US3914915A - Reinforcing mat structure for planar concrete construction units - Google Patents

Abstract

A composite reinforcing mat structure for use in planar construction units (slabs) comprises an infrastructure composed of a plurality of unit mats each consisting of two sets of intersecting longitudinal and transverse bars connected at their intersection points, said mats arranged with adjoining marginal longitudinal zones overlapping each other, and a multiplicity of mat strips each consisting of at least two longitudinal bars connected by transverse bars and overlying said infrastructure in predetermined spaced relation to each other and to the median lines of the overlap zones of said structure.

Description

United States Patent 1191 van Schyndel REINFORCING MAT STRUCTURE FOR PLANAR CONCRETE CONSTRUCTION UNITS [75] Inventor: Andreas van Schyndel, Sturzelberg near Neuss, Germany [73] Assignee: Baustahlgewebe GmbH,

Dusseldorf-Oberkassel, Germany [22] Filed: Dec. 3, 1969 [21] Appl. No.: 881,821

[30] 7 Foreign Application Priority Data 1 Oct. 28, 1975 FOREIGN PATENTS OR APPLICATIONS 1,104,156 4/1961 Germany 52/664 75,527 1/1918 Switzerland ..52/600 Primary ExaminerFrank L. Abbott Assistant Examiner-Leslie A. Braun Attorney, Agent, or Firm Frank L. Durr; Orville N. Greene ABSTRACT Y A composite reinforcing mat structure for use in planar construction units (slabs) comprises an infrastructure composed of a plurality of unit mats each consisting of two sets of intersecting longitudinal and transverse bars connected at their intersection points, said mats arranged with adjoining marginal longitudinal zones overlapping each other, and a multiplicity of mat strips each consisting of at least two longitudinal bars connected by transverse bars and overlying said infrastructure in predetermined spaced relation to [56] References Cited each other and to the median lines of the overlap UNITED STATES PATENTS zones of said structure.

2,814,943 12/1957 Simmons 52/602 3,302,360 2/1967 Bjerking 52/660 5 Chums 21 D'awmg F'gures 10 7 1 fifl o 14 "a a a A a 0 p a d r c I I l I 1 a d 7 u 7 a v o a v US. Patent Oct. 28, 1975 Sheetlof2 3,914,915

i gi P1? lOF? AR T fl' i f? loR ART IN VEN TOR. ANDRE/46 vn/v 66H Y/VDEL rrA/zl. BATH Arr-newer REINFORCING MAT STRUCTURE FOR PLANAR CONCRETE CONSTRUCTION UNITS The present invention relates to reinforcing arrangements for planar concrete construction units or slabs, more particularly of the type comprising a plurality of juxtaposed and mutually overlapping unit steel mats each composed of two sets of rectangularly intersecting longitudinal and transverse bars connected at the intersection points, preferably by spot welding.

Planar concrete construction units, such as ceiling slabs or plates, may be reinforced either by the use of single steel bars or by the aid of prefabricated reinforcing steel mats. In using single bars, it is possible to realize the required metal cross-section of the reinforcement as derived from static analysis in all the variety required and with any desired degree of accuracy. In order to achieve a certain metal cross-section, it is necessary simply to decrease or increase the distance between the bars of equal diameter. If such increase or decrease of the distances is unsuitable or unfeasable, bars of varying diameters may be used for the same purpose. As a consequence, any construction unit may be reinforced adequately from both a static and constructional point of view. Reinforcement by means of single bars has however the disadvantage of a considerable expenditure of labor, because each bar must be prepared and assembled separately.

The second possibility of reinforcing planar concrete constructions units consists in the use of prefabricated reinforcing mats. These mats consist of two sets of rectangularly intersecting longitudinal bars and transverse bars connected at the intersection points, preferably by electric spot welding. For reasons connected with the fabrication and transport of such mats, they cannot be provided in any desired sizes or dimensions. in order to achieve the desired reinforcement of a given construction unit, the mats must be superimposed with the marginal overlap zones or regions being such as to enable an adequate load or force transmission from one mat to the next. This overlap is sometimes referred to as the thrust of the mats in the composite structure or assembly. i

The advantage of the foregoing type of reinforcement is due to the fact that large surface reinforcing units may be realized practically and economically, as well as to relatively close specifications and tolerances. Since the separate operations involved in the use ofindividual bars, such as bending, correct laying and connections of the bars, are dispensed with by the use of prefabricated mat units, the mats can be layed or assembled expeditiously as well as securely. The rigid connection of the longitudinal and transverse bars by the spot welding joints has the further result of an intimate adherence of the reinforcement for the concrete.

On the other hand, the aforementioned advantages of the reinforcement by means of unit mat involves a certain rigidity of the system or assemblage. The metal cross-section per unit length of the longitudinal and transverse bars must be fixed for the prefabrication, both with regard to the distances of the individual bars from each other as well as in regard to the available rod or bar diameters. Considering the bar diameters offered by the steel or wiring industry, there has been evolved during the course of the years a certain standardization to the effect that only distances of 50 mm and multiples thereof and 75 mm and multiples thereof are being used in practice. The choice of the distances is further limited by the fact that load-supporting bars should have a distance not exceeding 200 mm and transverse bars a distance not exceeding 333 mm from each other.

Under the foregoing conditions, it is possible, for instance, to realize practically a cross-section range from 0.84 to 7.54 cm per meter by the provision of 18 different unit mats or types. In order to increase the crosssection range, it has been customary in the past to utilize so-called twin bars consisting of two closely adjacent individual bars, resulting thereby in a cross-section range up to 15.08 cm /m and a cross-section or type number of 2.18 36.

The multiplicity of the mat types and large number of bar diameters required for the fabrication of the mats have a considerable influence on the manufactur ing costs. Besides, this multiplicity of units is counter to prevailing trends of an automated fabrication of the mats, while the share of the total cost required for storage and stockpiling becomes considerable.

Nevertheless, the mentioned number of 36 different mat types has been found insufficient frequently in the effort of achieving economic concrete reinforcements in practice. For this reason, it has become customary to utilize two superposed layers of reinforcing mats in an effort to double the available metal cross-section and type number and to provide additional crosssection by the combination of various types and to reduce the differences between the consecutive bar diameters or cross-sections. By these expedients, however, the cost of laying of the mats is increased considerably.

A further problem involved in the use of reinforcing unit mats derives from the fact that the mats must be adequately overlapped, to ensure a proper force or load transmission from one mat to the next. Where the longitudinal bars have the same diameter up to the outer edges of the mats, the bars appear at twice the number per unit width in the overlap zones. This entails a certain excess metal or accumulations within said zones which, due to the great distance between the latter corresponding to the width of the mats, can no longer be considered as equally distributed across the width of the composite mat or structure.

Proposals have already been made to obviate the excess metal cross-section in the overlap zones. According to a well-known expedient, the cross-section of the longitudinal bars within the marginal or overlap zones isone-half of the cross-section of the bars within the remaining or intermediate zones of the mats. in this manner, it has become possible to achieve a substantially uniform metal cross-section distribution per unit width throughout the entire range or width of the composite mat structure.

Accordingly, an important general object of the present invention is the provision of means and a novel multiple reinforcing mat structure combining the advantages of the prefabricated unit mats with the flexibility and advantages of the reinforcement by means of individual bars, substantially without involving the drawbacks and disadvantages of either method or system of concret slab reinforcement.

With the foregoing object in view, the invention in volves generally the superposition upon a multiple mat arrangement composed of conventional unit mats, forming an infrastructure and providing a first basic reinforcement for the concrete part or slab to be reinforced, of a multiplicity of secondary mat units in the form 'of narrow mat strips each consisting of at least two longitudinal bars connected by transverse bars, said strips being distributed over said structure at such spacing distances from each otheprafid from the median lines of the overlap zones of said structure as to cause the ensuing consecutive local metal cross-section accumulations to be substantially uniformly distributed across said structure and to be effectively added in their resultant action to the basic reinforcement provided by said infrastructure, to thereby result in a final desired total reinforcement of the concrete slab or the like construction unit to be reinforced.

It has been found possible, in this manner, that is, by the use of two different types of standard mats or units, in the form of conventional unit mats, on the one hand, and of the additional mat strips according to the invention, on the other hand, to realize practically any desired range of reinforcing metal cross-section with the aid of a considerably limited number of unit mats and additional mat strip types, compared with conventional reinforcing practices utilizing multiple mat units.

In the new reinforcing arrangement, the basic reinforcement may be in the form of multiple or unit mats having longitudinal bars of constant cross-section across the entire width of the mats. In this case, the metal cross-section provided by the additional mat strips advantageously equals the excess cross-section in the overlap zones and the mat strips are distributed at equal distances from each other and said zones across the entire mat or infrastructure. Where means are provided to equalize the cross-section in the overlap zones, such as by the provision of longitudinal bars of half the cross-section within the latter, the metal cross-section provided by the mat strips advantageously equals the cross-section within the overlap zones and the strips are distributed at fixed distances from each other, on the one hand, and at half said distances from the overlap zones, on the other hand.

In order to utilize the transverse bars for the reinforcement, a pair of sets of narrow mat strips intersecting one another, may be provided oriented with the respective supporting axes of the slab or part to be reinforced. In many cases it is sufficient to provide a limited number of transverse bars for the additional mat strips to serve as means to secure the positions of the strips.

The small additional mat strips may be of reduced length conforming with the prevailing bending movement effective on the slab, and/or the strips may be bent upwardly towards the upper face of the slab or the like planar part to be reinforced.

The advantage of the reinforcing arrangement of the invention is to be seen primarily in the fact that the mats disposed in the lower layer (infrastructure) serve to provide the cross-section for the basic reinforcement which must extend from one abutment of the construction part to the other, while the upper layer formed by the second units or narrow mat strips serves to achieve the final metal cross-section or distribution. By the use of the second layer composed of small mat strips, it is possible, depending upon the number and distance of the strips, to realize a multiplicity of reinforcing crosssections up to double the cross-section of the first layer ofinfra-structure composed ofa single type of unit mat.

As a result of the subdivision of the reinforcing crosssection into a basic reinforcement and an additional reinforcement consisting of narrow mat strips, not only is the possibility of combinations increased considerably, and in turn the number of mat types to be stockpiled reduced, but the manufacture and stockpiling of the mats is greatly simplified thereby. Thus, it is possible, by means of a relatively small number of conventional mat types, and by not more than the same limited number of mat strip types to cover a practical cross-section range from 1.0 to 45.0 cm /m.

The special advantages of the new reinforcing arrangement according to the invention will become further apparent from the following, assuming, for instance, that 24 different mat types are required in using conventional unit mats for the coverage of crosssection range of 0.92 to 22.62 c /m and for the reinforcement of a construction part in the single axis, these 24 mat types involve 24 different metal crosssections. Inasmuch as the required metal cross-sections correspond in rare cases only to a predetermined crosssection of a standard series and since reinforcement below the required values is not permissible for reasons of safety of the units, excess reinforcements cannot be avoided in practice. The required additional consumption due to excess reinforcement varies practically between 10 and 20% in using conventional mat types or systems. I

According to the present invention, the same metal cross-section range may be realized by six conventional mat types in conjunction with five mat strip types according to the invention. With such six mat units and five mat strips, which may be distributed for instance at distances of 1.0; 0.90; 0.80; 0.70; 0.60; and 0.50 m across the entire reinforcing width, it is possible to realize 6 6X5 different metal cross-sections.

Whereas in a conventional mat series 18 different bar cross-sections are required, only six such cross-sections are necessary in a reinforcement according to the invention, since the mat types of the basic reinforcement (infrastructure) may consist of the same bars as the mat strips of the additional reinforcement.

A further advantage of a combination according to the invention comprising a basic reinforcement (infrastructure) composed of conventional unit mats, on the one hand, and additional mat strips, on the other hand, is due to the fact that the additional strips may, in the manner heretofore customary with many reinforcements, be cut short at a region of tensile stress, enabling thereby a reduction in length of the strips in conformity with the prevailing bending moments affecting the slab to be reinforced, on the one hand, and that, as has been heretofore possible only with single bar reinforcements, the strips may be bent upwardly towards the top face of the slab or the like planar construction unit. This now enables the realization of a stepped reinforcement heretofore impossible with conventional reinforcing mats due to inadequate shear resistance of the mats. As a consequence, it becomes possible in this manner to utilize within a region of tensile stress the no longer needed reinforcing parts for anchoring purposes by upwardly bending the same within a region of compression stress, on the one hand, as well as to utilize said part to absorb any negative bending moment within the supporting range in the case of slabs encompassing several fields of force or stress.

A further problem resides in the fact that, depending upon whether the part to be reinforced is to be supported in a single or two axes, different degrees of reinforcement by the transverse bars are required. In practice, the minimum transverse reinforcement in case of parts stressed in a single axis is of the metal crosssection of the supporting or longitudinal bars. In order to realize intermediate values, including parts stressed in two axes and fitted with a 100% transverse reinforcement, different mat types may be provided containing approximately 40, 60, 80 and 100% of the corresponding cross-section of the longitudinal bars. In this manner, the number of mat types to be stockpiled may be further reduced.

It has been found possible to realize, by the use of the improved reinforcing arrangement according to the invention and involving the provision of limited numbers of two different types of unit mats as described hereinbefore, any desired metal cross-section in a single or both rectangular supporting axes of a part or unit to be reinforced.

The invention, both as to the foregoing and ancillary objects, as well as novel aspects thereof, will be better understood from the following detailed description, taken in conjunction with the accompanying drawings forming part of this disclosure and in which:-

FIG. 1 is a fragmentary cross-sectional view through a known composite reinforcing mat structure composed of uniform unit mats, resulting in an excess metal cross-section within the overlap zones;

FIG. 2 is a sectional view similar to FIG. 1, showing a composite mat structure made of unit mats designed to result in a uniform metal cross-section distribution across the width of said structure;

FIGS. 3a 3f illustrate cross-sections of mat strips suitable for use in accordance with the improvement by the invention;

FIGS. 4 and 5 show concrete slabs reinforced respectively by mat structures according to FIGS. 1 and 2 and embodying the improvement according to the invention; and

FIGS. 6a to 6e, illustrate in a schematic manner various ways that the prior art structure of FIG. 6a can be modified with the strips as shown in FIGS. 4 and 5.

FIGS. 7a to 7d are views similar to FIGS. 6a to 6e, FIG. 7a being the prior art structure.

FIG. 8 is a view similar to FIG. 4, but showing a modified form of reinforcement which includes strips that cross each other.

FIG. 9 is a cross-sectional view of a modified form of reinforcing structure in which the end portions of the straps turn upwardly.

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

Referring more particularly to FIG. 1, presented for the sake of illustration of the invention, there is shown a section of a well-known composite reinforcing mat structure comprising a plurality of standard of unit mats 1 each consisting of longitudinal steel bars or rods 3 intersected by transverse bars 2 secured to the former at the intersection points, preferably by spot welding. The longitudinal bars 3 in the example shown, are of constant diameter throughout the width of the mats and mutually spaced by constant distances a. In the example shown, each two adjoining mats l overlap each other within a zone covering a single mesh, whereby the longitudinal bars 3 appear in double number within the overlap zones, to result thereby in an excess metal cross-section within said zones and in turn in nonuniform metal cross-section per unit width distribution across the width of the composite mat structure.

According to a well-known alternative construction, as shown by FIG. 2, the marginal or overlap zones of the unit mats 4 are fitted with longitudinal bars 5 whose cross-section is equal to one-half the cross-section of the remaining bars 6 in the intermediate zones of the mats, to achieve thereby a uniform metal cross-section distribution across the entire mat structure, that is, including the marginal or overlap zones.

FIG. 3 shows a few possible constructions of the additional mat strips according to the invention superimposed upon an infrastructure of unit mats according to FIGS. 1 and 2 or any equivalent multiple mat assembly. According to FIG. 3a, the mat strip 7 consists of two longitudinal bars 8 spaced by a distance b which may be equal to the spacing distance a, FIGS. 4 and 5. The longitudinal bars 8 are connected by way of transverse bars 9 which may be of any number to serve as securing means of the rods 8. The connections may be by means of welding, clamping, using metallic or synthetic clamps, by binding, or cementing preferably with the use of a synthetic glue or bonding material. Further more, the connections may be shear resistant, to cause the transverse rods to contribute to the anchoring effect to the concrete, or the connections may be of a non-shear resistant nature where the transverse rods 8, which may be of limited number, merely serve to secure the position of the longitudinal rods 8.

As shown by FIGS. 3b and 3c, one or both of the longitudinal rods 8 of the mat strips may be in the form of twin rods and, finally, three, four or five longitudinal rods 8 may be distributed over the same width b of at least 200 mm, as shown by FIGS. 3d 3f, respectively.

Referring to FIGS. 4 and 5, there is illustrated the application of the invention to the reinforcement of a concrete slab 10, such as a floor, ceiling, etc. In FIG. 4, the unit mats l of an infrastructure, according to FIG. 1 are combined with a single mat strip 7 disposed centrally between two successive overlap zones. If, in an arrangement of this type, the metal cross-section of the strip 7 corresponds to the excess metal or accumulation in the overlap zones, the successive accumuiations in the composite structure will result in a mean metal cross'section being uniformly distributed over the entire width of the structure and added to the basic cross-section of the infrastructure formed by the mats l, to result in a total reinforcement for the slab 10 in compliance with the particular requirements of the application at hand.

According to the example shown by FIG. 5, this applies to the application of the invention to the basic mat structure of the type according to FIG. 2 exhibiting basically a uniform metal cross-section distribution across the basic or infrastructure composed of unit mats 4. In this case, the mat strips 7 provided in addition to the mats 4 are advantageously spaced from the median lines of the overlap zones by distances equal to one-half of the constant mutual spacing distance between the mats, whereby to result in a uniform distribution of the metal accumulations added to the metal distribution of the infrastructure of the mats 4, across the entire width of the composite mat structure.

FIGS. 6a to 6e and 7a to 7d schematically illustrate arrangements of the type according to FIGS. 4 and 5, respectively, with means to control the metal crosssection distribution by the provision of varying numbers of mat strips between any two overlap zones of the basic or infrastructure, to enable the realization of a desired metal cross-section within a given practical operating range by means of a minimum number of unit mats and mat strips, respectively.

More particularly, FIG. 6a shows an infrastructure composed of unit mats 11 similar to "FIG. I, the distance between the median lines of the overlap zones of the mats being denoted by S. If a single mat strip 12 is added to the infrastructure, the same is advantageously disposed midway of each mat 11, FIGS, 6b, that is, the metal accumularion are spaced by distances of 8/2. In FIGS. 6c6e, two, three and four strips 12, respectively, are disposed in equi-spaced relation within the distance S, resulting in metal accumulations throughout the width of the composite mat spaced by distances respectively of 8/3, 8/4 and /5.

Finally, FIGS. 7a to 7d show an arrangement similar to FIGS. 6a to 62 except for the overlap zones of the infrastructure, FIG, 7a having the same metal crosssection as the remaining zones by the provision of the longitudinal bars 13 of half the cross-section as shown in FIG. 2 and indicated by the thin marginal overlap portions of the bars 13 in the drawing. With two, three and four mat strips 12 being applied to the basic structure, FIG. 7a, the strips are spaced from each other by equal distances 8/2, 8/3 and 5/4, on the one hand, while the marginal strips are spaced from the median lines of the adjacent overlap zones by distances of 8/4, 8/6, and 5/8, respectively, on the other hand, as indicated in the drawing, in an effort to obtain a desired total and uniform metal cross-section distribution across the entire width of the composite structure.

FIG. 8 is similar to FIG. 4, but shows the cross-strip 7 in addition to the strip 7.

FIG. 9 is a cross-sectional view of an end portion of a structure taken at right angles to the views of FIGS. 4 and 5 so as to show the bending of the strip 7" towards the upper face of the structure.

In the foregoing, the invention has been described in reference to a few illustrative and exemplary devices. It will be evident, however, that variations and modifi cations, as well as the substitution of equivalent elements and devices for those shown may be made without departing from the broader scope and spirit of the invention.

I claim:

1. A composite reinforcing steel mat structure for use in planar concrete construction units comprising a plurality of unit mats each composed of a pair ofintersecting sets of equi-spaced longitudinal and transverse bars connected at their intersection points, said mats arranged in juxtaposed relation with adjoining marginal longitudinal zones thereof overlapping each other over a distance of at least one mesh of the mats, to provide a reinforcing infrastructure of desired dimension and predetermined metal cross-section per unit width distribution across the width thereof, in combination with a multiplicity of relatively narrow reinforcing mat strip of approximately the width of the overlap in the infrastructure each composed of at least two longitudinal bars intersected by transverse bars connected thereto and overlying said infrastructure, said mat strips being spaced from each other and.the median lines of the overlap zone of said infrastructure, to cause the resultant metal cross-section accumulations by said strips in conjunction with the metal cross-section distribution of said infrastructure to produce a composite reinforcing structure with a predetermined total and substantially uniformly distributed metal reinforcement throughout the width of the composite mat structure.

2. A reinforcing mat structure as claimed in claim 1, wherein the longitudinal bars of said unit mats are of equal diameter throughout, whereby to result in an excess metal cross-section in the overlap zones of said infrastructure and wherein said strips provide an additional metal cross-section equal to said excess metal cross-section and are mutually spaced by whole number fractions of the total distance between the median lines of successive overlap zones.

3. A reinforcing mat structure as claimed in claim 1, wherein the longitudinal bars of said unit mats have a cross-section within their marginal overlapping zones equal to one-half the cross-section of the longitudinal barsyin the intermediate zones of the mats, to result in a substantially uniform metal cross-section distribution across the width of said infrastructure, and wherein said strips provide a metal cross-section equal to that of the overlap zones and are spaced respectively from each other by predetermined equal distances and from the median lines of the adjacent overlap zones by distances equal to one-half of said predetermined distances.

4. A reinforcing mat structure as claimed in claim 1, wherein intersecting sets of said narrow mat strips are provided in the construction unit to be reinforced.

5. A reinforcing mat structure as claimed in claim 1, wherein the ends of said strips are bent towards the upper face of the construction unit to be reinforced.

Claims (5)

1. A composite reinforcing steel mat structure for use in planar concrete construction units comprising a plurality of unit mats each composed of a pair of intersecting sets of equi-spaced longitudinal and transverse bars connected at their intersection points, said mats arranged in juxtaposed relation with adjoining marginal longitudinal zones thereof overlapping each other over a distance of at least one mesh of the mats, to provide a reinforcing infrastructure of desired dimension and predetermined metal cross-section per unit width distribution across the width thereof, in combination with a multiplicty of relatively narrow reinforcing mat strips of approximately the width of the overlap in the infrastructure each composed of at least two longitudinal bars intersected by transverse bars connected thereto and overlying said infrastructure, said mat strips being spaced from each other and the median lines of the overlap zone of said infrastructure, to cause the resultant metal cross-section accumulations by said strips in conjunction with the metal crosssection distribution of said infrastructure to produce a composite reinforcing structure with a predetermined total and substantially uniformly distributed metal reinforcement throughout the width of the composite mat structure.

2. A reinforcing mat structure as claimed in claim 1, wherein the longitudinal bars of said unit mats are of equal diameter throughout, whereby to result in an excess metal cross-section in the overlap zones of said infrastructure and wherein said strips provide an additional metal cross-section equal to said excess metal cross-section and are mutually spaced by whole number fractions of the total distance between the median lines of successive overlap zones.

3. A reinforcing mat structure as claimed in claim 1, wherein the longitudinal bars of said unit mats have a cross-section within their marginal overlapping zones equal to one-half the cross-section of the longitudinal bars in the intermediate zones of the mats, to result in a substantially uniform metal cross-section distribution across the width of said infrastructure, and wherein said strips provide a metal cross-section equal to that of the overlap zones and are spaced respectively from each other by predetermined equal distances and from the median lines of the adjacent overlap zones by distances equal to one-half of said predetermined distances.

4. A reinforcing mat structure as claimed in claim 1, wherein intersecting sets of said narrow mat strips are provided in the construction unit to be reinforced.

5. A reinforcing mat structure as claimed in claim 1, wherein the ends of said strips are bent towards the upper face of the construction unit to be reinforced.

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