US3437017A - Reinforced concrete road construction - Google Patents

Description

April 8, 1969 P. o. K. WALZ ET AL 3,437,017

REINFORCED CONCRETE ROAD CONSTRUCTION Filed Aug. s, 1965 sheet of 3 lat/L 0. A. WA LZ Andreas van SMM/3?. Max PASBERG A TTORIVEY April 8, 1969 P.o, K. wALz ET AL 3,437,017

REINFORCED CONCRETE ROAD CONSTRUCTION Filed Aug. s, 1965 sheet 2 of 5 Andreas von Sil/VMM Max Pasberg ay Wm A rmR/vey April 8, 1969 P. o. K. WALZ ET AL 3,437,017

REINFORCED CONCRETE ROAD CONSTRUCTION Filed Aug. s, 1965 sheet o of 5 Max Pasberg nited States Patent Oice 3,437,917 Patented Apr. 8, 1969 3,437,017 REINFORCED CONCRETE ROAD CGNSTRUC'ION Paul Otto Kurt Walz, Dusseldorf, Andreas Van Schyndel,

Sturzelberg, Neuss, and Max Pasberg, Dusseldorf, Germany, assignors to Bau-Stahlgewebe GmbH, Dusseldorf- Oberkassel, Germany, a corporation of Germany Filed Aug. 3, 1965, Ser. No. 477,672 Claims priority, application Germany, Aug. 5, 1964, B 77,971; Nov. 21, 1964, B 79,426; Apr. 17, 1965, B 81,498; May 31, 1965, B 82,181

Int. CL E01c 1]/16 U.S. Cl. 94-8 6 Claims ABSTRACT F THE DISCLSURE In a concrete roadway slab embodying a reinforcing steel mat composed of spaced longitudinal rods extending in the lengthwise direction of the slab and spaced transverse rods intersecting and being aixed to said longitudinal rods, the transverse rods are bunched or subdivided into groups with the rods Within each group having a predetermined spacing distance and with the groups being spaced by intermediate regions free from transverse rods and having dimensions in the lengthwise direction of the slab substantially in excess of said rod spacing distance. The intermediate regions serve as cushioning zones of the slab in cooperation with socalled false equalizing gaps in the form of transverse grooves provided in at least the upper surface of the slab at a position midway within said regions, said grooves defining fracture lines in the concrete. In order to afford ready equalization by the gaps formed at said lines during extreme temperature fluctuation cycles, the longitudinal rod sections coincident with said intermediate regions are fitted with means, such as adhesion-resistant coatings, to provide for slidable engagement therebetween and the surrounding concrete, to thereby act 'as anchoring dowels for the concrete bodies on either side of gaps formed upon initially subjecting the slab to a predetermined longitudinal stress in traffic.

The present invention relates to concrete road construction, more particularly to improvements in reinforced concrete road strips, slabs or plates provided with spaced gaps or weakened areas transverse of the longitudinal direction of the slabs, more particularly of the type known as false gaps in the art.

The incorporation of reinforcing inserts, such as steel mats or the like structures, in concrete road slabs or plates has the purpose to prevent or minimize the formation of cracks or fissures caused by longitudinal tensile stress or loads to which the slabs are subjected during use in trafiic. Ordinarily, or where only a relatively light load or traffic is expected, the formation of cracks may be avoided or held Within permissible limits by the assurance of an efficient and uniform connecting joint or adhesion between the concrete and the reinforcing structures or members throughout the entire length of the slabs or plates. `On the other hand, in order to avoid the formation of irregular cracks or fissures in the slabs caused by tensile stresses resulting from relatively heavy loads or traffic, as well as due to extreme temperature fiuctuation cycles and other contractile excessive forces or stresses acting upon the plates, it has been found desirable to subdivide each slab or plate into a multiplicity of sections by the provision of transverse equalizing gaps of either the spacial or false type.

It has already become known, in place of providing so-called spacial gaps, or gaps completely initially separating the plates across the entire width or cross-section, to enable expansion and contraction by proper design manner as to produce false gaps, across said grooves,

to substantially prevent or minimize the formation of irregular cracks or lfissures in the plates or slabs under the effect of heavy loads or trafiic.

`In the use of false gaps of this type, the normal reinforcements of the concrete are omitted or completely interrupted at or in the vicinity of the gaps, in an effort not to impede or prevent the formation of the gaps by the presence or effect of the reinforcing members or inserts. The portions of the slabs or plates on the opposite sides of the gaps providing a fracturing line, m'ay be connected by dowels or the like connecting members disposed advantageously in the central plane of the slabs, to resist vertical forces or loads on the plates, such additional joints or connections being substantially without effect on the main concrete reinforcement of the plates or slabs.

An important object of the present invention is the provision of a reinforced concrete road slab of the referred to type, being constructed to positively prevent or minimize the formation of irregular cracks or fissures under relatively heavy load or trafiic conditions.

A more specific object of the invention is the provision, in connection with a reinforced concrete road slab of the referred to type having a plurality of false gaps formed therein in spaced relation and transversely of the slab, of a reinforcing structure in the vicinity of the gaps designed to resiliently support or anchor the parts of the slabs on the opposite sides of the gaps, or to provide a cushioning effect against longitudinal tensile stresses on the plates under heavy loads or traffic.

Another object of the invention is the provision of additional reinforcing means adapted to withstand vertical loads on the plates, notwithstanding the resilient or cushioned mounting of the plates to withstand longitudinal stresses by the action of the false gaps and in the manner as will become more apparent as the description proceeds.

The invention, both as to the foregoing and lancillary objects as well as novel aspects, will be better understood from the following detailed description of a few preferred embodiments, taken in conjunction with the accompanying drawings forming part of this specification and wherein:

FIG. 1 is a fractional longitudinal section of a reinforced concrete road slab including a false gap and constructed in accordance with the principles of the invention;

FIG. 2 is a view similar to tion of FIG. 1;

FIG. 3 is a fractional longitudinal section of a reinforced concrete road slab, being similar to the preceding figures and showing an improved feature of the invention;

FIG. 4 is a plan view of the reinforcing steel mat of FIG. 3, embodying the improvements of the invention;

FIG. 5 is similar to and showing a modification of FIG. 4;

FIG. 6 is an enlarged fractional view of FIG. 3;

FIG. 7 is a transverse section, taken along a false gap, of a reinforced concrete road slab or plate, showing yet another modification of the invention;

and showing fa modifica- FIG. 8 is a plan view of the reinforcing mat of FIG. 7, including the improvements of the invention;

FIGS. 9 and l0 are transverse sectional and plan views similar to FIGS. 7 and 8, respectively, and showing still another modification of the invention;

FIG. 1l is similar to and shows a modification of the embodiment according to FIG. 2; and

FIG. l2 is a perspective view of the reinforcing structure of FIG. ll.

Like reference characters denote like parts in the different views of the drawings.

With the foregoing objects in view, the invention, according to one of its aspects, involves generally the provision, in a concrete road slab of the referred to type having a plurality of spaced transverse grooves or indentations in at least its upper surface adapted to create false gaps thereat by fracturing of the concrete upon the slab being initially subjected to a predetermined longitudinal stress or load, of a reinforcing steel mat structure embedded in and firmly adhering to the concrete of the slab, said structure comprising essentially a plurality of spaced longitudinal rods or bars extending in the lengthwise direction of the slab and a plurality of spaced transverse rods intersecting said longitudinal rods and connected thereto by welding or in any other suitable manner well known in the fabrication of reinforcing steel mats or the like structures for use in concrete constructions.

The transverse rods are omitted, in accordance with the improvement of the present invention, within predetermined intermediate cushioning zones or anchoring regions extending to preferably equal distances from the opposite sides of the gaps to be formed, whereby to provide longitudinal rod sections within said zones, only traversing the respective gap. In other words, the transverse rods are hunched or subdivided into groups with the rods of each group having a predetermined spacing distance and with the groups being spaced by intermediate regions free from transverse rods and having dimensions in the lengthwise direction of the slab substantially in excess of said rod spacing distance, to serve as equalizing or cushioning Zones for the gaps. Further means are provided to allow the longitudinal rod sections within said zones to expand and contract freely as a result of longitudinal forces or stresses normal to the gaps, under the conditions of heavy loads or traffic and substantially unimpeded by the surrounding concrete of the slab. In other words, the portions of the slab adjacent to the gaps are individually resiliently anchored by the intervening longitudinal rod sections acting as dowels, whereby to substantially prevent irregular and other cracks or fissures in the plates or slabs, in a manner as will become further apparent as the description proceeds.

According to a simple embodiment to achieve the foregoing result and effect, at least a fractional portion of the longitudinal rod sections Within said cushioning zones is coated with an adhesion-resistant substance, such as a bituminous material, :a synthetic (plastic) material or the like, to allow the rods to move freely relative to the surrounding concrete. Alternatively, the rod sections or parts thereof within the cushioning zones may be enveloped by sleeves or wrappings of adhesion-resistant material.

The cushioning zones or regions in the vicinity of the false gaps may either be integral parts or sections of a composite reinforcing steel mat or equivalent structure for the enti-re concrete slab or strip, or separate reinforcing structures for and in the vicinity of each gap and constructed in accordance with the principles of the invention may be provided.

In order to ensure adequate resistance against vertical forces or stresses on the slabs, that is, in the direction of the gaps, additional reinforcing means may be provided in the cushioning zones, such as in the form of longitudinal rods, tubes or bars, 'being supported either by the longitudinal rod sections or by special supporting means provided therefor, care to be taken to prevent the additional reinforcing members from interfering with or impeding the free relative movement between the longitudinal rod sections and the surrounding concrete. The foregoing aim may be achieved in a simple and eliicient manner by partially, that is, within the region on one side of the gaps only, coating the additional reinforcing members with Vadhesion-resistant material, to enable free relative movement of the concrete portions on the opposite sides of the gaps, or to provide an eicient resilient anchoring of the slabs, for the purpose and in a manner as will become further apparent from the following description in reference to the drawings.

Referring more particularly to FIG. 1 of the drawings, there is shown a longitudinal section of a fractional portion of a slab forming part of a reinforced concrete l.road and including a false gap section constructed in accordance with the invention, it being understood that the entire slab or plate is provided with a series of spaced gaps or weakened sections defining predetermined fracture lines, and associated reinforcing structures, only one of which is shown and described in the following.

More specifically, in the example shown by FIG. l, the slab section 1 is provided upon its upper surface 2 with a groove or indentation 3 extending transversely of and across the entire width of the slab, while a T-shaped insert 4 of synthetic or the like material is embedded in the undersurface of the slab in line with the groove 2, in an effort to further reduce the cross-section of the slab to be fractured for the forming of the false gap or fracture 5 upon the slab being initially subjected in traffic to an adequate longitudinal tensile stress or load. The effect or function of the gap or fracture 5 is to prevent the formation of irregular cracks or fissures in the concrete surface by enabling a ready expansion and contraction within a cushioning or anchoring region a on the opposite sides of the gaps, under relatively heavy load variations and temperature fluctuations to which the slab is subjected.

Mounted approximately in the central plane of the slab 1, FIG. l, is a reinforcing steel mat or structure 6 comprised, in the example shown, of longitudinal bars or rods 7 traversing the gap 5 and cross-rods 8 being normal to and secured to the rods 7 by Welding or in any other suitable manner. The regularly spaced cross-rods 8 are omitted within the predetermined cushioning zone or region a on the opposite sides of the gap 5 and the longitudinal rods 7, or the portions thereof within said region acting as dowels, are provided, either over the entire or a fractional length of the zone a, with an insulating coating 9 or the like adhesion-resistant covering adapted to prevent the formation of a close joint or adhesion between the coated rod portions and the surrounding concrete. The coating 9 may advantageously consist of a bituminous or synthetic material. Alternatively, a covering sleeve may be provided in lieu of coatings 9, as described in the folowing.

The omission of the transverse or cross-rods 8 within the zone a has the effect of weakening the connecting joint between the mat 6 and the surrounding concrete, while the adhesion-resistant coating 9 of the rods acts to provide a kind of resilient anchoring for the longitudinal rods 7 by virtue of the now possible expansion and contraction of the coated rod sections. Besides, there is ensured thereby a safe fracturing of the concrete at the desired cross-section or gap 5 for the purpose as pointed out hereinbefore.

It is understood that the mat 6 disposed in the center plane of the slab or plate 1 may be mounted in either the upper or lower third of the plate, to suit existing load or other operating conditions or requirements. Besides, a number of mats may be embedded in a single plate in spaced vertical relation and traversing the gap 5, in the manner shown. Furthermore, the mat 6 may be an integral part of a larger reinforcing mat or structure extending throughout the entire plate or slab 1, as indicated in FIG. 1, or individual unit mats or structures may be provided in the vicinity of each of the gaps 5, as shown in FIG. 2. Finally, the mat structures of FIGS. l and 2 may be combined and disposed in different vertical planes of a slab or plate 1, as will 4be understood. In order to support or properly position the mats within the slabs 1, suitable supporting or spacing devices may be provided in accordance with conventional practice. Alternatively, the concrete may be poured to a predetermined height or level and the mats positioned during the pouring or laying operation.

The sections of the longitudinal rods 7 located within the zones a on the opposite sides of the gaps 5 may serve to a certain extent to assume the transverse load or forces on the plates acting in the direction of said gaps. In order to resist additional transverse or vertical loads or forces, there are provided, in accordance with an improved feature of the invention, sleeves or tubular dowels concentrically enveloping the rods 7 within the Zones a and connecting the separate slab portions A and B on the opposite sides of the gap 5, in the manner more clearly shown in FIG. 3 of the drawings. This not only substantially increases the capability of the mats to resist vertical loads or forces, notwithstanding the omission of the crossrods within the zones a, but further acts to ensure a safe or positive fracturing of the concrete and formation of the false gaps, since the thus obtained expansion path of the horizontal rods 7 within the tubes or sleeves 10 enables an nnimpeded elastic expansion and contraction of the coated rod sections.

The reinforcing sleeves or tubular elements 10 should not affect the expansibility of the plate or slab 1 for which purpose they are coated upon at least the outer surface thereof with a layer of insulating or adhesionresistant material, as indicated by stippling in FIG. 4, or otherwise treated or conditioned so as not to impede the relative movement of the rods 7. In many cases, it will be suicient to achieve this aim by coating the sleeves 10 over about one half of their length with adhesionresistant material, as shown in FIG. 5, wherein the length c of the sleeves 11 is less than the length of the zones a, as compared with FIGS. 3 and 4, wherein the length b of the sleeves 10 equals the length of the zones a. Advantageously, the coatings upon the sleeves 11 should extend across the gaps 5 to a certain extent, as indicated in FIG. 5, to prevent corrosion in the region of the gap 5. In other words, in the latter case, the sleeves are coated and arranged to be in intimate connection with one of the plate sections A and B, while being free to move within the other section, in such a manner as to enable said sections to move freely if subjected to dimensional changes of the plates, such as expansion, contraction, creeping, etc. caused by load, temperature or other influences.

In order to further improve the free movement of the sleeves 10 and 11, a cap (not shown) or the like of metal, plastic, synthetic material, etc. may be mounted upon one end of the sleeves. The caps are advantageously disposed alternately upon the opposite ends of the sleeves With enough free space ybeing left therebetween and the sleeves, to enable the latter and in turn the rod section 7 to move freely in relation to the surrounding concrete.

The surface of the sleeves 10 and 11 is preferably circular, but may be elliptical or of any other desired shape. It is not necessary to provide sleeves upon all of the rod sections 7 within the cushioning zones a, nor is it necessary for the sleeves to extend over the entire length of the zones, as in the case of the sleeves 10 of FIG. 4. FIG. 5 shows a mat structure having auxiliary sleeves 11 of a length equal to a fraction c of but greater than one half of the Width of the cushioning Zone a. Finally, the sleeves 10 and 11 may be arranged upon the rods 7 Cil in irregular fashion, but should be symmetrical to the gaps 5 wherever possible.

Care should be taken to prevent liquid concrete to enter into the space between the rods 7 and the sleeves 10 or 11 during theI concrete laying or pouring operation, especially where the inner space of the sleeves is not completely occupied by the rods 7. If necessary, the ends of the sleeves may be closed yby means of seals 12 consisting of cork, putty, or a like sealing material, as shown in FIG. 6.

The constructions described in the foregoing make it possible to adapt the reinforcing structures to any existing design and operating conditions or requirements. The sleeves or dowels 10 and 11, if of suliiciently large diameter may have a reduced wall thickness compared with sleeves of smaller diameter, while the inner diameter may be such as to snugly fit the rods 7, whereby to utilize the latter as additional means to resist transverse or vertical forces, depending upon the' loads or moment of resistance of the slabs in respect to the gaps 5.

There is thus provided, in accordance with the present invention, a relatively ilexible or resilient anchoring of the slab sections on the opposite sides of the false gaps of a concrete road slab or plate of the type forming the subject of the invention, by the coated sections of the rods 7 within the Zones a being enabled to expand under the effect of heavy loads, to thereby avoid the formation of irregular cracks or fissures in t-he slabs or plates, as well as to eliminate other defects inherent in the prior concrete road slab constructions. Additionally, the coated rod sections 7 may serve to resist transverse forces or loads either separately or in conjunction with the additional reinforcing sleeves or dowels mounted upon the rods or carried by separate supporting means, substantially without impairing the resilient support or anchoring of the slabs, in the manner described and readily understood from the foregoing.

The provision of resilient anchoring zones adjoining the false gaps in the slabs or plates has the further advantage of preventing an unequal load distribution on the various gaps of a slab, whereby to in turn avoid concentrations of the total expansion upon a single gap or a limited number of gaps of a slab or plate.

Further embodiments of the invention to achieve the foregoing elfects and results are Shown by FIGS. 7-10. FIGS. 7 and 9 are transverse sections through a slab or plate, taken along a false gap 5, and FIGS. 8 and l0 are plan views of the respective reinforcing mat structures constructed in accordance with the invention. Again, the longitudinal rods 7 of the mats disposed in the central plane of the slabs traverse the gap 5 and the cross-rods 8 are omitted within the Zones a on both sides of the gaps, in substantially the same manner as in the preceding embodiments. Similarly to the latter, the rods 7 are covered by bituminous or the like coatings 9 within the zones a, in the manner and for the purpose specied.

Two different types of additional reinforcements for the assumption of transverse or vertical forces are shown in FIGS. 7, 8 and 9, 10, respectively. According to the FIG. 7 modification, sleeves or dowels 13 of reduced length d are provided supported by semi-circular bents or depressions 14 of a pair of auxiliary and transverse supporting rods 1S which are in turn supported, without being permanently aflixed thereto, by the longitudinal rods 7 engaging bents 16 in the rods 15 opposite to the bents 14, in the manner shown by the drawing. If desirable, the rods 15 may be positioned by loosely attaching them to the rods 7 by means of twisted wire elements 17, or in any other suitable manner, to allow of relative sliding movements upon the rods 7.

FIGS. 9 and 10 show different types of profiled dowels 18 and 19 mounted directly upon the rods 7 within the zones a. More particularly, the dowels 18 of substantially circular cross-section are formed with longitudinal grooves adapted to engage the coated sections lof the rods 7, while the members 19 are of angular cross-section to t or overlie the rods 7, in the manner shown and understood.

As is understood, the dowels 13 may have a suicient length, whereby to overlie the first cross-rods 8 at the opposite ends of the zones a. In the latter case, the respective rods 8 may be formed wit-h bents, eyelets or the like, to receive or support the ends of the -dowels 13, in a manner similar to the auxiliary supporting rods 15. In either case, the auxiliary dowels or rods should be provided wth adhesion-resistant coatings over at least one half the length thereof, to provide a yielding support or anchoring of the slab portions on the opposite sides of the gaps 5, in accordance with the basic concept and principles of the invention.

As pointed out hereinbefore, the special reinforcing structures Within the zones a of the false gaps S according to the invention may be an integral part of a composite steel mat or the like reinforcing structure extending over the entire concrete road slab or strip, as indicated in FIG. 1, or separate or discrete mat structures may be provided in the vicinity of each of the gaps, as shown in FIG. 2. Moreover, the reinforcing structures, in place of being in the form of planar mats or assemblies, may be of any, including a three-dimensional, type or construction with the cross-rods being omitted within the zones or regions a and with the longitudinal rods Within said zones designed to act as resilient cushioning or anchoring means for the slabs.

According to a further feature of improvement, especially where individual mats or reinforcing structures are provided for each gap 5, FIG. 2, the ends of the longitudinal rods may be bent to form feet for the mounting or positioning of the mats or the like structures upon a base or road bed 21, as shown in FIGS. 11 and 12. If desirable, the cross-rods connecting the feet or bent portions 20 may be omitted.

In order to further decrease the cross-section of the slabs 1 in the region of the gaps 5 to be formed, or to enhance the probability of tearing or rupturing of the concrete in forming the false gaps, the inserts 22 in FIGS. 11 and 12, corresponding to the sleeves 11 of FIG. 5, are shown itted with an edgewise plate or strip 23 disposed in line with the groove 3 and insert 4. Strip 23, consisting advantageously of synthetic material, is traversed by the longitudinal rods 7 with the inserts or sleeves 22 overlying said rods and taking the place of the bituminous or the like coatings of FIGS. 1 and 2 described hereinbefore. The effect of the strip 23 in further decreasing or weakening the cross-section of the slabs at the point where the gaps S are to be formed, is an added assurance of the formation of the gaps during the initial use under actual load or traic conditions.

In applying the coatings 9 to or mounting of the sleeves 10, 11, 22 upon the rods 7, care should be taken that the coatings or sleeves adhere closely to the rod surface without the danger of being impaired 4or distorted during the mounting and concrete pouring operations. The use of a synthetic strip. 23, FIG. 12, is of special importance or advantage where the upper groove 3i, instead of being cut into the hardened or cured concrete, is formed by the insertion of a movable bar or slat during the concrete pouring operation or forming of the slabs.

In the foregoing the invention has been described in reference to a few specific illustrative devices. It will be evident, however, that variations and modifications, as well as the substitution of equivalent parts or elements for those shown for illustration, may be made without departing from the broader scope and spirit of the invention as set forth in the appended claims. The specification and drawings are accordingly to be regarded in an illustrative rather than in a restrictive sense.

We claim:

1. A reinforced concrete roadway slab comprising in combination:

(1) a reinforcing mat structure embedded in said slab being composed of (a) a plurality of spaced longitudinal rods extending in the lengthwise direction of slab, and

(b) a plurality of spaced transverse rods intersecting and being affixed to said longitudinal rods,

(c) said transverse rods being subdivided into groups with the rods of each group having a predetermined rod Spacing distance and with each two adjacent groups being spaced from one another by an intermediate region of the slab free from transverse rods and having a dimension in the lengthwise direction of the slab substantially in excess of said rod spacing distance,

(2) said slab being provided, midway within said region, with a transverse groove in at least the upper surface of the slab dening a fracture line through said slab coincident with said groove, and

(3) means to provide for slidable engagement between the slab and at least a fraction of the longitudinal rod sections coincident with said intermediate slab region, whereby said longitudinal rod sections act as dowels for the concrete bodies of said slab on either side of said line.

2. In a concrete roadway slab as claimed in claim 1, said last means consisting of an adhesion-resistant coating upon at least one of the portions of the longitudinal rod sections located on either side of said line.

3. In a concrete roadway slab as claimed in claim 1, said last means consisting of a bituminous coating upon at least one of the portions of the longitudinal rod sections located on either side of said line.

4. In a concrete roadway slab as claimed in claim 1, said last means consisting of tubular elements embedded in said slab and closely enveloping at least one of the portions of the longitudinal rod sections on either side of said line.

5. In a concrete roadway slab as claimed in claim 1, said last means consisting of tubular elements embedded in said slab symmetrically to said groove and closely enveloping said longitudinal rod sections, and a platelike element embedded in said slab and extending normally to said tubular elements in line with said groove.

6. In a concrete roadway slab as claimed in claim 1, including an additional groove disposed in the undersurface of said slab in line with said rst groove.

References Cited UNITED STATES PATENTS 1,996,153 4/1935 Heltzel 94-39 2,015,340 9/ 1935 Fischer 94-8 2,060,326 11/1936 Lampert 94-17 2,080,124 5/1937 Friberg 94-18 X 2,116,697 5/1938 Geyer 94-18 2,309,538 1/1943 Robertson 94--18 2,806,414 9/1957 Woodman 94-17 3,022,713 2/ 1962 Friberg 94--18 X 3,045,566 7/ 1962 Houck 94-93 3,156,169 11/ 1964 Finsterwalder 94-8 2,106,095 1/ 1938 Heltzel 94-8 OTHER REFERENCES Engineering News Record: May 1957, p. 94.

JACOB L. NACKENOFF, Primary Examiner.

U.S. Cl. X.R. 94-18

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