US3072994A - Apparatus for making post-stressed reinforced cement-concrete structures - Google Patents

Description

Jan. 15, 1963 A. E. BRICKMAN 3,072,994

APPARATUS FOR MAKING POST-STRESSED REINFORCED CEMENT-CONCRETE STRUCTURES Original Filed June 6, 1955 2 SheetsSheet 1 g] 1 Q INVENTQR. h ALAN E.BR|CKMAN Jan. 15, 1963 A. E. BRICKMAN 3,072,994

APPARATUS FOR MAKING POST-STRESSED REINFORCED CEMENT-CONCRETE STRUCTURES Ongmal Filed June 6, 1955 2 Sheets-Sheet 2 aim /IIII IIIIIIIIIIM l I 'I'I'IA INVENTOR. ALAN E. BRICKMAN United States Patent Office 3,072,994 Patented .i'an. 15, 1963 3,072,994 APPARATUS FOR MAKING POST-STRESSED REIN- FGRCED QEMENT-CONCRETE STRUCTURES Alan E. Brickman, 281 Dale Road, Wethersfield, Conn. Original application June 6, 1955, Ser. No. 513,314, now Patent No. 2,950,517, dated Aug. 30, 1960. Divided and this application Aug. 23, 1960, Ser. No. 51,372

7 Claims. (Cl. 25118) This invention is concerned with post-stressed reinforced cement-concrete structures of considerable length and considerable width such as, for example, concrete highways, airport runways, and the like, and directed in particular to the stressed metal reinforcement members embedded in such concrete structures. More especially, it has to do with the application of tension to the metal reinforcement members in such structures.

The present application is a division of my copending application, Serial No. 513,314, filed June 6, 1955, entitled Method of Making Post-Stressed Reinforced Cement-Concrete Structures, and now to be issued as Patent No. 2,950,517, dated August 30, 1960.

The application of prestressed concrete, in which pretensioned steel or other reinforcement members are incorporated in a concrete element or structure, has been quite commonly used heretofore in the construction of various types of concrete structures such as bridge girders, beams, floor slabs, etc. In making such concrete structures the steel reinforcing or tension members, such as stranded wire structures, are stressed to a predetermined tension within the form, after which concrete is poured into the form or before the poured concrete has started any appreciable set. After the concrete has set the form is removed and the bond of the concrete to the metal reinforcement members reacts on the concrete to place it under compression. The most common way of applying tension to the stranded wire structures is by means of a cone socket member secured to each end of the stranded wire structure by means of a wedge with the socket members having a threaded portion which can be drawn up in various ways to apply the tensile stress.

To obtain the necessary prestress in the concrete, the stranded reinforcement is stressed initially under a tension on the order of 60% on its elastic limit values and in this condition applies compression forces to the adjacent concrete in a manner that puts the entire concrete structure in compression. In this state, stresses due to temperature changes and thermo-contraction which normally would cause cracking of the concrete are counteracted by the initial tension forces released by said reinforcing members and transmitted to the concrete thereby setting up compression therein and preventing occurrence of cracking or warping thereof.

Prestressing, however, has not been used extensively in cement-concrete highway construction because of the absence of a satisfactory means for applying tension to the steel or other metal reinforcement rods or wires which usually run lengthwise in the longitudinal direction of the pavement and are necessarily of a fixed length so that the pavement design therefore is not continuous but formed in slab units of a prescribed length which is considerable and would be so great as not to provide any practicable method of accomplishing the bringing of the individual metal reinforcement rods or wires under a condition of tensile stress during the laying of the wet pavement.

In accordance with the present invention, I have provided a practical means of tensioning, herein termed as post-tensioning, whereby each reinforcing tension member of a system of metal reinforcement consisting of steel or other metal rods or wires of uniform cross-section is placed under tensile stress through an external pulling force applied to one end or to both ends of each rod or wire, the tensioning being carried out in conjunction with the laying of the wet pavement. The rods or wires in being placed under tension are secured to anchorage members temporarily afiixed on the road forms. Both the anchorage members and the reinforcing tensioning rods preferably are centered with respect to the thickness of the pavement or halfway of the height of the road forms.

In accordance With my post-tensioning, the ultimate tensile stress placed on the reinforcing members is not applied until after the concrete has been poured and some initial set of said concrete has taken place. In the practice of my invention, tension is applied to each of the individual metal reinforcement members in one or more stages to lengthen them to a predetermined extent and to place them under prescribed tensile stress. For example, in the first tensioning stage, a tensile force is applied to the metal reinforcement rods or wires to securely fasten their ends within the limits of their anchorage to the road forms. In the second tensioning stage, additional tension is applied to each metal rod or Wire after the concrete has been poured. Due to the combined weight of the wet concrete to that of the road forms it is possible to apply greater tension at this stage thereby bringing the reinforcing tension members into proper position in the center of the slab Where they properly belong. After the concrete has set for a short time, such as, for example, approximately 1 /2 hours, full tension then is applied to the reinforcing tension members and they are so secured and maintained for the life of the pavement.

Apparatus embodying the present invention includes anchorage members adapted to be temporarily supported by the road forms inside the area in which the wet pavement is to be poured, and such apparatus additionally includes a number of detachable tension-applying means externally operated outside of the form and connectable through the forms to end couplings provided with step portions for stretching the rods or Wires to a predetermined extent and placing them under a precalculated or known tensile stress.

Upon prestressment of the rods or Wires to the ultimate required tensile stress, the externally-operated tension-applying means are detached from the stepped couplings on one or both ends of the reinforcing rods or wires and the latter then remain so tensioned by being securely held by their anchorage members to the road forms. The anchorage members are initially attached to the inside face of the road forms and are demountable therefrom so that they stay permanently in the concrete after the road forms are stripped from the finished pavement.

It therefore is an object of my invention to provide apparatus whereby pretensioned reinforced concrete struc tures of considerable length and considerable width for use as pavements in concrete highways, airport runways, and the like, can be made, in which the individual metal reinforcement members are brought under a condition of predetermined tensile stress by tension applied in two or more stages.

Another object of the invention is to provide a practical apparatus whereby a prestressed reinforced concrete structure of considerable length and width can be made in which the pavement will be continuous in both longitudinal and transverse directions and devoid of longitudinal joints and the numerous transverse expansion joints that characterize such concrete structures made in accordance with the present practice.

A further object of the invention is to provide apparatus of this character which is efficient, comparatively simple and practical in its construction and operation.

These and other objects will be more apparant after referring to the following specification and accompanying drawings, in which:

FIG. 1 represents a top plan view of a length of concrete highway during construction in accordance with my invention with a portion of the pavement being shown broken away to disclose the stressed diagonal tension members for reinforcing the concrete, and also showing the manner in which such metal reinforcement members are placed under tension and so maintained anchored to the various anchorage saddles therefor temporarily carried by the road forms during this stage of the highway construction;

FIG. 2 is a fragmentary plan view, on enlarged scale,

7 showing a side edge portion of the highway of FIG. 1

including two adajacent anchorage members each having a pair of diagonal oppositely-inclined tensioned reinforcement members secured thereto in various stages of tensioning, and the means associated with both anchorage saddles for tensioning the reinforcement members thereof;

FIG. 3 is a side elevation of the fragmental pavement portion of FIG. 2, as viewed from the outside of a road form with the tensioning means for one of the anchorage members removed to show the slotted opening in the form side through which said tensioning means is inserted into the anchorage saddle for alternate connection to the ends of the two diagonal reinforcement members thereof for tensioning the same;

FIG. 4 is a fragmentary cross-sectional view of the concrete pavement shown in FIG. 1 and taken along the line 4 -4 of that figure, looking in the direction of the arrows;

FIG. 5 is an enlarged fragmentary plan view, partly in section, of one of the numerous anchorage saddle members for initially securing the tensioned reinforcement members to the road forms and which, subsequently, is detached therefrom and embedded in the concrete, and including a pair of tensioned reinforcement members in place, one being shown secured in the position assumed in the first stage of tensioning thereof and the other being shown secured in its final tensioned position; and also showing one of, the tension-applying means associated with the anchorage saddles in alternate positions thereto for tensioning said reinforcement members respectively into their above-mentioned stressed positions;

FIG. 6 is an enlarged end elevation of the anchorage saddle with attached road form of FIG. 5 taken substantially on line 66 and showing the road form partly in section;

FIG. 7 is an end view of one of the stepped-wing tensioning coupling members as viewed from the threaded open socket end thereof;

FIG. 8 is a side elevational view of the coupling member shown in FIG. 7 and as viewed from the right side thereof;

FIG. 9 shows an end portion of one of the metal reinforcement members to be stressed and having secured thereon a swaged fitting which is to be received within the socket portions of the coupling members of FIG. 7; and

FIG. 10 is a view of a reinforcement or tension member having swaged fittings on both its ends.

Referring in detail to the drawings, and more specifically to FIGURE 1 thereof, the stressed reinforced elonone embodiment of my invention is shown in the form of a concrete highway and is generally indicated by the reference nuinerallt). As indicated at the left-hand end portion of FIGURE 1 where the concrete section is broken away, there are, exposed a number of stressed metal rein- .explained more in detail later. 'These reinforcement members are placed approximately 12 to inches apart within the trough defined bythe longitudinal road forms gated body or structure of cement-concrete constituting d 13 and are arranged in oppositely inclined groups diagonally with respect to the pavements length for substantially the full width of the pavement, and they are in contact with each other where they cross, as indicated at 14.

It is to be understood that there may be provided conventional supporting chairs (not shown) at the intersections of crossing reinforcements to eliminate the catenary sag thereof prior to the pouring of the concrete. Such a system of diagonally-inclined metal reinforcements permits theme of rods or wires of relatively short length whose ends are readily accessible to accomplish the bringing of the rods or wires under various conditions of tensile stress during laying of the wet pavement and without interruption of the continuity of the latter.

The road forms 13 are temporarymold parts which are fixedly arranged at opposite sides of the pavement during construction thereof, and they are provided at uniform intervals along their inside faces with a series of demountable anchorage saddle members 15 to each of which are anchored two oppositely inclined diagonallyextending reinforcement members 12 which are brought into an ultimate condition of predetermined tensile stress in a manner and by means as will be hereinafter described.

As shown in FIGS. 2, 3 and 4, the road forms 13 are held in place to the sub-grade during construction of the highway by means of form stakes passing through apertures in a series of brackets 16, as presently will be described, these brackets being disposed at uniform intervals longitudinally along the outer faces of each of the road forms. Accurate spacing between the road forms is accomplished by means of plates 17 arranged for longitudinal sliding movement on the bottom of the form between suitable transversely spaced abutments l8 and 19, the

plates 17 each being formed with an angular slot 20 through which is driven the usual form stake 21 which passes through a central transverse slot 22 of the web 23 of the bracket 16 and like underlying transverse slot 23 in the base of forms 13 (see FIG. 3) thus fixedly anchoring the form to the subgrade. By driving the plates 17 lengthwise of the forms, in either direction, the opposed road forms 13 may be moved in or out whereby the spacing between them may be accurately adjusted to a prescribed dimension.

As illustrated in FIGS. 3 and 5, the vertical sides of the road forms 13 at each location of an anchorage saddle member 15 is provided with suitable apertures 24 for the fastening bolts 24' which support the anchorage saddle members 15 in initial assembly on the inside face of the side forms 13, and a slotted opening 25 for insertion therethrough of a tension-applying device 26 temporarily associated with each anchorage saddle, as will be hereinafter described in detail. The same slotted opening 25 serves for passing the tension-applying device 26 for alternate connection with a pair of socketed tensioning coupling members 28 connected with the ends of the reinforcing rods 12 associated with'each of the anchorage saddles 15 and having step by-step interlocking engagement therewith as the rods are placed in tension, as will be hereinafter described. The slotted openings 25 and the anchorage saddle members 15 on opposite sides of the road forms are in alignment transversely of the pavement, as represented in FIG. 1.

The single rods or .wires of uniform cross-section employed as the reinforcement or tension members 12 in accordance with the practice of my invention are preferably of cylindrical form as shown in FIGS. 6, 9 and 10, and made of a steel with elastic limits in the range of from 190,000-220,000 pounds per square inch.

The words rods or wires of uniform cross-section as herein used, are intended to specify a standard rod or wire which is commercially smooth and whose circular crosssection is approximately uniform to such a degree as shall be readily and commercially feasible in the process of manufacture. A rod or wire of hard drawn steel of approximately /8 inch in diameter and a tensile strength of 195,000 pounds per square inch is found to be advantageously suited for this purpose in practice. Also a inch diameter steel wire having a tensile strength on the order of between 200,000216,000 pounds per square inch also would be practicable.

It is found that when a inch steel rod of the type having the above-mentioned tensile strength value is stressed under a tension on the order of 60% of its elastic limit value, the elongation for a 48 foot length will be on the order of 2.4 inches which would be the ultimate elongation or extent to which each reinforcing tensioning rod has been stretched at the completion of the final tensioning stage when the tensioning force is applied to one end only of the reinforcing rod. If the reinforcing tension rods or wires 12 are placed under the required tensile stress through an external pulling force applied to both ends of each rod or wire, then for a rod of the abovestated diameter and elongation characteristics the extent of stretch or elongation obtained when stressed under a tension on the order of 60% of its elastic limit value would be 1% inches and, therefore, the socketed tensioning coupling members 28 then would be only half the length required when tensioning is efiected at only one end of each of the rod or wire reinforcements.

In FIGS. 9 and 10 I have shown a reinforcing tension member 12 which consists of a rod made of high tensile steel having afiixed a predetermined distance apart thereto a pair of abutments or swaged ferrules 30 with the ends 31 of the rod extending through and projecting a short distance beyond the ferrules. Distance L between the opposed inner ends of the ferrules 30 must be accurately determined for the particular type and size of steel rod employed so that a prescribed initial tension will be applied to each tension member prior to pouring of the wet concrete within the side forms 13. Prior to swaging the ferrules 30 on the ends of each of the reinforcing rods 12 the rod is inserted through the socketed coupling members 28. The portion of the rod 12 on which the ferrules 30 are swaged have been prepared with surface indentations into which ferrule metal cold flows under swaging and so develops the required stripping strength.

The anchorage saddle members are of identical construction so that the description of one will suffice for the others, and as shown in FIGS. 5 and 6, each comprises an open-sided hollow casting having oppositely inclined oblique end walls 33 and 34 connected by an inwardly curved front wall 35. The end walls 33 and 34 as well as the top and bottom walls 36 and 37 respectively terminate in a vertical plane at the open back of the casting whereby the latter may be mounted in flat seating engagement with the inside face of the road forms 13 when attached thereto by the fastening bolts 24 which have threaded connection with suitable web portions 38 cast in the anchorage saddles. Suitable top and bottom stabilizing flanges 39 and 40 may be provided bordering the open side of the casting, if desired.

As shown in FIGS. 5 and 6, the end walls 33 and 34 of the anchorage saddle casting have a butterfly-shaped opening 41 and an elongated slotted opening 42 therethrough. Mounted within the butterfly-shaped openings 41 of each anchorage saddle for both longitudinal adjustment therein and slight axial rotation thereof are two of the socketed tensioning coupling members 28 provided for connecting the tension-applying device 26 to the ends of the pair of diagonally-extending reinforcing rods 12 during tensioning thereof and for securing them in their various tensioned states to their particular anchorage saddle mem bers 15.

As best shown in FIGS. 7 and 8, the tensioning coupling members 28 are alike in their structure in which each has an elongated body portion 44 formed with an enlarged 6 rod 12 and having a central hole 46 at the other end for insertion therethrough of the main rod portion of the reinforcing member 12. The entrance end of the bore 45 is internally threaded as indicated at 47 for connection with the tension-applying device 26 as will be hereinafter described.

The body portion 44 is of partially cylindrical formation as shown in FIG. 7, and it is provided exteriorly on opposite sides thereof with wing extensions 48 and 49 each having a series of lip steps 50, 51 and 52 for locking, in turn, behind the back edge of portions of the end walls 33 and 34 bordering the circular portions of the butterflyshaped openings 41 thereof through which pass the cylindrical body portions 44 of the coupling members 28. The positions of the lip steps 50, 51 and 52 are determined by the elongation characteristics of the particular rod or wire structure employed for the reinforcing tension members 12. The lip steps 50, 51 and 52 respectively are situated at identical positions but on'reversed faces of the wing extensions 48 and 49 so that at the completion of each tensioning stage the corresponding lip steps of both wing extensions will be interlocked at the same time with the end walls 33 and 34 of the anchorage saddle members 15.

For stretching and initially tensioning the reinforcing tension members 12 so as to draw up the coupling members 28 in the first stage of tensioning of the rods or wires, a hand lever device 55 may be used of a type such as depicted in FIGS. 1 and 5, said device having a fulcrum arm 56 one end of which is provided with a lug 57 adapted to be fulcrumed on the anchorage saddle casting 15 through the aperture 42 so that when the coupling 28 is forced inwardly of the saddle casting 15 by the pad 57 on the operating handle of the device 55 the first lip step 50 will engage behind the inside edges of the butterfly slots of the openings 41 in the end walls 33 and 34 of the casting and be held thereby after the individual coupling members 28 are given a little twist about their axes, as depicted in FIG. 6. The tension-applying devices 26 are attached to each socketed coupling member 28 to effect the slight twisting movement thereof above-mentioned, and before pouring of the concrete, to assure not losing the first stage hitch in the tensioning operation as well as for drawing it up in the remaining two stages of tensioning.

As shown in FIG. 5, this tension-applying device 26 comprises a long draw screw 53 having threaded connection at its lower end with the internally threaded socket portion 47 of a coupling member 28, this draw screw passing through the slotted opening 25 in the road form 13 and a suitable aperture in a transverse web member 59 of the saddle casting 15. A nut 60 having threaded connection with the outer end of the draw screw 58 bears against the outer end of a metal sleeve member 61 which is loosely mounted on the draw screw and has its inner end seated against the confronting face of the web mem ber 59. Manual turning of each of the nuts 60 by suitable ratchet wrenches in an appropriate direction operates to draw up the socketed coupling members 28 into the anchorage saddle members 15 to a point where the lip steps 50 of the wings 48 and 49 can shoulder seat by being engaged behind the butterfly slots 41 and locked thereby upon slight axial twisting movement of the couplings by means of a wrench applied to the squared head 58' of the draw screw 58.

In the second stage of tensioning, tension is applied to the reinforcement members 12 after the concrete has been poured between the road forms 13 but before appreciable setting of the concrete has started, the socketed coupling members 28 at this time being further drawn into the anchorage saddle members 15 until the intermediate lip steps 51 of the wings 48 and 49 can shoulder seat by being engaged behind the butterfly slots 41 and locked thereby upon being turned into a twisted position by wrench turning the squared head 58.

After the concrete has further set on the order of an 7 hour or more, additional tension is applied to the reinforcement members 12' by the draw screw tensioning device 26 to. further draw up the soc eted coupling members 28 in the anchorage members 15 to their third step 52 following which they are twisted into locking engagement with the end walls 33 and 34 of the anchorage saddle members 15. Obviously there will be no restraint to the torsional reaction of the coupling members 23 during twisting by the draw screw 53 by wrench turning its head 58 in the first or initial stage of tensioning of the reinforcement members 1'2. However, in the second stage of tensioning of the reinforcement members 12 it is found necessary to subject the couplings 28 to torsional force sufficient to twist the wings 43 and 49 in the wet concrete to bring about second stage locking of the couplings by means of the step lips 51.

To assure this second stage locking of the couplings 28 I effect the requisite additional torsional reaction on the draw screw 58 through use of the wrench on the squared end 53 thereof. This procedure also is employed for securing additional torsional force to efiect third stage locking of the couplings 23 to their respective anchorage saddle members 15 by means of the step lips 52, in which instance the wings 48 and 49 of the coupling 23 will have been drawn substantially completely inside of the saddle castings and, consequently, do not form a restraint to twisting which otherwise would be impossible in hardened concrete.

The reinforcing tensioning members 12 may be provided throughout their effective length with a coating of grease, asphalt, or similar material, or may be jacketed with a vinyl or similar plastic, so as to break bond with the concrete as may be necessary in the final tensioning step. After the concrete has hardened and set, the draw screw 58 of the tension-applying device 26 then is unscrewed from the socket portion of the coupling member 28 and the bolts 24 which hold the anchorage saddle members 15 in assembly with the road forms 13 are removed so that the road forms can be stripped from the finished pavement for installation and use in the construction of subsequent pavement laying operations. The anchorage saddle members 15 with the socketed coupling members 28 left inside remain embedded in the concrete after stripping of the road forms 13.

A particular advantage in stressing reinforced concrete structures of the class described in accordance with my invention, is that the pavement slab can be made considerably thinner to withstand the same loading as a pavement slab having the common fabric type of reinforce ment. The design and proper arrangement of the pretensioned diagonal reinforcing tension members permit compression of the concrete thereby in two directions at the same time, viz., laterally and longitudinally, with the com plete elimination of all tensile stress in the concrete body. Furthermore, all joints can be eliminated so that continuity of the pavement may be obtained. Thus, a dual lane highway may be poured, two lanes at a time, omitting the center longitudinal joint'as well as the usual transverse joints commonly used in a non-prestressed construction.

The term concrete as used herein comprehends mixtures of Portland cement, or other hydraulic cement, with water and any other suitable material such as sand and/ or crushed stone.

It is to be understood that stranded wire structures can be substituted for the rod or wire reinforcing members and jacketed in the manner above-explained for the purpose of breaking bond with the concrete.

=l.rApparatus for making prestressed elongated reinforced concrete structures of considerable length and considerable width for use as a highway or the like comprising a road form, an anchorage member on said road form and to which the ends of a pair of metal reinforcing tension members under tension are to be securely fastened, said anchorage member having two butterflyshaped openings therein facing in oppositely extending oblique directions, coupling members having wing extensions adapted to be received in the butterfly-shaped openings in said anchorage member and be capable of slight turning movement therein, each of said wing extensions being of stepped formation for successive interlocking engagement with said anchorage member during step-bystep tensioning of the reinforcing tension member, said coupling members each being formed with an open-ended socket portion adapted to receive a ferrule attached to a reinforcing tension member and formed with a hole at the other end to pass the intermediate body portion of the reinforcing tension member, the entrance opening of the socket portion of said coupling member being inter-- nally threaded, a draw screw having threaded connection at its lower end with the internally threaded socket portion of one of said coupling members, a sleeve member around said draw screw and arranged for its lower end to bear against a part of said anchorage member, a nut adapted to be threaded on the upper end of said sleeve to apply a predetermined tension to said tension member by appropriate turning of the nut on said draw screw to pull the coupling members up into interlocking positions with the anchorage member.

2. Apparatus for making prestressed elongated reinforced concrete structures of considerable length and considerable width for use as a highway or the like comprising a road form, an anchorage member on said road form and to which an end of a reinforcing tension memher under tension is to be securely fastened, said anchorage member having an opening therein adapted to receive an element with wing extensions on its opposite sides, a coupling member having oppositely extending external wing extensions adapted to be received in the opening in said anchorage member, said wing extensions each being of a stepped formation adapted for successive interlocking engagement with said adjacent anchorage member during periodic step-by-step tensioning of the reinforcing tension member so as to apply a predetermined tension to said tension member in reaching each of its successive stages of tensioning, said coupling member being formed with an open-ended socket portion adapted to receive a ferrule attached to the end portion of the reinforcing tension member and formed with a hole at the other end to pass the intermediate body portion of such reinforcing tension member, the entrance opening of the socket portion of aid coupling member being internally threaded, a draw screw having threaded connection at its lower end with the internally threaded socket portion of said coupling member, a s eeve member around said draw screw and arranged for its lower end to bear against a part of said anchorage member, a nut adapted to be threaded on the upper end of said draw screw and to bear against the upper end of said sleeve to apply a predetermined tension to said reinforcing tension member upon appropriate turning of the nut on said draw crew to pull the coupling member step-by-step into positions for interlocking with the anchorage member, and means associated with said draw screw adapted for turning the latter manually to effect slight twisting of the coupling relative to said opening and to swing and lock said wing extensions step-bystep to said anchorage member as the respective steps of the wing extensions are successively pulled by said not and the draw screw into positions where such interlocking can be effected during tensioning of the reinforcing tension member associated with said coupling member.

3. Apparatus for making prestressed elongated reinforced concrete structures of considerable length and considerable width for use as a highway or the like comprising a road form having a slotted opening through its upright wall, a hollow open-sided anchorage member attached to said road form over said opening and to which the ends of a pair of metal reinforcing tension members under tension are to be securely fastened, said anchorage member having two butterfly-shaped openings therein facing in oppositely extending oblique directions, coupling members having wing extensions adapted to be received in the butterfly-shaped openings in said anchorage member and be capable of slight turning movement therein, each of said wing extensions having a series of step lips for successive interlocking engagement with said anchorage member during step-by-step tension ing of a reinforcing tension member associated with each coupling member, said coupling members each being formed with an open-ended socket portion adapted to receive a ferrule attached to a reinforcing tension member and formed with a hole at the other end to pass the intermediate body portion of such reinforcing tension member, the entrance opening of the socket portion of said coupling member being internally threaded, a draw screw passing through said slotted opening in said road forms for'alternate connection to said coupling members, said-draw screw having threaded connection at its lower end with the internally threaded socket portionv of one of said coupling members, a sleeve member around said draw screw and arranged for its lower end to bear against a part of said anchorage member, a nut adapted to be threaded on the upper end of said draw screw and to bear against the upper end of said sleeve to apply a predetermined tension to said reinforcing tension member upon appropriate turning of the nut on said draw screw to pull the coupling members step-bystep into positions for interlocking with the anchorage member, and means associated with said draw screw adapted for turning the latter manually to effect slight twisting of the coupling in the particular butterfly-shaped opening and to swing and lock the step lips of said wing extensions to said anchorage member as the respective step lips are successively pulled by said nut and the draw screw into positions where such interlocking can be effected during tensioning of the particular reinforcement member.

4. Apparatus for making prestressed elongated reinforced concrete structures of considerable length and considerable width for use as a highway or the like, comprising, in combination, a fixed road side form, a hollow anchorage member carried by said road form and to which the ends of two oppositely inclined converging metal reinforcing tension members when under tension are to be securely fastened, said anchorage member having openings therein through which are inserted and housed such converging ends of said tensioning members, adjustable coupling means individual to said tension members as well as being mutually associated with said anchorage member and movable relative thereto, said individual coupling means having a stepped formation made up of definite lip steps adapted for successive interlocking detention relative to the same anchorage member of ferrules fast on such converging ends of said reinforcing tension members and contained therein during periodic step-by-step tensioning of the latter so as to apply a predetermined tension to said tension members in reaching each of their successive stages of progressive tensioning, and adjustable prestressing means including a draw screw element operatively connected with either of the said individual coupling means and effective to adjust the latter step-by-step separately on the common anchorage member into predetermined stages of tension-applying lip step positions thereon whereby each lip step will act in turn to apply a predetermined fixed amount of tension to the particular metal reinforcing tension member associated with the said coupling means as will be required preparatory to depositing a pourable wet concrete mixture in this apparatus, and thereafter when the stages of partial solidifiit) cation, hardening, and setting of such wet concrete mix occur there-in.

5. Apparatus for making prestressed elongated reinforced concrete structures of considerable length and considerable width for use as a highway or the like comprising a fixable side road form, a hollow anchorage member demountable on said road form and to which an end of a transverse reinforcing tension member under tension is to be securely fastened, said anchorage member having an apertured opening therein adapted to re ceive and movably cooperate with an element with wing extensions on its opposite sides, an elongated adjustable coupling member having oppositely extending external side wing extensions adapted to be movably received in the opening in said anchorage member and to be adjusted longitudinally thereinto, said coupling member having an internally threaded socket portion adapted to receive thereinto a ferrule attached to a reinforcing tension member and also arranged at the other end to pass outwardly therethrough the longitudinal intermediate portion of such reinforcing tension member, said Wing extensions on the coupling member each being of a stepped formation having several lip steps adapted for successive interlocking engagement with said adjacent anchorage member during periodic step-by-step tensioning of the reinforcing tension member so as to apply a predetermined tensionto said tension member in reaching each of its successive stages of tensioning, the positions of said lip steps being determined by the elongation characteristics of the metal employed for the reinforcing tension member whereby the latter will be stretched and brought to a condition of predetermined tensile stress at each of said lip step locations, the last of which being effective to permanently maintain the solidified and hardened concrete in a continual state of compression, and tension-applying draw means on the said anchorage member including a draw screw element disposed through said opening thereof and having threaded connection with the internally threaded socket portion of said coupling member whereby step-by-step adjusting movements of the latter can be effected relative to said anchorage memher into several predetermined stages of tension-applying lip step positions thereon.

6. Apparatus for making prestressed elongated reinforced concrete structures of considerable length and considerable width for use as a highway or the like comprising a fixable side road form, a hollow anchorage member demountable on said road form and to which the ends of a pair of diagonally-extending metal reinforcing tension members under tension are to be securely fastened, said anchorage member having two butterfly-shaped openings therein facing in oppositely extending oblique directions, elongated coupling members having wing extensions adapted to be movably received in the butterfly-shaped openings in said common anchorage member and to be capable of slight turning movement on insertion within the latter for subsequent adjustment of their respectively positions, each of said coupling members having an internally-threaded openended socket portion adapted to receive thereinto a ferrule attached to a reinforcing tension member and formed with a hole opening at the other end to pass outwardly therethrough the longitudinal intermediate portion of the reinforcing tension member, said wing extensions each being provided with several lip steps adapted for successive interlocking engagement with the associated anchorage means during periodic step-by-step tensioning of the reinforcing tension members, the positions of said lip steps being determined by the elongation characteristics of the metal employed for the reinforcing tension members whereby the latter will be stretched and brought to a condition of predetermined tensile stress and each of said lip step locations, the last of which being effective to permanently maintain the solidified and hardened concrete in a continual state of compression, and draw means interchangeably mounted on said anchorage member including ademountable draw screw disposed through either of said butterfly-shaped openings and having threaded connection with the internally-threaded socket portion of the particular coupling member occupying said opening whereby separate step-by-step adjusting movements of such coupling member can be effected relative to said anchorage member and in predetermined stages of tension-applying lip step positions thereon.

7. In combination, a fixed road form, a hollow anchorage member demountably carried by said road form and adapted for receiving therein an anchoring thereto one end portion of an exterior elongated concrete-reinforcing metal tension member which is required to be embedded in a solidified concrete slab moulded in situ with said road form, an exterior elongated concrete-reinforcing metal tension member fixed at one end and carrying an abutment fast on and adjacent its other end in which said abutment-carrying end last-named is disposed toward and directed into said anchorage member and is capable of longitudinal movement thereinto upon subsequent elongation and consequent tensioning of said metal tension member, stepped means mutually associated with said abutmentand said anchorage member and movable relative to the latter, said stepped means having a portion thereof provided with screw threads, and movable draw means on said anchorage member including a draw screw disposed therethrough threadingly connected with said stepped means effective to adjust the latter outwardly of said anchoring member and effect longitudinal tensioning and elongation of said tension member through the agency of said stepped means and said engaged abutment, said stepped means having its ofiset parts adapted to serially engage said anchoring member and retain said reinforcing tension member in its several successive stepby-step predetermined positions and also to apply to the latter member definite amounts of stress as it is brought under tension by adjustment of said movable draw means.

References Cited in the file of this patent UNITED STATES PATENTS 903,909 Steiner Nov. 17, 1908 2,655,846 Freyssinet Oct. 20, 1953 2,833,186 Dobell May 6, 1958 FOREIGN PATENTS 1,006,760 France Jan. 30, '1952 147,743 Australia Aug. 8, 1952 OTHER REFERENCES Road Prestressed, Engineering News, Redord, April 12, 195 1.

Claims (1)

1. APPARATUS FOR MAKING PRESTRESSED ELONGATED REINFORCED CONCRETE STRUCTURES OF CONSIDERABLE LENGTH AND CONSIDERABLE WIDTH FOR USE AS A HIGHWAY OR THE LIKE COMPRISING A ROAD FORM, AN ANCHORAGE MEMBER ON SAID ROAD FORM AND TO WHICH THE ENDS OF A PAIR OF METAL REINFORCING TENSION MEMBERS UNDER TENSION ARE TO BE SECURELY FASTENED, SAID ANCHORAGE MEMBER HAVING TWO BUTTERFLYSHAPED OPENINGS THEREIN FACING IN OPPOSITELY EXTENDING OBLIQUE DIRECTIONS, COUPLING MEMBERS HAVING WING EXTENSIONS ADAPTED TO BE RECEIVED IN THE BUTTERFLY-SHAPED OPENINGS IN SAID ANCHORAGE MEMBER AND BE CAPABLE OF SLIGHT TURNING MOVEMENT THEREIN, EACH OF SAID WING EXTENSIONS BEING OF STEPPED FORMATION FOR SUCCESSIVE INTERLOCKING ENGAGEMENT WITH SAID ANCHORAGE MEMBER DURING STEP-BYSTEP TENSIONING OF THE REINFORCING TENSION MEMBER, SAID COUPLING MEMBERS EACH BEING FORMED WITH AN OPEN-ENDED SOCKET PORTION ADAPTED TO RECEIVE A FERRULE ATTACHED TO A REINFORCING TENSION MEMBER AND FORMED WITH A HOLE AT THE OTHER END TO PASS THE INTERMEDIATE BODY PORTION OF THE REINFORCING TENSION MEMBER, THE ENTRANCE OPENING OF THE SOCKET PORTION OF SAID COUPLING MEMBER BEING INTERNALLY THREADED, A DRAW SCREW HAVING THREADED CONNECTION AT ITS LOWER END WITH THE INTERNALLY THREADED SOCKET PORTTION OF ONE OF SAID COUPLING MEMBER, A SLEEVE MEMBER AROUND SAID DRAW SCREW AND ARRANGED FOR ITS LOWER END TO BEAR AGAINST A PART OF SAID ANCHORAGE MEMBER, A NUT ADAPTED TO BE THREADED ON THE UPPER END OF SAID SLEEVE TO APPLY A PREDETERMINED TENSION TO SAID TENSION MEMBER BY APPROPRIATE TURNING OF THE NUT ON SAID DRAW SCREW TO PULL THE COUPLING MEMBERS UP INTO INTERLOCKING POSITIONS WITH THE ANCHORAGE MEMBER.

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