls which are capable of movement toward and from each other responsive to expansion and contraction of the slabs. This casing may be formed in one piece extending the full length of a joint, or it may be formed in separate sections individual to the respective dowel pin units. If it is formed in one piece, openings are formed therethrough at spaced intervals to accommodate the dowel pins, and if it is formed in separate sections, a dowel pin accommodating opening is formed through each section. As is understood, the casing or the casing sections, as the case may be is, or are, as-

sembled with the dowel pins prior to pouring of l the slabs.

In a completed construction the dowel pins are located approximately midway between the top and the bottom surfaces of the slabs III, III and as viewed in side elevation, into the slabs in downward and outward and upward and outward divergent relationship, respectively.

Because of the members I4, l5 being fixed to the pieces I2, I3 and to the dowel pin, respectively, and because of the arms I1, I I of each member I4, I5 extending as illustrated and described, any load imposed on either of the slabs obviously is not concentrated in the immediate vicinity of the dowel pins where they pass through the joint forming structure, but is distributed by the members I I, I5 throughout large areas of the slabs above and below and to each side of each dowel pin. Thereby rupturing and breaking away of the slabs is eliminated. Moreover, since the arms I1, I! of the members I4, I5 extend from the medial horizontal planes of the-slabs to the bottoms thereof, any load to which either slab is subjected is transmitted by said arms to the bottoms of the slabs. Thus, the adjacent end portions of the slabs function entirely, or substantially entirely, in compression to the exclusion, or substantially the exclusion, of tension, which is another important reason why the adjacent portions of slabs connected together by the present dowel devices are not easily ruptured or broken. Moreover, since the load or stress distributing members I 4 and I5 are located with respect to the tubular structure -I2, I3 and the dowel pin, respectively, so that in the completed joint the portions of said members in the immediate vicinity of the tubular structure and the dowel pin are located closely adjacent to the adjacent end faces of the respective slabs, any working of either the tubular structure or the dowel pin in its related slab with the consequent forming of a bell-mouthed recess in either slab about either the tubular structure or the dowel pin, is effectively prevented.

In the Figures 5 to 8 form of the invention the construction is quite similar to the Figures 1 to 4 construction and the same advantages are obtained as in the first described construction. Whereas the'load and stress distributing'members I4 and I5 of the Figures 1 to 4 form of the invention are, however, of one-piece construction, the Figures 5 to 8 form of the invention includes a pair of load or stress distributing members I4 for the tubular structure and another pair of load or stress distributing members I 5 for the dowel pin. A very material advantage of this is that the separate members I4, I5 may be economically produced each by a single stamping operation.

Each member I4, I5 comprises a short straight vertical portion I8 directed laterally outwardly at its upper end, as at 20 and a portion I1 extending downwardly from the portion I 8 at an angle thereto and directed laterally outward at its lower end as at I6, the said portions I6, I1 I8 and 20 all being disposed in a common plane.

The portions I8 of a pairo! the members I4 are welded or otherwise secured rigidly to the outer end of the tubular structure designated as I2, I3 at opposite sides thereof, respectively,

and the portions l8 of a pair of the members i5 are welded or otherwise secured rigidly to the dowel pin II at opposite sides thereof. respectively, at points spaced inwardly from its end which is embeded in one of the slabs Ill so that in the completed joint the said portions l8 are disposed at, or closely adjacent to, the adjacent end surfaces of the slabs.' Moreover, thedisposition of the members M, It* relative to the tubular structure and the dowel pin, respectively, is such that the plane of the portions l6, il and 20 of each member is disposed at an angle of approximately 45 to the dowel pin, with the said portions l6, H and 20 extending from the portion 3 into the material of the respective slabs and the portions l6 disposed horizontally at the bottoms of the slabs. The functioning of the members l4, I5 to distribute stresses imposed on the tubular structure and the dowel pin thus is the same as set forth in connection with the Figures 1 to 4 form of the invention.

As will be observed from Figure 8 of the drawings, the outer end wall of the piece l2 of the tubular structure may have its edges bent inwardly, as indicated at H to embrace the outer end portion of the piece l3, thereby to position the outer end of the piece l3 relative to the piece I2.

Y From the foregoing it will be apparent that the present invention primarily includes a dowel B and supports C therefor which not only provide a temporary chair like structure for the dowel as well as the joint forming means during installation, but which also perform the more important function of a permanent support for the dowel where it emerges from the slabs to span the joint space. In their fundamental aspect the supporting elements are bowed or bent cross-wise of the dowel so that the crowns or zeniths of the bends are relatively back to back at the point where the critical stresses are focused on the dowel. In other words, the supporting elements C are of wing-back or wedge formation as viewed in side elevation and the arms of the wings or wedge are relatively radially disposed to the dowel at an oblique angle. Thus the focused stresses are deplayed and distributed in the material of the slab so that chafing or abrasion between the dowel and concrete is avoided and the material of slab ends is strengthened because it is in compression throughout its beam loading depth.

Without further description it is thought 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.

I claim:

1. Connecting means for a pair of slabs comprising a dowel pin extending between and into the slabs, a tubular structure embedded in one of the slabs and slidably accommodating the related end portion of the dowel pin. and means for dispouring of the tributing stresses to which the tubular structure is subjected when either slab is loaded, said means comprising arms rigid with said tubular structure directly adjacent to the end face of the related slab and extending upwardly and outwardly and downwardly and outwardly, respectively, from said tubular structure into the material of the slab.

2. Connecting means for a pair of slabs comprising a tubular structure comprising a pair of interfltting U-shaped pieces embedded in one of the slabs, a dowel pin embedded at one end in the other slab and having its other end slidably engaged in said tubular structure, arms rigid with the tubular structure extending downwardly and outwardly therefrom into the material of the related slab, and arms rigid with the dowel pin extending downwardly and outwardly therefrom into the material of the other sla 3. A reinforced joint for concrete road slabs comprising in combination with an expansion joint structure extending vertically throughout the depth of the adjacent slabs and adapted to rest on the sub-grade, a reinforcing dowel extending between said adjacent slabs and through the said expansion joint structure, and reinforcing members having a supporting connection with the dowel on each side of the joint and including reinforcing elements extending from the sides of the joint into the slabs above and below the dowel and away from the joint and also-including base portions adapted also to rest on the sub-grade to support the entire unit during the concrete or equivalent plastic.

4. A reinforced self-supporting joint unit for concrete road slabs, comprising, in combination, with an expansion throughout the depth of the adjacent slabs and adapted to rest on the sub-grade, a reinforcing dowel extending between said adjacent slabs and through the'said expansion joint structure, and reinforcing members engaged with said dowel to prevent rotation thero said members being arranged on each side of the joint and including reinforcing elements diverging from the sides of the joint 'at the location of the dowel into the slabs above and below the dowel and also including base portions adapted to rest on the subgrade to support the entire unit during the pouring of the concrete or equivalent plastic.

5. A reinforced self-supporting expansion joint structure for concrete roadways, comprising, in combination, an expansion joint having load transferring dowels extending through the same and to opposite sides thereof for embodiment in adjacent concrete slabs, reinforcing members having a supporting engagement'with the dowels adjacent the sides of the joint, each reinforcing member including reinforcing elements extending into the slabs above and below the dowel, the portions of said elements extending below the dowel including base portions adapted to support and brace the entire unit during the pouring of the concrete.

- WALTER F. SCHULZ.

joint extending vertically'

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