US3862479A

US3862479A - Method for locating and supporting tendons in reinforced concrete structures

Info

Publication number: US3862479A
Application number: US352926A
Authority: US
Inventors: Maurice Laderoute
Original assignee: Individual
Current assignee: Individual
Priority date: 1972-10-06
Filing date: 1973-04-20
Publication date: 1975-01-28
Anticipated expiration: 1992-01-28

Abstract

A method is provided for locating and supporting tendon members in joist-forming channels of a concrete form. At spaced intervals tendon sections are received on suspension-type tendon supports. Means are provided for lifting the tendon sections into predetermined positions of vertical adjustment relative to the bottom of the joist sections. In this position, the lifted tendon sections are securely held against lateral displacement while concrete is being poured into the form. The suspension-type tendon support apparatus comprises upper rigid suspension bar elements transversely engageable across upper sides of the concrete form to bridge the joist-forming channels in the form, and provide a footing for workmen. The tendon supporting elements depending from the suspension bar elements may be drawn upwardly either by hand or by a power tool into any desired position of vertical adjustment to facilitate rapid and accurate positioning of tendon sections, and a workman''s labor is greatly simplified.

Description

United States Patent Laderoute METHOD FOR LOCATING AND SUPPORTING TENDONS lN REINFORCED CONCRETE STRUCTURES Maurice Laderoute, I I8 Samosct Ave., Hull, Mass. 02045 Filed: Apr. 20, 1973 Appl. No.: 352,926

Related U.S. Application Data Continuation-impart of Ser. No, 295,441, Oct. 6, 1972.

lnventor:

U.S. Cl. 29/155 R, 249/91 References Cited UNITED STATES PATENTS Primary Examiner-Thomas H. Eager Attorney, Agent, or Firm-Munroe H. Hamilton ABSTRACT A method is provided for locating and supporting tendon members in joist-forming channels of a concrete form. At spaced intervals tendon sections are received on suspension-type tendon supports. Means are provided for lifting the tendon sections into predetermined positions of vertical adjustment relative to the bottom of the joist sections. In this position, the lifted tendon sections are securely held against lateral displacement while concrete is being poured into the form. The suspension-type tendon support apparatus comprises upper rigid suspension bar elements transversely engageable across upper sides of the concrete form to bridge the joist-forming channels in the form, and provide a footing for workmen. The tendon supporting elements depending from the suspension bar elements may be drawn upwardly either by hand or by a power tool into any desired position of vertical adjustment to facilitate rapid and accurate positioning of tendon sections, and a workmans labor is greatly simplified.

5 Claims, 22 Drawing Figures PATENTED JANZ 8 I975 sum '3 or 5 I!!! Ill/fl METHOD FOR LOCATlNG AND SUPPORTING TENDONS IN REINFORCED CONCRETE STRUCTURES This invention is a continuation-in-part of my copending application Ser. No. 295,441 filed Oct. 6, 1972, entitled METHOD AND APPARATUS FOR SUPPORTING TENDONS IN REINFORCED CON- CRETE.

The instant invention relates to methods and apparatus for use in forming reinforced concrete structures. More particularly, the invention is concerned with methods and means for supporting and positioning reinforcing tendons and reinforcing rods of the class commonly employed in reinforcing concrete structures such as is exemplified by a joist and slab type of concrete construction.

As is well-known to those skilled in the art, it is customary to post-tension concrete masses which have been poured into a concrete form of some desired shape, and this is accomplished, in the joist and slab type of construction, for example, by locating steel tendon members in the joist forming portions of the form. Concrete is then poured and allowed to set until a suitable strength is realized. Thereafter, the tendon members are tensioned by hydraulic ram means or other suitable devices.

A highly important consideration in using a steel tendon is the matter of supporting the tendon in the joist forming section of the concrete form in a raised position relative to the bottom surface of the joist forming channel. This is customarily done by locating spaced apart sections of the tendons at varying positions of vertical adjustment in accordance with force stressing tables provided with engineering drawings of the structure being built.

Presently in use are tendon-supporting devices which are referred to in the trade as chairs and which are furnished in varying sizes. Each chair is made of wire-like sections formed into a U-shape and arranged at right angles to one another to provide four supporting legs whose length can be varied as desired to provide varying heights. At their point of crossing the wire sections are formed with a tenton-supporting cradle for receiving and supporting a section ofa tendon thereon.

Problems arise in connection with locating the chairs in the joist sections since the various stressing tables may include a wide range of vertical spacings, and therefore, the chairs have to be made available in all of these sizes. The operation of selecting chairs of correct size and locating these chairs of different heights in the bottom of the concrete form is time consuming and requires that the workman be on his knees under difficult working conditions. It is also necessary to secure each chair cradle to its supported tendon section by wire or other means, and since this may be necessary at spacing of every 6 feet, for example, a very considerable amount of time is used up in positioning tendons with the chair-support method. There is also the frequent occurrence of chairs being displaced or tipped over when concrete is poured, and this can lead to faulty post-tensioning and other problems.

It is a chief object of the invention to provide improved methods for supporting tendons in a concrete form in place of chairs commonly employed for this purpose.

LII

Another object of the invention is to devise a method of handling tendon-supporting structures which may be employed in a single size and which can be drawn into vertically adjusted positions to provide a wide range of supporting heights required for a post-tensioning operation.

Still another object is to provide a method which can be utilized by a workman from a point immediately above a concrete form with less labor and time being required to make necessary locations.

And still another object of the invention is to provide a method of handling a tendon-supporting apparatus having an adjustable tendon-lifting element which can be drawn upwardly by hand or mechanically raised to a desired point by a rotary driving force exerted through a power tool of conventional nature.

It is still another object of the invention to devise a method of handling a tendon-supporting and lifting apparatus which may also include means for retaining a plurality of tendons in side-by-side relationship and also for simultaneously receiving and retaining one or more retaining rods located at points below the tendon members.

With the foregoing objectives in mind, I have conceived of improved methods and means for supporting and locating tendon sections in a reinforced concrete structure such as, for example, a joist and slab type wherein a concrete form presenting joist-forming channels separated by flat bridging sections is secured to a horizontal shoring structure.

ln accordance with the invention, tendons are placed in the joist-forming channels in the usual manner. However, instead of positioning the conventional type chairs in the joist channel and lifting tendon sections up onto the chairs and thereafter tieing the tendons to respective chair cradles, the chairs are completely eliminated.

Tendon sections are engaged at their under sides by means of tendon holder elements. Each holder element and engaged tendon section is supported from a suspension bar opposite ends of which are solidly received on upper sides of adjacent bridgeing sections of the concrete form. With this arrangement of parts, a tendon section may be located in a desired position of vertical adjustment in several ways. ln some cases, the tendon holder may be secured to the suspension bar in fixed relationship.

The length of the tendon holder portion depending from the suspension bar thus determines the position of vertical adjustment of the tendon and the depending lengths may occur in a range of sizes. In other instances, a preferred procedure is to position a tendon section on the holder and then raise or lift both the holder and the supporting section up to a desired point or spacing from the bottom of the channel. This may be accomplished either manually or by exerting mechanical forces. When all of the sections of a tendon to be raised have been positioned by one of the other of these methods, it will be understood that concrete is poured covering the holders and suspension bars. After the concrete has set to a desired strength the tendons are post-tensioned in the customary manner.

As noted above, the invention includes means for adjusting tendonplacement both manually and by mechanical forces and in one desirable form of the invention, the use of mechanical forces is carried out.

An important feature of my improved method of positioning and supporting tendon sections at desired points is the use of a rotary driving force exerted from points above the concrete form to raise the holder elements and tendon sections as required in one simplified manual operation.

In this connection, I have devised a tool for engaging a tendon-supporting component and applying a rotary driving force by means of a power tool of well-known construction.

The nature of the invention and its other objects and novel features will be more fully understood and appreciated from the following description of a preferred embodiment of the invention selected for purposes of illustration and shown in the accompanying drawings, in which:

FIG. 1 is a fragmentary perspective view illustrating a first step in forming a reinforced concrete structure of the joist and slab type in which reinforcing rods and reinforcing tendons have been laid in channel portions of a concrete form indicated fragmentarily and being secured to shoring members;

FIG. 2 is a detail perspective view of tendonsupporting apparatus of the invention for use in the concrete form structure of FIG. 1;

FIG. 3 is a side elevational view of the concrete form and shoring indicated fragmentarily and illustrating the steps of locating the tendon-supporting apparatus of FIG. 2 in the concrete form in engagement with tendon members;

FIG. 4 is a detail cross section taken on the line 4-4 of FIG. 3;

FIG. 5 is a fragmentary plan view of one of the tendon-supporting units installed;

FIG. 6 is another elevational view of the concrete form and illustrating steps of lifting successive tendon sections into varying positions of vertical adjustment relative to the respective channel bottom of the form by means of a rotary driving force;

FIG. 7 illustrates the steps of pouring concrete while the tendons are held in positions in vertical adjustment;

FIGS. 8 and 9 are detail views of modification of tendon-supporting structures;

FIG. 10 is a cross section taken on the line 10-10 of FIG. 6;

FIGS. 11 14, inclusive, illustrate still another modification for use in supporting both reinforcing tendons and reinforcing rods;

FIGS. 15 is a detail view illustrating the tendon supporting apparatus of the invention utilized as a means for supporting additional cross-laid rod members at the upper side thereof;

FIG. 16 is a fragmentary detail view of a modified form of suspension bar means;

FIG. 17 is a perspective view of a modified means for supporting a tendon means;

FIG. 18 is a lifting frame for manually raising the supporting means of FIG. 17;

FIGS. 19 to 22 illustrate still other modified forms of the invention.

The combination of parts shown in FIGS. 1 to 16 constitute one desirable form of apparatus for carrying out the method of the invention, and FIGS. 17 to 22 illustrate other desirable forms of the invention. The principal parts of this embodiment of tendonsupporting apparatus shown in FIGS. 1 to 16 include suspension bar means for engagement at the upper side of a concrete form of the joist and slab type, and tendon holder means received in the suspension bar means in a depending position, and means for locating the tendon holder in a desired position of vertical adjustment relative to the suspension bar means.

Considering the structure of FIGS. 1 to 16 in more detail, reference character F generally indicates a concrete form of the joist and slab type supported on shoring means 2, as is most clearly shown in FIG. 1. As will be observed from an inspection of this FIGURE. the form F is made with joist-forming channel sections as 4, 6, 8, etc., and these channel sections are connected together by upper flat bridging sections as l0. l2 and 14. The channel sections are formed with retaining edges as l6, 18 (FIG. 10) anchored in shoring strips as 22, 24, transversely secured over the shoring timbers 2.

Numerals

30, 32 and 34 denote steel reinforcing rods of the type commonly employed in reinforced concrete construction to impart desirable tensile strength.

Numerals

36, 38 and 40 refer to steel tendons consisting of steel strands which are utilized for post-tensioning concrete in the joist-forming portions after the concrete has been poured and allowed to set to a predetermined strength.

In FIG. 2, I have shown one of the tendon-supporting units of the invention removed from a concrete form and FIGURES 3 to 7 show a number of tendon-holding units combined with the concrete form F in operative positions. As may be most clearly seen from an inspection of FIG. 2, there is provided a suspension bar member denoted by the numeral 42, and this bar is made of a size such that it may rest upon two adjacent bridging sections of the form in the manner indicated in FIG. 3.

The suspension bar member 42, in one preferred form, may be of a channelled cross section. as shown. and is designed to have sufficient strength to receive the weight of workmen without bending or breaking. It is intended that other cross-sectional shapes may also be used.

Loosely disposed in the suspension bar 42 is a tendon holder 44 formed with a hooked lower extremity 46 for underlying and supporting a section of a tendon member. It will be observed that the suspension bar 42 is formed with air-vent apertures as 42a and 42b and also with a centrally disposed opening through which an upper end of the tendon holder 44 is received and is free to move. The tendon holder, throughout a portion of its length, may be threaded, and threadably engaged about the projecting upper end 44a of the holder is a washer and nut assembly 48 which rests upon an upper side of the suspension member 42. Extending downwardly from the lower end of the suspension bar are channel engaging stops as 50 and 52. Also secured at the bottom of the hooked portion 44 is a transverse stop part 54 which is designed to fit into opposite sides of a channel bottom and secure the hooked end 46 in a centered position.

FIG. 3 illustrates the tendon support of FIG. 2 installed in channel portion 6 with the

stop elements

50 and 52 engaged against opposite inner sides of channel 6 and with the suspension bar 42 located across the bridging portions l0 and [2. Transverse stop 54 is also shown in engagement with the bottom of the channel. This Figure is also intended to illustrate the step of locating a section of tendon 38 on the hooked portion 46 of holder 44. A second unit having the same but primed numerals is shown at the right hand side of FIG. 3. In

FIG. 4 the raised section of holder 38 is shown in one position of predetermined vertical adjustment.

It will be understood that sections of the tendon 38 may be required to be vertically positioned at intervals of, of example, every 6 feet, and in each such case, a different height may be specified. There is thus created a need for using a plurality of tendon supports each of which has to be positioned at different vertical heights.

In FIG. 6, there is illustrated in more detail steps of positioning a series of tendon supports by the invention method. As noted therein, suspension bars 42, 42' and 42" are placed on bridging sections as 10, I2 and 14 and engaged with sections of

tendons

36, 38, 40, each of which is shown positioned at different levels.

In accordance with the invention, I provide for lifting the hooked holder portion by means of a rotary drive force exerted through a special driver frame which is designed to be powered by a drill or other rotary power tool. As shown in FIG. 6, the driver frame is denoted by numeral 70 and includes spaced vertical supporting legs having a nut engaging part for engaging over and gripping the nut 48". At its upper end, the frame 70 is provided with a stud portion 76 which is designed to be held in the chuck of a drill 78.

When the drill or other power tool is operated, it will be apparent that the frame turns about a vertical axis and threads the part and nut 48" around the correspondingly threaded portions of the holder 44", thus causing this member to be drawn upwardly through the suspension bar. The tendon section 36' is thereby lifted to some desired height.

As illustrated at the right hand side of FIG. 6, I may also provide in the frame 70 a scale of varying heights as suggested at 80, and slidably supported over this scale portion of the frame, I may further provide an indicator bar 82 which can be raised to a predetermined height and secured by a wing nut or other fastening 82a. By means of this arrangement, it will be apparent that a workman may very rapidly lift given tendon sections to predetermined heights by simply engaging the frame and rotating it with a power tool until the upper end of the holder 44" comes into contact with the member 82. It is pointed out that this whole operation, including the step of placing the suspension bar, engaging a tendon in the holder, and raising these two parts, is carried out in a comfortable and convenient working position for an operator, and this results in more rapid installation and substantial savings in labor costs.

After all of the tendons in a given construction area have been lifted into desired positions, the projecting upper ends of the holder elements may be bent over as suggested by the holder element 44 in FIG. 6 and concrete is then poured to completely cover the tendons and suspension bars and holders as suggested in FIG. 7. In this FIGURE, concrete joist portions are denoted by the numerals 3, 5, 7, and an overlying slab portion is denoted by the numeral 9.

It will be understood that concrete thus poured is allowed to set in the usual manner until is acquires a suitable tensile strength and then the tendons as 36, 38'and 40 are stressed by means of hydraulic ram means.

It is also intended that the invention structure may be modified in various ways. For example, I may provide a holder element 73 with a looped stop part 75, as illustrated in FIG. 8. The part 75 engages against opposite sides of a channel 75a in the manner earlier described with reference to the transverse stop 54.

l may also provide for lifting a tendon section as shown in FIG. 9 wherein a hooked portion 77 is secured to a threaded sleeve member 79 having a transverse stop part 770 Since the hooked portion 77. when supporting a tendon section 81, cannot turn until the threaded section of the holder 83 is rotated, sleeve portion 79 and tendon section 77 can be lifted into a desired position of vertical adjustment.

In FIG. 11, I have illustrated an arrangement including a holder element 85 and tendon 86. The threaded sleeve 87 suspended as earlier described from a suspension bar 89 provides for vertical adjustment. The sleeve 87 is also constructed with an aperture for loosely receiving and guiding a second holder element 91 which may also be used to engage and hold a bottom reinforcing rod as 93. Where is is desired to lift both a reinforcing rod and tendon, I may provide a holder 95, as shown in FIG. 12, with a hooked end 97 for supporting atendon 99, and secured to the member 95 by welding or other suitable means is a second hooked portion 101 for reinforcing rod- 103. Both the rod and the tendon may be raised simultaneously where this is desired.

InFlG. 13, there is illustrated a holder member 88 having a threaded sleeve as 90 and a suspension bar 97. A hooked portion 94 supports a tendon 96a. Also mounted loosely around the holder 88 at the lower end thereof is provided a sleeve having a hooked end 98 for supporting a reinforcing rod 102.

In FIG. 14, I have shown a suspension bar 105 in which is supported two

holder elements

107 and 109, bothv of which may be threaded and received through a sleeve 108. Both the

holders

107 and 109 are provided with threaded driver members 111 and 113, respectively, which rest upon the bar 105 as shown. With this arrangement, either one of the holder elements may be independently raised through the suspension bar and each of these members may be provided with tendon hooks as shown.

In FIG. 15, there is illustrated a type of reinforced concrete construction sometimes employed in buildings in which suspension bars as 115, I17 and 119 are mounted on a concrete form 120 and at their upper sides the suspension bars may receive cross-laid rods as 122, and over these rods another set of reinforcing rods as 124, 126, etc., may be installed.

In FIG. 16, I have shown a modified form of suspension bar which is provided with a stamped-out vertically depending stop portion 132 for engagement with a channelled section of a form.

As earlier suggested in the specification, it may be desired in some instances to raise or lift tendon sections by a manually exerted force rather than using power driven rotary forces as employed with the structures illustrated in FIGS. 1 to 16.

To provide for lifting a tendon section by hand, I have further devised a modified lift rod apparatus in the form illustrated in FIGS. 17 through 22. In general, this lift rod apparatus includes a channelled suspension bar of the type earlier described, tendon holder means received through the suspension bar, a lift rodand handle engageable with the holder means and a frame structure by means of which a tendon section may be lifted to a desired position of vertical adjustment.

Referring more in detail to FIGS. 17 and 18, numeral 11 denotes a suspension bar member which may be of channelled cross section similar to the suspension bar 42 in FIG. 2. At its upper side, there is formed an elongated slot 13 through which is loosely received a lift rod element 35 formed with a hooked upper end 17. Also provided are vent holes 110 and 11b. A split lock washer 19 is slidably engaged around the rod 35 in a position to allow the rod to be pulled upwardly and to prevent downward movement of the rod through the suspension bar.

At its lower end the lift rod element is formed with curved tendon-retaining

parts

21 and 23 which are arranged to define tendon-retaining

spaces

25 and 27 into which tendon sections may be located. The tendon-retaining sections have attached along bottom portions thereof a spreader member 29 which is of a size designed to engage between the sides of a channel in which the apparatus may be disposed. Also provided are two

U-shaped spreader elements

31 and 33 which are secured at the upper side of the suspension bar in a position to fit against opposite channel sides over which the suspension bar is placed. These

spreaders

31 and 33 are arranged to maintain the bar in a substantially right-angularly disposed position with respect to the channel.

In combination with the

tendon holder

15, 1 provide a lift rod 35 shown together with a channel member 11 in FIG. 18. The lift rod 35 is received through suspension bar 11 as shown and is formed at its lower end with a hooked part 37 for interlocking with the hooked end 17 ofthe tendon holder 15. At its upper end, the lift rod 35 is provided with a handle 39 by means of which the tendon holder 15 and the lift rod 35 may be pulled upwardly through a frame structure. The frame structure is formed with an annular head 41 in which the lift rod 35 is slidably guided. Extending downwardly from the head 41 are spaced apart sides 43 and 45 which terminate in supporting feet 49 and 51. The side 43 is provided with a scale and an adjustable stop 47. The stop 47 is movable along the frame into positions of register with the scale and can be secured by a thumb nut 47a. lt will be observed that the supporting feet 49 and 51 are designed to bear against the upper side of the channel suspension bar 11 when the lift rod is raised.

By means of this arrangement, the tendon support 15 when attached to the lift rod 35 can be raised into a desired position of vertical adjustment determined by the location of the adjustment stop 47 to thus position a tendon section in accordance with engineering specifications.

ln some instances, it may be desired to support tendons in side-by-side relationship and in FIG. 19 there is illustrated means for doing this. As shown in FIG. 19, a handle 39, lift rod 35 and suspension bar 11 are combined with a modified form of tendon holder 15a in which there is provided a triangularly-shaped holding part 53. The part 53 has a hooked end 55 which can be moved into and out of interlocking relationship, as suggested in dotted lines.

Supported in the base of part 53 are spaced apart tendon-retaining

clips

57, 59 and 61 in which a set of three tendons may be securely placed and held beside one another in aligned relationship. A spreader 63 is also provided with the part 53.

FIG. 20 illustrates another tendon holder 65 for holding tendons in side-by-side relationship and for rigidly bracing opposite ends of a horizontal retaining rod 67 on which tendon clips 69, 71 and 73 are supported. A vertical brace 75 is arranged, as shown, to provide rein forcement at the underside of rod 67.

In FIGS. 21 and 22, still another tendon supporting holder 79 for supporting a larger number of tendons in side-by-side relationship is illustrated. The holder 79 is received through a rigid bar element 81 on which are located tendon clips 83, 85, 87 and 89.

1 claim:

1. In a method of forming a reinforced concrete structure of the joist and slab type wherein a concrete form presenting joist forming channels separated by flat bridging sections is secured to a horizontal shoring structure and reinforcing tendons are placed in the joist forming channels and raised into predetermined positions of vertical adjustment, the steps which include locating a tendon member in a joist forming channel of a concrete form between two adjacent bridging sections of the concrete form and below upper surfaces of the adjacent bridging sections, engaging an underside of said tendon in the joist forming channel with a tendon holder member, suspending the tendon holder and engaged tendon section in suspension bar means supported at spaced apart points at upper sides of two adjacent flat bridging sections of the concrete form and then lifting the engaged tendon sections and tendon holder while suspended into a position of predetermined vertical spacing with respect to the bottom of the joist forming channel.

2. A method according to claim 1 in which the engaged tendon section and tendon holder are lifted by rotating an internally threaded element about a threaded section of the tendon holder.

3. A method according to claim 1 in which the engaged tendon section and tendon holder are suspended at spaced apart points from said suspension bar member and an internally threaded element mounted at the upper side of the suspension bar member. and said tendon holder and engaged tendon sections being lifted by rotating the internally threaded member about a threaded section of the tendon holder.

4. A method according to claim 3 in which the internally threaded element is rotated by engaging it in the bottom of a revolving frame and a rotary driving force is applied at the top of the frame to turn said frame about a vertical axis of rotation.

5. A method according to claim 2 in which the engaged tendon section and tendon holder are held in a fixed position between two adjacent channel sides.

Claims

3. A method according to claim 1 in which the engaged tendon section and tendon holder are suspended at spaced apart points from said suspension bar member and an internally threaded element mounted at the upper side of the suspension bar member, and said tendon holder and engaged tendon sections being lifted by rotating the internally threaded member about a threaded section of the tendon holder.