US2296756A - Load transfer device - Google Patents

Description

p 22,1942- c. YEOMAN 2,296,756

LOAD TRANSFER DEVICE Filed June 7, 1946 5 Sheets-Sheet 1 Z0 in d a! Z7 Z5 I J/ZDQ/ZZOP Rqy @r'us eomaxz Sept. '22, 1942. R; c. YEQMAN 2,296,756

LOAD TRANSFER DEVICE Filed June '7, 1940 3 Sheets-Sheet 3 E j'zve/zfor \pCZy C rasifizana/z ,wAiim-wg.

Patented Sept. 22, 1942 2,296,756 LOAD TRANSFER DEVICE Ray Cyrus Yeoman, Lufkin, Tex., assignor to Texas Foundries, Inc., Lufkin, Tex., a corporation of Texas Application June '7, 1940, Serial No. 339,319

9 Claims.

My present invention relates to the construction of bridges, masonry and other concrete structures, and particularly to the building of concrete pavements wherein the pavement is constructed from a series of slabs cast end to end, the joints formed between the slabs being reinforced with metallic members such as dowel bars; and more particularly to a load transfer device adapted to replace the common dowel, and wherein a pair of complemental units comprises the device, each unit having an appropriate bridging member and an integral bearing member adapted to partially enclose the related end portion of the bridging member of the associated unit within the adjacent slab, which serves to transmit a load from one slab to the next, preventing relative vertical displacement of the slabs regardless of subgrade conditions and yet permitting the slabs to move longitudinally with respect to one another clue to expansion or contraction. The bearing used also serves to reduce the high unit bearing pressure at the slab face, thereby preventing the so-called' funneling at this point, which usually prevails when the plain dowel bar is employed.

Like the common dowel, my device is adapted to be placed at spaced apart intervals along the slab edge at joint locations, to support the slab edge against local bending transverse to the joint when acted upon by a load applied to either one or both slabs and over any one or all of the devices in the series, but my invention differs materially from the common dowel even when the dowel is supported in conventional sleeves or bearings, in that the bridging members of my device, when put under load, ar not subjected to reversal of stress as are the common dowels. The constant and repeated reversal of stress in any metallic member is fatiguing to both the member and the surrounding concrete, and usually leads to the partial destruction of the load transfer member as well as the surrounding concrete, which renders the assemblage useless as a load transfer device.

This application is in part a continuation of my former invention as shown and described in my co-pending application, Serial No. 306,221, filed November 27, 1939, and in general has similar objects of invention which include; the building of the device with relatively counterpart and complemental units, self-aligning, free from wear, corrosion or freezing, inter-changeable, when used in pairs, inexpensive, simple and durable; the successful elimination of destructive stresses and strains due to misalignment, the reduction of high unit stresses at the slab face, the effective distribution of load to and within the slab, and the reduction of the deflection of the bridging member when under load; the production of a unit adaptable for installation in one slab only so that at a later period the adjoining slab may be poured without destroying the elficacy of load transfer, particular adaptability to fabrication from cast or malleable iron, using the full depth of the slab in shear, and simple installation; a device which may be installed in various positions within the slab, such as having the bridging portions actually below the bottom surface of the slab; and the provision of a hinge type joint to permit hinge action without impairing load transfer and resistance to slab curling.

Other objects of this invention are to provide an open side sleeve, or inverted channel, containing but a single bearing surface and adapted to enclose all but a portion of the associated bridging member, whereby substantially all foreign matter is excluded from within the sleeve or channel, thus allowing the free and unrestrained movement of the associated slabs, and;

To increase the load transmission capacity of the bearing member by extending the free sides thereof down to the base of the unit in the form of an inverted U or channel, to thus increase its structural strength,'increase its bond within the slab, facilitate alignment during installation, and increase the section modulus about the horizontal axis without increasing the quantity or amount of metal used; and

To form additional anchorage devices in the channel portion per se to reinforce the bearing against turning movement due to application of excessive load or impact; and

To remove excess metal t make the device cheaper to build by making the bridging portions substantially channel-shaped in cross-section and thus not impairing their original strength but in reality providing an additional base for support of a joint member; and

The provision of a specific form of horn for partially encircling a tie bar and for effectively holding the bar or load distributing edge bar in place and simplifying the tying of the bar to the anchors of my unit; and

The provision of but a single anchor extending from the bearing member, the anchor in itself being reinforced, and in addition being provided with a plurality of steps for the consecutive distribution of load within its related slab; and

The incorporation of a base plate for supporting the assembled units during installation, to

which the units may be attached and firmly held in place either with or without a joint assembly, and wherein the base plate may be a separate plat for assembling each individual pair of units comprising my device, or the base may be a continuous strip approximately the length of the joint and to which are assembled a plurality of devices in spaced relation to one another.

My present invention has these and other objects, all of which are explained in [detail and may be more readily understood when read in conjunction with the accompanying drawings (three sheets) which illustrate a preferred embodiment of my invention, it being manifest that changes and modifications may be resorted to without departure from the spirit of the claims forming a part hereof. And whereas I will now describe a particular embodiment of my invention, it is to be understood that the words I use are words of description and not of limitation. Similar reference characters refer to similar parts throughout the several views of the drawings, and wherein:

Fig. l is an elevational view of my device shown assembled in its operable relation to the adjoining or related slabs, the slabs have been shown in broken lines for purpose of illustration only;

Fig. 2 is a like View of the two units comprising my device shown separated prior to assembly;

Fig. 3 is a sectional View taken on line 3-3 of Fig. 1;

Fig. 4 is a similar section taken on line 4-4 of Fig. 2;

Fig. 5 is an end elevation of Fig. 2 taken on line 55 of Fig. 2;

Fig. 6 is an end elevation taken on line 66 of Fig. 2;

Fig. '7 is a side elevation of one-half of a simplified form of my device, illustrating but one of the two units employed;

Fig. 8 is an end view thereof taken on line 8-8 of Fig. '7

Fig. 9 is a view from the opposite end taken on line 9-9 of Fig. '7;

Fig. 10 is a bottom plan taken on line III-III of Fig. 7; and

Fig. 11 is a section taken on line II-II of Fig. "7.

The structure illustrated involves the specific application of one form of my invention to a con- :crete road, and contemplates a load transfer device for bridging a gap between the adjacent end faces of horizontally aligned concrete road slabs I and II, shown in broken lines as resting upon the subgrade I2. slabs is purely diagrammatical, for illustration only, as the slabs may be spaced apart by means of any one of many conventional forms of joints, including expansion or contraction joints, center strip, and construction joints, but as these form no part of my invention, the device is better i1- lustrated by their omission.

The load transfer device comprising my invention consists of a pair of preferably, but not necessarily, counterpart and relatively reversed rigid members in the form of malleable iron castings adapted to have their major portions respectively imbedded in the two slabs, positioned in longitudinal alignment at substantially the bottom portion of the slabs and spaced in pairs at intervals along the joint face throughout the width of the slab. Each one of the two units Comprising the device consists of a bearing member I3, a bridging member I4, and an anchor I5. Each unit is the counterpart of the other, complemental The gap or space between the and interchangeable; the bridging member of one is adapted to be partially enclosed by and seat on the .bearing member of the other.

The bearing member or body portion of the unit comprises a substantially channel-shaped, or inverted U-shaped casting having depending side portions I6-I6, a closed top or bearing portion I1, and an open bottom; the channel thus formed is further closed at one end with an end wall I8 and open at the opposite end adjacent the slab face. The bridging member I4 consists of the elongation or extension of one side wall I6, as the integral bridge is carried out and beyond the open end of the sleeve for a distance slightly less than the depth of the bore of the sleeve portion and its cross section is the shape of the usual channel-iron, the web portion being vertically disposed to present the greater section modulus opposing the bending moment, and having its laterally disposed flanges I9 and 20 facing inwardly. The top flange 20, only, is adapted to take bearing or seat upon the under-side of the bearing I1 of the associated unit, because there is a sliding clearance between the sides of the assembled bridge and the sides of the sleeve and because the bottom. of the sleeve is open, or if closed, a substantial space is provided between the bottom of the bridge and the bottom of the sleeve so that the bridge at no time has bearing on its bottom surface.

The anchor I5, rigid with the bearing I4, comprises a radial arm 2I inclined upwardly and backwardly from a point approximately adjacent the slab face and terminating preferably above the neutral axis of the slab, where it is bent downwardly at 22 to form a hook with a transverse bar portion 23, adapted to partially enclose a part of a load distribution bar 24, or edge reinforcement for the slab face. From the top portion of the hook and extending towards the slab face, is a raised projection 25 forming a horn, over which is passed the conventional form of U-shaped tie-wire 26, the ends of which wire terminate in loops arranged for engagement with a wire tying tool (not shown), and which wire 26 is then carried under the bar 24 and back up and over the transverse bar portion 23 of the hook, where the ends of the wire are twisted together at 21, thereby securely attaching the load distribution bar 24 to the anchor, as shown. Inter-mediate the ends of the anchor arm 2|, I provide a plurality of spaced apart steps or raised projections or ribs 11, b, c, d and e, which are adapted to extend into the body of the slab and in turn take up for distribution, any load applied to the bridge or integral bearing member. That is, as the load is applied, and as each rib or step is stressed to its limit in bearing, and since the material of the slab has a lower modulus of elasticity than the metal structure of the anchor arm, the material of the slab at the first rib or step (a) adjacent the bearing I 3, deforms elastically (compresses a bit) under the initial increment of loading, thus allowing the stronger and stiifer metal anchor 2| to carry the next increment of load to the next adjacent or second step (b), whereby steps (a) and (b) deform to pass on some load to step (0), etc. progressively to the end of the arm 2I. In this way the load is progressively distributed throughout the weaker materialconcrete, by the stronger metal anchor to which the load has been applied, and from where it is picked up by the load distribution bar 24 and carried throughout the width of the slab at the joint location.

For the purpose of further anchoring the bearing l3 to the concrete of its related slab, and to assist in overcoming the turning moment or partial rotating of the bearing occasioned by sudden impact or the application of excessive or concentrated load. I now proceed to form a series of transverse corrugations 28 and 29 across the outer face of the rear wall l8 into which the plastic concrete will flow and key, thus reinforcing the assembled unit against overturning,

With particular reference to Figs. '7 to 11 inclusive, it will be noted that the bearing member 49] is channel-shaped as before and has the integral bridge 4| and anchor 42. The anchor in this case, however, extends rearwardly at about 45 with the horizontal and is eifectively reinforced with an integral rib 83 which extends from the bearing portion upwardly tapering back flush with the underside of the anchor arm toa point near its uppermost end, where the arm terminates in a hook portion 44 adapted to receive the load distribution bar (not shown) and wherein the outer surface of the hook is indented at 55 and the arm is further provided with a pair of spaced apart tabs or raised portions 46-46 adapted to assist in retaining the tie wire 26 as before. The anchor arm is further provided with a plurality of transversely aligned spaced apart steps 41-41 which serve the same purpose as the ribs 1. to e before decribed, and the rear wall of the bearing likewise is provided with a series of parallelly aligned indentations 48-48 which serve as additional anchors into the material of the slab. This particular modification is illustrated to bring out a most effective manner of reinforcing the anchor arm at this particular point where it is required to take the greatest strain-namely, at the point of contact with the bearing, the web 43 being of the greatest dimension at this point and gradually tapering off as the load for distribution decreases.

In assembly, and for purpose of installation, it is usually considered expedient to first assemble the units in pairs spaced at intervals along the bottom edge of the joint, and next tie the load distribution bars to each unit in turn; then the entire assembly is placed upon the subgrade, staked in place, or otherwise held during the pouring of the plastic concrete. But I find that this procedure is not always conducive to proper alignment, and where the joint member is soft and very flexible, or in the case where there is no joint member per se, but where the units are set in to bridge a construction joint or gap between the end faces of the adjoining slabs, it is most advantageous to provide a definite support for the assembled units during installations. Therefore I have provided a base plate 30, somewhat wider than the combined width of the assembled units, and preferably, but not necessarily co-extensive in length with the width of the slabs. This plate in reality, may be cut up into a plurality of plates, one for each pair of units comprising my device, but I elect to show and describe a single plate for description only. The base plate 30 has four spaced apart tongues 3|, punched upwardly from the material of the plate, and so spaced as to bear against the sides I6 of the bearing members l3, and adapted to impinge against the sides of the bearings and hold the assembly against accidental lateral displacement, that is, movement transverse to the pavement slabs. At the same time, I further provide a pair of similar tongues 32, punches up from the plate, one at each end of the device directly adjacent the end walls l8, and

adapted to engage and lock over a lug 33 extending from the rear wall l8 of each unit (Fig. 3) thus not only securing the device to the plate, but also restricting the longitudinal movement of the associated bearing members comprising the device until the concrete has set, whereupon the movement of the slabs will sever or shear off the tongues, thus permitting the unrestricted and unrestrained movement of the slabs to accommodate the ever present expansion and contraction of the slabs.

It will be immediately apparent to those skilled in the art, that various modes and methods may be employed for securing the units together to make a complete operable device other than that just previously described, but which are not specific to my invention, and various forms and modifications of the load transfer features embodied in the structure illustrated are feasible without departing from the scope of my invention as expressed by the following claims.

I claim:

l. A hinge type load transfer for bridging a gap between the confronting faces of a pair of road paving slabs, said device including a pair of inter-dependent units adapted to have their major portion imbedded in their related slabs, each of said units including a bearing member of inverted U-shaped vertical section constituting a channel, said bearing member having a single bearing surface at the top of the member interior of said member, one of the legs of the channel being extended and acting as a bridging member spanning the gap and seated in the other bearing member in engagement with said bearing surface short of the inner end thereof.

2. A load transfer device as per claim 1 wherein each bearingmember is provided with an integral anchor having a T-shaped web portion constituting a reinforcement, a load distributing bar extending transversely beneath said reinforcement, and means for attaching the bar to the anchor.

3. A hinge type load transfer device for bridging a gap between adjacent edge faces of adjoining concrete slabs, said device comprising a pair of inter-dependent units adapted to have their major portions imbedded in their related slabs, each unit including a bearing member channel-shaped in horizontal plane, the inner face of one flange of the channel constituting a bearing surface, one side wall of the channel having an extended portion forming a bridging member rigid therewith and adapted to span the gap between the faces and to seat against the bearing surface of the associated unit comprising the device, the upper end of said channel-shaped member being closed and forming means engaging the upper edge of the bridging member of the associated unit, and a rigid anchor extending from the bearing member for anchoring said device within the concrete.

4. A load transfer device as per claim 3, wherein a portion of one wall of said bearing member is recessed to provide means for keying it to the concrete of its related slab independently of said rigid anchor.

5. A load transfer device as per claim 3, which includes a separable and flexible base for supporting said device, and means carried by said base for securing said device to said base.

6. A load transfer device as per claim 3, which includes a separable base plate for supporting a plurality of said devices in spaced relation, and wherein said base plate is provided with means for attaching said devices thereto, said means engaging portions of said devices.

7. A load transfer device as per claim 3, wherein is provided a base plate and means carried by said base plate for temporarily locking together said units comprising the device, and wherein each unit is provided with an element of said locking means.

8. A hinged type load transfer device for bridging a gap between adjacent end faces of adjoining concrete slabs, comprising two inter-dependent counterpart and relatively reversed rigid units, each unit consisting of a single unitary casting having the major portion of its integrated parts adapted to be imbedded in its respective slab and including an inverted channel-shaped bearing having its web portion at the top with its under side forming a bearing surface, said channelshaped portion having the end adjacent the slab face wherein it is embedded open and having its remaining end closed, the under face of the web forming a bearing surface, said member having its bore horizontal and at right angles to said slab end, a bridging member integral with one side wall of said bearing portion and forming an extension of said wall and adapted to project beyond the end face of its respective slab and to bridge the gap intervening between the adjacent end faces of the adjoining slabs and to extend into and have its upper edge slidably engage said bearing surface of the channel-shaped bearing portion of the other associated unit, and associated means for anchoring each unit to its related slab.

9. A load transfer device for bridging a gap between adjacent end faces of adjoining concrete slabs and adapted to engage a load distribution bar for imbedding in one of said slabs, said device including a load transmission member and an integral anchor member, said anchor member being arranged to be afiixed to said load distribution bar, the means of afiixment comprising a hooked portion extending fromsaid anchor and adapted to enclose a portion of said bar, and a horn extending from said anchor in a plane normal to said hook whereby a tie wire is adapted to engage said horn and pass under the assembled bar and thence over the related end portion of said hook.

RAY CYRUS YEOMAN.

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