US2716373A - Paving joint - Google Patents

Description

g- 30, 1955 F. H. SCRIVNER ET AL PAVING JOINT Filed Jan. 5, 1951 f3 m m mm c L M N A ATTORNEY Unite at 2,716,373 Patented Aug. 30, 1 955 PAVING m f i t J Frank H. Scrivner ahdlai C hollar, Austin, Application January 5, 1951, Serial No. 294,536 "2 Claims. (c1..94-.17 j"-.,j;

This inventionpertains to pavements and to paving joints and more particularly to contraction) cret'e roads and methods of making same. I 1

According to older practice, road. pavements :were built in slabsand periodically along the road at distances several slabs apart fairly large gaps were left between ad-: joining slabs, these gaps being'filled with wood or other material and known as expansion-joints. The purpose of such expansion joints is to leave space for expansion of the concrete in hot weather, thereby-avoiding'high come pressive stresses with resultant failure of the concrete by buckling, cracking, spalling or. crumbling. In cold weather each individual slab can contract separately and the joints between them are known as contraction joints; Contraction joints are desirable toprevent random cracks in the paving which might otherwise be produced due to contraction in cold weather, concrete being markedly weaker in tension than in compression. Both types of joints may allow the paving slabs to warp when exposed to dif-' ferent temperature on top and bottom. Variousmeans are used to sealthe expansion and contraction joints and. to"

interlock the adjoining slabs against vertical misalignment. H It has been found that in cold weather when the contraction joints are open they fillup with'debris andpnre: expansion of the concrete in the summer the contraction joints remain open and the paving slabssshift position The grooves are formed in the wet concrete, which is laid. as a monolithic slab, and the monolithic slab is supposed to break into several slabs along the grooves when the concrete shrinks during setting or immediately thereafter when-the paving is first loaded with traffic. However, oftentimes the concrete does not crack at each groove and. there are left long unbroken slabs .so that in cold 'oints for conjoint with tapering interlocking portions which will wedge bodily so that their mid-points,..r el ative to-which their ends move in expansion and contraction, move closer to the expansion joints. In other words, the widths of the expansion and contraction joints tend to equalize. This process is cumulative, and within a few years the expansion joints sometimesclose to the full extentperrpittedby the filler, and as a result such pavements have lieenobserved to sufier equal or greater damage from highcompressive stress than probably would, have been the had no expansion space been provided infthe first place. In addition, contraction, joints depending on,ag gregate interlock for load transfer (to be. described .below) lose this interlock and eventually suffer vertical mis alignment, thus increasing the impactof trafiic at the joint and leading to furtherdamage. f

Because of these phenomena,frnore thanone-third of the State Highway Departments 'otthe United States new build concrete highways without provision rqrexpgissien except at bridge ends and similar special loj ca "n Transverse paving joints 'may' be fclassi groups. In one group arefthcse jointsf pr various types of metal members, d wel p ing the joint to provide load. transfer; Ths quire extensive formsto beolaid before the poured. In the second groupthe joint' is a rn in the paving and the interlock is provided by th 1r g'u lar surface of the concrete at the'cjrack.,f j v lock is called aggre'g'atefinte' rlock and the cracks may be induced at regular intervals by gro vesthe tich inter weather the joints at the placeswhere the concrete does crack open up very wide with resultant leakage. and loss of interlock.

- According to the present invention a joint is provided combining the advantages of the known kinds of joints with additional advantages of its own while omitting the disadvantages. t

It is an object of the invention to provide. a pavement which will with certaintyhave joints at regular predetermined intervals.

It is another object of the invention to provide a joint which is interlocked over the whole vertical depth.

Itis another object of the invention to provide a joint which is interlocked continuously over the wholeface of the joint.

It is a further object of the invention to-provide a joint whose interlocking parts will not break off easily.

It is a further .object of the invention to provide a the adjoining concrete slabs into proper vertical alignment following wide separation instead of crushing the misaligned abutting protruberances.

It is a further object of the invention to provide a joint with interlocking portions that will maintain proper vertical alignment at all times during normal motion of separation and'return. I

It is still another object of the invention to provide ajoint that will be substantially sealed in all positions of expansion and contraction regardless of whether or not any auxiliary rubber or asphalt sealing compound is used to fill the joint, thereby preventing water from leaking into the subgrade and being pumped out again as a load passes over the joint, both of which tend to wash away the subgrade, and also preventing collection of debris inthe joint which might prevent its reclosure. i

It is still another object of the invention to provide a joint that will at all times maintain proper vertical alignment so as to prevent pumping and eliminate bumps and broken edges at high places.

It is still another object of the invention to provide a joint that will effectively transmit load from one slab to the next, regardless of the temperature, thereby avoiding cracks due to cantilever loading of the slab ends.

Yet another object of the invention is to provide a joint that is easy to install, that can be vibrated into place, that has wide tolerances as to its position in the concrete, that is rugged, that will withstand the considerable abuse of normal road construction operations, that will not interfere with pouring, that will leave a clean subgrade over which rolling equipment can easily travel.

Itis another object of the invention to provide a joint that will be very low in cost.

Other objects and advantages of'the invention'will be come apparent as the description thereof proceeds. I

Reference will now be made to the accompanying drawings illustrating a preferred embodiment of the invention wherein: l i a Figure 1 is an isometric view of a portion of a concrete road pavementjust after ithasbeen poured and showing the manner of formation of a joint therein according to the-invention; I 1

Figure 2 is an elevational sectional view taken along line 2 -2 of Figure l and shows a joint embodying the invention. h Figure 3 is an isometric viewof, a portion of apiece of joining hardware made according to the invention; and

I Referring .to Figure 1, there is'shown road pavement- 10 below the surfaceof which is set a'form 1'1. The form is shown best in Figures 2 and 3 and comprises .a.

piece of sheet steel, preferably not less than 28- gage (.0135 in.) inthickness and shaped by pressing, rolling, or other suitable manner to provide a rippled or wavy surface having parallel hills and valleys giving a sinuous or. S shaped cross section. Preferably. the parallel half waves '12 are'each half cylinders formed on a half inch radius and alternately concavely and convexly disposed when'viewed from one 'side of the form or the other. Along the stop edgeof the form'there is a straight tlat surface 13 lying in a plane that is midway between the crests. and valleys of-the halfwaves 12 w J The plane of the flat 13 may be consideredasa central. reference plane ofthe form, containing the axes of the half-cylinderswhich constitute the half waves '12, and also the lines "or straight line elements, along which these half-cylinders are tangentially joined. Moreover, when the reference plane is vertical; the surface of the corrugated form, at the line of tangehcy between two halfcylinder waves, is horizontal. As is apparent from Figure 4, a'tangent 16 to the corrugated surface, tangent at the juncture of two waves 15, is' horizontal: It is of-some significance that the half waves be joined along lines at whichthe surface of the form is substantially'horizontal. Phrased another way with Figure 3 in mind, ma be said that the corrugated surface comprises an infinite number of straight line elements, all of'which are parallel to each'other and substantially horizontal. The corrugations themselves, being formed of these straight-line ele ments, are horizontally disposed." Adjacent corrugations are joined by a horizontal element lying in the central reference plane and the corrugated surface, at'it's -inter-' section with the central reference plane, ishorizontal.

. llbreak. in p rat slabs a nathe. terms w en i shrinks during setting. The flat vertical tongue 13 causes the concrete above the formv-to crack in a vertical plane instead of slanting 01? leaving a wafer thin edge. If desired a similar tongue 14 may be provided at the bottom of the form, but the shape of the crack at the bottom is not as important since it is not exposed to trafiic and is supported on allsides. 1L

The forms are placed-at intervalssof ten to fifteen feet forthe usual road pavement This isshorterthan the length" of the slabs "into'jwhich a monolithic, concrete pavement would naturally'break updu'e to subgra'de friction resisting thecontraction' andexpansion of the concrete and building up stresses greater than the strength of the paving.

In use the joints permit temperature contraction of the undivided short slabs of pavement without further cracking: Totheextent .thatkgaps' are left due to shrinkage. during: setting, there is alsotprovided some space "for e'xpansion.- "The nearly horizontal upper and lower sides of each 'semicylindrical corrugation 'on the faces; of adjoining-slabs maintain-almost perfect-vertical alignment despite expansion or contraction, allowing a verticalmisalignme'rit'of lessizth'anrtwo one-hundredths of an inch upon an: extreme' separ'ation (stone-tenthof an inchs' 'In orderto illustrate' the very small vertical "clearance in'cohxpatison to'horizontal opening of-thejo'int, it was necessary 'inFigure -'4 to draw a' -ho'ri'zontal opening (des ignated by the 'arrow '17) which issome'eight times the normal maximum openings in'pavernents'without expansiori joint's,fjust to get a vertical clearance -18 large enough to be seen' in the drawing.- 1 Onthe'o'ther hand, the mating 1 gear tooth" like-protrusions 7 from the slab ends or faces Part slig tly throughout 'the entire 'face with ever so slight a horizontal-opening;thus permitting a free opening 'o'f the"joint w ithout placing ten 'si onal stressesonthe protrusions? l Following-even such anextreme separation asfillus-i Thatis, the'semi-cylindrical sections, at their intersections with the central reference-plane as at 15 in Figure 4, are

tangent to horizontal planes such as that indicated by thedash line 16 in Figure4. v

Immediately after the concrete has been poured on the subgr ade as shown in Figure 1, the forms '11 are pushed t:

greater distance in the middle ofthe central crowned PQ I g a The form isof suchheight as 'to'extend within an inch of the bottom of the pavement. I I

It is permissible for the form to extend all the way from the top to the bottom but that would necessitate cutting the form with an arcuate top exactly fitting the road contour of crowned roads and if the form were no't forced all the way to the bottom it would extend'above the surface of the road and cut the tires of vehicles'passf ing'over the road. Since a satisfactory jointis' achieved 3 large hofizontal adjoining slabs the-endswith the form extending only close to the bottomand top of the paving such construction is much to be preferred for it gives considerable tolerance in placing the forms. More important still, there is a saving in cost labm' time installing Burymg contactbPtWeeneach-adjoiningpair of elements and this theconcrete on both sides. This insures that the concrete sides with paint 9 trated in Figure 4, and during subsequent periods of higher temperature, the joint will close with no danger of jamming, sincejthe slopepffthe elementat a horizontal'distanceof'one-te'nthof an inch 'from'its center is lessthan twelve degrees (an'gular measurement) from the t n zontal; As the 'joint closes the elements act as wedges tore-align the adjoining-sections The roundededges' prevent crumbling or crackingduring thisprocess. [There are no stress concentrationsjsucli;as would occur with trapezoidal or square toothforms. v i 1 I 'Anotheradvant'agcof the 'sinuous shapelof the form lies i n 'the fact that isPlacedin lposition as much as l5"'degr'ejes away "from vertical it will still function satisfactorily. A further advantage of the sinuousfcross section"is".that'.it facilitatesivibratingthe forms into'place while assuring that the-concrete fills in completely on both sides oftheform andpac ks tight. x I v The forms are made of steel or like material having a high compressive strength so that the shapedpa'rt of the joint aswell as that portion above. and belowthetorm share load'equally, both compressive stressesnpon expansion andco'mpound stresses during passage of a vehicl over'the'jo intf Y i A "Sin the joint maintains interlock despite relatively of the slabs r'emainsupportedand'do not crack on benddown pump-'wat'e'r in'andout of the jointas traflic passes over, not 'jar thevehicles due" to vertical misalignment: "Also the joint is sealed along the area of tooprevents pumping' as well as'ke'eps surface water'froin entering'iand dirt", and debris from blocking'the'joint.

A morefull understandingof=whyithe joint 'ofthis inventioniis; so -greatly superior to other joints (as has "been proved by literally hundredsof miles of highwayzjoints withouta s ngle failure) can-be obtained onlywith an understanding of' the kinds ofmovem'ents which occur at joint. First, there is a horizontal opening and closing of the joints resulting from seasonal expansion and contraction in summer and winter.

Second, there is a movement in the nature of oscillating gears at each joint, which movement occurs almost daily. Each day when the sun comes up, the tops of the slabs heat sooner than the bottoms, with the result that the slab ends, i. e., the joints, move downward relative to the slab centers. Later in the day, the upper side of the slab cools faster than the lower side, and the slab ends move upward with respect to the centers of the slabs. In the morning the bottom of the joint opens while the top remains closed, and in the evening the top opens while the bottom remains closed or closes. Thus there is a small oscillative rotation of the slab ends about the slab centers, and this rotation, though small in amplitude, is of sufficient size to set up great stresses at joints which are not completely flexible to permit this rotation freely. The tooth form of this invention does permit this complete freedom of rotation, whether the joint is horizontally open or closed, without sacrificing the load transfer and other characteristics of the joint.

Third, as appears from the above, the joint must not permit appreciable vertical movement of slab ends before load transfer is effected, regardless of the amount of opening or warping that may be present at any given time. To do so sets up great tension stresses in the top of the slab a short distance from the joint, causing eventual failure. Failure to effect full load transfer without appreciable vertical movement also produces other deleterious effects not necessary to discuss here;

The requirements of structure to allow for the various movements and for efficient load transfer are such as to make the preferable form one having semi-cylindrical corrugation sections, pairs of semi-cylindrical sections being tangentiallly joined along lines where the surface is horizontal. The efiiciency of the joint is not affected by some of the sections being semicylinders of somewhat larger diameter than others, in which event the peaks may not all be exactly equidistant on opposite sides of the reference plane of the form. Also, a form in which the peaks of the half-waves have been cut off or mashed in somewhat, but without making sharp edges, is obviously the equivalent, for purposes of this invention, of the preferred form having all one inch diameter halfcylinder corrugations.

From the foregoing description it is believed that it will be apparent how the joint according to the invention achieves the stated objects of the inventor. ever, while a preferred embodiment of the invention has been shown and described, many modifications thereof can be made by one skilled in the art Without departing from the spirit of the invention and it is desired to protect by Letters Patent all forms of the invention falling within the scope of the following claims.

We claim:

1. A concrete pavement divided into a plurality of slabs by means of sheet members; said sheet members being corrugated into a predetermined wave form with alternate half waves extending substantially equal distances Howon each side of a central reference plane; said sheet members being disposed in said concrete with said plane vertical and with the corrugations horizontally disposed; each of said corrugation half waves being a semi-cylindrical section; said semi-cylindrical section being tangentially joined along lines located in said central reference plane; each semi-cylindrical section, at its intersection with the central reference plane, being tangent to a horizontal plane; said corrugated half waves being filled with dense concrete including aggregate; said sheet defining the form of the abutting faces of two adjacent slabs of pavement to be in the nature of cooperating gear teeth which may freely move horizontally to opened and closed positions with seasonal contraction and expansion of the slabs while continually interlocking sufficiently to effectively transfer load from one slab to the adjoining slab; said gear teeth form of abutting faces of the slabs also cooperating to permit the top and bottom of the joint between two adjacent slabs to alternately open and close with thermal warping of the slabs without introducing substantial stresses into said teeth.

2. A concrete pavement divided into a plurality of slabs by means of sheet members; said sheet members being corrugated into a predetermined wave form with alternate half waves extending on each side of a reference plane; said sheet members being disposed in said concrete with said plane substantially vertical and with said corrugations substantially horizontally disposed; each of said corrugation half waves being a semi-cylindrical section; said semi-cylindrical section being tangentially joined along lines located in said reference plane; each semicylindrical section, at its intersection with said reference plane, being substantially tangent to a horizontal plane; said corrugation half waves being filled with dense concrete including aggregate; said sheet defining the form of the abutting faces of two adjacent slabs of pavement to be in the nature of cooperating gear teeth which may freely move horizontally to opened and closed positions with seasonal contraction and expansion of the slabs while continually interlocking sufficiently to transfer load from one slab to the adjoining slab; said gear teeth form of abutting faces of the slabs also cooperating to permit the top and bottom of the joint between two adjacent slabs to alternately open and close with thermal warping of the slabs without introducing substantial stresses into said teeth.

References Cited in the file of this patent UNITED STATES PATENTS Re. 16,202 Briody Nov. 10, 1925 1,401,590 Del Turco Dec. 27, 1921 1,804,337 Heltzel May 5, 1931 1,974,240 Heltzel Sept. 18, 1934 2,016,858 Hall Oct. 8, 1935 2,060,326 Larnpert Nov. 10, 1935 2,112,489 Heltzel Mar. 29, 1938 2,148,595 Ulrich Feb. 28, 1939 2,311,286 Tufts Feb. 16, 1943 2,330,214 Heltzel Sept. 28, 1943 2,539,875 Van London Jan. 30, 1951

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