US2572552A - Load transfer device - Google Patents

Description

Cctl. 23, 1951 D, E, w|LLARD 2,572,552

LOAD TRANSFER DEVICE 5 sheets-sheet 1' Filed Aug. 21, 1946 anaZaE lll/ 1rd jf mm.

Oct. 23, 1951 D. E. wlLLARD LOAD TRANSFER DEVICE Filed Aug. :21l 1945 v 5 Sheets-Sheet 2 In z/ W 11: waldEWlI/dfd Oct. 23, 1951 D. E. wlLLARD "l 2,572,552

` LOAD TRANSFER DEVICE Filed Aug; 2 1, 194e 5 sheets-sheet 3 151%; 11 n; wzdgmzzqfd D. E. wlLLARD LOAD TRANSFER DEVICE O ct. 23, 1951 5 Sheets-Sheet 4 Filed Aug." 2l, 1946 E11/nim? onaaEWL/lard.

Oct. 23, 1951 n. E. wlLLARD LOAD TRANSFER DEVICE 5 Sheets-Sheet 5 Filed Aug.' 21, 1946 atentecl ct. 23, 195i LOAD TRANSFER DEVICE Donald E. Willard, Danville, Ill.

` Application August 21, 1946, Serial No. 692,068

e Claims.

My invention relates to load transfer devices and, while more particularly intended for use with concrete roadways as a means for transmitting loads between and permitting expanding and contracting movements of the slabs, is also capable of adaptation to concrete slab structures generally, including wall sections, where load transference is an important factor.

In concrete highway construction, for example, it is desirable to transfer loads between and to prevent relative vertical movements of adjoining slabs and thus maintain their top surfaces in coplanar relation. Where common dowels alone are used for these purposes, it has been ascertained that the passage of traic over the roadway and the upward pressure of the subsoil as affected by the condition of the latter sets up critical, localized pressures in the concrete around the bars adjacent the opposedor joint faces of the slabs. This action, known as funneling, crumbles the concrete around the bar sufficiently to permit definite relative movements of the adjacent slab sections which are objectionable.

It is therefore one object of, my invention to provide devices for use with common dowel bars which, in addition to preventing funneling by an efficient distribution of the operating loads, regardless of their direction of movement across the separating member between the slabs, and to reinforcing the joint facesof the slabsv against lateral flow due to vertical loads, also has limited contact with the dowels in the critical "regions so lthat adjacent slabs may move freely relative to each other along the length of the roadway without possibility of rust freezing of the devices and bars.

A further object is to devise a reinforcing member which may be arranged in a variety of ways to provide the desired load distribution between the bar and slab and to strengthen thev joint face of the slab, but which includes in any case'a skeleton-like formation in the funneling regiony having portions providing bearing for the dowel.

These and further objects of my invention will be set forth in the following specification, reference being had to the accompanyingA drawings, and the novel means by which said objects are effectuated will be definitely pointed out in the claims.

v In the drawings:

Fig. 1 is a sectional elevation of` one form of my improved' load transfer device, as taken along the line I-I in Fig. 2. showing the same-in operv2 ative relation to the adjoining slabs of a roadway.

Fig. 2 is a view of the device looking in the direction of the arrow 2 in Fig. 1, the slabs being omitted.

Fig. 3 is a plan view of the left hand, reinforce ing member of the device as it appears in Fig. 2.

Fig. 9 is a view similar to Fig. 4, but showing a variant method of arranging the bearing plates which transfer'load between the dowel bar and slabs.

Fig. 1o is a Sectional new/ation simnar' to Fig.

1 showing a further modification' of the device. Fig. 11 is a view of the device shown in Fig. 10 looking in the direction ofthe arrow l I, the slabs being omitted.

Fig. 12 is a section along the line I 2-l2 in Fig. l0, the slab being omitted.

Fig. 13 is an end view, partially in section, similar to Fig. 4, showing a modified reinforcing member having the bearing plates arranged to provide a greater area of Contact with the dowel bar.

Fig. 14 is a sectional elevation similar to Fig. l showing another modication of the device.

Figs. 15 and 16, respectively, are a plan view looking in the direction of the arrow I5 and a section along the line I-IS in Fig. 14, the slabs being omitted.

Fig. 17 is a sectional elevation similar to Fig. 1 showing another modification of the device.

Figs. 18 and 19, respectively, are a plan View looking in the direction of the arrow I8 and a section along the line lil-I9 in Fig. 17, the slabs being omitted.

Fig. 20 is a sectional detail showing a modification of the washers that may be used in any of the load transfer devices.

For purpose of illustration and as exemplifying one use of the improved device, the same will be described in connection with a roadway. It will be understood, however, that the essential conception involved is likewise susceptible of adaptation to structural sections in general, regardless of their composing material, where such sections are subject to expansion and contraction and it is desired to prevent buckling or cracking of adjoining sections by inserting a yielding member therebetween, or where such sections are subject to transverse pressures and it is desired to prevent any funneling action around the dowel or reinforcing bars which extend between adjoining sections.

Referring to Figs. l to 4, inclusive, of the drawings, the numerals ID and II designate a pair of adjoining concrete slabs which are spaced by an expansion strip I2. This strip may be composed of a bituminous mixture, such as is now commonly employed in the industry forstrips of this nature, or it may be formelof ncork or rubber, or the expansion may be accommodated by the so-called metal walled joint in which thin metal walls provide facings forthe opposed ends of the slabs, the walls being separated by an airspace or other yieldable filling." All of the foregoing expansion members or strips are well known in the art and in and of themselves form no part of the present invention. Inany case, it is contemplated that the strip will be arranged so that it will not only'yi'eld in response to movements of the slabs, but 'will be eoinpo'sed of a material that is resistant to Water, earth acids, or any other decomposing influences` which are commonly met with in use of structures. of this type. The thickness of the strip may be varied as, desired.

A dowel bar I3 is bridged betweenand has its opposite ends entered into the slabs IG and II, respectively, the intermediate portion of the barv passing through. a suitable aperture in the strip -I2,'thus establishing a characteristic road joint. It will be understood that a 'plurality of these bars are spaced across the width of the roadway in accordance withstandard practice, Athe spacing being generally dependent on the thickness of the slabs and the diameter of the bars. Preferably, the dowel bars are positioned at mid-depth or in the neutral plane of the slabs, parallel to the top surfaces and normal to the joint faces of the slabs. So far as described, the structure is typical of the so-'called common' dowel 'bar method of transferring loads between the slabs.

The inventiony consists inI associating with each dowelA bar a 'pair of reinforcing members which i.,

are identical and of a noveltypethe members of each pair being located in facing relation on opposite sides of the strip I2 and embedded in the respective slabs. Specifically, each reinforcing member I4 comprises a vertical plate I, 5 which is embedded in the joint face of the associated slab and isz apertured at IBfto, receive the. dowel barY I3. The lower end' Qf the plate I5 is bent to providea footing I'I vfor resting on the subgrade I8 and the, end of the` footing 4II, terminatesL in a load 'distributing wing vI9 which extends upward into the slab` below the dowel bar and may be shaped as desired to provide, adequate anchorage in the concrete.r 'The uppeiend of the plate I5 is bifurcated to provide apa'irofload distributing wings'20-20 vwhich arev bent out of theplane of the Aplate for emb'edm'ent and anchorage Vin the associated slababove the dowel bar. 'By reason of the position of the dowel bar in the slabsfit will be obvious that the wings L9` and`20 are disl posed in the tension ah/Vd'conpress'ion regionsof each slab, respectively. l

To provide further reinforcement and prevent deterioration of the'concifetev around the dowel bar adjacent the joint' face of each slab, a

skeleton structure 2| extends inwardly of the slab, is rmly connected to the adjacent plate I5 and is symmetrically related to the dowel bar I3. The structure 2| comprises a pair of rib-like bearing plates 22-22 which are diametrically related on opposite sides of and contact the dowel bar in the vertical plane thereof. The outer or joint face ends of the plates 22 are secured, as by welding, to the plate I5, while the inner ends are similarly connected to a wasl'ienZwhich encircles and may closely and continuously fit the bar i3, or the inner periphery of the washer may be relieved or cut away in locations 24-24 (see Fig. 4) so that the washer has bearing contact with the bar only adjacent the plates 22, i. e., inflocation close to the vertical plane which includes the longitudinal axis of the bar. This variant shaping of the washer 23 may also be employed in the modifications of the device presently described.

The expansionlstrip I2 is assembled with ,its dowel bars I ,3 whose. number willA depend upon .the width 0f the readwavand the Spacing of the bars and" with each bar having a pair f reinforcing membersv Idfabutting `opposite sides of the stripfall as shown in 1"ig.`1. To accommodate expanding and contracting movements of the slabs, each` dowel'bar I3 is greased o n one side ofthe strip I2 andthe end ofthe bar onV thesame side is partially entered intoa sleeve 25 whose remaining portion is filled with a suitable lubri-v cant that. retained by closing. the adjacent end of the sleeve as by pinching lat 26. Hence, on one side ,of the strip I2,the eoncrete forming the slab` II, forv example, will'ndt bond to the'bar while the lubricant filled space in the sleeve,2 5 permits expandingf'and contracting movements of the. slabs. The` concrete-forming the slab I0, for example, bonds directly. to the! bar I3 on the opposite side of thestrip `I2I However, it may be preferable te grease, both ends of the dowel bar.

The jointstructure lratlzing been assembled as above described, it is laidwith the footings I'I resting on the subgrade I.8. The footings have sufcient area toprovide. a', stable support for. the. assembly untilfthe` eenerete poured, but itis'. desirable'toV .definitely -hold the assembly against sidewise movementuueto, the' peering 'impact or the concrete` y the usual'ground locating' stakes which maybe driven'into'the. ground along'the side of the, strip' I2, orthrough apertures in the footings; V

Under opeigating. conditions, theV plate I5 is embedded and provides. lateral support forgthe concrete at the joint faceY of "the slab adjacent the dowel bar due to its connection' with therwings ISand 2.0 whicharermly anchored. in the. slab, While, the bearingfplates 22 and the washer, 23, which in, effect4 donstitutean enlargement of the. dowel ball., Seli-Ye', toreducehefunit pressune on the. adjoiningV concrete.aridso reduces the nelingY tendencyr aroundthefbar adjacent the jointl f-aceof thed'slab. The plate I5, bearing plates 22'andwas'her 23'have bearing contactwitl-r the. doweibar I3 andere. vernardispesitien of the plates 2 insures the-most.eflicient'transfer of load. betweenthe barand'. slab. An outstand ing feature of thecons'truction is that whilealdequate bearing is provided forthedowel bal-in 23V serves to strengthen and tie the skeleton 2| and the whole arrangement is such that the concrete will ow freely around the assembly without cavitation during the pouring operation. The

' stresses which are set up in the funneling region are carried into the body of the slab sections by the wings I9 and 20, the bearingr plates 22 and the washer 23, .as further reinforced by the dowel bar I3. These elements serve to better distribute the imposed loads without setting up critical pressures in the concrete, to more adequately utilize the compressive strength of the concrete, and to develop substantially the maximum shearing strength of the concrete, one of the wings I9 or 20 being always in tension and the other in compression, dependent upon the location of the load and the slab to which it is applied. Any tendency of one of the slabs to move downwardly is resisted by the dowel bar I3, the skeleton structure 2| and the engagement of the wings I9 and 29 with the slabs, and, further, since the skeleton and wings are located above and below the bar, the construction is most efficiently designed to resist the vertical loads commonly encountered in roadways.

In Figs. 5 to '7, inclusive, is illustrated a modication of my improved device which includes the skeleton bearing structure in the funneling region in conjunction with a variant arrangement of load distributing arms lor wings- As in Fig. 1, a dowel bar I3 is bridged at mid-depth between slabs IIJ and II vwhich are separated by an expansion strip I2 through which the bar extends. Associated with the bar on opposite sides of the strip I2 and through which the bar extends is a pair of reinforcing members 28, each of which includes a skeleton structure 29 composed of a washer 30 which is embedded in the joint face of the particular slab, a pair of bearing lplates 3 I-3I each connected at one end to the washer 30 and projecting into the slab in diametral relation on opposite sides of andlying in the vertical plane of the dowel bar I3, and a web 32 connected to the opposite ends of the plates 3| and having a pair ofdiverging arms 33 and 34 extending into theslab above and below the dowel bar, respectively.

The dowel bar is greased on one side of the strip I2 to prevent bonding with the concrete and relative movements of the slabs I and II towards and away from each other are accommodated as in Fig. 1 by a cup 35 partially lled with lubricant and into which the greased end of the bar I3 partially extends. Support for the assembly when initially rested on the subgrade is provided by a standard 36 which depends from each washer 3D and carries at its lower end a footing 31 for contact with the subgrade.

' The characteristics of this modication are generally identical with that illustrated in Fig. 1. The washer 30 provides lateral reinforcement for the concrete in the funneling region and it, together with the bars 3I and Web 32, comprise the skeleton structure 29 which reduces the unit pressure on the concrete and along with the arms 33 and 34 transmits and distributes loads between the dowel bar and slabs into the tension and compression regions of the latter. As before, the skeleton 29 has bearing contact with the dowel bar I3 and rust freezing of the latter is prevented by .theA nature of its limited contact with the skeleton.

In Fig. 8 which illustrates a modification of the loadtransfer device shown in Figs. to 7, inclusive, the-change consists in reversing the positions of the web 39 and Washer 40, respectively, corresponding to the web`32 and washer 30 ln Fig. 6. This arrangement abuts the web 39 against the expansion strip I2 so that it instead of the washer provides lateral restraint for the concrete at the joint face of the slab in the fun'- neling region. Otherwise, the operation and characteristics of this modification are the same as for that shown in Fig. 5. It Awill be understood that a section along the line 8-8 in Fig. 8 is the same 4as that shown in Fig. 7, except that the standard 36 depends from the web 39 instead of the washer 40 and hence the web 39 and washer 40 are connected by vertical bearing plates 4I above and below the dowel bar I3 and lying in the vertical plane of the latter and the ends of the web 39 terminate in diverging pairs of arms which extend into the slab. above and below thevdowel bar, only the upper arms 42 being shown in Fig. 8.

Fig. 9 illustrates a modified arrangement of the reinforcing member I4 shown in Fig. 4 which consists in providing slightly more bearing contact between the dowel bar I3 and skeleton structure 2I. Like parts are designated by the same-numerals in the two gures. 43, corresponding to the lowermost bearing plate 22 in Fig. 4, lies in the vertical plane of the bar, but above the bar, two radial bearing plates 44 are'bridged between the plate I5 and washer 23. The plates 44 are positioned on opposite sides of and are symmetrically related to the vertical plane of the bar, the preferred angular relation between the plates being of the order of 45, or

about 221/2 on each side of the vertical plane of the bar.

In Figs. l0 to 12, inclusive, is illustrated a further modication of the device. The dowel bar and lubricant lled cup are identical with the form shown in Fig. 5 and are accordingly denoted by the same numerals, as are the slabs and expansion strip. A pair of L-shaped stampings 45 constitute the major reinforcing elements of the structure on each side ofthe strip and they are positioned to lie in the vertical plane of and above and below the bar,-respectively. The vertical limbs 46-46 bear on the dowel bar I3v and theiropposite, vertical edges are firmly attached to washers 41 and 43 which also have bearing on the bar with the washer 41 embedded in the joint face of the associated slab and abuttingV the expansion strip I2. The horizontal limbs 49 act as load distributing arms'and respectively extend into the compression and tension regions of the slab. The characteristics and advantages of this arrangement are the same as those described above, with the additionthat the use of' this shape of stamping provides load distributing arms and bearing plates for the dowel bar in a single element. It will be understood that `,the limbs 49 need not be horizontal, but may extend into the slab at any angle.

To provide support on the subgrade for the as. sembly shown in Fig. 10, the ends of the vlimbs 49 may be enlarged and drilled to receive through the lower limbs only positioning stakes 50, or the indicated ends of the limbs 49 may be simpl curled for the same purpose.

Fig. 13 illustrates a further variation of the reinforcing member shown in Fig. 4 wherein additional surface contact of the bearing plates with the dowel bar may be secured even if only* A lower bearing platea .-vide.l addedv bearing surface for the bar.

.agseassz 7 .ingfplates are *indicated by. the numeral 5 I and, asin Eg'..4,theyv lie inthe vertical planeof: the fbarr: However, the .dowel bar, contacting faces infr-the. piatesare coined or; upset as at.52 .to proyOtherwise, the; construction is. .identical .with .that

Shown in FgA.

a 1ReferringtoFigs- 14. to 16, inclusive-.therefis illustrated av further variation ofthedevice in which the vertical bearing platesv are shaped. and :arranged for tying in with the Slabs as loaddis- 'tribu-ting elements, -in addition to y performing `,their:primary functions. Since-the Vdowel bar andilubricant filled cup are identical .with those sliqwnjin Fig..5,1they are denoted bythe same '.numerals,asare the. slabs and expansionrsrip. `Reinf'orcing members; 53. are located on opposite sides ofthestrip `I Zand-.each comprises awasher L54; embedded in the joint: face of the associated slab and abutting the adjacent side of thef-fstrip lft2', hand diametrally related, bearing .plates Ses-55: positioned in the= funneling region on opposite' sidesiof and-.in the vertical-plane of the f-bar t3. @ne end of-each bar isiirmly attached, as byA welding, to thezwasher `t'nflanclthe, opposite end fis@ horizontally split fora predetermined 'dis- -tancietowards .the `joint face of ltheslab to form .arms Mie-5.6 which are. bent in opposite directionsfor anchored embedment in theslab and yfor Aacting asV load distributing elements. This vconstructionprovides a. .pair of such. arms above and1-below the dowel' bar on opposite sides of .the4 strip.- l2. Each washer 54. is preferably prot vided with. a. downward,v extension 54e which in- 'cludesan adequate: footingllb for. resting on the subgrade. The characteristics of this modification areV the salinev as those described above.

A further variationis: shown in Figs.. 17 to 19, inclusive, :which bears some similarity to that illustrated in: Fig. 11i-.in respect of the positive anchorage-of the bearingV in the slabs. The slabs, expansion strip, dowel bar and lubricant filled cuplare identified bythe same numerals as in Fig; Enf..Vv Reinforcing.. members 5.1v are; `positioned on opposite sides.v of the. strip I2 and each comprises-a .washer 158 embedded inthe joint face off .the f associatedslab, diametrally related, bear:- ng-:plates 59:-.-5S-.1ocated in the funn'eling'region on; opposite sides. of and-inA the vertical plane of `the bar |23', the oppcsite...fend.s4 of .eachllate bef ing secured; as by welding, to the washer-53 and .aa washer 60; inwardly of the slab, and a horizon.- tal element. 6| .transverse to and extending throughv each`- plate 59. AEach elementA 6 I extends for-the same distance on; each side of the associatedv plate 59a and the ends thereofare preferably-enlarged as.v at 62 tof provide` anchorage in thefslab, thus providing` a, pair of load distributing'arms eachabove and below thedowel bar on eachside of the strip I2. The modev of operation of this arrangement is the same as in the preceding modifications.

l In Fig, 2,0 is illustrated a modifiedY detail which may; be employed with any 0f the 'other designs. The'fnumeral 63 designates a dowel bar, but instead of associating therewith one or more'circular Washers as illustrated in the'various modifications, a squarc'lwasher' 64 may be used and positioned with its diagonals vertical and horizontal, respectively.

While all of themodications--are indicated' as incorporating round dowels, it willbeunderstood that thezshape ofv ihisnbar may be varied' as: desired; .including those having square .and rectangular. cross` sections` and sections .other .than

round which. are characterized byl continuous lateral surfaces. Further, in allvariationsof :the device, both ends of :the dowel bar .,mayvbe greased, if desired. I

From the foregoing, it will be understood` that all of the above described modiiications have certain characteristics in common, namelygthe use of a skeleton structure in the funnelingregion of theslabwwhich provides adequate bearingzfor the dowel bar and insures a reduction in thefunit pressuref'on the concrete around the bardu-ring load'transfer, a substantial freedomfromrust freezing of the dowel whichwou-ld otherwiseulock the. adjacent slabs against `.relative movement lengthwise of the roadwayand cause fracture of the concrete, a. denite lateralsupport for'. the concrete around the dowelat the joint :facecf ea'ch slab, and an effective distribution ofthe applied load from one slab to the next.

I claim: v

l, A load transfer device for concrete slab joint construction` comprising a dowel bar, anda pair of spaced, skeleton, reinforcing structures-surrounding the bar at an intermediate part thereA of, each structure including spaced plate-means through which the bar extends .inf bearing.V relation thereto, one of the plate vmeans beingadapted for embedment in the joint face of the associated slab andrib-like bearing plates extending-between the plate means above andbelow and having edge contact only with the bar.

2. A load transfer device for concrete :slab joint construction comprising a dowelbar,a'nd av pair of spaced, skeleton, reinforcing strucitn-'es surrounding the bar at an intermediate Apart thereof, each structure including spaced plate means through which the bar extends inbear-ing relation thereto, one of the plate'meansxbeing adapted for embedment in the joint face of the associated slab, a rib-like bearing plate extending between the' plate means below and` lying in the vertical plane of the bar, and aI pair of rib-like bearing plates-extending between the plate means above and radially related to and symmetrically positioned on opposite sides of the vertical plane ofthe bar, all of the bearing plates having-edge contact only with the bar.

3. A loadv transfer device for concrete 1- slab joint construction comprising a dowel barpapair of spaced, skeleton, reinforcing structures sur rounding the bar at an intermediate-part'-there4 of, each structure including spaced plate means through lwhich the bar extends in bearing relaf tien thereto,l one of the plate means being adapted for embedment in the joint face of the-associated slab, rib-like bearing platesextending between `the platemeans above and below and having edge contact only with the bar, and stress Acarrying arms extending from said one plate# means above and below the bar.

4. A load transfer Vdevice for concrete slab jointconstruction comprising a dowelbarf and av pair-A ofspaced, skeleton, reinforcing structures surrounding the bar at an intermediate-part 'T thereof, each structure including rstandv ses` ond, spaced plate means through which the bar extendsin bear-ing relation thereto, theiflrstl'plate' means being adapted for embedment. in. the- `joint face ofthe associated slab, rib-like bearing platesextending betweenthe Yplate-means aboveuand below and having edge. contact only'withnthebar', and stress carrying arms extending from' .the second plate means above and'below the bar.:

5. :A load transfer device; forv concreteslab` joint. construction: comprising anzdowelnbar,.` and .a

of spaced, skeleton, reinforcing structure surrounding the bar at an intermediate part thereof, each structure including spaced plate means through which the bar extends in bearing relation thereto, one of the plate means being adapted for embedment in the joint face of the associated slab, and a pair of stress carrying, L-shaped, flat and relatively thin members positioned, respectively, above and below and in the Vertical plane of the bar, the vertical limbs of each member 10 having their vertical edges firmly secured to the opposed faces of the plate means and their inner horizontal edges having bearing contact with the bar, and the horizontal limbs of the members being adapted to extend into the associated slab.

6. A reinforcing member for concrete slab joint construction having a dowel bar bridged between adjoining slabs comprising spaced, plate means apertured to bearingly receive the bar, one of the plate means being adapted for embedment in the joint face of the associated slab, and rib-like bearing plates extending between the plate means above and below the apertures, the facing edge surfaces of the bearing plates being continuations of the adjacent surface portions of the apertures.

DONALD E. WILLARD.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,158,953 Wilcox May 16, 1939 2,187,428 Mier et al Jan. 16, 1940 2,189,156 Willard Feb. 6, 1940 2,196,727 Fremont Apr. 9, 1940 2,208,454 Geyer et al July 16, 1940 2,212,492 Brickman et al. Aug. 27, 1940 2,256,930 Willard Sept. 23, 1941 2,263,150 Westcott Nov. 18, 1941 2,267,024 Godwin Dec. 23, 1941 2,410,099 Olmsted et al Oct. 29, 1946

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