US2072381A - Concrete slab joint - Google Patents

Description

2 Sheets-Sheet l -65 @5 67 fzz/enzlor /eJfS/tlf. P055 '2 ,JM afjv/U C. L. POST CONCRETE SLAB JOINT Filed June 8, 1954 c. L. PQST CONCRETE SLAB JOINT 2 Sheets-Sheet 2 Filed June 8, 1954 contraction longitudinal joints.

Parenteel Mer. 2, i937 gunstig ,uN1TEo-srATes rMen-r oFFicE... y. l i ooncaa'lzsln .ronvr i r.. reet-chime, n1.,l V` Application June s, 1934 sere11ve 129,569-

My invention relates te devices providing joints between contiguous -edgesy oi' slabs or other concrete sections, andlmore particularlyit relates to i what are commonly Vknov'vn as expansion and In "highway pavements 'and 4concrete constructions, it is common' practice to providel devices at predetermined spaced apartintervals.

between which concrete is poured. such devices thereby forming expansion vand contraction joints to minimize cracking which would otherwise result from contractionof `the masonry in c'old `weather and also eliminating the tendency to, 'buckle which. otherwise results from expansionV inwarm weather. No load can be transmitted from one slab toanothe'i; through the spaces between contiguous slabs unless some means'is especially. provided for that' purpose. The pavement deteriorates more rapidly adjacent the joints than at intermediate points because of the heavy concentrated. loads to-which modern.

highways are subjected and alsobecause of the inadequacy vof present joint structures as means for carrying loa'ds from one slabto another across the joint spaces. This deterioration is due primarily t'o` the yielding. of the* sub-base immediately underlying vthe edges' of the slabs carrying .the 'undistributed Awheel loads. The

the joints becomelow points in the otherwise 'smooth surface of the pavement. Even though the slabs remain intact under heavy loads, the load carryinglslab and its underlying sub-base yield noticeably -under the ,undisia'ibuted load while the adiacentlslab is not depressed. The advancing wheels thereby suddenly contact the undepressed adjacent slabs, resulting in a shock 40 to the vehicle and slab and' abrasion-of the exposed -edg'e of the forward slab so contacted.

The intermittent overloading ofthe sub-base on each side of the joint tends to cause the sub` base material'to ilow and force its way upwardly into thejoint space andl interfere with the efiicient functioning ofthe joint lto permit expansion of the slabs. The use of devices such as dowel bars to transmit loads from one slabto another through the jointspace has proven un- 59 satisfactory because of the relatively low Avalue of concrete and the tendency of such bars to produce high compressive stresses at the iaces of the concrete, resulting in horizontal planes of cleavage orin crushing the concrete and in cross-sectionin 2;

' between concrete slabs 20.

.. concime.J (diei- 18) ,eventually forming cone-shaped spaces in the concrete preventing the bars from functioning.

Among the objects of the invention is the pro-V vision of improved devices adapted to provideA expansion spaces between the slabs; to transfer 5 loads transversely from one slab to another across the intervening spaces; to preserve" th true .alignment of the pavement surface; to eliminate jar-or shock fromV or to vehicles passingioveil the joints; to 'prevent passage ofwater and for- 10 eign material from the pavement into the jointf, spaces'and to the sub-base; and to seal the joint 'spaces against inltration of soiland foreign matter from the sub-base.

.Still anotherobject of the invention is the 15 provision of structural devices of the kind Vcier scribed, adapted to provide expansion `and con- Y traction joints which are durable, simple andI inexpensive, easily installed and satisfactory for' 1 their intended purposes..

2 Many'of the objects and 'advantages of the o construction herein shown and described will be obvious to those skilled in the art from the disclosures heren given. .j

To 'this end, my `'invention consists of the novel 25 construction and arrangement and combination of parts herein shown and described and more particularly shown in the claims. yielding of the sub-base 'subjects the slabs to 3b stresses causing them to crack and disintegrate adjacent the joints andV in the course of time' Referring now to the drawingsz'V i' pavement providing devices embodying the principles of thebinvention shown in Figs. `2 to 5,

inclusive;- e Fig. 2 is a sectional view along the 1ine 2-2 of Fig. 1, drawn to a'. larger scale; 35

Fig. 3 is a perspective view. of `the device shown Fig. 4; is a cross-sectional view through adevice adaptedeither as a longitudinal ora contraction joint; 40

Fig. 5 is a view along the line 4-4 of Fig. '1,

. drawn to a larger scale;

' Fig. 6 is a plan view. partially in section, of an alternative form of construction providing a longitudinally extending' joint; 45

Fig. 'I is a View along the line l5-I5 of Fig. 6, showing the construction as embedded in a slab. Referring now more particularly to the draw- Fig. 2 .shows in cross-section a preferred con-A 50 structionadapted to form a space 2| and to provide an expansion and load transmittingv joint I A rigid plate 22 extending the full length of the 'joint closes the space 2| at the bottom. The plate 22 maybe 55 screws or bolts 55. The lower end of the plate 24 is turned outwardly and rests upon and projects beyond the plate 22 to provide an. apron forming a clearance space 25 between the slab and the The bottom of the plate 23 is also Sub-base Il.

-tln'ned outwardly, resting upon and projecting beyond the other edge of the plate 22 to provide an apronforming a clearance space 25.

'I'he upper portion of the Ajoint space 2| is sealed by a member 41 comprising bituminous material. 'Ihe member 41 is carried, by a plate 217 forming an additional seal for the top of the space 21|. The plate 21 ispreferably constructed of noncorrosive metal, and has its mid-portion forming a trench 28, fprojectingdownwalrd1y between the plates 23 and 24.' lThe plate 21, adjacent the trench 28, extends laterally beyond the plates 23 and 24 to form members 29 projecting into' the adjacent concrete slabs.- The plate 21' extends downwardly and inwardly from the members 29 -into contact with the adjacent plates 23 and 24 and has its edge portions bent outwardly.

and slightly upwardly to form ilanges 30. The edges of .the anges provide'beads 3 which are' opeativelyuengaged by clips 26, integrally formed with theplates 23 and 2 4 by cutting the latter along' closely 'spaced lparallel lines and bending the interveningn material outwardly as shown. Pressure exerted Vvupon the member 41 will force the projections 29 outwardly into contact withY the slabs, and any foreign material that might possibly work down between` the member p 41 and into the trench28 will further tend to, maintain the members 29 in closelyspaced posirelative to the slabs. The ilanges 30 are embeddedrin the concrete a substantial amount and combine with the members 29 to provide a double seal making it impossible for any moisture or. foreign material toA enter the space between the plates 23 and 24 or the. slabsand the plates `from the top of the pavement.'A

A plurality of bars 32 embeddedin the slab's 2l provide reinforcement for the slabs ,and also provide means for transmitting loads y(from one slab to another through' the plate 22. The lower ends of the bars 32v are threaded and project'V through oval apertures formed in the plate 22 von opposite sides of the joint. In assembling the device, the bars-32 are fastened tothe plate 22v between upper collars sa. threaded to the position' shown and nuts 3 4 and washers 3B on the under side of the plate. As the slabsrZIl expand or contract the bars 32 are correspondingly moved in the'apertnres 35 leaving the plate 22 stationj ary. The bars 32-are inclined upwardly and outwardly away from the joint in the'general direc- 'load-transmitting rigid 'plate 22 is a relatively .heavy and therefore a permanent, structural eletion of the resultant of the stresses inthe slab. The bars are" shown as providing loops with their intermediate portion: extending horizontally a 'short distance ben'ath the upper surface of The loopsmaybe' omittedandv anchors 32 used slnslyylith a nut 34 and washers 33 and 33. The either looped or single mayhavea head upset on their lower ends infaces of through the plate 22 into the bars 32 embeddedin the adjacent slab and the over-hanging portion of the plate, thereby maintaining the sur-f the slabs lconstantly in alignment. The slabs in expanding and contracting carry with them the plates 23 and 24. The prescribed corikstruction of the seal plate 21v is such that the corrugation- 28 yields to permit contraction and expansion of the slabs due to temperature changes. The plates 23 and-24 maybe made oi' any sheet metal and should the same disintegrate by corrosion, the plate 22 will continue to function as a seal for .the bottom of the space 2| and the plate 21 will similarly function throughout the normal life of the pavement.

A modified form of construction is shown in Fig. 4 wherein plates 38a and 39h aremounted on the plate 24 and form side walls for the adjacent slabs. This construction is adapted to providev contraction joints. and also is adapted as a longitudinal joint by omitting the oval apertures 35 and substituting circular apertures of normal diameter. The lower portions of the plates 38a and 38h are' positioned in contact and the upper" portion of the joint is sealed by a plate 21 and a bituminous member 41, in the same manner as described for the construction shown in Fig. 2. This construction provides for -a hlnge'action of -the slabs 20 about the plate 24 as the slabs exvtion adapted as a longitudinal. joint. A single plate 31 has its lower portion turned outwardly and resting upon one edge of .the plate 24 and its upper edge terminating near the top of the slab. B ars 32 are embedded in the slab 20 on each side of ,the joint and are 'xedly fastened to the plate 24, thereby preventing expansion 'of the bottom portion of the slab and permitting a hinge actionl about lthe plate 24 as the slab contracts and expands. A'plat'e 63 having its middle.A portion forming a close foldfis mounted on the upper edge of the. plate 31 with its edges forming iianges projecting substantially into the concrete on: each side. As the slab contracts, it will crack-- along its upper surface in a line coinciding with the plane of the plate 31. The folded portion of the plate 63 yields as the upper portions of the slab separate and provides a seal preventing surface moisture from passing below the plate. The cracks thus formed in the surface of the slab may be filled with bituminous material. By pro- -viding the.ova1 apertures si indicated indotted lines, the construction of Fig. 6 will function as .a contraction joint. Thepconstruction `of Figs.

4 and `5 perform the same functions, except that of Fig. 4l does not require subsequent filling with bituminous material fect hinge action.

It will be noted that the loadf-receiving'and ment having awidth suilicient to underlie the adjacent ends ofthe two slabs toan extent adequate to .receive the load imposed vertically upon vthe overlying end 'without possibility of 70 causing rupture' of the slab. The exact lateral dimension 'of this'plate, at right angles to the joint, will, of course, be dependent upon the loads which are to be imposed upon the slab, and, as will be'readily understood by any .competent enand also provides more perof element 6l will be put under tension.

gineer, may be determined by proper computa- Y o tions according to' methods well understood.

Referring to Fig. 2, and supposing a vertical load to beimposed upon the en d of a left-hand slab, sucha 'load will be'transmitted by the left-hand slab verticallyupon the left-hand yedge of plate 22, thereby imposing a tension upon the reinforcing element 32 and a compression upon me under surface of the right-hand slab to the right .ofthe connection between plate 22 and,y .right-hand reinforcement 32. The lateral extent of the right-hand edge of plate 22 should,

. therefore, be such that the compression value of the superjacent' slab, with a. proper factor of safety,is'not exceeded. 'I'he size and extent of the reinforcing element 32 is similarly determined by well-known methods. It will also be readily understood thatthe dimensions of plate 22 and the reinforcing elements 32 must be determined invlewof the character ofV the subgrade, heavier resistance valuesin these elements beingrequired where soft.v

It will also beV noted that plate 22 serves to inthe subgrade is relatively crease the bearingof each slab end upon'L1 the t subgrade to the extent of the projection of said .plate beyond that slab end. s

It will also benot'ed that, in order that the '.'plate 22 may properly function; in an expansion joint, it is essential that as to at least one .ofi the slab ends there must be a capability of movement of 'plate 22 relativeto that slab at right angles to the line of the joint, and consequently the yconcrete of one of the slabs must not-contact the subjacent vertical edge of plate 22, as

indicated at 25 in Fig." 2.

1t will. also be noted that because of the slotted' connection between plate 22 and atleast one series of the reinforcing elements 32, the amount of relative movement between plate 22 and the superjacent slab is limited.' This l`=is especially 'advantageous where a pavement is at a substan- F tial anglev because it serves to prevent a long series of slabs from cumulatively slipping downhill.

The above analysis of load transfer applied to the contraction joint illustrated in Figs. Gland ,7.

*` Vertical load'on the horizontaly arm of the left hand angle 65 will be taken in `part by the attached right hand angle; and the lft'hand end Figs; 6 and 7 illustrate amodiiied form of con--V struction, adapted to provide a longitudinal joint, comprising a plate t2 surmounted by a 'cap plate 6 3. A plurality of angles 65 are positioned on opposite sides of the plate 62 with their con- -Y tiguous ends overlapping and fastened together yby rivets or bolts 66." 'Ihe horizontal legs'of the.

angles G5 project away from the plate 62, and

provide a base support for the construction with `the rivets .or bolts 6 6 oi' a size to edectively prervent' spreaf.i1lg 0f the angles as the slab ,contracts. A rod 6l; projecting through the vertical legs of the 'angles-65, at each joint provides a means for transmitting loads from one side of the construction to the othe The middle portion of the rod 3B is V-sha d and prevents the bottom of the slabs from separatingwhen the concrete contracts, but permits the upper portion of the slab to separate so. that Ythe slab sections are'hinged about the lower portion of the construction. 'Ihe inclination-.f the V-shaped porprovideadditional anchorage. -"Upon contraction of theslab a crack will form along the line immediately above the plate 62 whichv can be filled t ,with bituminous material-to provide a waterproof seal. The base portion ofthe construction comprising the angles 65, fastened by the rivets 68, remains intact for allconditions of expansion or contraction of the joint and eliminates any possibility of; sub-base material entering the joint. 5 I

Thus, it -will be seen that I have provided a novel. construction adapted to form `iloints inv slabs or other concrete sections, and to transmit 'loads across the joints from one slab to another.`v

, l5 4Having thus Adescribed my invention', it is lobvi-` `ous that various immaterial 'modifications may be made in the same without departing from the spirit of my invention; hence I do not wish vto be understood as limiting myself to the exact form, construction, arrangement andcombina-v tion o f parts herein shown and described or use's mentioned.

What I claimas new and desire to secure by ALetters Patentls i 1. A joint for concrete slabs comprising a relatively-permanent load-carrying structure t0\ substantially underlie adjacent edges of two slabs.. load-transmitting embediblemembers.projecting i upwardly from said load-carrying structure on opposite sides of its medial line and each capable of transmitting slab loads 'from the load-carry relatively weak ,non-load-transmitting slabeend dening-sheet material supported by said loadcarrying structure' between said embedible mem- 2. A joint for concrete' slabsy comprisingfa relfported by said load-carrying structure between ing structure to the slab in which it is embedded', v

atively-permanent structure to substantiallyun- 'd erlie adjacent edges. vofy two slabs and capable of transmitting substantial verticallyapplied said divergent members, and a transversely ex-.

lpansible and collapsible |sealing-plate overlying'4 said slab-end defining-means with edge portions tion of the rods 61 substantially-coincides with the resultant of the stresses in the slab sections andl their extremities are preferably straight to "specinedin claim 2 wherein one thereof embedible in adjacent slab ends.

3. A joint for concrete slabs of the character speciiled in claim 1 wherein theconnection 4be tween the load-transmitting embedible members '-and load-carrying structure to one side of the medial line of the load-earrying structure is. such as to permit relative horizontal movement.

4. A joint for-concrete slabs ofthe character 60 specified in claimZ wherein the connection between the load-transmitting embedible members and load-carrying structure to one side of the medial line ofthe load-carrying structure is such as to permit relative horizontal movement.

5. A joint for concrete slabsv of the character speciiled in claim l wherein one edge of the load'- carrying structure is overlaid by a relatively weakelement projecting beyond said edge an amount suilicient, to guard against deposit of' concrete immediately adjacent .said edge. 1

6.. A- joint for concrete slabs edge of the loadcarrying structure is overlaid by a relatively weak.

, element projecting beyond said edge an amount 7. A joint for doliente slabs comprising felotivelyv permanent load-.carryin'l structure to l'iibstantially underlie adjacent edges of two slabs. two upwardly and oppoxitely divergent loadtransmitting and reinforcing elements carried by said load-carrying structure .dnd vertically immovable relative thereto, one of ssidJOM-tnns mitting members being-shittable relative to the load-cerrying struoture parallelto the rslab plane.

seid two loed-tansmittinz elementl'heing apart to accommodate vertilly-extendinx rela- A tively weak winload-transmitting sheet materiel lor sieb nd definition.

8. A' structure' ot the chargqter ,lpecied in Gleim 'I wherein slabfenddennim sheet materiel is extended beyond one vertical edle of the loadcuryinz/stmeiur'e to guard said edge from i m medtgteiy ezbedc/ling concrete.

' CHESTER L

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