US3367084A

US3367084A - Load bearing reinforced concrete structure

Info

Publication number: US3367084A
Application number: US463764A
Authority: US
Inventors: Frank D Reiland
Original assignee: Gateway Erectors Inc
Current assignee: Gateway Erectors Inc; Gateway Construction Co Inc
Priority date: 1965-06-14
Filing date: 1965-06-14
Publication date: 1968-02-06
Anticipated expiration: 1985-02-06

Description

Feb. 6, 1968 F. 0. REILAND 3,367,084

LOAD BEARING REINFORCED CONCRETE STRUCTURE Filed June 14, 1965 4 Sheets-Sheet '1 INVENTOR. FHA/VA D. RE/LA/VD Feb. 6, 1968 F. D. REILAND 3,367,084

LOAD BEARING REINFORCED CONCRETE STRUCTURE Filedflune 14, 1965 4 Sheets-Sheet 3 INVENTOR. FRANK 0. RE/LA/VD F. D. REILAND 3,367,084

LOAD BEARING REINFORCED CONCRETE STRUCTURE Feb. 6, 1968 4 Sheets-Sheet 4 Filed June 14, 1965 m/vmro/a FRANK D. RE/LA/VD United States Patent 3,367,084 LOAD BEARING REINFORCED CONCRETE STRUCTURE Frank I). Reiland, Chicago, Ill., assignor to Gateway Erectors, Inc., Chicago, Ill., a corporation of Delaware Filed June 14, 1965, Ser. No. 463,764 4 Claims. (Cl. 52733) ABSTRACT OF THE DISCLOSURE A load-bearing steel-reinforced concrete column, beam, or like structure including a multiplicity of individual stress equalizers for interlocking the mass of concrete with one or more longitudinal steel reinforcing bars. The steel reinforcing bars are of conventional construction having a multiplicity of circumferentially extending ridges. Each of the stress equalizers is formed from strip spring steel and includes a C-shaped mounting portion having an internal diameter approximately equal to the diameter of the steel reinforcing bar upon which the stress equalizer is mounted. Each stress equalizer further includes at least one cantilever extension, also formed of strip spring steel, that projects radially outwardly of the open part of the C-shaped mounting portion, terminating in anchor flanges for interlocking the cantilever extension with the mass of concrete. In the preferred construction, two cantilever extensions are provided and each has a number of apertures for additional interlocking with the concrete mass. The stress equalizer is located on the reinforcing bar and is wedged into a firm encompassing grip on the bar by locking means at the junction of the mounting portion of the cantilever extensions. In the preferred construction, the entire stress equalizer is shaped from a single continuous strip of spring steel and the locking means includes four locking fingers that project inwardly at acute angles from the cantilever extensions into end-abutting engagement with the reinforcing bar to maintain the stress equalizer in fixed angular and longitudinal position on the reinforcing bar.

Background 0] the invention This invention relates to anew and improved loadbearing reinforced concrete structure. The invention is particularly advantageous as applied to vertical columns but is also of substantial value in connection with reinforced concrete walls and beams, as appears more fully hereinafter.

In a conventional reinforced concrete column, a plurality of steel reinforcing bars are first mounted in position. The initial positioning of the bars may be effected by means of a template located at the base of the column to establish predetermined spacing between the bars. A series of stirrups or ties are then secured to the vertically extending reinforcing bars, at spaced points, to maintain substantial consistency in the spacing and alignment of the bars. These ties, usually formed from small diameter reinforcing bar stock, are wrapped around the assembly of vertical reinforcing bars on the job. A form is then erected in encompassing relation to the reinforcing bar assembly, the concrete is poured into the form and permitted to set, and the form is then removed, the column structure being complete.

In a concentrically loaded column, the principal stress applied to the column is a vertical compressive stress. This stress is carried conjointly by the steel and by the concrete, the relative strengths of these materials in compression being quite well known. Concentric loading, however, is the exception rather than the rule; most structures entail at least some eccentric loading of the "ice columns. The current trend in architectural design is toward generally open structures with light curtain walls, frequently formed primarily of glass. In these structures, the columns are subject to bending from substantial wind loadings. Moreover, the outer columns in a structure of this kind are loaded by floor loads from one side only. In many such modern structures, relatively large bending forces are encountered with respect to the columns; these bending forces frequently cause compressive stresses in the reinforcing bars that add to, and are of greater magnitude than, the original compressive forces resulting from gravity loads.

In eccentrically loaded columns there is substantial tendency toward failure due to bending of the column. The continued existence of the column as an integrated and effective load-bearing structure is dependent upon maintenance of a good bond between the steel reinforcing bars and the concrete, each of which carries a major portion of the load. Because concrete has little capacity to deform elastically, loads which tend to bend or buckle the bars may crack the comparatively brittle exterior shell of the concrete, which is usually only a couple of inches in depth around the outside of the reinforcing bars, causing the column to fail by splitting out of the encompassing concrete shell. Failure is seldom if ever initiated in the massive central concrete core of the column.

The external stirrups or ties incorporated in the reinforcing structure of the column serve to hold the reinforcement, and hence the column, together. The ties are never fully effective. Even at corners, the two portions of a tie develop forces at approximately 45 from the desired direction toward the center of the column. Tie hooks, or points of overlap, are points of definite weakness. And bars located intermediate the corners of a tie receive little support from the tie. Moreover, considerable labor time and expense is entailed in individually wrapping the stirrups or ties around the reinforcing concrete bars, to the extent that the work entailed in mounting the ties on the main reinforcing bars constitutes a substantial portion of the cost of erection of the column.

A similar situation is presented with respect to vertical load bearing walls that are subject to substantial Wind forces or other forms of eccentric loading. In such wall structures, as in columns, failure is likely to occur from buckling of bars under excessive compression. The problem of bending failures is more pronounced in connection with narrow stems of beams, when the compressive strength of the reinforcing steel becomes a principal loadbearing component of the structure.

Summary of the invention It is a principal object of the invention, therefore, to provide substantially improved integration between the compressive reinforcing bars and the concrete mass in a load-bearing reinforced concrete structure and particu larly in a reinforced concrete column.

Another object of the invention is to reduce the number of ties or stirrups required in the erection of a load-bearing reinforced concrete structure, such as a load-bearing column, and at the same time to improve the overall strength of the column, particularly with respect to eccentric loading.

A specific object of the invention is to provide a multiplicity of improved stress equalizer members, in a reinforced concrete structure, that may be conveniently located at any desired points within the structure and that may be applied to advantage in column, wall, and beam structures. It is another object of the invention to afford a simple, inexpensive snap-on form of stress equalizer that elfectively anchors a reinforcing bar to a large mass of concrete, in a reinforced concrete structure, and not mere- 1y to the outside cage of the reinforcing bar assembly and the surface shell of the concrete.

Accordingly, the invention relates to a load-bearing reinforced concrete structure comprising at least one elongated load-bearing steelreinforcing bar that extends longitudinally of that structure. Usually, several reinforcing bars are present. A multiplicity of individual spring steel stress equalizer members are mounted on each reinforcing bar at spaced points along its length. Each of these stressequalizer members are mounted on each reinforcing bar at spaced points along its length. Each of these stress equalizer members includes a mounting portion that is wedged into a firm encompassing grip on the bar and at least one cantilever extension projecting radially from the mounting'portion on the bar. In one form of the invention, the cantilever extensions are provided with anchor flanges projecting laterally therefrom at a substantial distance from the bar; in another form, preferably combined with the flanged form, a multiplicity of anchor apertures are formed in the extension portions of the stress equalizer members. The reinforced concrete structure further includes a load bearing concrete mass enveloping and bonded to the bar and all of the stress equalizer members. The stress equalizer members interlock longitudinally spaced portions of the bar with substantial portions of the concrete mass to inhibit bending and buckling distortion of the bar under heavy compressive loads. In most instances, the concrete structure includes a plurality of reinforcing bars located around the periphery of the structure and each carrying a multiplicity of the stress equalizer members, which project into the interior of the concrete mass and anchor the bar to the complete concrete mass.

Other and further objects of the present invention will be apparent from the following description and claims and are illustrated in the accompanying drawings which, by way of illustration, show preferred embodiments of the present invention and the principles thereof and what is now considered to be the best mode contemplated for applying these principles. Other embodiments of the invention embodying the same or equivalent principles may be made as desired by those skilled in the art without departing from the present invention.

Brief description of the drawings FIG. 1 is a perspective view of a disassembled stress equalizer member utilized in one embodiment of the present invention;

FIG. 2 is a front perspective view of the stress equalizer member of FIG. 1 mounted upon a reinforcing bar;

FIG. 3 is a rear perspective view of the same stress equalizer. member mounted upon a reinforcing bar;

FIG. 4 is a perspective view of a load-bearing reinforced concrete column constructed in accordance with one embodiment of the present invention, utilizing the stress equalizer members of FIGS. 1-3, with a portion of the concrete broken away to illustrate the steel reinforcing structure in the interior of the column;

FIG. 5 is a sectional view taken approximately along line 5-5 in FIG. 4;

FIG. 6 is a plan view of a spring steel stress equalizer member utilized in another embodiment of the present invention;

FIG. 7 is a side elevation viewof the stress equalizer member of FIG. 6;

FIG. 8 is an end elevation view of the stress equalizer member of FIGS. 6 and 7;

FIG. 9 is an enlarged perspective view of the stress equalizer member of FIGS. 6-8 in mounted position on a reinforcing bar;

FIGS. 10 and 11 are perspective views illustrating the sequence of steps followed in installing the stress equalizer member of FIGS. 6-9 on a reinforcing bar;

FIG. 12 is a perspective view of a load bearing reinforced concrete column constructed in accordance with one embodiment of the invention and utilizing the stress equalizer members of FIGS. 6-11;

FIG. 13 is a sectional view of the column structure of FIG. 12 taken approximately along line 1313 therein;

FIG. 14 is a perspective view of a reinforced concrete structure constructed with the stress equalizer members of FIGS. 6-11 but employ-ing only one reinforcing bar;

FIG. 15 is an elevation view illustrating the steel reinforcing structure utilized in a reinforced concrete wall constructed in accordance with the present invention, the concrete portion of the wall being illustrated only in phantom outline;

FIG. 16 is a sectional view of the wall of FIG. 15 taken approximately as indicated by line 16-I6 in FIG. 15

FIG. 17 illustrates a reinforced concrete column and beam structure constituting a modification of the present invention;

FIG. 18 is a section view of the beam taken approximately along line 1818 in FIG. 17; and

FIG. 19 is a section view of one column taken approximately along line 1919 in FIG. 17.

Description of the preferred embodiments FIGS. 1 through 5 illustrate a first embodiment of the present invention comprising a load bearing reinforced concrete column 20 illustrated in FIGS. 4 and 5. The load bearing column 20 includes a plurality of vertically extending elongated load-bearing

steel reinforcing bars

21, 22, 23 and 24. Reinforcing bars 21-24 are of conventional construction and are each provided with a multiplicity of projecting ridges or like deformations 25 to bind the reinforcing bars into an encompassing concrete mass 26. In this respect, the construction of column 20 is substantially conventional.

Load bearing column 20 further comprises a multiplicity of individual spring steel stress equalizer members 30 mounted upon each of the steel reinforcing bars 21-24 at spaced points along the lengths of the bars. For an eight foot column, for example, there may be as many as fifteen or more stress equalizers along the length of each reinforcing bar. The construction and mounting of one of the stress equalizer members 30, mounted upon reinforcing bar 21, is shown in detail in FIGS. 1-3.

As illustrated in FIGS. 1-3, stress equalizer 30 comprises a spring steel clip 31 of C-shaped configuration. Clip 31 is provided with a pair of

flanges

32 and 33 extending along the edges thereof; the flanges are not parallel to each other but diverge slightly from top to bottom. The C-shaped clip 31 is the mounting portion of stress equalizer 30 as described more fully hereinafter.

Stress equalizer 30 further includes a cantilever extension 34. Cantilever extension 34 is formed from two strips of spring steel that are welded or otherwise suitably secured to each other throughout a major portion of their lengths. At one end, the left'hand end as seen in FIG. 1, the two spring steel strips forming the cantilever extension 34 diverge to form two

clip elements

36 and 37 that terminate in

individual flanges

38 and 39 respectively. At the opposite end of the cantilever extension 34, the two spring steel strips again are formed to project laterally with respect to each other, affording a pair of

anchor flanges

40 and 41. These flanges afford a means for anchoring the stress equalizer 30 in the concrete mass of the column.

The mounting of stress equalizer 30 on reinforcing bar 21 is illustrated in FIGS. 2 and 3. At the outset, the cantilever extension 34, which has an internal diameter across

clip elements

36 and 37 approximately the same as the overall external diameter of reinforcing rod 21, is pressed onto bar 21 so that the

clip elements

36 and 37 are disposed in partially encompassing relation to the reinforcing bar as shown in FIGS. 2 and 3. The C-shaped clip 31 of the stress equalizer is then engaged with the cantilever extension 34, the

flanges

38 and 39 of the cantilever extension being hooked into the

flanges

32 and 33 on the mounting clip. The C-shaped clip 31 is then driven downwardly to wedge the clip and the extension portion 34 into a firm encompassing grip on reinforcing bar 21 as illustrated in FIG. 2. The entire mounting operation can be accomplished by an unskilled workman in a short time, usually less than one minute.

In the load-bearing column 20, the individual stress equalizers 30 are all mounted on the reinforcing bars 21-24 with their extension portions 34 projecting in toward the center of the column structure, as shown in FIGS. 4 and 5. In the illustrated structure, as shown in stress equalizers is at approximately the same vertical position as corresponding stress equalizers on the other reinforcing bars. Each of the mounting clips on the stress equalizers is provided with a small bracket member 43. Thus, a conventional tie rod 44 can be quickly and conveniently mounted upon the reinforcing bar assembly at each level of the stress equalizers, as best shown in FIGS. 4 and 5. However, it is not essential that a tie be used for each group of stress equalizers. Instead, only enough 'es to hold the reinforcing bars in position for the pouring of concrete may be employed.

When all of the steel work has been completed as de scribed above, an appropriate form is erected in encompassing relation thereto. Since the form is of quite conventional construction, it has not been illustrated in the drawing. The form is filled with concrete, which is permitted to set, following which the form is removed and the load-bearing column structure is complete. The loadbearing concrete mass 26 thus formed as a part of column envelopes and is bonded to all of the reinforcing bars 21-24, all of the tie rods 44, and all of the stress equalizer members 30. It is important to note that the extension portion 34 of each of the stress equalizers projects well into the central or core portion 27 of the concrete mass 26.

In most structures the greatest tendency toward failure of a load bearing column such as column 20 is toward failure as a result of excessive compressive loading forces, concentric or eccentric, applied to the column. Thus, as column 20 is increasingly loaded, there is a substantial tendency for reinforcing bar 24 to bend or buckle outwardly as indicated by the phantom outline 24A. The other reinforcing bars would also tend to buckle or bend outwardly to a greater or lesser extent, depending in part upon the concentricity of the increasing load. In a conventional column, the principal structural elements resisting this buckling action are tie rods like the ties 44, all located in the peripheral portion of the column. Under excessive loads, the ties may not be able to prevent buckling of the column reinforcement, with accompanying cracking and peeling of the external portion of concrete mass 26. and ultimate failure of the column.

This tendency toward failure as a result of excessive loading is resisted by the stress equalizer members in column 26. Each of the stress equalizer members interlocks a portion of the reinforcing bar 21-24 on which it is mounted with the central core 27 of concrete mass 26. As reinforcing bar 24 tends to bend. or buckle outwardly toward position 24A, the stress equalizer 30 mounted upon bar 24 resist this movement, due to the anchoring of their extension portions 34 within the interior mass of the concrete. This interlocking action is materially assisted by the anchor flanges 4t] and 41 on each of the stress equalizers. Thus, the stress equalizers inhibit bending of the reinforcing bars under heavy loads and enable column 20 to withstand greater loads than would otherwise be possible. Stated differently, for a column 20 of given load-bearing capacity, the total number of tie rods 44 may be reduced without weakening the column because of the action of the stress equalizers tending to hold the column together against the bending and buckling forces presented by both concentric and eccentric loading.

FIGS. 6-11 illustrate a modified form of stress equalizer construction that may be utilized in another embodiment of the present invention. The stress equalizer 130 illustrated in detail in FIGS. 6-9 is a continuous C- shaped spring steel clip having a mounting portion 131 constituting the curved portion of the C-shaped structure. Two separate

cantilever extension portions

132 and 133 project from the mounting portion of the stress equalizer clip. The free end of the first cantilever extension portion 132 terminates in an anchor flange 134 that projects laterally from the cantilever extension. Similarly, an anchor flange 135 is formed at the free end of extension 133. Preferably, a plurality of anchor apertures 136 are formed in the stress equalizer 130 at spaced points along both of the

cantilever extensions

132, 133 and in the anchor flanges and mounting portion of the stress equalizer. In this embodiment,

flanges

134 and 135 and openings 136 conjointly constitute anchoring means for interlocking the stress equalizer in aconcrete mass.

Near the mounting portion 131 of stress equalizer clip 130, a pair of locking fingers 138, formed as an integral part of cantilever extension 132, project inwardly from the cantilever extension at an acute angle. Similarly, a

pair of locking fingers 139 are struck from and project inwardly at an acute angle from cantilever extension 133.

The simple and virtually instantaneous mounting technique for stress equalizer clip 130 is illustrated in FIGS. 10 and 11. To mount the stress equalizer on a conventional reinforcing bar 121, the ironworker simply grasps the base or mounting portion of the stress equalizer and aligns the clip with the bar as shown in FIG. 10. The stress equalizer clip is then forced over the periphery of the reinforcing bar to the position shown in FIG. 11. The locking

fingers

138 and 139, which bend outwardly as the clip is forced over the bar, spring back into their original positions and engage the bar as most clearly shown in FIG. 9. With the locking fingers thus engaging the bar, the stress equalizer is firmly mounted on the bar with the mounting portion 131 wedged into engagement with the bar, encompassing and firmly gripping the bar.

FIGS. 12 and 13 illustrate the stress equalizer 130 of FIGS. 69 incorporated in a load-bearing reinforced concrete column constructed in accordance with a preferred embodiment of the present invention. In constructing the column 120, a plurality'of elongated steel reinforcing bars such as the bars 121-124 are first mounted in spaced relation to each other in the positions they are intended to occupy within the column. Usually, a template is employed at the base of the column to obtain the desired accurate spacing for the reinforcing bars. With the reinforcing bars in vertically aligned position, a small number of conventional stirrups or ties 144 are secured to the reinforcing bars to hold the bars in aligned position until after pouring of the concrete. In a given installation, it may be possible to proceed on the basis of two ties, one located near the base of the column and one near the top. One or two additional centrally located ties may be required, particularly in a relatively tall column.

With the steel reinforcing bars 121-124, which are conventional round bars having the usual ridges or like deformations in the surfaces thereof, in position, the ironworkers proceed to mount the stress equalizers on the bars. A multiplicity of individual stress equalizers are mounted on each of the reinforcing bars at spaced points along the length of the bar. Again, in a typical eight foot column it may be desirable to mount as many as fifteen or more stress equalizers on each of the bars.

The cantilever portions of each stress equalizer project inwardly from the reinforcing bar on which the stress equalizer is mounted, toward the center of the column structure. However, it is not necessary to get precise alignment of the stress equalizers so that they all point directly toward the exact center of the column. Approximate alignment is quite satisfactory. Moreover, in this embodiment there is no necessity for having the stress equalizers arranged in vertically aligned groups as shown in FIG. 12. Instead, the stress equalizers on the individual bars may be vertically displaced from each other to some extent. The mounting of the stress equalizers on the reinforcing bars requires only a minimum time, since each stress equalizer can be installed in a matter of seconds.

With the stress equalizers in position, an appropriate form is erected and the concrete mass 126 for the column is poured. In the center or core portion 127 of the column, the concrete flows into each of the anchor apertures 136 in each of the stress equalizers and around the

anchor flanges

134, 135. This aifords a strong bond between the central core of the column and each of the stress equalizers and assures an effective interlock between the reinforcing bars and the central portion of the concrete mass throughout the lengths of the bars.

In the construction of a column such as column 120 of FIGS. 12 and 13, the maximum benefit from the stress equalizers is realized if the cantilever extension portions of each of the stress equalizers projects well into the center of the concrete in the column. If the stress equalizers are to be mounted upon corresponding levels on each bar, they may be selected with a length just short of interference with each other as illustrated in FIG. 13. On the other hand, if the stress equalizers are displaced slightly from each other in a vertical direction, on adjacent bars, then longer stress equalizers may be employed, projecting across the central core of the column. Satisfactory results are not-obtained, however, with short stubby stress equalizers that terminate in the peripheral portion of the column.

The interlocking action of the stress equalizers, joining each of the reinforcing bars to the central concrete mass of the column, effectively inhibits bending or buckling of the reinforcing bars due to loading of the columns. Thus, the overall strength of the column, with respect to both concentric and eccentric loading, may be materially improved even though the number of ties or stirrups 144 is reduced as compared with conventional construction. Be cause the stress equalizers are simple and inexpensive spring steel devices, and because they can be installed in seconds simply for forcing them over the reinforcing bars, the total cost of the steel erection is substantially reduced. The completed reinforced column 120 is an effectively integrated structure affording superior strength characteristics in comparison with conventional structures of comparable cost.

FIG. 14 illustrates another modification of the present invention in which a single reinforcing rod 151 is utilized in a short segment of a wall or like structure. In this instance, a multiplicity of individual stress equalizers 130 are mounted upon the conventional steel reinforcing rod 151 as described above in connection with FIGS. and 11. The stress equalizers 130 project outwardly from the reinforcing bar at varying angles to interlock the reinforcing bar with a concrete mass 152, the reinforcing bar being located approximately in the center of the concrete mass. This construction may be utilized in reinforced walls or in like structures in which one or more reinforcing bars 151 are distributed along the wall.

FIGS. 15 and 16 illustrate another form of reinforced wall construction in which stress equalizers 130 are employed. As shown therein, the load bearing wall structure 160, along its back run 161, comprises a plurality of vertically extending

steel reinforcing bars

162, 163 and 164. This portion of the wall terminates at a corner, two additional steel reinforcing bars 165 and 166 being located at the wall corner. From the corner, an additional portion of the wall 167 extends in a direction normal to portion 161 and this part of the wall is also provided with a series of vertical load-bearing steel reinforcing bars as exemplified by the bars 168 and 169. In each section of the Wall, the reinforcing bars are located alternately near the front and rear faces of the wall. A series of horizontal ties or stirrups 171 are incorporated in the wall section 161 and are appropriately secured to the vertically extending steel reinforcing bars in that section of the wall. Similarly, a plurality of horizontal ties 172 may be employed in the other section 167 of the wall.

In wall section 161, a multiplicity of individual spring steel stress equalizer members are mounted upon each of the vertically extending

steel reinforcing bars

162, 163 and 164. The stress equalizers mounted upon bar 162 extend from the back of the wall forwardly into the central portion of the wall. The same arrangement is used with respect to the stress equalizers mounted upon the bar164. The stress equalizers on bar 163, which is located near the front face of the wall, extend backwardly from the reinforcing bar and again project across the interior portion of the wall. At the corner of wall 160, the stress equalizers mounted upon reinforcing bars 165 and 166 project toward each other and into the inner part of the wall corner as best shown in FIG. 16. The alternating arrangement of the reinforcing bars and the stress equalizers described above in connection with wall section 161 is also em ployed in the other Wall section 167.

As in the column constructions described above, the

vertical reinforcing bars are first erected and are then tied together by the stirrups or

ties

171 and 172 to maintain the bars in aligned position during pouring of the concrete. With the steel reinforcing bars thus located, the stress equalizers 130 are mounted upon the reinforcing bars. This operation takes only a very short time because of the simple and rapid mounting procedure as described above in connection with FIGS. 10 and 11. As before, it is not essential that the stress equalizers be aligned precisely at right angles to the wall surfaces, as illustrated in the drawings; approximate alignment is quite adequate. It is essential that the stress equalizers be long enough to project into and preferably across the central portion of the wall structure to afford adequate anchorage and to interlock the reinforcing bars with as much of the concrete mass as possible.

Once the steel work is completed, appropriate forms are erected and the concrete mass 175 is poured and allowed to set. Thereafter, the forms are removed and the wall structure is complete. When subjected to relatively heavy loads, the reinforcing bars of wall 160 tend to bend or buckle in the same manner as described above in connection with the column structures. This tendency is effectively inhibited by the interlocking of the individual reinforcing bars with substantial portions of the concrete mass. As a consequence, a strong wall capable of withstanding relatively heavy loads is afforded, even though a substantially fewer number of ties may be employed than in conventional practice.

FIGS. 17, 18 and 19 illustrate a combined column and beam structure constructed with the preferred form of stress equalizer 130. As shown in FIG. 17, this structure includes a first column 201 and a second column 202, the two columns being bridged by a beam 203.

Columns

201 and 202 are quite similar in construction to column 120, FIGS. 12 and 13, except that the stress equalizers 130 are staggered on the vertical reinforcing bars. This vertical staggered relationship is illustrated in FIG. 17 and makes it possible for the stress equalizers to extend acrossthe central portion of the core as shown in the cross-sectional view of column 201, FIG. 18. A corresponding construction is used in column 202.

Beam 203 is essentially similar in construction to

columns

201 and 202. The similarity is apparent from the cross-sectional view of the beam, FIG. 19. Again, the stress equalizers 130 are staggered so that they project across the central portion of the concrete mass of the beam. It is usually not necessary to employ conventional stirrups or ties in the central portion of the beam. The operational advantages and features of the beam and column structure illustrated in FIGS. 17 to 19 are essen' tially as described above in connection with the reinforced columns of the invention, even though the forces on these structures are dilferent as to location of force and steel placement in the structures. In a beam, in particular, the stress equalizers help prevent the top reinforcing bars from bending or buckling under compression, and help the bottom bars to transfer part of their tension loads to other parts of the beam.

To accommodate column, beam, and wall structures of materially different dimensions, stress equalizers of difierent lengths may be necessary. Moreover, it is necessary that the stress equalizers fit the reinforcing bars with which they are used. However, there is no requirement that the cantilever stress equalizer members be of an exact dimension to fit a specific column so long as they have suflicient length to extend well into the core of the column. The same considerations apply with respect to wall and beam structures. Thus, the invention can be put into practice for virtually any variations in structure with only a rather limited number of different sizes of stress equalizer,

Hence, while preferred embodiments of the invention have been described and illustrated, it is to be understood that they are capable of variation and modification.

I claim:

1. A stress equalizer for a load-bearing concrete column or like structure comprising a plurality of loadbearing steel reinforcing bars of given diameter and a load-bearing concrete mass enveloping and bonded to all of said bars, in which said bars and said concrete mass are interlocked by means of a multiplicity of individual stress equalizers mounted on each bar and extending into said concrete mass, said stress equalizer comprising:

a C-shaped mounting portion formed from a strip of spring steel and having an internal diameter approximately equal to the diameter of said steel reinforcing bars;

at least one elongated cantilever extension, formed from said strip of spring steel, projecting radially outwardly of the open part of said C-shaped mounting portion and having anchor means for firmly interlocking said cantilever extension with said concrete mass;

and locking means formed integrally With said strip of spring steel and including two pair of locking fingers projecting rearwardly and inwardly at an acute angle from the opposite edges of the open ends of said C-shaped mounting portion with the inner end of each locking finger formed at an angle to afford a relatively sharp point in end-abutting engagement with the reinforcing bar for wedging said mounting portion into a firm encompassing grip on the reinforcing bar and maintaining said stress equalizer in fixed angular and longitudinal position on the bar.

2. A load-bearing reinforced concrete structure comprising:

at least one elongated load-bearing steel reinforcing bar having circumferentially extending ridges thereon, extending longitudinally of the load-bearing structure;

a multiplicity of individual one-piece stress equalizer members, each formed from a single continuous strip of spring steel, mounted on said reinforcing bar at spaced points along the length of the bar, each of said stress equalizer members including a C- shaped mounting portion and a pair of cantilever extensions projecting radially outwardly of the bar from said mounting portion, each of said cantilever extensions terminating at its free end in an anchor flange projecting laterally therefrom at a substantial distance from the bar;

each of said cantilever extensions further having a pair of integral spring steel locking fingers; pro- Mi jecting inwardly from the opposite edges of the extension; at an acute angle thereto into end-abutting engagement with said reinforcing bar to wedge said stress equalizer into a firm encompassing grip on the bar and maintain said stress equalizer in fixed angular and longitudinal position on the bar;

and a load-bearing concrete mass enveloping and bonded to said bar and all of said stress equalizer members, said stress equalizer members interlocking longitudinally spaced portions of said bar with substantial portions of said concrete mass to inhibit buckling and bending distortion of said bar under heavy loads.

3. A load-bearing reinforced concrete structure comprising:

at least one elongated load-bearing steel reinforcing bar having circumferentially extending ridges thereon extending longitudinally of the load-bearing structure;

a multiplicity of individual one-piece stress equalizer members, each formed from a single continuous strip of spring steel, mounted on said reinforcing bar at space points along the length of the bar, each of said stress equalizer members including a C- shaped mounting portion and a pair of cantilever extensions projecting radially outwardly of the bar from said mounting portion, each of said cantilever extensions having a plurality of anchor openings therein for anchoring said extension in a concrete mass;

each of said cantilever extensions further having a pair of integral spring steel locking fingers projecting inwardly at an acute angle thereto into endabutting engagement with said reinforcing bar to wedge said stress equalizer into a fir m encompassing grip on the bar and maintain said stress equalizer in fixed angular and longitudinal position on the bar;

4. A stress equalizer for a load-bearing concrete column or like structure comprising a plurality of loadbearing steel reinforcing bars of given diameter and loadbearing concrete mass enveloping and bonded to all of said bars, in which said bars and said concrete mass are interlocked by means of a multiplicity of individual stress equalizers mounted on each bar and extending into said concrete mass, said stress equalizer comprising:

a pair of cantilever extensions formed integrally with said mounting portion from said strip of spring steel and projecting radially outwardly of the open ends of said C-shaped mounting portion, said cantilever extensions each having anchor means, comprising a series of anchor apertures distributed along the length thereof and an anchor flange at the free end thereof, for firmly interlocking said cantilever extension with said concrete mass;

and a pair of individual spring steel locking fingers formed integrally with and projecting inwardly of each of said cantilever extensions at acute angles for engaging the reinforcing bar in end abutting relation, the ends of said locking fingers that engage the reinforcing bar being angled to afford relatively sharp points for wedging said mounting portion into a firm encompassing grip on the reinforcing bar and maintaining said stress equalizer in fixed angular and longitudinal position on the bar.

References Cited UNITED STATES PATENTS 12 Snowball 52-733 Collins 52-735 X Schirra 52-733 Crane 52-733 Schade 52-651 Connell 52-651 Pitt 52-733 Trumbull 248-316 X CASMIR A. NUNBERG, Primary Examiner.

A. M. CALVERT, Assistant Examiner.