US3033087A - Dowel bar supporting structure for concrete expansion and contraction joints - Google Patents

Description

y 1962 B. HILLBERG 3,033,087

DOWEL BAR SUPPORTING STRUCTURE FOR CONCRETE EXPANSION AND CONTRACTION JOINTS Filed Dec. 24, 1958 2 Sheets-Sheet 1 INVENTOR. BR R Humane.

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May 8, 1962 B. HILLBERG DOWEL BAR SUPPORTING STRUCTURE FOR CONCRETE EXPANSION AND CONTRACTION JOINTS 2 Sheets-Sheet 2 Filed Dec. 24, 1958 INVENTOR. BRoR HILLBERG A'r'rY.

United States Patent DOWEL BAR SUPPORTING STRUCTURE FOR CONCRETE EXPANSION AND CONTRAC- TION JOINTS Bror Hillberg, Franklin Park, 11]., assignor, by mesne assignments, to Superior Concrete Accessories, Inc., a corporation of Delaware Filed Dec. 24, 1958, Ser. No. 782,859 2 Claims. (Cl. 948) The present invention relates to concrete road constructions and has particular reference to contraction and ex ansion joints of the dowel bar type in which the dowel bars are assembled and arranged to be held in proper spaced relationship with respect to one another in a joint assembly adapted to be positioned on the sub-grade transversely of a roadbed, with the dowel bars extending into adjacent slabs on opposite sides of the joint. Still more specifically, the invention is concerned with a novel dowel bar frame or supporting structure for holding and deter mining the position of the dowel bars during the pouring and solidification of the concrete.

It is among the general objects of the present invention to provide an improved and simplified form of road joint assembly which is comprised of properly positioned supports for holding a plurality of dowel bars in spaced parallel relationship with respect to one another for embedment in a pair of adjacent concrete slabs associated with a roadway or other concrete ground structure or pavement.

It is common knowledge that the coefficient of expansion of concrete roads, streets, sidewalks and similar pavements is relatively high, thus resulting in damage to the concrete unless efiicient means are provided to permit the concrete to expand and contract without exerting stress on the concrete. For this reason it is the practice to make such pavements in the form of individual slabs, the inner edges of which are spaced apart a distance suf ficient to permit the slabs to expand fully without contacting the inner edges thereof. The dowel bars, which usually are coated with grease on one or both sides of the joint, are employed for the purpose of maintaining the adjacent slabs in proper alignment, toward which end they serve as load transfer devices. It is obvious that these dowels, as they are commonly termed, must be properly placed in parallelism and that they must accurately maintain their parallel relationship during pouring of the concrete. Heretofore various means have been employed for properly positioning the dowels and maintaining them in position. Among such means have been the use of chairs which are supported on the sub-grade; stakes which are driven into the sub-grade; and hangers which are suspended from a supporting bar above the road and which are removed after the concrete is poured. The use of chairs and stakes not only involves the expenditure of time for properly aligning these devices but it involves a waste of material since these chairs and stakes serve no useful function other than acting as a temporary support for the dowels. The use of hangers presents a problem of removal because, in removing them, the dowels .are frequently forced out of alignment. Various frame structures for holding the dowels in position during concrete pouring operations have been proposed, but these usually require careful assembly in the field and the use of skilled labor in their assembly.

The present invention is designed to overcome many of the limitations that are attendant upon the construction and use of the above noted dowel positioning devices including frame structures and, toward this end it contemplates the provision of a novel frame or truss structure for holding a plurality of dowel bars in spaced parallel Patented May 8, 1962 relationship with respect to one another for embedding in concrete road or other pavement slabs and which is capable of being fabricated in its entirety in the shop as a package type composite unit consisting of but two parts or assemblies, and subsequently shipped to the scene of road construction where the two parts or assemblies may be easily assembled in the field without requiring the use of skilled labor to produce a dowel-supporting framework which is possessed of a degree of rigidity and resistance to deformation under the influence of the poured concrete that has hitherto been unattainable in connection with conventional dowel supporting frame or truss structures. A similar and related object of the invention is to provide such a dowel-supporting frame or truss structure wherein the same, after embedment in the hardened concrete, lends to the slabs with which it is associated a high degree or resistance to distortion under the influence of traflic loads so that the concrete slabs will remain permanently in proper longitudinal alignment with little or no shear stress being applied to the dowels during load transfer operations.

A further object of the invention is to provide a pair of cooperating dowel-supporting structures adapted to be assembled, each upon the other in the field and in which many of the principal parts thereof, because of the fabricated construction of the structures, may be formed from rolled steel strip stock which is inherently reinforced as it is rolled, thus contributing toward rigidity in the finished structures.

Another object of the invention is to provide a dowelsupporting assembly of this character wherein the reinforced strip stock parts serve as base supports for the entire assembly, resting upon the sub-grade and, because of their relatively broad expanse, will not sink below subgrade level as is the case with chair and rod supports.

A still further and important object of the invention is to provide such a dowel-supporting assembly wherein the dowels are supported above the sub-grade in their proper positions of parallelism by frame patterns which incorporate isosceles trapezoidal frame units formed from a.

sturdy rod stock suitably welded together, such frame patterns, architecturally, offering maximum strength and rigidity to the frame structure as a whole.

Yet another object of the invention is to provide such a dowel-supporting framework having associated therewith novel means for seating and supporting the end portions of the dowels while allowing for a limited amount of slippage between the dowels and their seats so that when slippage does occur due to normal thermal concrete contraction and expansion the frame structure will remain effective to support the dowels from the sub-grade at all times.

The provision of a dowel-supporting framework which is comprised, in the main, of rolled steel strip stock and shaped rod stock suitably welded together and which therefore is not costly to manufacture; one which includes anchoring strips having provision for the reception therethrough of conventional retaining stakes for holding the joint forming structure in position on opposite sides of the joint; one which will permit wide tolerance in its manufacture yet which may easily be adjusted during assembly for proper positioning of the dowels; and one which, otherwise, is well adapted to perform the services required of it, are further desirable features which have been borne in mind in the production and development of the present invention.

In the accompanying two sheets of drawings forming a part of this specification, one illustrative embodiment of the invention has been shown.

In these drawings:

FIG. 1 is a fragmentary perspective view, partly in section, of a portion cf a roadbed pavement showing a a dowel-supporting structure manufactured in accordance with the principles of the present invention operatively applied thereto;

FIG. 2 is a sectional view taken substantially along the plane indicated by the line 22 in the direction indicated by the arrows;

FIG. 3 is a fragmentary side elevational view of the dowel-supporting structure shown in FIG. 1;

FIG. 4 is an enlarged sectional view taken substantially along the line 4-4 of FIG. 3; and

FIG. 5 is a diminutive extended sectional view taken substantially along the line 55 of PEG. 3.

Referring now to the drawings in detail and in particular to FIG. 1, the improved dowel-supporting frame or truss structure of the present invention is shown as being operatively applied to a road sub-grade for embedment in the concrete of adjacent concrete slabs 12 and 1 respectively, constituting sections of a pavement. The pavement 12, 14 may constitute a road proper, a sidewalk, a base for a bituminous or brick surfacing or any other traffic bearing structure. Irrespective however of the particular use to which the frame or truss structure may be put, the essential features of the invention remain substantially the same. It will be understood that the pavement will be divided at regular intervals by expansion joints such as the joint designated at 16, the joint being formed in any suitable manner as for example by first effecting a transverse cut across the partially hardened concrete after pouring thereof to provide a narrow groove 18, and thereafter, when the concrete has hardened fully, rolling a heavy truck or the like over the thus scored pavement to crack the same as at and separate the two slabs 112 and 14.

The frame structure of the present invention is placed in position on the roadbed 10 prior to pouring of the concrete of the sections 12 and 14 and serves to properly orient a series of dowel bars 22, hereinafter referred to simply as dowels, and maintain them in spaced parallelism longitudinally of the roadbed and at a predetermined distance above the sub-grade 10. The frame structure is of an elongated nature and only a fragment in the vicinity of two of the dowels 22 has been illustrated in FIG. 1, it being understood that the frame structure will extend substantially completely transversely across the roadbed and that it will have associated therewith a large number of the dowels which are positioned preferably at regularly spaced intervals across the roadbed.

Still referring to FIG. 1, the frame structure is comprised of two separable frame sections designated at 24 and 26 respectively. These sections are each comprised largely of rolled metal strip stock and construction rod stock suitably welded together, the assembly being effected at the factory or shop and the separate sections being transported to the scene of installation for placement of the sections and assembly thereof in the installation. Generally speaking, the frame section or unit 24 serves to support one end of each of the dowels 22 while the frame section or unit 26 serves to support the other end of each dowel.

The frame section 26 involves in its general organization a base strip 30 (all views) which is preferably rolled from flat strip stock and which comprises a generally corrugated strip formed with three corrugations or upwardly facing troughs 32, 34 and 36 respectively (FIGS. 3 and 4), the medial trough 34 being joined to the other troughs 32 and 36 by fiat intervening portions 38 and 40. The troughs 32 and 36 have short width lateral side flanges 42 and 44 respectively.

Seated within the medial trough 34 and welded therein as at 46 are the base portions 48 of a plurality of spaced spacer rods 50. Each spacer rod 50 is generally of upright U-shape design and in addition to the base portion 48 has upwardly diverging arms 52 and 54. Common to and extending across the upper ends of the arms 52 and 54 of the various spacer rods 50 is a tie rod 56, the rod in combination with the base portion 48 and arms 4- 52 and 54 of each spacer rod 50 forming an isosceles trapezoidal structure. The rod 56 is welded as at 58 to the various arms 52 and 54.

The various dowels 22 are welded adjacent one end thereof as at 66 (FIGS. 1 and 4) to the tie rod 56 at spaced points along the latter and in such a manner that the dowels 22 extend in exact parallelism. At medial points on the dowel rods 22 a second tie rod 62 is welded as indicated at 64.

The frame section 24 involves in its general organization a base strip 70. The base strip 70 like the base strip 3! is rolled from flat strip stock and is identical in its configuration with the strip 38 so that needless repetition of description may be avoided by the application to the corresponding parts of this strip of identical reference numerals 32, 34, 36, 38, 40, 42 and 44 respectively. The medial trough 34 of the strip 78 has seated and welded therein the base portions 72 of a plurality of spacer rods 74, identical in construction to the spacer rods 50. Each spacer rod 74, in addition to the base portion 72, has upstanding diverging arms 76 and "78 respectively. Each spacer rod 74, in combination with a common tie rod 80 forms an isosceles trapezoidal frame structure similar to the trapezoidal frame structures associated with the frame section 26. The tie rod 30 is welded as at 82 to the upper ends of the various arms 76 and 78.

The tie rod 2%, instead of being welded directly to the dowel bars 22 as in the case of the tie rod 56, is welded as at $4 to a trough support 36 of semi-cylindrical cross sectional des n. The trough support 36 is connected by an end plate 38 (FIGS. 3 and 4) to an inverted crown or cap 90, likewise of semi-cylindrical cross sectional shape. The trough support 86 and cap 90, in combination with the plate 88, in effect provides a split cup assembly designated in its entirety at 92 in which one end of a dowel 22 is adapted to be telescopically and slidably received with the weight of the dowel being supported on the trough support 86. The trough support 86 and cap member frictionally receive the ends of the dowels 22 therein so that when the frame sections 24 and 26 are assembled each upon the other, the frame structure will be self supporting during attachment thereof to the road sub-grade 10.

In making an installation of the frame structure of the present invention on a road sub-grade 10, the base strip 24- may first be applied to the sub-grade and to facilitate anchoring of the base strip to the sub-grade, the intervening portions 38 and 46 between the various troughs 32, 34 and 36 are formed with a series of stake holes 93 (FIG. 4) adapted to receive therethrough conventional anchoring stake pins 94, with the various pins being wired in position as at in a manner well known in the art. After the base strip 70 has been thus anchored in position by the stake pins 94 with the spacer rods 74 extending in a common vertical plane, the frame assembly 26 may be brought into juxtaposition and the distal ends of the dowels 22 inserted in the split cup devices 92 so that the ends of the dowels 22 engage or are in close proximity to the base plate 88. The base strip 30 is then positioned on the sub-grade 10 and is anchored thereto by means of wire stakes 94 in a manner similar to the staking of the base plate 70. The frame assembly of the present invention is thus complete and ready for concrete pouring operations.

It will be observed that the diameter of the medial troughs 34 provided in the base strips 30 and 70 are substantially equal to the diameters of the rod stock which forms the spacer rods 50 and 74 so that a very intimate and strong welded bond may be attained between these parts, thus serving to maintain the spacer rods 50 normal to the general plane of the base strips. Architecturally a pyramidal or isosceles trapezoidal frame structure is possessed of great strength so that the frame structure of the present invention will withstand an appreciable degree of vertical compressional force when embedded in a road pavement. Since the split cup devices 92 permit limited sliding movement of the distal ends of the dowels '22 therein, wide tolerances in manufacturing operations are permitted because, in the assembly of the two parts 24 and 26, it is not essential that each dowel 22 actually engage the end plate 88 of a cup device 92. Finally, in the embedded concrete, the sliding of the dowel ends in the cup device 92 in no way restricts the normal and well known sliding functions of such dowels.

While there have been illustrated and described herein a highly practical embodiment of the present invention, no attempt has been made to illustrate further modifications or adaptations which are contemplated, since it is believed that this disclosure will enable those skilled in the art to embody or adapt the invention as may be desired within the scope of the appended claims.

Having thus described the invention what I claim as new and desire to secure by Letters Patent is:

1. In a two-part, separable dowel bar supporting structure for the expansion joints associated with concrete pavements, a pair of elongated parallel base strips, one for each part, formed of rolled sheet metal stock, each base strip being corrugated lengthwise to provide a series of spaced parallel troughs which are arcuate in transverse cross section and which are joined together by intervening fiat portions, said troughs including a medial trough and a pair of marginal side troughs, a plurality of spacer rods secured to each of said base strips in longitudinal spaced relationship, each spacer rod being in the form of a length of cylindrical rod stock bent to provide an upright U-shaped frame member having a straight linear base and upwardly and outwardly diverging arms, the diameter of said rod stock being substantially equal to the radius of curvature of the medial trough, said base being seated coextensively within the medial trough of its associated base strip and welded in position therein, a

tie rod overlying and parallel to each base strip and spaced thercabove in parallelism therewith, the upper end regions of the diverging arms of the spacer rods associated with each base strip being welded to the tie rod which overlies said strip to produce a series of isosceles trapezoidal frame structures along the strip, a series of elongated open upwardly facing semi-cylindrical sheet metal dowelsupporting trough members secured by welding to and overlying one of said tie rods at spaced points therealong, a relatively short open downwardly facing cap member parallel to and overlying each trough member and spaced therefrom, an end plate connecting each trough member to its overlying cap member, thus forming a split cup assembly, and a series of dowels having corresponding end regions thereof welded to the other of said tie rods, said dowels extending in parallelism and having a major extent of their other corresponding end regions slidably and loosely disposed within said dowelsupporting trough members, and having a limited portion of their extreme end regions underlying said downwardly facing cap members and in sliding frictional contact therewith.

2. In a two-part dowel bar supporting structure, the combination set forth in claim 1 including, additionally, a medial tie rod spanning the distances between each pair of adjacent dowels, extending at right angles thereto, and welded to each dowel.

References Cited in the file of this patent UNITED STATES PATENTS Re.21,99 6 Oates Jan. 6, 1942. 1,651,032 Macomber Nov. 29, 1927 2,299,318 Forsberg Oct. 20, 1942 2,331,548 Geyer Oct. 12, 1943 2,467,806 Brickrnan Apr. '19, 1949 2,829,572 Vanek Apr. 8, 1958

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