Concrete international OctOber 2013 47

The Story of Eugène Freyssinetthe development of prestressing

by Kenneth W. Shushkewich

I t is widely accepted that Eugène Freyssinet (1879-1962), (Fig. 1), invented prestressed concrete.1-6 However, it is not as well known that he was a skilled craftsman and

prolific bridge builder, and this is what prepared him to make such a great innovation. His first influence was working alongside the villagers in the countryside near Objat, France, where he was born, in anything that involved using his hands. By the age of 20, he was a competent craftsman. His second influence was at l’Ecole Nationale des Ponts et Chaussées, one of the top civil engineering schools in France, where he studied under three eminent professors: Jean Résal, Paul Séjourné, and Charles Rabut. Rabut undoubtedly had the greatest influence on his career, stressing the importance of experimentation and practical experience.

After graduating in 1905, Freyssinet built a number of concrete arch bridges, each of which successively broke his own world record for span length. This enabled him to develop an appreciation for creep of concrete, leading to his insight that high-strength steel along with high-quality concrete are necessary to create permanent prestressing in concrete. (The tensioned, high-strength steel overcomes the effects of creep and shrinkage to give a reserve of compression, while the high-quality concrete greatly reduces the effects of creep and shrinkage to be overcome—both are important in prestressed concrete.)

Although Freyssinet applied for a patent for the first of his three inventions for prestressing in 1928,7-9 his world-wide reputation in the field developed only after his spectacular rescue of the Le Havre Maritime Station in 1934. This article describes the journey taken to create this “entirely new material”1 that led to a “revolution in the art of building”1—a revolution that included his design of the first pre-tensioned concrete bridge in 1936 and the first post-tensioned concrete bridge in 1941. His vision was that prestressing allowed concrete to become a quasi-elastic material similar to steel for the service life of the structure.

World-Record Span-Length Arch BridgesFreyssinet’s first structures were small arch bridges that

looked like masonry but were made of concrete. He moved on to larger and larger concrete arch bridges, each of which broke his own world record for span length. Along the way, he counteracted the effects of shrinkage (which were known) and discovered the effects of creep (which were previously unknown).

In 1907, Freyssinet designed and built the Prairéal-sur-Besbre Bridge (Fig. 2), a three-hinged arch having a span length of 26 m (85 ft). This project was the world’s first application of precompression in a concrete arch as a means of removing its formwork. Jacks installed within the arch compressed the concrete, offsetting the shrinkage that occurred during setting and hardening of the concrete, and lifted the arch off the formwork so that it could easily be removed.

The world-record span-length bridges subsequently designed and built by Freyssinet (Fig. 3) were: • Le Veurdre Bridge (72.5 m [238 ft] span) in 1911-1912;

Fig. 1: Eugène Freyssinet (left) at the construction site (photo courtesy of Freyssinet International [FI])

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• Villeneuve-sur-Lot Bridge (96 m [315 ft] span) in 1914-1920;

• Saint-Pierre-du-Vauvray Bridge (131 m [430 ft] span) in 1922-1923; and

• Plougastel Bridge (three spans of 186 m [610 ft]) in 1924-1930. Detailed descriptions of these bridges can be found in

References 1 to 5.

Perseverance to Understand CreepThe construction of these bridges gave Freyssinet an

appreciation for the time-dependent behavior of concrete under load, a phenomenon that he termed “deferred deformation” and which we now know as creep. This is something that the administrative authorities at the time obstinately denied the existence of, and the official laboratories neglected or refused to measure over sufficiently long periods of time.

In his design of Le Veurdre Bridge (Fig. 3(a)), Freyssinet complied with the 1906 French Regulations, which mandated

a three-hinged arch (rather than a two-hinged arch as he had used for a 50 m [164 ft] test model) and erroneously stated that Young’s modulus for concrete is constant. The initial bliss after the completion of construction of this bridge was soon followed by a dreadful agony as disconcerting deformations started appearing, first slowly and then progressively more rapidly, until there was no possible outcome imaginable other than collapse.

According to Freyssinet: “It was evening when I reached Moulins and I got on my bicycle and went to Le Veurdre to wake up Biguet and three reliable men. Between the five of us, we replaced the decentering jacks, and as soon as there was enough light to use the levels and the staffs, we began to raise all three vaults at once. Le Veurdre Bridge regained its shape and was cured of the disease which had been about to finish it off. It behaved perfectly until 1940; it was destroyed in the war.”1,2

On future bridges, Freyssinet eliminated the crown hinge, and continued “studying the problem of deferred deformation in concrete which seemed to me to be the only possible obstacle to making initial stress…into something permanent.”1

It was for the construction of the Plougastel Bridge (Fig. 3(d)) that Freyssinet conducted detailed creep tests during the 2-1/2 year period between August 1926 and February 1929. These tests allowed him to obtain complex creep curves that verified his theory for the time-dependent behavior of concrete under load.10,11 Figures 2 and 3 in References 10 and 11, respectively, show the setup of the creep tests and the creep curves as observed and predicted by Freyssinet. These results allowed him to become confident that the time-dependent deformation of concrete was limited in magnitude and would eventually dissipate with time. He was therefore convinced that he could overcome its effects in the design of prestressed concrete elements.

It was through his understanding of the time-dependent behavior of concrete (creep and shrinkage) that Freyssinet was able to introduce prestressed concrete, which used both high-strength steel and high-quality concrete. The high-strength steel counteracted the losses due to creep and shrinkage so there would always be a reserve of compression in the concrete. The high-quality concrete made using vibration (mechanical means), compression (expulsion of water), and heating (steam curing) minimized the losses by reducing the water-cement ratio (w/c) at initial set.

Development of PrestressingIn 1928, Freyssinet patented the first of his three inventions

for applying compression to concrete. This was a process of applying compression by “pre-tension and bonded wires,” which allowed the manufacture of precast elements (this is the birth of prestressing and pre-tensioning). His other two methods for applying compression to concrete were his 1938 patent of the flat jack and his 1939 patent of the concrete anchorage (this is the birth of post-tensioning).

Fig. 2: Prairéal-sur-Besbre Bridge, a three-hinged arch with a span length of 26 m (85 ft) built in 1907 (photo courtesy of Association Eugène Freyssinet [AEF])

Fig. 3: Bridges designed and built by Freyssinet: (a) Le Veurdre Bridge built 1911-1912, 72.5 m (238 ft) span; (b) Villeneuve-sur-Lot Bridge built 1914-1920, 96 m (315 ft) span; (c) Saint-Pierre-du-Vauvray Bridge built 1922-1923, 131 m (430 ft) span; and (d) Plougastel Bridge built 1924-1930, three spans of 186 m (610 ft) (photos courtesy of AEF)

(a)

(c) (d)

(b)

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On October 2, 1928, Eugène Freyssinet and Jean Séailles applied for a patent titled “fabrication process for reinforced concrete elements,” a process adapted to the manufacture of precast beams, poles, pipes, sleepers, and more. This patent was registered under the number 680,547 in France. The patent was issued on January 22, 1930, and published on May 1, 1930. Reference 7 is an English version of this patent. Freyssinet and Séailles described, with absolute precision, the theory of permanent precompression in concretes or other materials and their overall potential.

At the time of the 1928 patent, the scientific community did not believe in prestressing. Thus, Freyssinet had to go out alone in the world to demonstrate the merits and possibilities of prestressing. He became an industrialist producing electricity poles at the Forclum plant at Montargis in France (Fig. 4). The result was a complete technical success, but a commercial failure due to the 1929 world-wide economic depression.

Freyssinet had perfected the grinding fineness of cement, improved on his previous invention for mechanical vibration of concrete, invented steam curing to accelerate the rate of concrete hardening and rate of production, and perfected the industrial precasting process for precast concrete elements. However, in the 5 years from 1929 to 1933, he had lost the entire fortune he had accumulated during the previous part of his career.

Freyssinet was, fortunately, saved by a miracle. At that very moment, the Maritime Station at Le Havre in France, completed in 1933 for the gigantic ocean liner, the Norman-die, was sinking 25 mm (1 in.) per month into a recent filling of dredged material (Fig. 5). According to Freyssinet: “Imminent collapse seemed to be inevitable. I proposed a solution which, despite its boldness, was adopted without argument as it consisted in the only possible hope of avoiding disaster.”3

The strengthening of the building was completed in 1934. The first part of Freyssinet’s solution consisted of

adding new footings between the existing footings. To make the new and existing concrete a monolithic prestressed horizontal element, the unit was prestressed with parallel wires turned around two reinforced concrete end anchorages. One anchorage was displaced by hydraulic jacks having a force of up to 1000 tonnes (1100 tons).

The second part of Freyssinet’s solution was to install 700 piles at the locations of the new footings, 25 to 30 m (82 to 98 ft) long, that extended into firm layers of soil (Fig. 5). The piles were cast inside the building in 2 m (6.6 ft) sections (because of the limited headroom), and were assembled together and driven into the ground using special jacks designed by Freyssinet. Vibration, compression, and steam curing were all used to improve the rate of casting and quality of concrete. The piles were then prestressed against the footing using hydraulic jacks having a vertical prestressing force of 320 tonnes (352 tons). The settlement ceased as soon as the first piles were installed.

The result was both spectacular and convincing, and at once earned Freyssinet a worldwide reputation. This started the collaboration between Eugène Freyssinet and Edme Campenon in 1934 on the entire range of construction projects of the Campenon Bernard group, both in France and Algeria—a collaboration that finally was destined to ensure the development of prestressing.

Freyssinet next invented the flat jack (Fig. 6) in 1936 for compressing the raft of the Portes-de-Fer Dam in Algeria, and then, immediately after that, at a much grander scale, for raising the height of the Beni Badhel Dam in Algeria by 7 m (23 ft) to bring it up to 67 m (220 ft). He applied for a patent on August 1, 1938, titled “combination of jacks and their application in construction, especially in reinforced concrete constructions” and the patent was validated on August 21, 1939. Reference 8 is an English version of this patent.

The flat jack (Fig. 6) consists of two stamped steel sheets that are connected together. By hydraulically introducing a

Fig. 4: Forclum pre-tensioned concrete electricity poles (first prestressed concrete elements in history) (photo courtesy of AEF) Fig. 5: Rescue of the Le Havre Maritime Station (illustration courtesy

of AEF)

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fluid under pressure, the flat jack is inflated and can develop considerable force. It can be used to compress a concrete element or lift a structure. It is a remarkable device for its power, lightness, and low cost. The fluid can be oil, resin, grout, cement, or other ingredients. The flat jack can be used to vary the compressive forces applied with time to allow for the adjustment of structures.

Freyssinet then introduced post-tensioning (Fig. 7), whereupon he said: “At the beginning of the war, in September 1939, I made the most decisive progress since 1928 in the methods of cable tensioning, by creating systems making it possible to anchor a group of wires under tension, by means of self-locking off inside the cones.”3 He added: “I consider this anchorage to be the greatest step forward which I have made in the idea of prestressing since the idea first came to me in 1903.”1

On August 26, 1939, Eugène Freyssinet applied for a patent titled “tensioned cable anchorage system for prestressed concrete construction.” This patent was registered under the number 926,505 in France. The patent was issued on April 21, 1947 (because of the war) and published on October 3, 1947. Reference 9 is an English version of this patent.

The post-tensioning anchorage system consists of 12 x 5 mm (0.20 in.) diameter parallel steel wires locked or anchored in a concrete anchorage cone by a tensioning jack (Fig. 7). The reinforced concrete anchorage cone consists of a cylindrical block having a central conical hole and a central conical fluted block (or pin). The tensioning jack is comprised of two pistons: an outer piston which tensions the wires and an inner piston which pushes the pin into the conical hole while under tension. The steel wires are threaded through the anchorage and tensioned with the jack and locked-off, thus transmitting their tension to the structure directly via the anchorage. Grout is introduced into the jack after stressing and enters the post-tensioning duct through a hole in the pin. Figure 7(b) shows a tendon being stressed, a stressed tendon with elongated wires, and a stressed tendon with the tails of the wires trimmed and bent over.

As aptly stated by Ordoñez: “The prestressing jack and Freyssinet’s conical anchorage are of remarkable technical simplicity and beauty. Without doubt, this invention is one of the purest, most universal works of genius in the whole history of building, comparable in importance to the wedge, the rivet, or the weld.”1

First Prestressed Concrete BridgesFreyssinet designed and built the first prestressed concrete

(pre-tensioned) bridge1,12 at the site of the Portes-de-Fer Dam at Oued Fodda in Algeria in 1936 (Fig. 8). The bridge is on the downstream side of the dam. It has four simply supported spans of 19 m (62 ft) with a width of 4.6 m (15 ft) and is comprised of 12 pre-tensioned precast concrete I girders (Fig. 8(a) and (b)). The concrete of the girders was vibrated, compacted, and heated to accelerate curing, as Freyssinet previously did at Forclum and Le Havre. The bridge is still in use today, carrying a significant amount of traffic (Fig. 8(c)).

Freyssinet also designed the first post-tensioned concrete bridge6,12 in 1941 (Fig. 9), which also happens to be the first precast concrete segmental bridge. The Luzancy Bridge over the Marne River in France has a span of 55 m (180 ft), which was yet another world record at the time. It is very light in appearance and has a remarkable span-depth ratio of 43. Construction started in 1941, but was interrupted by the war, and not completed until 1946.

The bridge was cast in segments and erected (Fig. 9(a)) by launching equipment consisting of masts and stay cables, one of the most imaginative systems ever used for the assembly of prefabricated bridge elements. The first three segments at each end were cantilevered by this high-line method, and then the central 16 segments, having a length of 39 m (128 ft) and a weight of 90 tonnes (99 tons), were launched and lowered into place. Post-tensioning tendons were then stressed and flat jacks were activated at the abutments. The bridge was post-tensioned in all three directions (longitudinal, vertical, and transverse).

The Luzancy Bridge was visited by the author in October 2007—60 years after its completion (Fig. 9(b)). It is in

Fig. 6: Flat jack (schematic) (adapted from Reference 3)

Fig. 7: Post-tensioning: (a) concrete anchorage cone (photo courtesy of AEF); and (b) tensioning jack (photo courtesy of FI)

Load

Pump

Load

PumpBearingplates

Cross section

Plan

Inactive state In�ated state

Inlet

Purge

(a) (b)

Concrete international OctOber 2013 51

pristine condition and the concrete of the precast segments is of excellent quality—looking like that of a new bridge. The only work that has been done to the bridge is that flat jacks have been rejacked and shimmed a few times to make adjustments for creep.

The great success of the Luzancy Bridge allowed Freyssinet and the Campenon Bernard group to build five similar bridges having spans of 74 m (243 ft) on the Marne River, between 1947 and 1951. All precast segments were made at a central plant. They were assembled in sections using temporary prestressing, transported to the site by barge, installed by the mast and stay-cable system, and completed with the addition of permanent post-tensioning.

Legacy of Eugène FreyssinetThe concept of prestressed concrete developed by

Eugène Freyssinet made him known all over the world, and more precisely all over the construction community. His contribution, however, is immensely larger than the development of a specific technique. He was always trying to use materials to their utmost to give the best of their capacity. The concept of prestressing was one method he used to reach this final target.

Even though precast, prestressed concrete has since been widely used throughout the world and has generated very large and profitable companies, this would not have been the inventor’s main concern. He was less interested in

Fig. 9: First post-tensioned and precast concrete segmental bridge, Luzancy Bridge over the Marne River in France, with a span of 55 m (180 ft): (a) during construction (photo courtesy of AEF); and (b) in 2007 (photo courtesy of the author)

Fig. 8: First prestressed concrete (pre-tensioned) bridge at the site of the Portes-de-Fer Dam at Oued Fodda in Algeria: (a) after construction in 1936 (Reference 1); (b) pre-tensioned precast concrete I girder used for the bridge (Reference 1); and (c) in 2009 (photo courtesy of Zivotije)

(a)

(b)

(c)

(a)

(b)

making money and being in the public eye than designing and building economical and long-lasting structures. Since a great number of his structures (those not bombed during the war) are still standing today and in exceptional condition, we must say that he reached his objective.

Freyssinet has been proclaimed “one of the most complete engineers of the 20th century and one of the greatest builders in history.”1 This article celebrates five of the significant engineering and construction achievements of this prolific genius, namely: • Designing and constructing world-record span-length

arch bridges; • Being the first to understand the time-dependent

deformation of concrete under load (creep); • Developing prestressing (pre-tensioning, flat jacks, and

post-tensioning); • Rescuing the Le Havre Maritime Station from collapse; and • Designing the first pre-tensioned concrete bridge and

the first post-tensioned concrete bridge.Readers interested in taking a more detailed look at the

prolific career and the vast achievements of Eugène Freyssinet are encouraged to consult References 1 to 6.

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References1. Ordoñez, J.A.F., Eugène Freyssinet, Editions Eyrolles, Paris,

France, 1979, 444 pp. (in English and French)2. Lemoine, H.; Xercavins, P.; and Marrey, B., Eugène Freyssinet—

Un Amour Sans Limite, Editions du Linteau, Paris, France, 1993, 187 pp. (in French)

3. Fargeot, B.; Montagnon, J.; Xercavins, P.; de la Fuente, C.; Guyon, F.; and Jartoux, P., Eugène Freyssinet: A Revolution in the Art of Construction, Presses de l’Ecole National des Ponts et Chaussees, Paris, France, 2004, 200 pp.

4. Xercavins, P.; Demarthe, D.; and Shushkewich K., “Eugène Freyssinet—The Invention of Prestressed Concrete and Precast Segmental Construction,” paper on the Association Eugène Freyssinet website, 2008, 24 pp. (http://efreyssinet-association.com/association/documents/doc/P.%20Xercavins%20D.%20Demarthe%20K.%20Shushkewich.pdf)

5. Xercavins, P.; Demarthe D.; and Shushkewich K., “Eugène Freyssinet—His Incredible Journey to Invent and Revolutionize Prestressed Concrete Construction,” paper presented at the 3rd fib International Congress, Washington, DC, June 2010, 28 pp. (http://aspirebridge.com/resources/fib_Congress_Freyssinet_by_Shushkewich.pdf)

6. Shushkewich, K.W., “Eugène Freyssinet—Invention of Prestressed Concrete and Precast Semental Construction,” Structural Engineering International, Journal of the IABSE, V. 22, No. 3, Aug. 2012, pp. 415-420.

7. Freyssinet, E., and Séailles, J., “Process for the Manufacture of Articles of Reinforced Concrete,” UK Patent 338864, filed in France Oct. 2, 1928, and issued Nov. 18, 1930.

8. Freyssinet, E., “Jack Apparatus,” US Patent 2226201, filed in France Aug. 1, 1938, and issued Dec. 24, 1940.

9. Freyssinet, E., “Anchoring of Tensioned Cables in Concrete Constructions,” US Patent 2270240, filed in France Aug. 26, 1939, and issued Jan. 20, 1942.

AcI member Kenneth W. Shushkewich is with KSI bridge engineers and for over 38 years has specialized in the design and construction of unique and innovative prestressed concrete bridges. He was formerly with Jean Muller International and t.Y. Lin International. He is a member of Joint AcI-ASce committees 343, concrete

bridge Design, and 423, Prestressed concrete.

Table 1:Freyssinet prestressing patent numbers

Priority date France United Kingdom United States

Pre-tensioning

Oct. 2, 1928 Fr 680,547 Gb 338,864 —

Nov. 19, 1928Fr 36,703

1st addition to Fr 680,547Gb 338,934 —

Sep. 3, 1929Fr 38,276

2nd addition to Fr 680,547Gb 364,621 —

Flat jacksAug. 1, 1938 not found

Gb 589,019 US 2,226,201June 3, 1939 Fr 859,903

Post-tensioning

Aug. 26, 1939 Fr 926,505 Gb 591,218 US 2,270,240

Oct. 28, 1940 Fr 870,070 Gb 592,839 US 2,371,882

Sep. 30, 1941Fr 54,603

1st addition to Fr 926,505Gb 592,430 US 2,618,147

Apr. 27, 1948 Fr 1,010,101 Gb 657,738 US 2,686,963

10. Freyssinet, E., Une révolution dans les techniques du béton, Librairie Eyrolles, Paris, France, 1936, 118 pp. (in French)

11. Freyssinet, E., “Aspects nouveaux des problèms du ciment armé,” AIPC / IABSE / IVBH Publications, Zurich, Switzerland, 1936, pp. 265-304. (in French)

12. Freyssinet, E., “Une révolution dans l’art de bâtir : les constructions précontraintes,” Travaux, No. 101, Nov. 1941, pp. 335-359. (in French)

Selected for reader interest by the editors.

Prestressing Patents of Eugène Freyssinet

The patent numbers for Freyssinet’s three inventions for prestressing are given in Table 1 along with their priority date (original filing date in France). Copies of selected patents are available in English (or French) with the online version of this article on the CI website. The patents are interesting and insightful.

Patent Priority Patent

Number Date Date

1 FR598811 (A) Système de barrage à vannes en arc 1925-05-26 1925-12-26

2 FR623278 (A) Perfectionnement à la construction des ponts suspendus en béton armé 1926-10-18 1927-06-21

3 FR628224 (A) Perfectionnements apportés à la construction des portes roulantes à panneaux multiples 1927-01-29 1927-10-20

4 FR629668 (A) Perfectionnements apportés à la construction des portes roulantes de grands hangars d'aviation ou d'aérostation 1927-02-22 1927-11-15

5 FR644726 (A) Sheds en béton armé de grande portée 1927-11-29 1928-10-12

6 FR670525 (A) Perfectionnement apporté aux constructions voûtées en béton armé 1928-06-22 1929-11-29

7 FR680547 (A) Process for the manufacture of articles of reinforced concrete 1928-10-02 1930-05-01

8 FR36703 (E) Procédé de fabrication de pièces en béton armé 1928-11-19 1930-08-02

9 FR678983 (A) Procédé d'obtention d'éléments de construction légers et très résistants 1928-11-22 1930-04-07

10 FR38276 (E) Procédé de fabrication de pièces en béton armé 1929-09-03 1931-05-12

11 FR692313 (A) Procédé de fabrication de pièces ou corps moulés à partir de mortiers ou béton 1929-09-04 1930-11-04

12 FR703157 (A) Procédé et dispositif particulièrement destinés à la désaération de mélanges liquides ou plastiques 1929-12-30 1931-04-25

13 FR708726 (A) Procédé d'assemblage ou de jonction de pièces en béton armé 1930-04-08 1931-07-28

14 FR717763 (A) Procédé de construction de surfaces de ruissellement de réfrigérants d'eau 1930-09-22 1932-01-14

15 FR720297 (A) Perfectionnements aux matériaux de construction 1930-10-14 1932-02-17

16 FR43381 (E) Improvements in apparatus for manufacturing articles of reinforced concrete 1930-11-27 1934-05-11

17 FR726510 (A) Flotteurs pouvant être immergés à de grandes profondeurs 1931-01-19 1932-05-30

18 FR711694 (A) Procédé et appareil permettant de fabriquer des bétons et mortiers et plus généralement tous mélanges privés d'air1931-05-28 1931-09-15

19 FR750729 (A) Accouplement élastique 1932-05-14 1933-08-17

20 FR42796 (E) Accouplement élastique 1932-06-01 1933-10-10

21 FR762477 (A) Dalles de revêtement 1933-01-05 1934-04-12

22 FR764495 (A) Procédé de fabrication de pièces ou corps moulés en mortiers ou bétons 1933-02-09 1934-05-22

23 FR764505 (A) Procédé de fabrication de corps creux en béton armé et appareils destinés à sa mise en pratique 1933-02-10 1934-05-23

24 FR781388 (A) Perfectionnements à la fabrication de pièces ou corps moulés en mortiers ou bétons 1934-01-22 1935-05-15

25 FR798203 (A) Dispositif permettant la solidarisation ainsi que la désolidarisation instantanées de deux corps ou deux objets et applicable enparticulier au battage, fonçage ou vissage de pieux 1935-01-11 1936-05-12

26 FR797785 (A) Procédé et dispositif pour l'exécution de constructions monolithes en béton armé 1935-01-11 1936-05-04

27 FR797786 (A) Procédé d'accélération du durcissement des mortiers et bétons 1935-01-15 1936-05-04

28 FR46379 (E) Procédé et appareils particulièrement destinés à la fabrication des pièces en béton armé 1935-01-29 1936-06-02

29 FR46772 (E) Procédé d'accélération du durcissement des mortiers et bétons 1935-04-29 1936-09-11

Freyssinet Patents in France - compiled by Ken Shushkewich of KSI Bridge Engineers in Oct 2013

Patent Priority Patent

Number Date Date

30 FR50665 (E) Improvements in and relating to joint-making packing devices 1938-07-29 1941-02-20

31 not found Dispositif de vérin et ses applications notamment dans les constructions et plus particulièrement dans les constructions en béton armé1938-08-01 1939-08-21

32 FR859903 (A) Dispositif de vérin et ses applications 1939-06-03 1941-01-02

33 FR860164 (A) Perfectionnements aux procédés et appareils de frettage au moyen de fils ou câbles enroulés sous tension et produits frettés ainsi obtenus1939-06-14 1941-01-08

34 FR860440 (A) Système de déversoir de surface à grand débit et faible encombrement 1939-06-23 1941-01-14

35 FR926505 (A) Système d'ancrages de câbles sous tension destinés à la réalisation de constructions en béton précontraint1939-08-26 1947-10-03

36 FR865956 (A) Procédé de fabrication de pièces moulées, notamment de pales d'hélice, en matières fibreuses agglomérées1940-02-19 1941-06-11

37 FR865955 (A) Procédé d'obtention d'ébauches ou de pièces en matières fibro-plastiques comprimées et appareil permettant sa réalisation1940-02-19 1941-06-11

38 FR870070 (A) Dispositif de mise en tension et d'ancrage de câbles convenant en particulier à la réalisation de constructions en béton précontraint 1940-10-28 1942-03-02

39 FR874805 (A) Supports à base immergée, procédé et dispositifs servant à les construire 1941-04-19 1942-08-27

40 FR54603 (E) Système d'ancrages de câbles sous tension destinés à la réalisation de constructions en béton précontraint1941-09-30 1950-07-07

41 FR928258 (A) Procédé et dispositifs de mise en tension d'armatures, notamment des frettes, particulièrement applicables à la réalisation de réservoirs et autres corps creux en béton et produits ainsi obtenus 1943-06-29 1947-11-24

42 FR989666 (A) Constructions et éléments de construction soumis à des contraintes préalables etleurs procédés d'obtention1944-02-24 1951-09-12

43 FR927829 (A) Construction en forme de systèmes articulés ou réticulés, éventuellement haubannées, et cas particulier des pylônes1944-04-22 1947-11-11

44 FR991703 (A) Procédés d'ancrage d'armatures mises en tension et appareils permettant la mise entension et l'ancrage 1944-04-28 1951-10-09

45 FR992210 (A) Procédé et dispositifs d'ancrages d'armatures et pièces munies de tels ancrages 1944-05-26 1951-10-16

46 FR55767 (E) Procédé et dispositifs de mise en tension d'armatures, notamment de frettes, particulièrement applicables à la réalisation de réservoirs et autres corps creux en béton et produits ainsi obtenus 1944-06-08 1952-09-05

47 FR927832 (A) Procédé de réalisation par éléments séparés de constructions foncées, et notamment de pieux, et constructions ainsi obtenues 1944-07-19 1947-11-11

48 FR992934 (A) Système de vannes particulièrement adapté aux usines marémotrices 1944-10-05 1951-10-24

49 FR994012 (A) Câbles destinés à soumettre une matière à des contraintes préalables, leurs procédés de fabrication et leurs modes d'application 1944-12-05 1951-11-09

50 FR995550 (A) Procédé d'amélioration des fils ou tiges d'armatures destinés principalement au béton précontraint et armatures ainsi améliorées 1945-03-23 1951-12-04

51 FR995556 (A) Transporteur à câbles à trajectoire rectiligne ou quasi rectiligne 1945-03-26 1951-12-04

52 FR927833 (A) Dispositifs d'assemblage des rails et de leurs traverses particulièrement applicables aux traverses en béton précontraint1945-04-27 1947-11-11

53 FR928272 (A) Procédé d'ancrage des armatures dans les pièces armées précontraintes et ancrages ainsi réalisés 1945-05-15 1947-11-24

54 FR997871 (A) Procédé de réalisation d'aires en béton de très grandes dimensions pouvant recevoir de fortes charges et application aux pistes d'envol d'avions lourds 1945-08-14 1952-01-11

55 FR1000644 (A) Perfectionnements aux procédés et aux appareils de fabrication des pièces moulées de révolution, en particulier de tuyaux en béton1946-03-18 1952-02-14

56 FR1001281 (A) Procédé d'accroissement de la résistance offerte par les terrains et de mesure précise de ladite résistance et ouvrages faisant application du procédé 1946-04-08 1952-02-21

57 FR1005209 (A) Constructions en béton précontraint et leur procédé de fabrication 1947-06-18 1952-04-08

58 FR1005342 (A) Procédé de réalisation de barrages-réservoirs et barrages ainsi obtenus 1947-07-04 1952-04-09

Freyssinet Patents in France - compiled by Ken Shushkewich of KSI Bridge Engineers in Oct 2013

Patent Priority Patent

Number Date Date

59 FR1006559 (A) Procédé de réalisation de quais en terrain vaseux et quais réalisés selon ce procédé 1948-02-02 1952-04-24

60 FR57308 (E) Procédé de réalisation de barrages-réservoirs et barrages ainsi obtenus 1948-03-16 1953-01-02

61 FR1010101 (A) Dispositif et procédé d'ancrage d'armatures sur les pièces armées 1948-04-27 1952-06-09

62 FR58586 (E) Procédé et dispositif de réalisation de constructions creuses precontraintes radialement applicables en particulier aux travaux souterrains 1948-04-29 1954-01-27

63 FR58593 (E) Procédé de réalisation d'aires en béton de très grandes dimensions pouvant recevoir de fortes charges et application aux pistes d'envol d'avions lourds1948-07-03 1954-01-27

64 FR1010404 (A) Perfectionnements aux vibrateurs électromagnétiques 1948-08-11 1952-06-11

65 FR1011419 (A) Perfectionnements aux câbles destinés à la réalisation de constructions en béton précontraint 1949-02-03 1952-06-23

66 FR60908 (E) Procédé et dispositifs de réalisation de constructions creuses précontraintes radialement applicables en particulier aux travaux souterrains 1949-02-04 1955-02-21

67 FR1000168 (A) Perfectionnement aux gaines pour câbles de mise en précontrainte d'ouvrages en béton 1949-11-08 1952-02-08

68 FR1018442 (A) Procédé et dispositifs de mise à l'eau de corps flottants 1950-05-03 1953-01-07

69 FR1018469 (A) Couvertures, en particulier pour grands espaces tels que hangars d'aviation 1950-05-08 1953-01-08

70 FR1035366 (A) Routes en béton précontraint et leur procédé d'exécution 1951-04-13 1953-08-24

71 FR1048469 (A) Procédé et dispositifs de prise en charge d'efforts sensiblement horizontaux dans les constructions installées en terrain médiocre 1951-09-12 1953-12-22

72 FR1043459 (A) Réservoir enterré en béton précontraint convenant en particulier au stockage deshydrocarbures et son procédé d'obtention 1951-10-04 1953-11-09

73 FR1044267 (A) Dispositif d'assemblage entre une structure porteuse et un support vertical 1951-10-29 1953-11-16

74 FR1063854 (A) Procédé et dispositifs de réalisation de fondations d'ouvrages maritimes 1952-05-24 1954-05-07

75 FR1081727 (A) Vérin hydraulique de mise en tension et d'ancrage d'armatures de précontrainte 1952-07-30 1954-12-22

76 FR1080664 (A) Perfectionnements aux vérins 1953-04-15 1954-12-13

77 FR1080735 (A) Structures composites de béton et d'acier, en particulier structures fléchies 1953-04-22 1954-12-13

78 FR1092412 (A) Aires en béton précontraint et leur procédé de réalisation 1953-10-21 1955-04-21

79 FR66109 (E) Aires en béton précontraint et leur procédé de réalisation 1954-01-06 1956-05-16

80 FR1110285 (A) Dispositif de liaison élastique à un ou plusieurs degrés de liberté 1954-05-25 1956-02-10

81 FR1133932 (A) Procédé et dispositifs pour la construction d'immeubles à multiples étages 1955-06-08 1957-04-03

82 FR1230014 (A) Procédé et dispositifs de pose et de dépose d'une canalisation sous-marine 1959-03-27 1960-09-13

83 FR1234868 (A) Perfectionnements aux canalisations de gaz sous-marines flottant entre le fond et la surface 1959-05-22 1960-10-19

84 FR1238866 (A) Procédé et dispositifs de fabrication en place de tuyaux continus sans joints apparents 1959-07-08 1960-08-19

85 FR1269606 (A) Improvements in or relating to methods for forming members embodying prestressed concrete and members made by such methods1960-03-28 1961-08-18

86 FR1271062 (A) Gazoducs transmarins flottants et leur procédé d'exécution 1960-04-27 1961-09-08

87 FR1344173 (A) Perfectionnements aux poutres en treillis et autres systèmes triangulés en béton,applicables, notamment, aux ponts à grande portée1961-08-25 1963-11-29

Freyssinet Patents in France - compiled by Ken Shushkewich of KSI Bridge Engineers in Oct 2013

Patent Priority Patent

Number Date Date

1 GB338864 (A) Process for the manufacture of articles of reinforced concrete 1928-10-02 1930-11-18

2 GB338934 (A) Process for the manufacture of reinforced concrete 1928-11-19 1930-11-25

3 GB344007 (A) Process for obtaining light structural elements of great strength 1928-11-22 1931-02-23

4 GB364621 (A) Process and apparatus for the manufacture of articles of reinforced concrete 1929-09-03 1932-01-04

5 GB366544 (A) Process and apparatus for the manufacture of moulded articles from mortar or concrete 1929-09-04 1932-02-03

6 GB365290 (A) Process and apparatus for deaeration of hydraulic binding agents and mixtures for use in connection with the manufacture of concrete, agglomerates and artificial stone 1929-12-30 1932-01-21

7 GB376308 (A) Improvements in method of assembling or joining preformed building and paving elements of reinforced concrete1930-04-08 1932-07-08

8 GB367242 (A) Improvements in process and apparatus for manufacturing concretes and mortars and generally all mixtures free from air1930-05-28 1932-02-18

9 GB422741 (A) Improvements in apparatus for manufacturing articles of reinforced concrete 1930-11-27 1935-01-17

10 GB393576 (A) Improvements in process and apparatus for manufacturing pieces of reinforced concrete 1930-11-27 1933-05-26

11 GB393606 (A) Improvements in process for manufacturing pieces of reinforced concrete 1930-11-27 1933-05-26

12 GB431484 (A) Improvements in methods and apparatus for the manufacture of moulded bodies from mortars or concretes1933-02-09 1935-07-09

13 GB433059 (A) Process and apparatus for the manufacture of reinforced concrete hollow bodies 1933-02-10 1935-08-08

14 GB468706 (A) Method and apparatus for the construction of reinforced concrete monolithic structures 1935-01-11 1937-07-09

15 GB453555 (A) Method of accelerating the hardening of mortars and concrete 1935-01-15 1936-09-14

16 GB544003 (A) Improvements in and relating to joint-making packing devices 1938-07-29 1942-03-24

17 GB589019 (A) Improvements in and relating to jack apparatus 1938-08-01 1947-06-10

18 GB619071 (A) Improvements relating to the hooping of bodies with tensioned wire 1939-06-14 1949-03-03

19 GB591218 (A) IMPROVEMENTS IN PROCESSES AND DEVICES FOR ANCHORING WIRES REINFORCING PRESTRESSED CONCRETE STRUCTURES 1939-08-26 1947-08-12

20 GB592839 (A) IMPROVEMENTS IN PROCESSES AND DEVICES FOR ANCHORING WIRES REINFORCING PRE-STRESSED CONCRETE AND ORTHER STRUCTURES 1940-10-28 1947-10-01

21 GB592430 (A) IMPROVEMENTS TO OR RELATING TO DEVICES FOR ANCHORING TENSIONED CABLES FOR PRE-STRESSED CONCRETE CONSTRUCTIONS 1941-09-30 1947-09-17

22 GB629872 (A) Railway sleepers and other articles made of pre-stressed reinforced concrete, and a method of and apparatus for manufacturing such parts 1942-02-14 1949-09-29

23 GB600211 (A) Improvements in or relating to method and means for tensioning reinforcements and products obtained thereby1943-06-29 1948-04-02

24 GB612324 (A) A method of and apparatus for anchoring reinforcements, in pre-stressed concrete andstructures provided with such anchorings 1944-05-26 1948-11-11

25 GB602105 (A) Process for producing by separate elements structures to be driven into the ground, and particularly piles, and structures thus obtained 1944-07-19 1948-05-20

26 GB646708 (A) A reinforcement for use in connection with pre-stressed concrete 1945-03-23 1950-11-29

27 GB636174 (A) A process for manufacturing pre-stressed reinforced concrete members 1945-05-15 1950-04-26

28 GB623729 (A) Method of constructing concrete surfaces adapted to accommodate heavy loads, and applicable more particularly to runways for heavy aircraft1945-08-14 1949-05-23

29 GB628750 (A) Process for the manufacture of pre-stressed concrete articles, particularly railway sleepers and articles thus obtained1946-02-12 1949-09-05

30 GB655129 (A) Improvements in or relating to retaining dams 1948-03-16 1951-07-11

31 GB657738 (A) IMPROVEMENTS IN OR RELATING TO METHODAND MEANS FOR ANCHORING REINFORCEMENTS 1948-04-27 1951-09-26

32 GB707358 (A) Buried reservoir of pre-stressed concrete suitable in particular for storing hydro-carbons and its method of preparation1951-10-04 1954-04-14

33 GB719284 (A) Improvements in assembly systems between a carrier structure and a vertical standardor the like 1951-10-29 1954-12-01

34 GB740172 (A) Improvement in hydraulic jack for putting under tension and anchoring the re-inforcement wires or rods of pre-stressed concrete 1952-07-30 1955-11-09

35 GB740121 (A) Composite structures of concrete and steel, and, in particular, flexed structures 1953-04-22 1955-11-09

36 GB948096 (A) Improvements in or relating to methods for forming members embodying prestressed concrete and members made by such methods 1960-03-28 1964-01-29

Freyssinet Patents in Great Britain - compiled by Ken Shushkewich of KSI Bridge Engineers in Oct 2013

PATENT SPECIFICATION

Oonventlon Date (France): Oct. 2, 7928. 338,864 Application Date (in United Kingdom): June 18, 1929. No. 18,711/29.

O()mplete Accepted: Nov. 18, 7980. 2. J~N i9'" COMPLETE SPECIFICATION.

Process for the Manufacture of Articles of Reinforced Concrete.

1Ve, EUGENE FREYSSI:t-I""ET', a French Citizen, of 28, rue Saint J ames, N euilly­sur-Seine (Seine), France, and JEAN SEAII,Ll!:S, a French Citizen, of 280, Boule-

5 vaI'd Raspail, Paris, :France, do hereby declare the nature of this invention and in what manner the same is to be per­formed, to be particularly described and ascertained in and by the following statement ;-

10 The present invention has for its object a method of manufacturing articles <If reinforced concrete moulded in advance and adapted to be employed or put in posi­tion only after setting and hardening has

15 taken piace, such articles being in the form of posts, girders, plates, railway sleepers, gutters, fences, panels or the like.

It is known that aIter setting and the 20 first hardening which follows setting has

taken place, the roncrete contracts suh~ stantially, and under the actj,on of this

.' contraction is put under tension whilst the 25 reinforcing mmr:bers are compressed.

This may have the 1'(:'sult of creating fis­sures in the concrete members, these being called" contraction fissures ", which may lead to premature fracture qf the articles.

To avoid these contraction fissures it 3() has already been proposed to subject tho

reinforcing members to a preliminary tension which effects longitudinal expan­sion of these reinforcing member·s which is adapted, when the said reinforcing

35 members are released, to compensate for the shortening of the concrete due to contraction.

Apart from this drawback as to con­traction, the reinforced concrete in actual

40 practice has a further drawback which i!'l as follmvs:

1Vhen the degree o£ tension imposed 011

the concrete is .substantial, the deform~· tion of the reinforced concrete is differen t

li5 from that of the reinforcing members alone, and either the concrete is plastic­ally expanded under constant tension, or else it becomes fissured. The result is that the distribution of' the forces or con-

50 straint in ordinary systems of reinf.orced concrete is much less favourable than in a member which has th';)

same resistance both to compression and tension. 55

rrhe applicants have discovered that It is theoretically possible to avoid these drawbacks and to impart to the concreto articles resistances which are much higher than those which can be obtained with the 60 ordinary methods of reinforcing concrete, ,by imparting to them properties identical with those of homogeneous articles eudowed with high resistance to tensinll if certain permanent strains have been 65 set up in the concrete prior to the appli­eation of the forces which the articles are intended to resist.

In this case it is necessary to subjed the reinforcing members, prior to the 70 setting of the concrete, to an initial ten-sion such that after distributing this ten-sion over the ooncrete, once .setting and hardening have taken place and note has been made of the drop in tension due to 75 contraction of the concrete, losses of ten­sion due to the elastic contraction of the concrete under compression forces tl'ans­mitted by the reinforcing members, and losses of tension which may be due to other causes, the metal still retains a 80 residual tension sufficient to transmit to the concrete compression forces of a per~ manent and certain nature and distributed in accordance with a predetermined plan according to the nature of the service 85 which the article in ql1estion is to carry out.

It has already been proposed to form CDnCl'ete poles, beams and the like having 90 reinforcing bars and wires, which are ten­·sioned below their elastic limit, this ten­sion being utilised to compress the con­crete after the concrete has set, but. om invention isdistinguislled in that a high 95 tensile steel, strained substant.ially beyonrl the elastic limit of steel as normally used in reinforced concrete, is used.

rrhe process which forms the subject or the present invention assumes that know- lOt) ledge has been obtained in advance by theDreticul calculations 01' 1)y empirical Olles as to the most dangerous strains to which the article \vill be subjected in use, and the tension necessary in the reinforc- 105 iug members to set up' in the concrete

2 338,864

forces acting in a direction contrary to that of those dangerous forces, as well as the different falls in tension which may Le caused in the reinforcing members by

5 the causes which have just been en umera ted.

The process consists in subjecting the reinforcing members to an initial tension equal to the sum of the falls in tension

10 and to the permanent tension necessary to set up stresses in the concrete.

Naturally, the tensions to be set up in the reinforcing members may be tlxtremely high and may reach arid even

i5 exceed the elastic limits of the metal, and it will therefore be necessary to employ for the reinforcing members metals of very high resistance, of which one could at need artificially increase the elastic limit

20 by drawing 01'· wire drawing. To obtain these initial tensions it will be necessary to employ powerful mechanical means, such as hydraulic jacks or similar devices.

25 Finally, it is necessary to provide on the reinforcing members means to pre­vent their setting relatively to the con­crete when the tension-applying device,,; are released, these means comprising, for

30 example, Jevices for anchoring the rein. forcing memibers in the concrete. In eel'tain exceptional cases the mere adher­ence of the reinforcing members to the concrete might be relied on.

35 One form of construction of the inven-tion is illustrated by way of example in the annexed drawings, in which:-

Fig. 1 shows the invention as applied to a mould £01' a block in the shape of it

~o parallelopiped, this view being a longi­tudinal vertical section.

Fig. 2 is a vertical section on the line 2-2 of Fig. 1.

Fig. 3 i8 a longitudinal transverse se('· 45 tion, showing the moulding of aligned

conical or pyramidal blocks. Figs. 4a and 4b are ve,rtical transverse

sections of Fig. :i, taken on the line 4-4 and corre:>ponding respectively to mem­

pO hers in the form of pyramids and cones. Fig. 5 illustrates the moulding in a

line of a plurality of lon~itudinal mem­. bel'S in a single mould.

Fig. 6 shows a method of keying an UJ anrhol'ing device to a reinforcing

member. Fig. "{ is a vertical longitudinal section

()£ a cylinder adapted for the centrifugal moulding of pipes.

CO Fig. 8 is a section on the line 8-8 of Fig.l.

To carry out the process there is employed a tensioning de,ice for the r£·in­forcing- members, which device may hear

g:; ag'ainst the mould or be intc:'!!;Ial with it or be independent of it and of the devices

for anchoring the reinforcing member in the concrete,

The shape {If the mould merely depend"! upon the shape of the article to he pro- 70' dueed and the tensioning deviee employed, so that if the said tensioning device bear:.; against the mould the latter provides the necessary resi'.ltance.

The device adapted to impart the 75 : initial tension to the reinforcing member before casting may be of any desire!l nature; it is only necessary that it should be capable of producing the required ten~ sioning force. For example, an hydraulie so. or other jack might be employed, or a nut and bolt device (the bolt being inde­pendent or not of the reinforcing' member to he stretched), or a system {)I levers, ·winches, cams, wedges 01' the like. 86

Use could further be made of the linear expansion of the metal by heating it to a suitable temperature, by means of an electric current for example; the tension \vill then be imparted to the metal auto- go. matically when cooling' takes place if the ends of the reinforcing members are suit­ably dampeu during the period of heating.

If the bearing surface is formed by th,~ 95-mould, a plate or member for closing' the t'mds of the mould could, for exampfe, be utilized for this purpose, the tensioning' devices being mounted ()u the plate or closing member. i()()

If the bearing' surface is independent ;1 VI fif tlH:I iilDUld, fixed anchorage points

could, for example, be el1lployed, these anchorage points carrying' the tensioJ1in!,l' de\·ices, between whi.ch ~!le mouhls would fO~ , be plaep(I. as ShC>WIl 1Il 1< 19'5. 1 unfi 2. Jr.

I

these Figs. a and b are the side walls of the mould and a is the bottom plate, the mould heingo tra,veI'~ed by the l'E'inforciug­members 1 and 2, which have anchoring' HO devicps 0, 4, 5 and G, and whieh are sub-jected t{) tension by a suitable device (v"]li('h would be on the right of the Fig. Inn. which is not slle"VI"il), the said rein­forcing memhers being held in this state H5-of tension between two hE'aring blocks A and B by means. for example, of nuts; two dynamometers dl d~ are provided . The bearing surface might, for example, be independent of the mould and in the 1?O form of concrete members prE'pared hi arlvance and arranged inside or {)utside the mould to absorb the forcE'S applied dming· the manufacture. These members would be surrounded by concrete, which is then 125 pourE'rl into the mould or the 111embeI'~ could Le recovE'red alter use. Thev eould also be arranged in the interior' of the mould when ho]]oW" ::>rtir-jo.;;. either tuhuhl' <Jr not, arE' to he llIandndnrefl, 01' they iSG ('ould he arranged ext"Tnully of th(~ hydraulie jaeks.

338,864

The anchoring devices should permit or the transmission of the tensional forces in the metal to the concrete aIter it has set 50 that it is compressed.

5 For enmple, each metal rod could be located in a member of which the surface bearing on the concrete is of suitable dimensions, and which would be made integral with the rod either by welding,

10 or by means of a serew-thread, 01' by means of a key (.Fig. 6 shews the rein torcing member 10 connected to the anchorage device 11 through the medium of a tapering key 12), or by means of

~5 wedges, or by anv other suitable device. A concrete header could be utilised as ft

bearing- surface, this header being previ­ously brought into contact with the rein­forcing member or permanently connected

20 to it. 'fhe bearing surfaces described above need not be limited to a single rod, but could serve to group together all or part of the reinforcing members under tension.

25 It has been found by the present appli-cants that all mechanical anchorage devices could be eliminated and reliance merely be placed upon the dired; anchorage in the concrete which results

30 from ,setting and hardening, which will result in the fixation ,of the reinforcing member und;)r tension in its position by the adherence of the concrete when the lllitial tension has been eliminated. In

35 this case the anchorage would only 'be perfect at a certain distance from th~ ends, which is of no importance in the majority or cases. Known dev~ces, in the form of hooks. clamps or the hke, could

40 be additionally employed to reinforce the direct anchorage. 'rite end or a rod under tension or of a group of rod,s could also be sUl'l'ounded by hoops of concrete for the purpose of reinforcing the anchorage

45 described above, these devices being inter­conner-ted if required.

In the process according to this inven­tion, it is to be no'ti3d that as the concrete is subjected to an initial COT,.l-

50 pres~ion beford being subjected to any load, it is desirable to employ concrete which has a high resistance to compres­sion and consequently to employ any pro­cess adapted to produee this result, either

55 singly or in combination, as follows :-::1) composition of the most suitable

granular Iorm, b) vibration to eUSUI'a complete filling

of the mould, £0 c) centrifugal process producing the

same results and in general any methorl which, during the filling of the moulds. would rau!'<e variations of inertia in th'l t'l.ements rOll'stiiTting the ('OllCl'ete.

1)5 cl) a lmo,Y;1 proee~s of hooping' the con-

crete which would increase its resistance to compression.

It is; to be understood that the sug­getlted methods could be combined with the employment of reinforcing members 70 not under tension and the further employ~ ment of straps in known manner.

One method of carrying out the inven­tion consists in manufacturing several articles simultaneously and arranged in 76 line end to end, as shewn in 1!'igs. 3 and 5. Each length -of the reinforcing mem-,bel' under tension is in this caSe formed by a continuous metal rod stretched at its end by a tensioning device which is 8(}. thus common to several moulds. After the moulds have been filled and the con­crete hardened the rods are cut between each successive mould, and a correspond-ing number of separate articles is thus 85 obtained, it being understood that the necessary anchorage device, if any, had previously bel?n put in place at each end of each successive mould.

When conical or wedged shaped posts 90-are to be produced, the reinforcing mem­bers of several consecutive posts are first of all subjected to tension, the reinforc-ing members are then held at the nal'l'OWest part against a member which at 95 the sama time forms an abutment for the mould (Cl, ez, -e3), the straps, the anchor-ing devices and, if any, the supplementary l'einfol'elng members are placed in pOS1-tion, and the sides of the mould being in 100 place, the concrete is poured in and pre­ferably vibrated. After hardening ha:! taken place the reinforcing members are cut at each end of each post; the articles could equally well be manufactured in all i05 end to end manner iby means of the pro-cess without dividing the mould into com­partments as if a single article of con­siderable length were to be produced, and the concrete and the metal would be sawn HO or divided into sections at the requirecl places, the sections being formed' as she'wn at 13-13 or 14-14 in Fig. 5.

In the case of centrifugal production, the pr;)cess comprising preliminary ten- ii5 sioning of th? reinfOl'ciIlg' uemberfl has a particlllar advantage because it eliminates the disadvantages which arise from the lack of homogeneity of the concrete and also eliminates cracks which are usuall v i2a. pr-oducell and which are probably due t'() unequal shrinkage of the internal anri c:xte1'llal parts. ·of the articles.

Pigs. i alld 8 shew one form 01 thill method ,01 !nanufaeture; VI V 2 V3 V. are ~25 hyul'aulw Jacks adaptea to apply tension to the reilllOl'ein;(' 1J1pmb0rs 17 18, 19 and 'J(l '1" I' 1· C ' . -. jH-' !',\' llH 'cr ('an l'obb In !mrnnl Ill,Ullll' 1'.

'1'0 pl,'n-'lt tll, tellsiolled Jein£ol'eing' 130

338,864

members frum being' visible at the ends of the articles, they could be lodged in suitable bmings which can then be filled with concrete <lr protective material.

5 It should be noted that the process described produces products having entirely new properties in that the com­pression of the concrete and the tension­ing of the reinforcing members of steel

iO can be cOIl1.1lined in such a manner that the concrete, which is never stretched be­yond given limits, is not liable to have fissures when subjected to l{)ad.

in the case of a post in particular it is i5 also possible to obtain with symmetrical

reinforcing members an article which can serve under all circumstances in the same way as a wooden post without any dis­advantage.

20 To obtain the maximum amount of economy from tue process it is desirable to employ concrete having a high lesist­ance to compres-sion, and stael of high resistance and a high limit of elasticity,

25 Also the advantages of-the process can be increased by surrounding the reinfoTcinj! members under tension by a thin spIral thread rolled around them, and by employ­ing steel reinforcing members with a limit

30 of elasticity which has been artificially increased by drawing or wire-drawing.

The regulation of the tension can be carriec1 out in any suitable mahner. In any case the employment ()f hydraulic

35 jacks automatically regulated by the pres­sure employed, ,or dynamometers, or of €.xpansiou by heat will ensure great accuracy in the exact determination of the injtial tension employed. The use of

40 jacks or dynamometers might be limited to the application of tension, a locking device such as a key permitting the ten­sioning device w be put out of action immediately. This arrangement should

45 be preferably employed if the tension is applied by expansion due to heat.

Having ,now pllrticularly described an (1 ascertained the nature of our said inven­tion and in what manner the same is t{)

50 be performed, we declare that what we claim is :-

1. A process of manufacture ()f rein­forced concrete articles, characterised in that reinforcing members of high tensile

55 steel are distributed in the concrete and are ,subjected to an initial tension sub· stantially greater than the elastic limit of steel as normally used in reinforced con­crete, whereby after all shrinking of the

60 concrete due to setting and hardening has taken place, the concrete remains under permanent compressive and the reinforc­ing members under permanent tensile :-.tresses.

65 Z. A proceS3 !lccording to Claim 1, in

which forces for tensioning tne' reinforc-­ing members are combined with the mould and with devices for anchoring' the rein­forcing members in the concrete.

3. In a process according to Claim 1, 'le) the use or not of hydraulic jacks, of nuts and bolts, {)I levers, cams or wedges, of winches, or ()f expansion of the metal by heat, to obtain the initial tension.

4. A process according w Claim lr in 75- : which the application of the tension and the precise regulation of the initial teDsion is e:f!ected by the regulation of the p1!'es-sure of an hydraulic jack or by the read-ings Qf a dynarrwmeter or by expansion at combined Or not with a locking device which permits of the release of the ten­sioning means._

5. In '1 process according to Claim 1, the employment as a bearing surface, 85 when the tension is to be applied, of the mould itself, or of an anchoring deVIce external to the mould.

6. In a process accordiilg t() claim 1 the employment of anchoring devices to 90 transmit the -tensional forces of the metal to the concrete, after setting of the latter, by compression of the concrete, these anchoring devices being ill the form of a member welded, screwed, keyed or 950 wedged to the rod under tension, or a header of concrete already set and rendered integral with the rod by any known means, 01' directly in the concrete ()wing to the setting and hardening of the 100 ;!I',

latter, with or without supplementary devices in the form of hooks, claws or the like, and with or without hoops to rein-force the said anchoring device. ~

7. In a process according to claim 1 the 1()5, employment of concrete which is vibrated or sl.l'bjected t-o centrifugal action, 01' strengthened with hoops, either separately or in combination, to increase the resist~ ance of the concrete to compression. ~i(»

8. In a process ar.cording to claim 1. the use of reinforcing members, either under tension 01' not ill. combinati{)n with reinforcing members under tension.

9. In a process according to claim 1 u'5 the use of _ continuous lengths of a rein­forcing member to reinforce a plurality of articles arranged end to end consecntively in moulds, each of these lengths being subjected to tension by OM single tension- i2() ing device, whilst the metal is only divided into sections after setting and hardening to separate the various articles thus simultaneously reinforced and manu-factured. :1.25-

10. In the application of the process according to claim 1 to the production of wedge-shaped articles the employment of gripping members to bring the reinIorc-ing membe~'s to the desil'ad positions. 13()

338,864 6

11. A process according :to claim 1, in \rhich continuous lengths of reinforcing members are employed and in which a single artic.le .of considerable len(5th is

ts produced without break of contllluity, the concrete and the metal being cut or divided into sections at the desired locality.

12. In a process according to Claim 1 '!i'10 the employment of centrifugal moulds.

13. In a process according to Claim 1 the recessing of the ends of the reinforc­ing members relatively to the concrete and filling or the housings provided £01'

this purpose with concrete or other protec- 15 tive material.

14. In a process according to Claim 1 the use Or a metal, of which the elastic limit is artificially increased by pre-liminary drawing or wire-drawing. 2()

15. Articles manufactured in accord­ance with a process according to Claim 1.

Dated this 18th day of June, 1929. AB EL & IMRAY,

Agents for the Applicants, 30 Southampton Buildings, London,

W.C.2.

Redhill: Printed for His Majesty's StAtionery Office. by Love & M ... lnomson, Ltd.-1080

[This Drawing is a reproduction 01 the Original On ~ reduced scale]

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PAtfENT SPECIFICATION Oonvention Date (France): Nov. 79, 7928. ~l~8 11 934

Applioation Date (in United Kingdom): July 25, 1929, No. 22,898/29:,

(Patent ot Addition to No. 888,864. Oonvention Date (France): Dot. 2,7928,)

Complete Aocepted: Nov. 26, 1930.

COMPLETE SPEOIFICATION.

Process for '~lle lVll1Jnul8'Jcture oE ReiI(Jd1orced Concrew.

We, EUGENE FIiEYSSlNET, 11 French Citizen, ·of 28, rue Saint J ames, N emlly­sUT-Seine (Sdne), France, and JEAN SEAU_LES,' a French. Oitizen, of 280, DauIe-

l) vard Raspail, P,al'ls, France, do hereby declare the nature or this invention and in what manner the same is to be per­formed, to be particularly described and ascertained in and by the following state-

1.0 ment:-Concrete has a high resistance to com­

pression which can ibe considerably in­creased by the applic'.ltian of recent dis­coveries in the dome.in of the manulaciure

i5 of cements and concretes, and a consider­ably smaller resistance to tension, the latter being scarcely Ij12th of the rormer.

In any concrete structure, the existiilg 20 forces c~.use tensioning forces l.vhich are

usually of the same order ,as the fOTces or compression.

These tensioning' forces cause frachiI'e of the COllerete by tensile struin long

25 bel ore its I'esistance to compression has been completely utilised.

To avoid this draviback members, called rrimal'yones, ale employed to absorb the tension fOT(,(>S

30 which are parallel to the axis of the article in question, whilst so·,called secondary reinforcing members are employed to absol'b the tension forces wllicll are not parallel to thi" Hnd which normally

35 result ill owing: to shearing: or torsional 10rces.

'rhe reinrorcing members employed in known systems to reinforce concrete only accomplish the task very incompletely for

40 three mail·. reas)ns. In the first, place, these reinrm'cing

memhers which arc inboduced into the concrete to absol~b certain forces contr.ul'Y to the end desired and owing to the shrink-

65 ing· or the concrete, set up important internal forces; actually the concrete in !:ontracting is put under tension and com­presses the reinforcing membe.rs.

These internal IorcesoIten cause break-50 .age or the concrete '01' so-called contraction

fissures. and in any case they definitely prevent the possibility of relying on the . .

resistance of the concrete to tension in .a certain manner, either as regards the primary 01' the secondary Iorces. 55

In the second place, and even apart from any force of contraction, when the concrete is substantially elongated it is fractured. 'fhe principal rE-sult ot this is that steels of high l'esist.ance and capable. 60 of considerable extension cannot be utilised in reinforcing concrete.

In the main specification, whilst taking into account the fact previously described, it was. specified that high tensile steel 65 reinforcing members in the concrete articles .are subjected to an initial tension before setting and hardening took place, in such manne!' that in th3 reinforced con­crete finally obtained the metal was 70 already under tension an d the concrete under compression to a considerable de­gree, independently of any forces due to the load and excess load.

According to this invention, ,ve m.ake '161 general this method or the application in the finished article of permanent artificial tensional to the metal, and per­m~ment artificial compression constraint to the concrete, which constraints 00nQ 80 stitute a system of internal forces in the articles treated, having no reslllianh force nor exterior reaction and capable of act-ing' in one. tw;) or three directions.

The reinforcing members may be put 85 under tension not only prior t·o setting and hardening but also during or alter this.

This method of heatmenl results in imparting to articles which have been sub­jected to it entirely new important and ~o surprising properties which are as follows:

1) According to the present invention, the nature or the internally applied forces -that is concrete in tension and steel in 95 compression-which renders the concrete fragile by putting it in a state of equili­brium near the breakage point is reversed. The resistance of the concrete to tension the?- becomes a J?ositive quality UP)1l 100 whICh absolute rehance can be placed· . . :upture no longer being able to occur, a~ In the case of all the elements· generally used in construction when, the forces o~

rupture being exceeded, this occurs under considerable resistance against shearing, the actioQ of external forces. In the and thus renders the transverse or case or articles thus treated the resistance seoondary aI'matures unnecess.a~y, o~'.per­of the concrete to ·tension can rightly be mits them to be c()nsiderably sImplIfied.

5 included in the resistance forcel>, provided The experiments of the applicants as 70 , that the deformation of the stretched con- regards torsion in hollow unreinforced

crete does not exceed the li.'1lits which ex- cylinders have proved that the. resistance perience has indic.ated. to fracture due to tension resulting from

2) It is possible to employ steels of shearing forces reaches 20 kgs. for a cer-10 very high resistance up to their elastic tain kind of concrete. The presence of ,75

limit. It is easy to obtain steels ha'ving longitudinal reinforcing members by -an elastic limit or 160 kgs., that is wire- creating ten3ional furces due to C(lntrac­drawn rods, instead of 24 kgs. which is tion lowers this figure by at least 5 kgs. the ordinary figl.<re, and this limit might A.ninitiaL cpmpl'ession of 100 kgs. per

t5 be extended even further. square centimetre acting on the axis of 80 3) The concrete being previously com-, the cylinders raises it by 50, a figure

'Pressed, the articles when subjected to which renders possible a. strain of 15 kgs. !bending act as homogeneous article& as per square centimetre, or substantially so, long as the bending force does not exceed without the use of transverse reinforcing

20 the initial compression imparte9. to the members. 85 ooncrete and increased by the re.sistance In cases where shearing accompanies

"- of the latter to tension. :bending it should be noted that the rate , The result of this is that in spite of the of maximum displacement only exists

initial compression the total compressive opposite the neutral material in the case 25 force, which includes initial compression of an article treated in accordance with 90 c and compression due to bending, is in cer- this invention, and decreases very rapidly - tain cases considerably lower than the both in the zone affected and in the zone

force of compression due to bending alone, of compression, whilst in the case of an which would be existent in an identical article reinforced by known means and

80 article not treated in this manner. ' showing fissures .it only decr:eas~s in th.e 95 ;." Figs. 1-12 of the accompanying draw~ rone of compreSSlOn and retams Its maXi-

ings illustrate. the invention. mum value !between the neutral material .Moreover, the compressive forces set up and the reinforcing- members. This is one

in accordance with this invention need of the advantages of the present inven- ~ 30 also not be uniform. In .the case or a T tion. The amount of slipping of the 1'e- iOQ

beam (Figs. 1 and 2) having a group of inforcing members involves ,1 similnr . primary reinforcing members A, and a advantage, the displacement value (£ the

further group of primary reinforcing reinforcing members in articles treated l:r.l.:.embers B, the reinforcing members A by the present process making allowance

40 and B could be handled in 811Ch a manner for the anchorage forces, giving rise to lOO that the C(lncrete is initially strongly figures very much lower than those which .

. compressed in the zone near B and result in the case of an article not so stretched in the zone near A. The design treated. of such an article allowing for existing A.nother advantage derived from the

45 internal forces is of considerable advan- pr,esent invention is that owing to the HO ,. tage as regards the compressive limits compression of the concrete very superior

~ reached at a given moment, and increases and remarkable water-tight properties .1.re the resistance or the article t-o rupture by obtained in many cases either !rom the bending; experience has confirmed the point of view of the life .of the

50 e:;pectations of the paper calculations. . installation or from the point of it5 4) In any concrete article reinforced by view of its utilisation. In addi~

'known processes and sl1!bjected to a simple tion to these main advantages there is also shearing force, tensions caused even by the ability to utilil'Je in the normal manner the existence of the shearing f.orce deve.lop the high resistance to compression of

55 and cause fracture of the article. modem concretes, and more particularly i2Q Also the presence of tensional forces due concretes which have been subjected to

to contraction or be.nding which are added vibration or centrifugal force, because ~n to the tensions caused by shearing render the case of a reinforced concrete in accord­the resistance of the concrete to shearing ance with the present invention the initial

60 pI'actically nil or at least very small. and cO,mpression can be increased within the i25. render the presence'Qf seoondary shearing limits allowed by this high resistance, and

. reinforcing members absolutely neCe~8al'y, the advantages of the process are accord~ while the existence of internal compression ingly increased. ' in the concrete. in accordance with the The means adapted to impart the initial

(to invention imparts to it a definite and tension to the reinforcing memlbers may ~

338,934 3

be of any suitable kind; it is only neces~ 1ll3.ry to permit of the pr,oduction of the necessary tensional forces. For e.xample, an hydraulic or other jack might be

the mould, which are not shown jn Fig. 6 of the drawings, abut.

The reinforcing membel's might consist

};) employed, or a nut and bolt device, the screw-threaded member being independent or not of the reinforcing member to be subjected to tension, or a system of levers, winche.s, cams, wedges or the like.

of closed rings, soldered ,or Lound.ed to­gether, and in "this case the. header would .70 advantageously be in the form of a hollow roller. rrhe reinforcing members could then Ibe simply passed oyer the roller, which would serve to apply the tension. A contimwus spiral roller, us seen in Fig. ,5 7 could be used with an anchoring device.

10 Use might even be made or the torsion on itself of .a rod already held in posi­tion, or the mutual torsi-on of several rods already anchored in position. The same result could be obtained by dividing a

i5 plurality of bal's 33, which were originally parallel to one another, and uniting them by junction members 34 so that they form broken lines as shown in Fig. 3.

'In the case of an article of variable stress approximating to a solid ot equal resistance, those of the reinforcing mem­bers which need not be continuous oyer 80 the whole article might be in the form of anchorages at desired parts of the frame,

Use might also be made, by the linear 20 expansion, of the metal by heating it to

& suitable temperature, by means of an ~lectric current £'01' example.

In one construction the constructional parts already existing can be utilised as an

25 attachment point for the, tensioning devices. A bearing surface independent of the mould or of the £rame might, for example, form part of concrete elements previously manufactured, and which could

30 be thrown away or used again. Jacks 4 might be located in the interior of the

articles, or on the exterior in the case of the production of hollow bodies

In the case of a beam this might be 35 channel shaped, as shown at 35, Fig. 4,

and the jack 36 housed in the hollow por~ 'lion of the beam and the latter strengthened with bars 37 placed under tension Iby any me.ans whatever to avoid buckling of the

40 beam. Each metal rod could be caused to

engage a member., of which the surface that bears on the concrete is suitably designed, and which can be rendered

45 integral with the rod either by welding or a screw-thread or key, or in any other suit­able device.

A concrete header could also be employed as an anchoring device, this

50 header being also connected to the rein­forcing member or rendered. solid with it. The he.ader could obviously be employed as a connecting piece for one reinforcing member or a plurality of them.

55 For example, if it is desired to produce articles with symmetrical reinf{)rcing members, use. could be made or ,a rein­forcing member anchored to two concrete headers 39 (Fig. 5), and tensioning could

60 be effected by acting on the two headers which could form abutments for the mould. A perforation 40 could be formed in the header surrace enabling tension to be applied through the medium of a re-

65 movable ,axle, on which two surfaces of

and tension ,applied at another part of the mould. A suitable device would in this case consist in securing the reinforc- 85 ing' member to metal washers 41 mounted on shafts 42 which are preferably slightly conical and are themselves mounted in the wall of the mould 43 (Fig. 8). The 90 washers will then serve as members for distributing pressure on the concrete after the two axles have been removed at the time of removal from the mould.

It has been found by the inventors that all mechanical anchoring devices can be 95 eliminated Ih.Y the mere direct anchoring in the concrete, which is the result of setting and hardening, which by the mere adherence of the concrete will hold in place a reinforcing member under tension ~.QQ when the initial tension Ot manufacture has been eliminated, this result being due to creeping of the metal in the concrete due to its expansion ,and contraction in ":I;nt!. the zone near its ends. -~

Anchorage can be improved by the empl,oyment of known devices in the form of hooks, claws and the like. The end of a rod uuder tension or of a group of rods no could be surrounded by a suitable band or" -concrete to prevent creeping of these devices. Or means c,ould naturallv be combined together or assocjated. "

In certain cases, a triple constraint is advisable in order to impart compression 115 to the concrete in all directi{)ns.

For this purpose various processes could naturally be emp10yed; for example:

Bands or stirrups could ba arranCl'ed 120 around the longitudinal reinforcing m~m-" -Iber under tension. At the moment whea the tension {)f the reinforcing members is to be applied to the concrete the resuitinCl' compression would. bri~g about. creeping t~ 10£ t~e concrete, whICh In turn wIll impart ---" tenSIOn to the hands or stirrups.

This latter process could further be e~ployed to impart tension in one direc-tIOn ,only. F'or exa~ple, in a machine,~~ such as that shown III Fig. 9, the (lOn ..

338,934

crete member adapted to serve as a rail­way sleeper could be introduced. rrhis article is reinforced with longitudinall'ods

, 44, and it is hollowed {)ut axially Into '5 this hollow portion a rubber pouch 45 is

inserted, to , .. hi ch pouch a high preSSllre of the nature of 1000 kgs. per sqUl:U8

centimetre for example, can be imparted, whilst a similar pressure is applied to an

iO external rubber pouch 46. The pressure {)n the upper piston 47 is, on the (lther hand, progressively diminished: in these conditions the concrete is plastically de­formed longitudinally within a limit

i5 which c.an ba regulated. The transverse deformation is then obtained by reducing the pressure in the external pOllen. The deformations obtained are permanent and have the consequence that all the l'ein-

20 forcing members are subjected to tension with consequential compression '0£ the con­crete' in all directions.

The manufacture of reinforced concrete in conformity with the present process

25 starting with concrete already manufac­tured without reinforcing members (or comprising' reinforcing members corre­sponding to other conditions than those aimed at by the present invention) is or.

:30 c.onsiderable importance because the posi­tioning' oy the artrcle a£ ter the reinforcing member has be.en placed under tension in ar::cordance with the present. invt:lnti{)ll will often b(~ a more simple anti easier ope:w-

"35 tion th:Ul the application of tension be10re setting and hurdening_. This method o£ carrying out the in7ention is made P0ti­

sible because as previously explained, the secondary reinforcing members or the

4:0 struts can be. eliminated, the reinforced concrete in conformity v,'ith the present invention having itself properties or resistance to shearing w 1ioh are only acquired by concrete reinforced in Hle

45 ordinary way by. the. use o~ the said secondary reinforcmg members III the con­crete.

For example, a post could be manu­factured by leaving housings for the metal

50 either in grooves or in pipes. After thEl metal, in the form or bars

or cables for example, has been placed in position and subjected to tension, the grooves or pipes c{)uld be filled with

ID cement or protective material such as asphalt. Th~ post could then be in the form or a

hollow non-reinforced member and tension _ applied by a· bar of metal placed on the

60 axis and putting the concrete in a state of compression by means for example of two plates which ,apply the pressure to the two ends of the hollow member.

In the case o(grooves (Figs. 10 and 11) ,65 the. reinforcing memoer might for example

be in the form Qf two metal rings 47 .and 48 'placed in position when heated, two. opposite g1100ves being c<?nnec.ted at their apices and bases by a J1.111ctlOn member forming an arch and '\vhic.:h might in uchli- 'i0 tion comprise a metal bearing surface.

In the. case of pipes (Fig. 12) it is simple to insert and .apply tenSi(lll 1.0 each steel rod in its tube and to transmit the pressure in the concrete to a suitable bear- 75 ing member.

The reinforcing member!; can in addi­tionequally well be pla~ed in posit~on during manufacture y,-hllst pl'e\entmg them from adhering to the concerete by 80 any suitable me.an:; la covering of paper) paraffin (lr the like). After setting', hardening. and withdrawal of the concrete tension is applied to the reinforcing mem­bers which will be in position but under 85 restraint.

In one construction, articles not rein­forced or provided with special reinforce­ments might even be employed and sup­plied in accordance ',vith the im-ention 90 with reinforcing members which, owing to the.ir tension, will induce a state Q£ permanent cOlllpresaion in the concrete.

For example, a receptacle v,-ould con­sist of a cylindrical structure either not 95 l'einforced or only slightly so ; on the outer wall of this will be uni-lnge.d bv me~UlS descrihed a band under ten:;ion ~~-hich is protected with a coating' of cement.

When reinforced concrete is proG.ttc6d 100 aecording to the present proCESS starling from COlicrete already mairuIf:dul'ed \',-ich· out reinforcing melubers (01' cOPl)1!'ising l'einfol'ci.ng illE:lllbei& CQi rE'5TJtmdi llg (0

other sil'uctures than tl:ose (;jmed .at by 105 the pre.sent invention), it is possible to ptochfce- a whole by nieulls of ele­ments arranged ill a suitable manner rela­tively to {lue anothel' and plac<:!d under compression by reinforcing members under HO tension "hich render the said elements integral with one another and gi-;-c them the properties pI'eviously described. In this ease no usa is made of the l'esis"b:mce of the concrete to tension, but the other ii5 properties indicated are retajned (the utilisation of the metal to its elastic limit and the use of its residance to shearing which ~ created bv compression). '

For examule, a po;t could be construct.ed 12$1 which is ea7sily transportahle in sections by means o()£ segments arnmged end to end for mounting and connected together by metal ties which compress them one against the other. i2\>.. W~th the process which has just been

descnbed there could also be combined the use of reinforcing members not under tension and of complementary struts· to increase if necessary the advant~ges 130

338~_934

,obtained from this invention, any known eleme.nts which are welded, screwed, keyed pl'OCe~8 which enables concrete with aQr :wedged. to..the .rod under tension, or maximum resistance to compression to be' in the form of a 'concrete h-eader which o.btainerl can be employed (gr,anular treat- does or does not serve for the applic,ation

5 ment, vibration, centrifugal action, hoop- of tension and is l'endel'ed integral with 70 ing', etc.). the stretched reinforcing member by the

It is to hi! Jjoted that compression {)f p!()cesses described (simple anchorage, the ~oncI'ete and tensioning .0£ the rein- fitting into rings, rolling in plain or in forcing' membe1'l.l can be combined in such counter spii'aIs etc-) or by the direct

10 manner th.at the concrete is never under a anchorage resulting from the setting and 75 tensioning' load beyond a given limit, and hardening of the concrete itself with or this will result in articles which will not without supplementary devices in the form develop cracks under prevailing' condi- of hooks, claws or the like, and with or tions. without a hooping member adapted to rein_

i5 Having now particularly described and force the said direct anchorage. 80 ascertained the nature of our said inven- 7. In a process according to Claims 1 tion and in what manner the same is to and 2, the use of reinf{)I'cing members sub-be performed, we declare that what we jected to tension afterwards on or in the claim is:- articles, elements or parts of the concrete

20 1. A modification of or improvement in device previously produced without a re- 85 the process described in Specification No. inforcing member (01' with reinforcing 18,711 of 1929 (Serial No. 338,864), in members confor.ning to requirements which high tensile steel reinforcing mem- other th.an those to which the present bel'S, subjected to an initial tension sub- invention is applicable), these reinforcing

25 stantially greater than that normally used members being introduced during manu- 90 for reinforcing concrete, are employed in faQture, but being in this case protected the manufacture of l'einforced concrete ag'ainst the ,adherence of the. concrete structures. which permits tension to be applied to

2. A process for the manufacture of them afterwards as described. 30 reinforced concrete structures according to 8. In the appHcatio:n of the invention 95

Claim 1, characterised in that the rein- to the process covere.d by Claims 1 and 2, forcing members are subjected to tension the transformation into a single whole of not only before. setting and hardening, but sep.arate elementary members joined also during' -or after setting. together and adapted to resist sheiaring

35 3. A process according to Claims 1 and owing to the fact that they are in a state 100 2, in which a fmme or moulcl is com- {)f compression lby means of reinforcing :bined with a device for applying tension members under tension as described. to the reinforcing members and a device 9. A process according to Claims 1 and 101' anchoring these members in the con- 2, in which the. metal rings temporarily

40 crete. fixed to desired points by means of mOT- 105 4. A process according to Claims 1 and able axles serVG as ',anchorages.

2, in which tension is applied by means 10. A process according to Claims 1 and of jacks which are hydraulic or not, of 2, in which the concretes employed are

45 screws, or l?vers, of winches or cams or subjected to vibration 01' centrifugal force, wedges. or by means of the torsion of the or are provided with hoops to increase UO metal or by means of its expansion owing their resistance to compression either col-to heat. ' lectivelyor separately.

5. A process according to Claims 1 and 11. A process according to Claims 1 2, in which the bearing surface at which and 2-. in which reinforcing members

50 tension is applied to the metal is the mould which are not subjected to tension and H5 or exte.rnal anchor.age or compressed meril- strut members oonnected to them ,are bel'S arranged in the mould or outside it employed with the rein:forcing memhers and adapted to be used only once 01' to be which are subjected to tension in accord-

55 recovered, or ~s a concrete article itseH ance with the invention. previously manufactured and subjected 1'2. A proce'lS according to Claims 1 and 1::0 to compression by the reinforcing members 2, in which the steel employed has a. hig>h connected together .and placed under ten- e~asticity artificially inC'reased by pi'e­sion, these reinforcing members them- VlOUS drawing or wire-drawing.

60 selves being', if desired, encased in con- 13. A proce.1S according- to Claims 1-crete or protective material. 12, in which the concrete is subjected to 125

6. A nrocess according to Claims 1 amI compression in every direction llT'usino' at 2, in which thE\ anchorage devires serve the time of manufacture reinforcinO' n~m-to transmit the tensional force of the metal bel'S stretched in 'one direction . .aI~d l'ein-

65 to the concrete by compressing it, these forcing members or hoops which are not: anchorage devices being in the £.orm of stretched in the other directions, the latter i3Q

6 338,934:

ibeing subjected to tension by creeping of the concrete when it is put into a state of compression by the rein£orcing members under tension.

5 14. A process according to Claims 1-13, in which the compression of the con­crete and the tensioning of the reinforc­ing members.in one direction is effected

by means of t.he plastic deformation of the reinforced concrete. under the influence of 10 varying compressi'on forces as described.

Dated this 25th day of July, 1929. ABEL & IMRAY,

Agents for the Applicants, 30, Southampton Buildings, London,

W.O.2.

Redhill ~ Printet1. for His Majesty's Stationery Office, by Love & MaIcomaon. Ltd.-l980.

338,934 C MPLETE SPECIFICATION I 1 SHEET

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'i")j~TENT SPECIFICATION

CQnrention Date (France): Sept. 8, I e29. 364,621 Application Date (in United Kingdom): Sept. 8, 7980. No. 26,32b /30,

(Patent of Addition to No. 338,864: dated Oct. 2, 7928.)

Complete Accepted: Jan. 4, 1932.

UO~lPLETE tiPEOIFICATION.

Process and Apparatus for the 1'I.lanufacture of Articles of Reinforced Concrete;.

Weo, Et;'G.k~·E JrnEYSSIXET, a French Citizen, of :2~, Hue Saint J ames, X eui11:y­slll'-tieille, (tieine), :France, illnd JE.:\S tiKULLES, t\ ]Trench Citizen, of 280, Bouie-

5 yard Uaspail, Paris, France, do hereby declare the nature of this inyention and in wltat munner the same is to be per­fOl'llled, to be particularly described and aseertained in and by the following state-

lO lllent:-'rite present invention consists in im­

pl'UYelllPnts in or modifications of the in­vention de:;crihed in our prior Specifica­tion X o. 338,864.

i5 III our main specification we huye dest'rihe<l a process for the munufacture of articles of reinforced concrete in "hich reinforcing' members, of high tensile steel and strained suhstantialh- lleYond

20 the elastic limit 'of steel as llormullr 'used in reinfol'C'ed concrete, lUre subjected to tl preliminary tension in the neighbour­hood of their elastic lIilllit in such manner as to h.'lllSmit to the concrete which has

25 set ancI hardened, l1ig-It and permanent compression forces. In rel'hlin cuses, howeyer, it is llecessary to stretch rein­forcing members ,dJieh ure shorter than the mould, or, speaking generally, to grip

30 the l'eillfol'eillg 'members at intermediate points to subject them to tension.

'fhe present application has for its ob­je("'/; deyices which permit of soh-ing this pl'Olllem. These de,ices f:omprise 'f?ssen-

35 ,1ia1.1;\' a wedge or other gripping- 'elf?ment .whIch trayerses the wall of the mould through IUn opening formed at a suitable point in .the said ,,~all and is adaptef/ to grip the reinforring melllher, this wedo'e

. 40 Iml!lg displacealle aJlong the openillQ' l~~T ~llealJs of (In element ('npahle of «e,-plop­lng c!0llsidel'ul1Je force. suC'h as a ~(,l'ew. wedge or the like, and aclantecl to bear og-ainst the w~all of the mould.

45 .It is desirallle to employ in comhination WIth. such l} (}E'viC'e l'einforring- lnpmhers !ll'oYHlecl wltll projertioll s wlliph Inn~' he lIlif'g'ral or llot. ana which fncilitatp. tIle .aption of tIle l'einforeing' llH'1ll her. In

r Prir.e 1/-J

the main specification it lIaS been stated 50 that these projections can be applied to the reinforcing memuers by welding, Iwrewing', keying or wedging. .

The lllveution is jHustrated III the annexed drawings, in which:- 55

l!'ig. 1 shows a bar formed with pro­jections.

l!'ig', ~ shows a bar with all enlarged eud, and

.Fig. ;3 shows a bur with ~l metal block 60 clamped to it,

'fIte use of un attached member cau be avoided by forgIng, swaging or upset­ting etc. the member, either in the hot or eolct state, so as to form enlurgements 1 65 of !Ully shape on the bar 2 (Fig. 1) or to provide an enlarged end 3 (ll'ig. 2). It is obvious that the enlargements should not be ,abrupt, in order to avoid the formation of weak places in the hal' : the.Y ic' should t,lso have the form most suitable for applying the tension and for anchor~ ing.

A satisfaetol'Y method of anchoring by lIlNIllS of an aHadlf.'d memller consists ill ,75 horing and damping' n pipce of metal·to t he hal' to be tensioneod. For exump'le, a metal bloC'1\ 4 (l"i~. :\) with n horing i) of thediametel' of the wire to he an('hol'edc'an he clampecl to it. hy a screw or other suit- 80' ahle mcans. '1'he part of the wire en­gageel hy the block can be rong'hened, (:01'-

1'1lgutf?Cl' et!', t·o increase the Ilulhereuee. ()hvj()nsl~r, tlle different nrrang-cmenhl

f'olllcl he ('ol1lhineil Us showl! for example 85 in }!'iQ·s. 4 and 5.

(t has heen fOHJlcl also that ~ convenient. 1l1'()c'e:'1S for C'arr~'ing out the illvlmtioll c'omli;;i':-; ill using ns the almtment for the jPllsiollillg' apparntus the same or ilimilar 90 'Hrl'UlIg'Plllents ~s for the uu(']\Oring. The llpp1i('ntioll 0.£ ihe ten:'1ion neC'essiiatps in faet a trnetive'foree on tlle wire of the ~ame ol'deor aR that whie'll is neecssnrv to !;UPpOl't the an('hol'illg' appnrahls, alld ~'on- 95 ~f'rtllPlln.V the anchoring' applll'ahlS ('ml al:"o h~lllSec1 for gripping' the wire, so tJlUt it. sCl'YPS iwo JlllrpOSf?S, first to aJlpJ~' Ihn

2 364,621

ten~ioll and '<lftel'wul'ds the anehol'ing, or t\Yo or more points lllay be pl'o'dded eaeh havi.ng its own separate function, SOllie ~ernng for the applicntion of the tension

ti and other:; for the ~llchoring. In this method, and in .all the cases

in whirl! the movement of the tension pro­<luting deviee is limited, it is convenient to utllise a wire or bar provided Trith

10 several points of attachment, and to re­latoiwly :::p:lC'e these apart at a distance less than the path {)f the tensioning mem­her, ~he points cOll~tituting', ~\s previously llH'utlOned, uncho1'l1lg' points.

ij The ten:;ion in the ctlse in which the abutments are on the mould. can be con­TenientIy applied by means of sectol'S (memhers formed as wetlgei'l, helices 01'

('i1'('ula1' ares) whieh are displaced either ~o at right angles or pamllel to the axis of

the wire to be siretr'heel or other suitable devices,

In thE' 3l'l'UngPlllent (reprE'sented in • section by the -side view in Fig. ()

23 and in end "dew in Fig. 7) the tension is applied to the bar 2 pro­-drIed 'rith enhl1'gements 1 by means of an arcuate member G. This member is proyidecl with a wedge 7 gripping the

30 bar ~! h;v a fork 8 and ad.apted to he dis­plaeed in an :aperture 9ro. provided in the wall 9 of the 1ll0t11d (A indieates the in­terior of the mould). The member (l i~ displaced br a push rod 10 actuated hy

35 a screw 11 rotated h:;.' ,.means of a aqual'€, llenel 12 ~nd threaded in a nut 13 fixefl to a ,mll 14 a hutting' ag'ainst the mould.

In a modification (Fig'. 8) the memller ];j g'l'ippinQ' the hal' Z is tensioned in 1he

40 clireetion FI hy the simultaneous clisTlhn'-, lllent of the wedge::; 1 (j and 17 in tIle direc­

tion F2, werlges ",hie11 almt against pHrts 18 and 19 pl'oyided hl the wan of the mould. l'he pl'actic,al ponstruction of this

4:'i modification is shown in seetion in Fig'. 9 _and in plan in Fig. 10. The member 15

('onsists of :a hal' cQrrving at one enel a f()l'k whir11 grips the bu'1' 2: .and tlw wed!!eR Hi and 17 ha,ea circular form. "rIle

~() member Ii5 abuts ag'aiust a mo,.ahle sup­port 20 takinQ' up the applierl tension flna pre,enting' the said member from rock­in!!'. This arrangement combines all the advantages of precision at the moment of

55 applying- the tE'nsion WitllOut thedifficua­_ tief! 'of the preparatol';\" operations.

It may be iemarked tllUt the use of the sertol'~, 'wedg-es or slirles described. llav­

'60 ill'!: their supporting points on the mould, allows the bars to be stretched between

: any two poiutR of the mould without the wire pxt!'nrliug' beyond tlle mould.

InstE'ad of sing-Ie reinforcing mem l)ers 65 separate on!'s arranged fnd tn end and ip­

tercnnlleC'tE'fl h~' elem('nts whiC'h trllllilmlt

the tension from one member to another may be employed.

ill the parent sIleeificatioll it is pro­posed, ill ('al'l'.ving' out the iuYention, to u:;e high tenslle steel straiu('d substan- 70 tially be.yond the elastic limit of steel us normully used ill reinforeed eoncl'ete, the tensile strength being artificially aug­llu'llterl by preliminary dnming' or roll­ing': it has been fOlllld thut steel cau be 75 uclliserl u(h-.antag'eous.ly with its l'eSistallee automatically augmented In· tempering' and annealing, and by this !11eans Femal'k~ able results ~lS regards cost anrl llghtlless ean 01.' obtailled. In fact, 011 the DUE! llun!! the properties of the tempered steel 80 eun be utilised to the best advantage since the pl'f.'liminary tension enabl~s m-emlJers 1{) be obtained of which the deformations (11'1.' ~xtl'elllely reduced Ul:cler loael, as tlle . 85 HpphNl!ltS have proved III the ('oursI.' of their experiments, and on the other hand the fact 'of u6ilig tIie metal in t('nsion and Us elements pra-ctically roe.tiline:!r allow'! the use of tempored hal'S Sl1l('e they have 90 not to he fashioned or 'Yol'li:ed as in known reinforcement methods.

[t is impor1ant to control the opel'U­tinll:! wldeh SPlTe the pm-pose of trHnsmit­tillg' to the concrete hy compressing; it the 95 tensional forces of the reinforcing' mem­bers. Actuall~r, if first of all a sing-In reinforcing' mem l)e1' is released from ten­sion, whilst the others are under tension, only the COIu'rete in the neig'1111flUl'hood of 100 this l'einfol'rillg' member will he COIll­Ilressec1, and in cOllseqne,JlPP of this 10ea]-isecl f01'('e the artiele wou:l£1 he snhjeci('ll to undesirnhle deformation. To ayoid thi::; drawhuek. a prop-re::siye ndioll might 105 h.e pro(luC'erl by slightly l:eduring' the tell­slon of the firilt l'eirdol'ClIlg llH'lllhel' nIlIl then or the seC'onrl. nneI So on, and tll(,11 further l'eduein!l: the tension of tll!' :lhs1 memher ~mc1 again of the sel'ond. lUlu1 1'10 1HI on. Th!,l'ewoulcl tlwn ne,er 1)e iflll exces-sive difference betwt"en the tensions of two l'eillfol'ring llH-'tnhe::::-:.

Silllultuneou:-; removal of all the l'eill­Turping members could then he f'ffecterl h~' 11,) acting- at the same tiIlle on all the tension­produC'illg' deyices. This method of operation is f'nti1'ely possihle if. for (lxampll'. there is elllnlop·d n ten!'lioning deyiC'(-' common to ull the l'einfo1'eing' i~O members. ' Finan~ .. when thA eoncrete is ~E-'t unl!

lHll'dened it 1ms a certain adhel'PlIC'e to thl' mould. ",hi('h adherence opnoses t11(, de- _ formation whi(·It ille relaxed reinforC'ill!.!' i!?::. members fend to produce by. f'Olnpre::;l'ling' tllp ('ol1rr!'te.

The wec1!re '/ of Fh'. () nnrl the wpd~rf' Hi of Fig. 9 nre removed aft!"), spttiJl!!' .of thp ('ollrretf h;v ~trikiIlg' them, for r~-- 1;:[\

9

! .. 21 : ~

/J'his Drawing is a reprodaclJiJn 01' lIu! Origutal on a reduced SCalR j

o o ~ " . r m -I m en

" m 9 ." (5

~ o z

i f '-' ~ -~ ~ ;' . ., a.L-______________________________________________________ ~~

364,621 COMPLETE SPECIFICATION

, SHEET

, ,. t :~p,

,

ChArles' flud ltd. Phot.o litho

PATENT SPECIFICATION 589,019

Convention Dates (France)

Aug. I, 1938. June 3, 1939.

Corresponding ApplIt;atlQns In United Kingdom .

No. 21968/39} dated July 28 1939.-No. 21969/39 '

(One Complete Specification left under Section 91 (2) of the Patents and Designs Acts, 1907 to 1942.). '

Specification Accepted: June 10, 1947.

COlYIPLETE SPECIFICATION

Improvements in and reh~.ting to jack Apparatus-

I, EUGENE FREYSSINET, a citizen o£the Republic of France, {)f 28, Rue Saint­James, N euilly-sur-Seine, Seine Depart­ment, France, do hereby declare thc

5 nature of this invention and in- what manner the same is to be . performed, J() be particularly. described, and ascertained in and by the following statement :

1'he present invention -,- concerns 10 apparatus intended t{) act as- jacks.

'1'he chief object of the present inven­tion is to provide an apparatus of this kind which, whilst of an extremely small volume, permits {)f exerting very high

15 pressures, such as those which are .neces­sary, in particular, for civil engineering, such an apparatus being simple to manu­facture and of low cost.

The apparatus according to the. inven-20 tion essentially includes a kind of bag of

malleable metal, which includes two plates, forming the bearing faces of the apparatus and connected together, along their edges, by welded joints, _0r other

25 fluid-tig-ht joints, thr{)ugh the medium of a cylindrical ()r tore-shaped metal element which enables the plates to move with respect to each other without being deformed when the pressure of the fluid

30 fed into the· bag is modified. A conduit fixed on the cylindrical. or tore-shaped element or to any other suitable part of the apparatus permits of injecting liquid into the bag.

35 Several methods of applications of such aEparatus will' be hereinafter set forth. ~According to an important feature of

the present invention, when the apparatus is to be left in a permanent manner in a

4Q piece of work so as t{) create permanent forces' therein, the apparatus is inflated with a material whichis injected in the liquid state and which solidifies sub­sequently without· substantialval'iation

45 of volume and remains in the solid state under normal conditions of use, such a matter consisting, for instance ,0£ cement, a fusible matter ()r a suitable

synthetic resin. Va.rious applications ()f the apparatus, 50

according to the invention, will be herein­after explained.

Other features of the present invention will result from the following detailed description of some specific embodiments 55 thereof.

Preferred embodiments of the present invention will be hereinafter described, with reference to the accompanying drawings, given merely by way o£ 60. example, and in which:-

Fig. 1 is a diagrammatic sectional view of an apparatus made according to the present invention before the pressure is applied.' 65

Fig. 2 is a plan view, on a smaller scale, o£ the apparatus of Fig. 1.

Fig. 3 is a sectional view analogous to Fig. 1, showing the apparatus after the pressure has been applied. 70

Fig. 4 is a diagrammatic partial view, in section, on a larger scale, of the annular element provided along the periphery of the apparatus.

Fig. 5 is a section, on an enlarged scale, 75 of a removable block formed by apparatus according to the invention, embedded in concrete.

Fig. 6 is an elevation, partly in section, of an apparatus provided with 80 two conduits.

Fig. 7 isa horizontal section o£ another embodiment of an apparatus according to the invention provided with -, two conduits. 8~'

Fig. 8 shows the arrangement of clevices arranged side by side according­to the invention.

Fig. 9 shows a fluid-tight packing' made by means of the apparatus accord- 90 ing to the invention, between two parts of a structure.

Fig. 10 is a seotional view of a device for tensioning rectilinear reinforcements.

Fig. 11 is a plan view ()f an apparatus 95 according' to the invention. . .

2 589,019

Fig. 12 is 3r sectional view on the line Another advantage olthe apparatus XII-XII of Fig. 11. according to the invention is that its bear-

Fig. 13 shows, in plan view, a modi~ ing surfaces can be arranged in such fication of the apparatus, permitting of manner that they do not remain parallel;

5. simultaneously tensioning several rein- they can even be of a' shape {)ther than 70 forcemerits: plane. As a matter of fact, it will be

Fig. 14 is a sectional view on the line readily understood that it would be XIV-XIVoI Fig. 13. possible to replace plates 1 and 2 of the

Fig. 15 is an axial section 01 a device example above described by sheets having 10 lor tensioning circular reinforcements. any desired shape in section." 76

Fig. 16 shows the end of a ring In ·order to obtain a stroke as great as segment which constitutes one of the may be necessary, I can employ several apparatus included in the device 01 Fig. apparatus of the type above described, 15. acting simultaneously, these apparatus

15 Figs. 17 and 18. are sections along being separated from one another by 80 planes passing through lines XVII- elements {)f suitable shape, so as to obtain XVII and XVIII-XVIII'of Fig. 16. their proper bearing {)n plates 1 and 2

In the embodiment shown by Figs. 1 and elements a (3 b f {)fthe peripheral to 3, the apparatus includes two parallel parts 3 above-mentioned. .

20 plates 1 and 2, for instance of highly As shown in Fig. 5, two superposed 85 malleable steel sheet or any other metal jack apparatus 9 are embedded in rich of the same quality. These plates are-~!l..oncrete 9a. Before the pouring of this connected along their edges . by tore- concrete ea, the peripheral portion of the shaped or cylindrical elements 3, fluid- jacKa'pparatus is fitted with welded lugs

25tightness being obtained in a perfect or projections 9b so as to ensure their 90 manner by interconnecting the plates and anchoring' in the concrete, the latter the tore-shaped or cylindrical surfaces by being strongly· reinforced above and below electric welding or any other equivalent the jack apparatus and also between them, means. for instance by means {)f a system {)f bars

30 A tube 4 welded on t,he peripheral 10 at right angles t-o one another. 95 element 3' or at any other suitable place The concrete 9a which encloses the permits of injecting a liquid under jack is poured either tangentially to the pressure which moves plates 1 and 2 away outer surface of the jack in such manner from each other j while modifying by that the latter surface exactly fills the

35 plastic deformation the shape of the tore- concrete section of the said concrete 100 shaped or cylindrical elements the radius block {)r merely in a Iorm that accommo~ of which increases. dates itseH t-o the contour of the jack. In

The presence {)f this peripheral element the first case the concrete block is in fact . which deforms under the effect of the composed of three superposed blocks

40 pressure.that is transmitted enables plates separated by the jacks and during ill!- 105 1 and 2 to be displaced without being flation no difficulties are encountered deformed, and Fig. 3 approximately since the three blocks are separated from shows the shape of the inflated device. one another .

. Before taking this shape, the apparatus In the second case the four parts of the 45 passes through a series of intermediate concrete are fractured along planes which 110

shapes. The active stroke of the contain the tangential· lines of the three apparatus is equal to the variation hl-h tore~shaped parts 3 of the jacks. These of the distance between the two plates. fissures open widely when the movements

As shown by Fig. 4, the section of the of the jacks increases. The concrete 50 peripheral element 3 {)f the apparatus blocks do not fracture along other planes 116

includes a circular arc am·b and two by reason of the reinforcing members curves a e and b f tangential to this nrc which are provided parallel' to the jacks at a and b respectively and joined to as shown in Fig. 5. -' plates 1 and 2. It is particularly advisable to have

55 Experience teaches that, with mild steel recourse to the following method in order 120 sheets of a thickness of 2 millimeters, the to ensure the maintaining {)£ the pressure -pressure in the apparatus can be made as independently of the -fluid-tightness of high as several hundreds of kilograms per the jack apparatus. square centimeter .. As the apparatus can The jack apparatus is inflated with a

60 be made with metal sheets {)f a size as material which is first perfectly fluid in 125 great as it may be desired, that is to say order Iully to transmit the pressures and with a bearing surface as wide as it may to ensure the correct working 01 the jack be desired,· I can exert, at low cost and apparatus, this material being capable 01 without any complicated mechanical solidilying subsequently and of resisting .

65 device, enormous forces. all causes of destruction, even in the case 130:

689,019 8

of disappearance of the bags of the jack apparatus by corrosion.

As a material of this kind, I may cite cements or other substances which are

Ii solid at ordinary temperature but have a relatively low melting point. It is then necessary to provide an internal or external, electric· or steam system for heating the jacks in advance.

10 I have found that it is advantageous to make use- of synthetio resins whioh, under the effect of a relatively small variation of temperature or through the mere action of time at a constant temperature,

15 pass from the liquid state to the solid state in which they are very strong fro111 a mechanical point of view. The applica­tion of a formaldehyde-phenol synthetic resin hardening at a low temperature or

20 even in the cold state, has proved to be particularly advantageous. It is in­jected into the jack apparatus in the liquid state at the desired pressure and allowed subsequently to set automatically, .

25 or this setting' can be facilitated by a heating of the jack apparatus, according to the adjustment of the composition of the initial liquid. ..

It may be necessary to vary, in the 30 course of time, the stresses created by the

jack apparatus in the mass of masonry in which they are incorporated or again to modify the expansion of the jacks so as to keep the force they produce to a

35 constant value, despite the slow modifica­tions of the elastic conditions of their bearing . points. This will be, in particular, the case when, the structure being constituted by conorete, either

40 reinforced or not, it is desired to obtain constant compression stresses . in the concrete mass despite its shrinkage and its slow deformation under load.

H the jack apparatus is filled with a 45 body which remains constantly liquid, it

will suffice to connect such apparatus by means of pipes with hydraulic pumps or ncc:umulntors through which their pressure can be controlled.

5.0 When the_ jack apparatus is first filled with a body which is first liquid then solidified, but fusible at a temperature which can be obtained in practice, I may proceed to melting and inject into the

65 jack apparatus a new amount of molten . matter or, 011 the contrary, withdraw

frOll1. such jack apparatus a portion of the matter they contain.

This solution· involves a danger if the 60 jack apparatus has lost its fluid-tightness,

because the elastic situation created by them can then be destroyed as a whole, as soon as the~ filling material of the j a(!k apparatus comes back into the solid state.

65 This danger can oe avoided _by the com-

bined use of a solidifiable matter and a matter which remains liquid or can very easily be liquefied. -

1 inject into the upper part of the jack apparatus, immediately after the injec- 70 tion of the solidifiable matter, such as the synthetic resin, a small amount of a liquid which does not mix with this resin, for instance ordinary mineral oil. This liquid occupies the portions of the 75 jack close to the inlet conduit and permits of the injection of new amounts of resin for periodically re-establishing the pres­sure in the jack apparatus.

It is advantageous to make use for this 80 purpose of a jack with two conduits con­nected with each other through the zone in . which the oil is localized, in such manner as to permit of the evacuation of the latter at low pressure before the 85 injection of the supplementary amount of resin.

Fig. 6 shows a jack apparatus of this kind which is placed vertically to act in the horizontal direction. This jack is 90 first filled with resin 11, injected in the liquid state at the desired pressure and, after this injection, I introduce, through tubes 4a and 4b connected to the upper part of the jack apparatus and fitted with 95 valves 40, an amount of mineral oil sufficient to . ensure that this oil, pushing the resin not y.et solidified· ahead of it, fills a small volume 12 in communication with the two tubes. 100

When, after solidification of the resin, it is desired to ill(~rease the expansion of the jack apparatus, resin is injected in the liquid state through one of the tubes 4a,the other tube 4b being used for the 105 dischargeo! the oil contained in 12 which is driven out by the resin that is injected.

When the whole of the volume 12 is filled with resin, tube 4b is closed and, through tube 4a, I keep injecting liquid 110· resin under the desired pressure for causing it to tear from the walls of the jack apparatus the matter already hardened at 11 and forming, between these walls and this matter, a film of the 115 desired thickness, which will harden subsequently. But, prior to this harden-ing, I effect anew injection of oil under pressure through tubes 4a and 4b so as again to form the upper volume of oil 12 120 which will permit of further injections of resin in case of need.

I have found that it is advantageous to part the matter already hardened from the walls of the jack apparatus, not 125 directly through the liquid resin but by means of an injection of oil under pressure, performed before the introduc­tionof the liquid resin.

After this result has been obtained 130

4 589,019

through the action of. oil under pressure, which will also permit {If checking fluid­tightness, the pressure is allowed to drop and the oil is driven out by the liquid

5 resin, as above explained. When the jack apparatus is placed

horizontally to act vertically I may pro­vide, at its center, a kind of bell-shaped part 13 (see Fig. 7), which will be con-

10 nectecl to tubes 4a and 4b and will sene to receive the small volume of oil 12.

One of the tubes can be replaced by a fine· tube passing through the inside of the other.

15 One of the tubes may drop down to a certain level so as to establish a low level of the oil, which is .a protection against the danger of total filling by resin.

In the arrangement shown in Fig. 8 20 two jacks 14, 15 are arranged side by side

between the masses Hi to be compressed, one .of which jacks 14 for instance,is inflated with oil, while the other, 15, is inflated with a solidi:fiable matter such as

25 resin. The pressure of jack 14 having beim allowecl to drop to zero, jack 15 alone will :first be brought into play and, after injection ·of the resin a small amount o(oil is admitted into the conduit Df this

30 jack apparatus 15, as above explained. Then, jack apparatus 14 is connected with a constant pressure hydraulic accumulator. This connection has for ;its object to maintain the pressure in the

35 jack 14 constant and therefore the latter is inflatedDl' deflated automatically according to whether the reaction which it receives from its supports is weaker or stronger than the pressure Df the

. 40 accumulator. As the .blocks 16 are b~ing moved, the eXpanSl{)ll of the Jack apparatus increases, while keeping the force at a constant value. \Then the expansion 'cif apparatus 14" reaches a

45 value such that a leak which WQuid destroy the pressure in this app!1ratus niight be dangerous, liqnid resin is fed into jack apparatus 15 under a pressure slightly higher than that exist.ing in

50 jack apparatus 14, preferably WIth the .. use ofa double conduit, as above

explained. This resin forms a film at the surface of the resin already hardened, then it itself hardens. The injection of

55:resin into apparatus 15 is followed by an injection of oil. The expansion ·of jack apparatus 14 has thus been brought back to zero. In the course of a subsequent movement of the blocks it increases; a

60 further amount of resin is then injected into jack apparatus 15, and so {In.

The two jack apparatus might be dis­posed inside a block of concrete poured around them, as above described with

65 reference to Fig. 5. This arrangement

can, of course. be utilized for one or several jacks.

The jack appuratus according to the invention is adapted to a great number of applications. As above explained, it .70 permits of maintaining permanent com·· pression stresses in reinIDrced conerete constructions ()r parts of constructions in such manner as to oppose the formation in this material of detrimental tractiYe 75 stresses, and this is a very important application of the jack apparatus accord­ing to the invention. From this point of view, it can be utilized independently of the preliminary tensioning of the concrete 80 reinforcements or in combination with this tensioning for the production of which they can be utilized.

The apparatus according to the inven­tion also permits Df creating horizontal 85 forces between the joints .of structures, for instance between the joints of big dams for neutralizing the stresses result­ing from sliding of the ground along the side of a hill. 90

I may take advantage of the fittfllg in position of the jack apparatus in these joints for ensuring fluid-tightness thereot.

Fig. 9 shows an arrangement which can be utilized for this purpose. I have 95 shown, in this fig., in horizontal section, two blocks 17 Dr a dam, separated from each other by a joint 18. In this joint or packing device, I place a series of jacks 9 according to the invention. These jacks 100 transmit their pressure to the blocks 17 through wedges 19 and cushions 20 of plastic material such as rubber, bitumen and asbestos, etc. A metal sheet 21, bent and held between wedges 19 and blocks 105 17. ensures fluid tightness.

In Fig. 10, the jack apparatus is applied to the tensioning of a group of rectilinear reinforcements 101 of a con­crete or masonry block 102. The 1'ein- 110 forcements are anchored at .one of their ends 103 in the block and, oyer the re­mainder Df their length they are free in a cylindrical chamber 104 provided in the course of the construction of the block. 115 1,'he jack apparatus that is utilizedin~ cludes, as shown by Figs. 11 and 12, two flat rings 105 and 106 .of a malleable metal, the edges of which are connected t,wo by two through tore~shaped peri- 120 pheral elements 107 and 108. The annular jack apparatus thus formed has, at its central part, an aperture 109 through which the reinforcements to be tensioned can be passed, and it is fitted, 125 on one ·of the peripheral tore~shaped elements, with an inlet conduit 110 for the introduction of the liquid matter nnder pressure. .-

In Fig. 10, I have shown three of these 130

jacks V 1 , V 2 , Va, superposed with the inter­position of wedges 111 which can be made of concrete or any other suitable mate­rial. After the fitting in position of these

5 jacks, the mass of concrete 112 in which the upper ends 113 of the reinforcements to be tensioned are anchored is poured above the upper jack. When the concrete mass 112 has set and hardened, I simul-

10 tuneously expand all of the jacks, which move the mass 112 away fr·om the block 102, thus tensioning th~ reinforcements. The number of jacks to be employed yaries of course according to the expan-

15 sion of these jacks and according to the value of the elastic elongation which is to be undergone by the reinforcements.

The tension of the reinforcements can be maintained by the solidification of the

20 matter injected into the jacks and, if necessary, as soon as the jacks have acted. it is possible to pOUl' concrete be­tween the block 102 and the anchoring head 112. I may provide in this head

25 channels such as 114, which will serve to fill the chamber 104 ·of the reinforcements and the central .opening of the jacks with concrete.

If it is desired subsequently to 30 eliminate the tensioning of the reinforce­

ments, it suffices to destroy one or several of the intermediate wedges 111 which are made sufficiently thick to permit them to be reached between the jacks.

35. The jack apparatus may be designed in such manner as to permit the simul­taneous tensioning of several groups of reinforcements. Thus, it is seen, in Figs. 13 and 14, that a jack may be provided

40 with four holes 109a, 109b, 10ge, 109d through which four groups of reinforce­ments to be tensioned 104a, 104b, 104e, 104d can be passed.

The tensions imparted to the reinforce-45 ments may be equal or unequal according

to the arrangement of the cables, which is determined as a functi{)nof the desired distribution of the tensions, account being taken of the fact that the center of

50 gravity of the reactions exerted by the cables on a jack coincides with the center of gravity of the surface of action of the jack.

The jack apparatus according to the 55 invention affords a solution .of the diffi­

cult pr{)blem of tensioning thereinf{)rce­ments of blocks of circular section. As a matter .of fact, it is possible to dispose a series of such jack devices between the

60 block to be compressed and the circular reinforcements to be tensioned. H{)wever it is more advantageOu.s to make the jack in the form of a flattened tube, which can easily be housed between. the block

60 and the reinforcement. For instance, in

the embodiment of Fig. 15, I have shown in section a block of concrete 115 in the form ·of an annulus of revolution having

'0

its axis at A-,,-A. Each of the circular reinforcements of this block to be ten- 70 sianed is constituted by a plurality of turns 116 'Of a metallic cable, wound on one another, preferably on the inside of a ring' 117 of U-shaped section which can also form a part of the reinforcement. 76 This element 117 is elastically elongated simultaneously with the reinforcing mem­bers when the jack is subjected to pres­sure. Between this ring 117 and the block, there is interposed an annular jack 80 according to the invention. This apparatus can be made, for instance, by assembling along their edges, through tore-shaped elements 118, 119, two cylin­drical annular parts 120, 121 .concentric 85 and coaxial. Intermediate wedges 122, 123 of reinforced concrete of other mate­rial matter are pr.ovided on either side of the jack apparatus. . When the reinforcements to be ten- 90

sioned are to be embedded .on the inside of . the block to be compressed and placed under tension after pouring of the whole of the block, I arrange the whole of the j aok and the reinforcements inside a 95 sleeve or casing 124 leaving the space necessary for the increase of diameter of the reinforcement when the jack is in­flated. This jack is fitted with an in:fiat-ing conduit 125 whichean be reached 100 both from the outside and the inside of the block or only from the inside or the outside. The element 124 forms in the concrete a spaee serving to house the jack the reinforcements 116 and the gutter 10.6 117. This space is sufficient to provide loi'an increase in diameter in the mem­bers 116 and the member 117. The mem-ber 124 thus plays a passive part which is to permit of this increase in· diameter. llQ At its oase it is comprised by a hooping action as well as by the adjacent concrete.

The jack may consist of a complete ring or it may be formed of a plurality of elementary j aoks each in the form of 115 an annular segment and placed end to end.' This last mentioned arrangement is advantageous from the point of view of safety and protection against leakage of the liquid matter, when the jack is in- 120 flated. If, in this case, one()f the jacks should leak, the ()thers will keep working and the only consequenee .of the leakage is an increase of. the expansion of the elements adjoining the defective element. 125

The flattened tube which forms each of the segments and the transverse section of which is visible on Fig. 17 can be closed at its ends by covering it with a kind ()f flat cap 126 provided with a horse-shoe- 180

589,019

shaped peripheral element 127 which con~ nects the edge elements 128, 129 of the flat tube. -The cap and the tube are assembled together in a fluid tight manner, for

6 instance by welding at 126a. The tube can be made of a single piece

without any welding) that is a tube pro­perly so called and not a junction of the end caps with the tube by drawing a

10 malleable metal such as copper, steel or the like, or it can also be made of two parts welded together on the edges at 130, 131, as in the case of Figs. 16 to 18. rfhe same is true of the caps 126 which can be

15 made of a single piece by stamping or call be made of two parts welded together along their edges.

The use of weldless tubes, tested before they are fitted in position, eliminates or

20 reduces the risks of inefficient function­ing of an element at the time of inflating.

It is possible to make use of several superposed annular jack elements or several superposed ring segments, which

25 -permits ·of increasing the expansion of the jack apparatus and also the safety.

This arrangement is also well adapted to the tensioning of helical reinforce­ments or even of reinforcements

30 of any desired curvature, the ten­sion obtained at each point being in­versely proportional to' the radius of -cUrvature at this point. . The jack apparatus permits of effecting

35 the tensioning of circular reinforcements, not only on the outside of a block but also on the inside, which is a very consider­able advantage. This last mentioned case is that of Fig. 15. In the case in which

.. 40 the block is hollow and the circular rings to' be tensioned are near the inner surface "of the block, it is advisable to connect -them with the rem.ainder of said block through suitable reinforcements, for in-

45 .stance helical reinforcements wQlmd around the circular reinforcements. In ,Fig. 15 the numerals 132 refer to a steel thread rolled helically in the concrete around the element 124 which contains

60 -the circular tensioned reinforcements 116. In order to limit the risks of leakage, I

may mi~with the liquid used for inflat­ing. the jack' apparatus substances such as _wood flour, keiselguhr, or others capable

c 55 of filling a crack. I: have also Iound that re-inflating or

the jack apparatus in the course ()f its use CUll be effected by making a hole through . the. -feed (lDnduit into the

. 60 hardened -material and injecting- through -this holEf a new amount of liquid under a _,high- pressure which may be several hun­dreds of kilograms per square centimeter. This'material forms a path through the

_ J~;; .h[l.J'de_ned.material by causip.g it t9 burst,

and the jack apparatus is thus reinflated~ When it is not possible to drive a hole

through the conduit which has been 11sed for initially inflatiugthe jack device, it suffices to provide a hole at an accessible 70 point of the apparatus alid to drive there­into a conical needle, provided, in the direction of its axis, with a passage through which the liquid matter is in-j eeted under high pressure. 75

Besides, when leakage occurs in a jack) at an accessible point thereof, it is possible to repair ()n the spot by electric or blowpipe welding by taking the pre­caution of driving a hole in the wall of 80 the device close to the point to be re~ paired, for the escape of the gases or vapours given off by the filling matter, this hole being subsequently closed by a conical spindle driven in with a hammer. 85

A leak . can also be stopped by per­manently deforming the metal or tightly applying thereon an element of suitable shape, with the interposition of a plastic. joint. 90

The jack apparatus according to the in,ention can be employed for compress-ing not only solid blocks but also liquid, pasty, or powdery masses, such as con­cretes, -earth formations and the like. By 95 . providing the jack on the inside of these masses, I obtain their setting in com~ pression directly, without requiring ele­ments for the transmission of pressure. The external deformation of said masses 100 can be limited or prevented, either by means of solid blocks or by means of enve~ lopes,or by a combination of these two means, the compression of said solid blocks or the setting intension of the 105 envelopes of . the compressed materials being in this case obtained in addition.

In particular, the jack apparatus according to the invention c.an be used with great facility for modifying the 110 state of equilibrium of earth formations, -sands, muds or days. They can thus be given the form of elongated plates which will be lowered into the ground by beat-ing, either between two plates of suitable 115 shape, ()r by injection of water, ()r in any other way.

This method permits of opposing, in some cases, the settling of ground forma­tions under the effect of certain weights 120

, such for instance as those of buildings, of compensating for settling in some con­structions, such as ground dams, and so on, of compressing the ground formations under masonrystrnctures, of ensuring the 125 fluid tightness of a ground formation, of restoring the equilibrium of a. COll'lt~uc­tion or bringing it back to a desired level.

In a general manner, while I have, in the above description, dis.closedwhat I 130

589,019 7

deem to be practical and efficient embodi~ ments of the present invention, it should be understood that I do not wish to be limited thereto as chang'es mig'ht be made

5 in the arrangement, disposition and form of the parts without departing' from the principle of the present invention as com­prehended within the scope or the appended claims.

10 Having now particularly described and ascertained the nature of my said inven~ tion ancl in what manner the same is to be performed, I declare that what I claim is:-

15 1. A jack device characterised in that it ineludes a kind ·of bag or malleable metal which is constituted by two plates forming the bearing faces of the jack de­vice and connected al{mg their edges by

20 welded joints or other fluidtig'ht joints, through the medium of a cylindrical or tore-shaped annular metal structure which enables the plates to be displaced without being' deformed, when the pl'es~

25 sure of the fluid fed to the bag is modified. 2. An application ()f the jack device set

forth in Claim 1, characterised by the combination of one or several jacks with wedge-shaped distance pieces; disposed

30 between the j ackol' jacks and the sur­faces along which they bear and adapted to permit of replacing' one or several jacks in case of its or their fa'ilure thereof to function.

35 3. A method of application of the jack device specified in Claim 1, characterised in that one or several jack devices are em­bedded in concrete, preferably rich and strongly reinforced, surrounding said

40 jack or jacks and forming a block there­with.

4. A method of application of the jack device specified in claim 1, characterised in that said jack is filled with a material

45 introduced in the liquid state and under the desired pressure, but capable of subse~ quently solidifying and of remaining solid under normal conditions of use, such for instance as a cement, a fusible matter,

5.0 of a synthetic resin. -5. A method of application according

to claim 4 further characterized in that, after the injecti()n ()f the solidifiable mate~ rial, there is introduced into th~ jack a

55 small amount ()f a material remaining in a liquid or easily liquefiable state; as for instance a mineral oil which is localized in the jack in the vicinity of the feed con~ duit thereof, this liquid permitting the

60 future injection of further amounts of solidifiable matter, with a view to modi­fying' the pressure or the expansion of the jack, the jack being eventually provided, for this purpose, with two tubes or

channels connected to the place where the 65 liquid matter, such as oil, tends to be localized, which permits of removing this oil through one of the tubes or channels when the Bolidifiable matter is injected through the other, one of the tubes beins' 70 eventually. formed by a fine tube extend­ing through the other.

6. A method of application ac.cording to claim 4 and 6, characterized by the combination of two jacks, one of which is 75 loaded with a liquid the pressure of which can be varied within certain limits and in which the pressure can be lliaintained at a constant value by connecting it, for instance, to a hydraulic accumulator and 80 the other is loaded with a solidifiable matter, while, however, inje'.;ting, after introcluction of said matter, a small amount of a liquid. which does not mix with the solidifiable matter, which per~ 85 mits, through supplementary injections ofsolidifiable matter -into this second­mentiolledjack, {)f maintaining the pres~ suree()£ the first, or its expansion below the value at which a defect of :B.uid- 90 tightness would become dangerous, these two jacks being ·preferably embedded in concrete for forming a block.

7. A jack devi0e according' to claim 1, characterizf\d :in that it js provided with 95 holes for the passage of reinforcements or other (:llements to be tensioned.

. 8. A jack cleviea according to claim 1, characterized in ;;hat it is of the shape of a flat tube which can be curved for in- 100 stance into rings {)r ring segments, per­mitting' of tensioning curvilinear, circular or helical reinforcements, for instance.

9. A device according to claim 1 for tensioning curvilinear reinforcements, 10& for instance circular or helical l'einfQrce­ments, characterized in that it includes one or several jacks, in the form of flat tubes interposed 'between the reinforce­ment to be tensioned and the mass or 110 structure to be acted upon, each jack de-vice being preferably made of several ele­mentary jacks in the form of curvilinear segments, mounted end to end.

10. A device according to claim 9, 115 applimtble to the case in which the rein­forcement to be tensioned are located on the inside ·of the structure, this device in~ eluding, around the jack and the rein­forcements to be tensioned are located on' 120 casing fixed in position before the con~ struction of the structure and preserving' the space necessary for the expansion of the jacks and the reinforcements.

11. A jack device substantially as 125 descri'bedwith reference to any of the Figures of the accompanying drawing'S.

8

Dated this 28th day of July, 1939. ABEL & BIRAY, Agents for the Applicant,

Quality House, Quality Oourt, Chancery Lane, London, W.C.2.

Leamington Spa: Printed for His Majesty's Statio eery Office, by the Courier Press.-1947. Published at The Pi>tent Office, 25, Southampton Buildings, London, W.C.2, from which

copies, price Is. Gd. each (inland) Is. ld. (abroad) may be obtained

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Filed July 5, 1939 5 Sheets-Sheet 3

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Patented Dec. 24, 1940,

' UNITED ‘STATES

' 2,226,201

PATENT OFFICE ‘2,220,201 . . . ‘ ~

JACK APPARATUS Eugene Freyssinet, Neuilly-lnr-Seinc, m .

Application

200mm. The present invention concerns apparatus in

tended to act as jacks. The chief object of the present invention is to

provide an apparatus of this kind which, under 5 an extremely small volume, permits of exerting

very high efforts, such as those which are neces sary, in particular, for civil engineering, such an

. apparatus being simple to manufacture and of low

10 cost. ' -

The apparatus according to the invention es sentially includes a kind of bag of a malleable metal, which may include two plates, forming the bearing faces of the apparatus and connected to gether, along their edges, by welded joints, or

15, other ?uid-tight joints, preferably through. the

.20

intermediate or a cylindrical or tore-shaped ele ment which enables the plates to move with re spect to each other without being deformed when 'the pressure of the ?uid fed into the bag is modi- ' ?ed. A conduit ?xed on the cylindrical or tore shaped element or to any other suitable part of the apparatus permits of injecting liquid into the bag. , '

Several methods of applications of such ap paratusvwill be hereinafter set forth.‘ . ‘

According to an important feature of the present invention, when the apparatus is to be left in a permanent manner in a piece ofwork so as to create permanent efforts therein, the apparatus is in?ated with a matter which is in jected in the liquid state and which solidi?es sub sequently without substantial variation of volume and remains in the solid state under normal con ditions of use, such a matter consisting, for in stance, of cement,‘a fusible matter or a suitable synthetic resin. _

Various applications of the apparatus, accord ing to the invention, will be hereinafter explained. Other features of the present invention will

result from the following detailed description of some speci?c embodiments thereof.

Preferred embodiments of the present inven tion will be hereinafter described, with reference to .‘the accompanying drawings, given merely by way of example, and in which: '

Fig. 1 is a diagrammatic sectional view of an _ apparatus made according to the present inven tion before the pressure is applied; Fig.2 is a plan view, on a smaller scale, of the

apparatus of Fig. 1; '

Fig. 3 is a sectional view analogous to Fig. 1, showing the apparatus after the pressure has been applied;

Fig. 4 is a diagrammatic partial view, in section, ‘

July 5, 1939. ‘Serial No. zazssr France August 1, 1938

(oLei-so) ' ' '>

on a larger scale, of the annular element pro vided along the periphery of the apparatus;

Fig. 5 illustrates a method 01' applicationof an apparatus according to the invention;

Fig. 6 is a detail view-on an enlarged scale of a portion of Fig. 5, in section by a plane parallel to the plane of Fig. 5;

, Fig. 7 is a section ‘on the line,V'II—-VII of

Fig. 8 is a section,~o'n an enlarged scale, of a removable block formed by apparatus according to the invention, embedded in concrete; ~

Fig. 9 is an elevational view, partly in section, of an apparatus provided with two- conduits;

Fig. 10 is'a horizontal section of another em bodiment of an apparatus according to the in-' vention provided with two conduits; ‘Fig. 11 shows‘the arrangement of two super

posed apparatus according to‘ the invention; 7 Fig. 12'shows a ?uidtight packing made by

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20 means of ‘the apparatusaccording to the inven- _ ‘ tion, between two parts of a construction;

Fig. 13 is a sectional view of a device for ten sioning rectilinear reinforcements;

Fig. 14 is a plan view of an apparatus accord ing to the invention incorporated in a system;

Fig. 15 is a sectional view on the line XV-XV of Fig. 14; ~ . -

Fig. 16 shows, in plan view, a modi?cation of the apparatus, permitting oi’ simultaneously ten sioning several reinforcements; . ‘

- Fig. 17 is a sectional view on the line" XVII-XVII of Fig. 16;

. Fig. 18 is an axial section of'a device for .ten vsioning circular reinforcements;

Fig. 19 shows the end ‘of a ring ‘segment which constitutes one of the apparatus included in the device of Fig. 18; _

Figs. 20 and 21 are sections by planes passing through lines xx-xx and XXI-XXI of Fig. 19;

Fig. 22 shows, in vertical section, a modi?cation which constitutes a kind of in?atable post; ' '

Fig. 23 is a sectional view on the line xxm-xxm ‘of Fig. 22. ' On this ?gure

XXIEEXXII designates the trace of the plane of Fig. . . '

In the embodiment shown by Figs. 1 to 3, the apparatus includes two parallel plates l and 2, for instance of highly malleable steel sheet or any other metal of the same quality. These plates are connected along their edges by tore shaped or cylindrical elements 3, ?uidtightness being obtained in a perfect manner by inter connecting the plates and the tore-shaped or

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2 cylindrical surfaces by‘electric welding or any ‘other equivalent means. A tube 4 welded on the peripheral element 3

or at any other suitable place permits of in jecting a liquid under pressure which moves plates l and 2 away from each other, while modifying by plastic deformation .the shape of the tore-shapedor cylindrical elements the radius of which increases. ‘ '

The presence of this peripheral element which deforms under the effect of the pressure that is transmitted enables plates 1 and 2 of being dis placed without being deformed, and Fig. 3 ap proximately shows the shape of the in?ated de vice. Before taking this shape, the apparatus passes through a series of intermediate shapes. The active stroke of the apparatus is equal to the variation h1-—h of the distance between the two plates. , As shown by Fig. 4, the section of the periph

eral element 3 of the apparatus includes a cir cular arc amb and two curves ac and bf tangent to this are at a and b respectively and joined to plates 1 and 2. The masses 0 and p to be com pressed have surfaces which correspond to the shape of plates l and 2, in such manner that the surface along which the apparatus according to the invention bears on the masses is limited on either face of the apparatus by the curve which is the geometric locus of points a and b on the respective faces. If the masses in question are not shaped to correspond to the shape of these bearing surfaces, the apparatus according to the invention may be embedded in concrete before they are ?tted in position, the embedding concrete being limited by surfaces corresponding to those of the above mentioned masses, in particular ?at surfaces as it will be hereinafter explained. When plates I and 2 are moved away from each

other, the radius and length of arc amb increases, at the expense of elements a e and b j, which are ?rst applied against the masses 0 and p and which are detached from said masses so as to. assume a circular shape over lengths a g and b 1. ‘Thus arc amb becomes are 9' m’ 1’, the masses 0 and p being moved away from each other with a translatory motion, so as to come at o’ and p’. By varying the shape and inclination of elements .a e and b f it is possible to modify displacement mm’, either by displacing m’ toward the outside with respect to m or by moving it toward the in ‘side, or again by rendering this displacement equal to zero, in which case m’ coincides with m, ‘the displacement, if any, complying with a given law, which can be chosen. For instance, by mak !ing a e and b j of rectilinear shape and inclining 'them at an angle of about 45° with respect to the Iplates, point m is not substantially displaced.

Experience teaches that, with mild steel sheets of a thickness of 2 millimeters, the pressure in .‘the apparatus can be made as high as several hundreds of kilograms per square centimeter. As the apparatus can be made with metal sheets of a size as great as it may be desired, that is to say with a bearing surface as wide as it may be desired, I can exert, at low cost and without any ‘complicated mechanical device, enormous e?orts, as high as several millions of tons. * Another advantage of the apparatus accord ring to the invention is that its bearing surfaces can be arranged in such maner that they do not remain parallel; they can even be of a shape other ‘than plane. As a matter of fact, it will be readily 'understood that it would be possible to replace ‘plates l and 2 of the example above described by

2,226,201 sheets having any desired shape in section. ‘ Therefore, it is possible to produce complex ef ‘forts which have not a single resultant.

In order to obtain a stroke as great as it may be necessary, I can superpose several apparatus of the type above described, acting simultaneous ‘ly, these apparatus being separated from one an other by elementsof suitable shape, so as to ob tain their proper bearing on plates I and 2 and ‘elements a e b j of the peripheral parts 3 above ‘mentioned.

Fig. 5 shows the application of the apparatus according to the invention, as above described, to a multiple arch dam 6, diagrammatically shown :in transverse section.

For instance, it is desired, in order to raise the level of the dam, to establish at ‘I a supplemen tary support for prop 8 which has become in su?icient. If one waits until the elastic deforma tions of the dam and of part 8, at the time of the lifting of the whole, produce an effective bearing in plane A'—A, there may occur, as a consequence ‘displacements of the mass which will disintegrate it and destroy the liquid-tightness of the dam. .The supplementary resistance created at. ‘I will come into play only after the occurring of the disorders it was intended to avoid. Everything iwill take place in a very different manner if there is arti?cially created, before the operation, or gradually in the course of this operation, an ac 'tive effort on element 8 equal to the reaction which it has been deemed useful to rely upon from part ‘I. The deformation of the whole can thus be reduced to a value compatible with the possibilities of plastic deformations of the forma tions.

In order to produce the desired effort in plane A-A, it is necessary to have apparatus, adapted to act as jacks, which are of very high power with a volume as reduced as possible. The apparatus according to the invention as above described are particularly well adapted to this use and they do not involve considerable expenses.

Several of these apparatus may be placed side by side and they will act simultaneously for ob taining the desired efforts.

In the case of apparatus of this kind which are kept under pressure in such manner as to .transmit permanent efforts to masonry works, ar rangements must be taken for permitting of with drawing and replacing the aparatus which would, [prove defective for lack of ?uidtightness.

It is possible, for this purpose, to insert, be tween the apparatus and the parts against which they bear, wedge-shaped packing elements. An arrangement of this kind is shown by Figs. 6 to 8. On either side of the plane A—-A in which the

‘prop or buttress 8 and the supplementary foun

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dation ‘I are to bear against each other, I pro- ' vide masses or blocks ‘la, 80 of concrete which is rich and su?iciently reinforced for being able to support the efforts tobe transmitted, which are particularly important in the vicinity of the plane A-A in which the apparatus according to the invention will be disposed. These blocks are dis posed in adjoining relation respectively to foun wdation 1 and buttress 8. They bear against each 'other, through a series of dry joints ‘lb which form in plane A——A a kind of castellated struc ture (Fig. '7). The recesses 1c in this structure serve to house the apparatus according to the in vention (on the left hand side of Fig. 7, I have shown two of these recesses which are not yet provided with the apparatus according to the invention). These apparatus are brought into play, in a.

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2,220,201 particularly advantageous manner, in the form of a block embedded in concrete, including for instance, as shown by Fig. 8, two superposed jack apparatus 9, embedded in concrete 9a. Before the pouring of this concrete 9a, the peripheral portion of the jack: apparatus is ‘?tted with welded lugs or projections 9b so as to ensure their anchoring in the concrete, the latter being strongly reinforced above and below the jack apparatus and also between them, for instance by means of a system of bars ill at right angles to one another. _

In a given recess 1c, 1 dispose, as shown by Fig. 6, a system including a plurality of jack ap paratus and a mass of concrete made as above explained, and a wedge Na, which can be con stituted, for instance, by a piece of reinforced concrete covered by two metal sheet plates lllb. The intervals lllc between block hand the

system constituted by the jack apparatus, the concrete mass and the wedge, and between this system and block 8a are ?lled with jagged con crete. -

When the jack apparatus are subjected to the action of pressure, they are in?ated and transmit their effort to buttress ‘I and to founda

. tion I through the concrete which embeds them

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and the various intermediate elements, especially wedges Illa. The dry joints lb are opened a dis- , tance equal to the stroke or displacement of the jack apparatus.

If lack of ?uid tightness occurs in one of the jack apparatus units, the corresponding wedge Illa is driven out or it is destroyed by reducing into powder the concrete of which it is made. It is thus possible to remove the jack apparatus unit, which is replaced by a new unit.

It is particularly advisable to have recourse to the following method in order to ensure the maintaining of the pressure independently of the ?uid-tightness of the jack apparatus: The jack apparatus are in?ated with a matter

which is ?rst perfectly ?uid in order fully to transmit the pressures and to ensure the correct working of the jack apparatus, this matter be ing capable of solidifying subsequently and of resisting all causes of destruction, even in the case of disappearance of the bags of the jack apparatus by corrosion. As matter of this kind, I may cite cements or

matters which are solid at ordinary temperature but have a relatively low boiling point. It is then necessary to provide an internal or external, electric or steam system for heating the jacks in advance.

I have found that it is advantageous to make use of synthetic resins which, under the effect of a relatively small variation of temperature or through the mere action of time at constant tem perature, pass from the liquid state to the solid state in which they are very strong from a me chanical point of view. The application of a formaldehyde-phenol synthetic resin hardening at low temperature or even in the cold state, such as the resin sold on the market under the name of “brauthite” has proved to be particularly ad; vantageous. It will be injected into the jack ap paratus in the liquid state at the desired pressure and it will be allowed subsequently to set auto matically. or this setting will be facilitated by a heating of the jack apparatus, according to the adjustment of the composition of the initial liquid.

It may be necessary to vary, in the course of time, the efforts created by the jack apparatus, in the mass of masonry in which they are in

.hardening, I

3 corporated or again to modify the expansion of the jacks so as to keep the effort they produce to a constant value, despite the slow modi?cations of the elastic conditions of their bearing points. This will be, in particular, the case when, the structure being constituted by concrete, either reinforced or not, it is desired to obtain constant compression stresses in the concrete mass despite its shrinkage and its slow deformation under load. I . ' a

If the jack apparatus are ?lled with a body which remains constantly liquid, it ‘will su?ice to connect these jack apparatus through pipes with hydraulic pumps or accumulators through which their pressure can be controlled. When the jack apparatus are ?rst ?lled with

a body which is ?rst liquid then solidi?ed, but fusible at a temperature which can be obtained in practice, I may proceed to a melting and inject into the jack apparatus a new amount of molten matter or, on the contrary, withdraw from these jack apparatus a portion of the matter they con

n-. -'

This solution involves a danger if the jack ap paratus have lost their ?uidtightness, because the elastic situation created by them can then be destroyed‘ as a-whole, as soon as the ?lling matter of the jack apparatus comes back into the solid state. This danger can be avoided by the com bined use of a, solidi?able matter and a matter which remains liquid or can very easily be lique ?ed. ‘

I-inject into the upper part of the jack appa ratus, immediately after the injection of the vsolidi?able matter, such as the synthetic resin, a small amount of a liquid which does not mix with this resin, for instance ordinary mineral oil. This liquid comes to occupy the portions of the jack close to the inlet conduit and permits the injection of new amounts of resin for periodically re-establishing ‘the pressure in the jack appa

' ratus.

It will be advantageous to make use for this purpose of a jack with two conduits connected with each other through the zone in which the oil is localized, in such manner as to permit the evacuation of the latter at low pressure before the injection of thesupplementary amount of resin.

Fig. 9 shows a jack apparatus of this kind which is supposed to act in the vertical direction. This jack is ?rst ?lled with resin ll, injectedin the liquid state at the desired pressure and, after this injection, I introduce, through tubes 4a and lb, connected to the upper part of the jack ap paratus and ?tted with valves 40, an amount of mineral oil sufficient in order that this oil, push ing the resin not yet solidi?ed ahead of it, ?lls a small volume I2 in communication with the two tubes. When, after solidi?cation of the resin, it is de

sired to increase the expansion of the jack appa ratus, resin is injected in the liquid state through one of the tubes la, the other tube 4b being used for the discharge of the oil contained in f 2

' which is driven out by the resin that is injected. When the whole of the volume I! is ?lled with

resin, tube lb| is closed and, through tube in, I keep injecting liquid resin under the desired pres sure for causing it to tear the walls of the jack apparatus fromthe matter already hardened at H and forming, between these walls and this matter, a ?lm of the desired thickness, which will harden subsequently. ' But, prior to this

will proceed to a new injection of oil under pressure through tubes to and 4b so as

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again to form the upper volume of oil I2 which will permit further injections of resin in case of need.

I have found that it is advantageous to part the matter already hardened from the walls of the jack apparatus, not directly through the liq uid resin but by means of an injection of oil under, pressure, performed before the introduc tion of the liquid resin. This parting is relative ly easy in the case of “brauthite” because it does not adhere to sheet iron.

After this result has been obtained through the action of oil under pressure, which will also permit of checking ?uidtightness, the pressure is allowed to drop and the oil is driven out by the liquid resin, as above explained. When the jack apparatus are used in the hori

zontal direction, I may provide, at their center, a kind of bell-shaped part I3 (see Fig. 10), which will be connected to tubes 4a and 4b and will serve to receive the small volume of oil I2. One of the tubes can be replaced by a ?ne

tube passing through the inside of the other. One of the tubes may drop down to a certain

level so as to establish a low level of the oil, which is a protection against the danger of total ?lling by resin. A particularly interesting arrangement con

sists in superposing two jack apparatus ll, I5 (Fig. 11) between the masses I6 to be compressed, one of which jack apparatus, II for instance, will be in?ated with oil, while the other, I5, is in?ated with a solidi?able matter such as resin. The pressure of jack I4 having been allowed to drop to zero, jack I5 alone will ?rst be brought into play and, after injection of the resin a small amount of oil will be sent into the conduit of this jack apparatus ‘I5, as above explained. Then, jack apparatus It will be connected with a constant pressure hydraulic accumulator. As blocks It are being moved, the expansionof the jack apparatus increases, while keeping the ef fort at a constant value. When the expansion of apparatus I4 reaches a value such that a leak which would destroy the pressure in this appa ratus might be dangerous, liquid resin is fed into jack apparatus I5 under a pressure slightly higher than that existing in jack apparatus Il, with the eventual use of a double conduit, as above explained. This resin will come to form a ?lm at the surface of the resin already hardened, then it will itself harden. The injection of resin into apparatus I5 is followed by an injection of oil. The expansion of jack apparatus I4 has thus been brought back to zero. In the course of a subsequent movement of the blocks it will increase; a further amount of resin will then be injected into jack apparatus I5, and so on. The two jack apparatus might be disposed in

side a block of concrete poured around them, as above described with reference to Fig. 8. This arrangement can, of course, be utilized for one or several jacks. As a matter of fact, the jack apparatus ac—

cording to the invention are adapted to a great number of applications. As above explained, they permit of maintaining permanent compres sion stresses in reinforced concrete constructions or parts of constructions in such manner as to oppose the formation in this material of detri mental tractive stresses, and this is a very im portant application of the jack apparatus ac cording to the invention. From this point of view, they can be utilized independently of the preliminary tensioning of the concrete reinforce

2,226,201 ments or in combination with this tensioning for the production of which they can be utilized. The apparatus according to the invention also ,

permit of creating horizontal eiforts between the joints oi.’ structures, for instance between the Joints or big dams for neutralizing the stresses resulting from sliding of the ground along the side of a hill.

I may take advantage of the ?tting in position of the jack apparatus in these joints for ensuring ?uidtightness thereof. -

Fig. 12 shows an arrangement which can be utilized for this purpose. I have shown, in this ?gure, in horizontal section, two blocks II of a dam, separated from each other by a joint I0. In this joint or packing device, I place a series of jack apparatus 9 according to the invention. These jack apparatus transmit their pressure to blocks I'I through wedges I9 and cushions 20» of a plastic material such as rubber, bitumen and asbestos, etc. A metal sheet 2|, bent and held between wedges I9 and blocks I‘I, ensures ?uid tightness.

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In Fig. 13, the jack apparatus is applied to the ' tensioning of a group of rectilinear reinforce ments IOI of a concrete or masonry block I02. Reinforcements are anchored at one of their ends I03 in the block and, over the remainder of their length they are free in a cylindrical chamber I04 provided in the course of the construction of the block. The jack apparatus that is utilized in cludes, as shown by Figs. 14 and 15, two ?at rings I05 and I06 of a malleable metal the edges of which are connected two by two through tore shaped peripheral elements I01 and I08. The annular jack apparatus thus formed has, at its central part, an aperture I09 through which the reinforcements to be tensioned can be passed, and it is ?tted, on one of the peripheral tore shaped elements, with an inlet conduit IIO for the introduction of the liquid matter under pres sure. In Fig. 13, I have shown three of these jack

apparatus 01, v2, v3, superposed with the interposi tion of wedges III which can be made of con crete or any other suitable material. After the ?tting in position of these jack apparatus, the mass of concrete H2 in which the upper ends I I3 of the reinforcements to be tensioned are an chored is poured above the upper jack apparatus. When the concrete of mass I I2 has set and hard ened, I simultaneously expand all of the jack ap paratus, which move mass “2 away from block I02, thus tensiom'ng the reinforcements. The number of jacks to be employed varies of course according to the expansion of these jacks and according to the value of the elastic elongation which is to be undergone by the reinforcements. The tension of the reinforcements can be

maintained by the solidi?cation of the matter injected into the jack apparatus and, if neces sary, as soon as the jack apparatus have acted, it is possible to pour concrete between block I02 and the anchoring head III. I may provide in this head channels such as Ill, which will serve to ?ll the chamber I00 oi the reinforcements and the central opening of the jacks with con crete.

If it is desired subsequently to eliminate the tensioning oi the reinforcements, it su?lces to destroy one or several of the intermediate wedges III Which are made su?iciently thick for per mitting to reach them between the jacks. The jack apparatus may be designed in such

manner as to permit the simultaneous tensioning

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2,226,201 5 of several groups of reinforcements. Thus, it is seen, in Figs. 16 and 17, that a jack may be pro vided .with four holes "9a, "9b, I090, "I911 through which four groups of reinforcements to

5 be tensioned IlMa, IIMb, IMc, Illld can be passed. The tensions imparted to the reinforcements

may be equal or unequal according to the ar rangement of the cables, which is determined as Y a function of the desired distribution of the ten

10 sions, account being taken of the fact that the center of gravity of the reactions exerted by the cables on a jackcoincides with the'center of gravity of the surface of action of the jack. The jack apparatus according to the inven

15 tion afford a solution of the di?icult problem of tensioning the reinforcements of blocks of cir cular section. As a matter of fact, it is possible to disposev a series of such jack apparatus be tween the block to be compressed and the circu

20 lar reinforcements to be tensioned. However, it is more advantageous to make the jack in the form of a ?attened tube, which can easily be housed between the block and the reinforcement. For instance, in the embodiment “of Fig. 18, I

25 have shown in section a block of concrete H5 in the form of an annulus of revolution having its axis at A-—A. Each of the circular reinforce ments of this block to be tensioned is constituted by a plurality of spires II 6 of a metalliccable,

30 wound on one another, preferably on the inside of a ring II‘! of U-shaped section which can also form a part of the reinforcement. Between this ring II‘! and the block, there is interposed an an nular jack apparatus according to the invention.

35 This apparatus can be made, for instance, by assembling along their edges, through tore shaped elements H8, H9, two cylindrical annu lar parts, concentric and coaxial I20, I2I. Inter mediate wedges I22, I23 of reinforced concrete

40 or any other matter are provided on either side of‘ the jack apparatus. ’ When the reinforcements to be tensioned are

to be embedded on the inside of the block to be compressed and placed under tension after pour

45 ing of the whole of the block, I arrange the whole of the jack and the reinforcements inside a sleeve or casing I24 leaving the space neces sary for the increase of diameter of the rein forcement when the jack is in?ated. This jack is

50 ?tted with an in?ating conduit I25 which-can be reached both from the outside and the in

. side of the block or only from the inside or the outside. .

The jack apparatus may consist of a complete 55 ring or it may be formed of a plurality of ele

mentary jacks each in the form of an annular segment and which are placed end to end. This last mentioned arrangement is advantageous from the point of view of safety and protection

60 against leakage of the liquid matter, when the ' jack apparatus is in?ated. If, in this case, one of the jack apparatus happened to leak, the others keep working and the only consequence of the leakage is an increase .of the expansion‘ of the

65 elements adjoining the defective element. The ?attened tube which forms each of the

segments and the transverse section of which is visible on Fig. 20 can be closed at‘ its ends by covering it with a kind of flat cap I26 provided

70 with a horse-shoe-shaped peripheral element I21 which connects the edge elements I28, I29 of the ?at tube. The cap and the tube are assembled together in a ?uidt?ight manner, for instance by welding at mm.

75 The tube can be made of a single piece with_

out any welding by drawing a malleable metal such as copper, steel or the like, or it can also be made of two parts welded together on the edges at I30, I3I, as in the case of Figs. 19 to 21. The same is true of caps I26 which can 5 be made of a single piece by stamping orcan be made of two parts welded together along their edges. The use of weldless tubes, tested. before they

are ?tted in position, eliminates or reduces the 10 risks of bad working of an element at the time of in?ating. .

Of course, it is possible to make use of several superposed annular jack elements or several su perposed ring segments, which permits of in- 15 creasing the expansion of the jack apparatus and ‘ also the safety. This arrangement is also well adapted to the

tensioning of helical reinforcements or even of reinforcements having the shape of any desired 20 curve, the tension obtained at each point being inversely proportional to the radius of curvature at this point. ‘ '

The jack apparatus permits of'obtaining the tensioning of circular reinforcements, not only 25 on the outside of a block but also on the inside, which is a very considerable advantage. This last mentioned case is that considered by Fig. 18. In the case in which the block is hollow and the circular rings to be tensioned are near the inner 30 surface of the block, it is advisable to connect them with the remainder of said block through suitable reinforcements, for instance helical re inforcements wound around the circular rein forcements. ‘ 35

In order to limit the risks of leakage, I may mix with the liquid matters used for in?ating the jack apparatus substances such as wood ?our, kiesel- ‘ guhr, or others capable of ?lling a crack.

I have also found that re-in?ating ofv the jack 4" apparatus in the course of its use can be obtained by making a hole through the feed conduit into the hardened matter and injecting ‘through this hole a new amount of liquid matter under a high pressure which can be of several hundreds of kilo- 45 grams per square centimeter. This matter, under high pressure, forms a paththrough the hardened matter by causing it to burst, and the jack appa ratus is thus rein?ated. When it is not possible to drive a hole through 5°

the conduit which‘ has been used for initially in ?ating the jack device, it su?ices to provide a hole at an accessible point of the jack apparatus and to drive thereinto a conical needle, provided, 55 in the direction of its axis, with a passage through which the liquid matter is injected under high pressure.

Besides, when leakage occurs in a jack appa ratus, at an accessible point‘thereof, it is pos- 60 sible to repair on the spot by electric or blowpipe welding by taking the precaution of driving a hole in the wall of the device close to the point to be repaired, for the escape of the gases or vapours given 011’ by the ?lling matter, subsequently closed by a conical spindle driven with a hammer. A leak can also be stopped by matting oi’ the

metal or tightly applying thereon a piece of suit able shape, with the interposition of a plastic joint. . ‘ 7°

The jack apparatus according to the invention can be employed for compressing not only solid blocks but also liquid, pasty, or powdery masses, such as concretes, earth formations and the like. 75 By providing the jack apparatus on the inside of

this hole being 65

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6 these masses,-I obtain their setting in compres sion directly, without requiring elements for the transmission of pressure. The external deforma tion of said masses can be limited or prevented, either by means of solid blocks or by means of envelopes, or by a combination of these two means, the compression of said solid blocks or the setting in tension of the envelopes of the com pressed materials being in this case obtained in addition. > In particular, the jack apparatus according to

the invention can be applied with a great facility for modifying the state of equilibrium of earth formations, sands, muds or clays. They can thus be given the form of elongated plates which will be lowered into the ground by beating, either between two plates of suitable shape, or by giving them a suitable resistance to beating, or by in jection of water, or in any'other way. This method will permit of opposing, in some

cases, the settling of ground formations under the effect of certain weights such for instance as those of buildings, of compensating for settling in some constructions, such as ground dams, and so on, of compressing the ground formations under masonry structures, of ensuring the ?uid tightness of a ground formation, of restoring the equilibrium of a construction, or bringing it back to a desired level.

In these applications, it would be too expensive to ?ll the jack apparatus with synthetic resin. The apparatus can be ?lled either with concrete, in particular fused cement injected by means of a pump, or with sand, easy to introduce by driving it by means of water under pressure, ac cording to known methods. The same jack apparatus can be applied with

advantage instead of explosives, when operating on great masses of rocks with a view to removing them or cutting them into portions. The jack apparatus will then be introduced into holes or grooves provided in the rock to be cut into ele ments, and they are ?xed with respect to the rock walls by means of hydraulically settled ?ne sand or cement. They permit of developing pressures as high as 1000 atmospheres and even more, ca pable of producing the breaking and the displace ment of rocky blocks of very big size, without shocks capable of altering the masses to be cut into parts or of producing disturbances in the vicinity. In these various applications, it may be advis

able to cause the jacks to act on the inside of a bore hole of very small size, and it is advanta geous that the jacks, when expanded, may have a volume as great as possible. A jack apparatus according to the invention

which complies with this condition is illustrated by Figs. 22 and 23. Its wall is provided, after it has been in?ated, with a great number of folds or the like I33 which are inscribed inside a cylinder I34 of a diameter corresponding to the application that is being considered, for instance

» the introduction of the jack apparatus into a cy 65 lindrical bore-hole. It will be readily understood -

that, in the course of the gradual in?ating of such a jack, these folds or projections disappear and the section becomes that of a circle of large di

~ ameter. Near the ends of the jack apparatus, the m

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folds diminish gradually until they form a per fectly cylindrical wall l34a, as shown by the in clined line B C, in Fig. 22. Each of the cylin drical ends 1340. can be closed by means of a cover I35 welded at I36. One of these covers can be provided with a feed tube I31 for the introduc-v

2,226,201 tion of the in?ating matter into the jack appa ratus. In Fig. 22, the dotted lines I38 diagrammati

cally illustrate the form of the deformable wall, after it has been in?ated. In Fig. 23, I have also shown at I38 2. ?lling

of reinforced concrete or another matter in the folds of the wall which communicate with the outside. This ?lling, which can be replaced by metallic bars for instance, is intended to stiffen the apparatus after it has been in?ated, whereby it can be driven into the ground. The in?ating can be obtained by means of

water and, after it has been in?ated, the jack apparatus can be ?lled with gravel or concrete introduced, for instance, under pressure by means of an intermediate pressure chamber. The circonvolutions of the wall can be ob

tained by bending the metal sheets in a machine and subsequently assembling them by welding, for instance along the outer ridges of the cir convolutions. In a general manner, while I have, in the above

description, disclosed what I deem to be prac tical and efficient embodiments of the present invention, it should be well understood that I do not wish to be limited thereto as there might be changes made in the arrangement, disposi tion and form. of the parts without departing from the principle of the present invention as comprehended within the scope of the appended claims. What I claim is: l. A jack apparatus which comprises, in com

bination, a malleable metal bag including two plates constituting the bearing faces of the jack and deformable means forming a ?uidtight joint between said plates, and at least one feed con duit opening into said bag so as to permit of in?ating it. .

2. A jack apparatus which comprises, in com bination, a malleable metal bag including two plates constituting the bearing faces of the jack and at least one‘ deformable tore-shaped ele ment interconnecting the corresponding edges of said plates in a ?uidtight manner, and at least one feed conduit opening into said bag so as to permit of in?ating it.

3. A jack apparatus which comprises, in com- _ bination, a malleable metal bag including two plates constituting the bearing faces of the jack and at least one deformable tore-shaped element interconnecting the corresponding edges of said plates in a ?uidtight manner, and at least one

‘ feed conduit carried by said tore-shaped element ' and opening into said bag so as to permit of in?ating it.

4. A jack apparatus which comprises, in com bination, a malleable metal bag including two plates constituting the bearing faces of the jack ' and provided with at least one hole formed in each of them, in registering position for these two plates, for the passage of elements to be ten sioned, deformable joints interconnecting in a ?uidtight manner the corresponding edges of

, said plates, and at least one feed conduit opening into said bag so as to permit of in?ating it.

5. A jack apparatus which comprises, in com bination, a malleable metal bag including two plates constituting the bearing faces of the jack and deformable means forming a ?uidtight joint

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between said plates, and two feed conduits open- ‘ ing into said bag close to each other, so as to

, permit of in?ating said bag with a matter which is initially ?uid and hardens subsequently when 75

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2,226,201 introduced into said bag, and of introducing and withdrawing, at will, a small amount of a matter which remains ?uid, around the openings of said two feed conduits into said bag.

6. A jack apparatus which comprises, in com bination, a malleable metal bag including two horizontal plates constituting the bearing faces of the jack, one of said faces forming a bell-like chamber in its central face, and two feed con-‘ duits opening into said chamber, so as to permit of in?atingsaid bag with a matter which is in itially ?uid and hardens after its introduction into said bag, and of introducing and withdraw ing, at will, a small amount of a matter which remains ?uid, in said chamber.

7. A jack apparatus which comprises, in com bination, two malleable metal bags including each two substantially parallel plates and deformable means forming a ?uidtight joint between said two plates, said plates being arranged in parallel re lation and interconnected so as to transmit thrusts from one to the other, means for feeding a ?uid capable of remaining permanently in the ?uid state to one of said bags, and means for feeding a matter in the ?uid state and adapted to harden subsequently to the other of said bags.

8. A system adapted to form a joint between two structure elements, which comprises, in com bination, at least one jack interposed between said elements and constituted by a malleable metal bag including two plates forming the bear ing faces of the jack and deformable means forming a ?uidtight joint between said plates, and at least one feed conduit for-a liquid under pres sure opening into said bag, so as to permit of in?ating said bag, intermediate pieces on either side of said jack interposed between said plates and said structure elements, packing means made of a plastic material caught between each of said

41' intermediate pieces and the corresponding struc ture element, and a rounded metal sheet having its edges caught between said intermediate ele ments and said structure elements, so as to cover the joint in a ?uidtight manner. ‘

9. A system for forcing two blocks away from each other, which comprises, in combination, at least one jack constituted by a malleable metal bag including two plates forming the bearing faces of the jack, deformable means forming a ?uid tight joint between said plates and means for feeding a liquid under pressure into said bag, and at least one wedge-shaped piece associated with said jack so as to transmit the thrust thereof to one of said blocks, whereby, once the blocks have been ?xed to a distance from each other, it is possible, by withdrawing said wedge-shaped piece, to remove said Jack from between said blocks.

10. A system for forcing two blocks away from each other, which comprises, in combination, at least two jacks in series, constituted each by a malleable metal bag including two plates form ing the bearing faces of the jack and deformable means forming a ?uidtight joint between said plates, and means for feeding a liquid under pressure into said bags, said two bags being ar ranged with their plates in parallel relation, and concrete embedding said two jacks so as to inter connect them.

11. A lack apparatus which comprises, in com bination, a malleable metal bag including‘ two parallel cylindrical plates constituting the bear

7 ing faces of the jack and deformable means forming a ?uidtight joint between said plates, and at least one conduit opening into said bag for feeding a liquid under pressure. thereinto so as to permit of in?ating it. .

12. A jack apparatus which comprises, in com bination, a malleable metal bag including two parallel cylindrical plates constituting the bear ing faces of the jack, deformable tore-shaped elements forming ?uidtight joints between the corresponding edges of said cylindrical plates, and at least one conduit openinginto said bag for feeding a liquid under pressure thereinto so as to permit of in?ating it.

13. A jack apparatus which comprises, in com bination, a plurality of elementary malleable metal bags including each two parallel cylindri~ cal plates constituting the bearing faces of the jack element, and deformable means forming a ?uidtight joint between said plates, at least one conduit opening into each bag for feeding a liq uid under pressure thereinto so as to permit of in?ating it, said elementary bags being so dimen

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sioned and arranged that the whole forms a com- ' plete annular jack system. '

14. A jack apparatus according to claim 13 in which said deformable means consist of tore shaped elements.

15. A jack apparatus which comprises, in combination, a malleable metal bag constituted by a ?exible wall folded annularly in zig-zag fashion whereby the whole, when not in?ated, is inscribed in a circular section of a diameter much smaller than the diameter of the unfolded structure, and means for feeding a liquid under pressure into said bag for causing it to expand.

16. A jack apparatus according to claim 15 further including hard elements inserted in the

’ inner folds so as to stiffen the whole. 17. A jack apparatus according to claim 15

further including hard concrete‘ bars ?lling the inner folds of said folded wall, so as to stiil’en the whole. , '

18. A method of utilizing a jack apparatus in cluding two parallel plates assembled in a ?uid tight manner by deformable joint means, which comprises injecting into said structure a matter which is initially ?uid but hardens after a time.

19. A method of utilizing a- jack‘ apparatus formed by‘a malleable metal bag including two parallel plates assembled in a ?uidtight manner by deformable jointmeans, which comprises in jecting into said has a matter which is initially ?uid but hardens after a time leaving a small free space in said bag, and completing the ?lling of said space by means of a liquid which remains permanently in the liquid state.

20. A methodof utilizing a jack apparatus formed by two malleable metal bags each consti tuted by two parallel plates assembled in a ?uid tight manner by deformable joint means, said bags being superposed with respect to each other, a which comprises injecting a permanent liquid into one of said bags, until a predetermined pres sure is reached therein, then injecting into the other bag a matter which is initially ?uid but solidi?es subsequently, so as-to permit the ?rst mentioned liquid to escape from the first bag, and so on,

EUGnNE FREYSSINET.

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2,270,240 Jan. 20, 1942. E. FREYSSINET ANCHORING OF TENSIONED CABLES IN CONCRETE CONSTRUCTIONS

Filed Feb. 1, 1941

.............................. I

Q My

BY

Patented Jan. 20, 1942 2,270,240

“UNITED STATES PATENT' OFFICE '‘ ANCHORING ‘OF TENSIONED CABLES IN

. CONCRETE CONSTRUCTIONS ‘

Eugene Freyssinet, Neuilly~sur-Seinc, France Application February 1,1941, Serial No. 377,040

' ‘ In France August 26, 1939

14 Claims.

I have already shown that the characteristics ‘ of various constructions of this nature can be considerably ‘improved by utilizing reenforce ments of steel having a high elastic limit sub jected initially to strong tensile stresses which produce in the construction a set of preliminary stresses opposite in direction to those produced by the application‘ of loads (see U. S. Patent 2,080,074). The tensile strain may be imparted to the reenforcements before or after‘the setting of the concrete. In the latter case, the reen forcements, composed of cables or bundles of high resistance, drawn out, steel wires,'are laid out in hollows left in the concrete to this effect. These reenforcements,- which in this case, do not adhere to the concrete, vare subjected to tensile stresses when using the hardened concrete as fulcrum for the tensioning devices. _ A di?iculty of this well known process, lies in

the anchoring members to be established on the Wires or cables under tension to prevent sliding of the latter in the concrete. To this effect, steel or concrete gripping mem

bers have already been devised comparable to those used in the anchorage of the cables of sus pension bridges and consequently exterior to the construction, the tension in the reenforcements being obtained by the use of jacks acting be tween‘ these vgripping members and the main

' part of the construction. These devices are ex- ?‘ pensive and the space they occupy prevents 'an extension. of their application to current con_ structions such as bridges or buildings. My present invention has for its object to pro

vide gripping memberswhich, among other ad- 53‘ vantages, eliminate all projections exterior to constructions of concrete or other materials sub jected to preliminary compression‘stresses. ‘ ‘

This process is'particularly applicable to con~ structions of concrete when the tensile strain is “ imparted to the reenforcements after the setting of the concrete, although it can also be utilized in constructions other than concrete or in con crete constructions when theylreenforcements are

, strained before the setting of the concrete. ‘In what follows, only the‘ application of the

‘process to ‘concrete will be considered for the sake of simplicity, it being understood that the other applications ‘fall within the scope of the invention. ‘

The general principle of my new process is as follows: In the construction, at the point where the extremity of the cable to be strained is lo cated, a very resisting element or member is em bedded in the concrete or in whatever other ma

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terial of the construction-t0 be subjected to preliminary stresses. The said member is pro vided with a ‘cavity through which the cable passes; the elemental wires or strands of this cable are spread out against the inner surface of the cavity, they are then put under tension and, while they are so strained, they are pressed against the inner surface of the cavity with sum cient compressive force to produce between said wires or strands and said surface a friction capable of counterbalancing the tension of the wires and thus to prevent the sliding of the ten sioned wires in the concrete. '

It is preferable to increase this compressive force to such a value that it will produce'an elastic expansion of the wall of the cavity which condition will contribute to holding the wires fast. The compression of the wires of the cable

against the inner surface of the cavity can be obtained by means of metallic wedges or pegs driven in by a jack or by a hammer in the axis of the cable or between its wires, or by hydraulic jacks composed of a sort of malleable bag which can be in?ated by the injection under pressure, in the liquid state, of a substance capable of ulti mate hardening such as synthetic resin. One method of obtaining this condition con

sists in embedding the wires-.of the cable, against the inner surface of the cavity, while these wires are under tension, in a substance adhering to the wires and capable of hardening, such as cement

- mortar to which it is pro?table to mix silicious or aluminous sand and asbestos to increase the friction of the wires on the mortar. Then a

. strong compression of this mortar against the

if)

inner surface of the cavity is obtained by intro ducing into the latter a suitable instrument. It is advisable to line the inside surface of the cavity‘ with a metallic lining and to put grease or an equivalent lubricant between the said lining and the inner wall of the cavity in~ order to reduce the friction. The cavity having the shape of a ‘truncated cone, and the compression of the mor tar being obtained by a male cone wedged in the axis of the cable, the'slipping, which tends to occur on the greased surface as a result of the tension of the wires when tensioning apparatus is released, compresses still more the mortar and increases the anchorage of the wires. The body‘ containing the cavity of which the

cable is held fast may be constructed in reen forced concrete; in this case, the cavity where the cable is held fast will be hollowed out in the concrete itself and the inner surface of

2 this cavity will be made capable of resisting the stresses of expansion by embedding in the con crete a steel reenforcement which encircles the cavity and is put in place before the concrete‘ is poured. vThis reenforcement may consist of a steel tube or of helicoid turns of steel wire, having preferably a ‘high elastic limit or~ of a combination of such'a tube and turns of wire wound about it. v -

’ In order to obtain an eifective transfer to the concrete of the strains borne by the said reen forcement, it is possible to provide a second transverse reenforcement of the concrete and composed either of a second coil formed by a steel wire, helically wound and located at a cer tain distance from the ?rst one, or of rectangu lar reenforcements perpendicular to the axis of the cable. My invention also comprises the apparatus

necessary to the practical realization of my process. _ The appended drawing, purely illustrative, and not inclusive of all cases, represents various em bodiments of my invention. Figure 1 represents a transverse sectional view ~

of the cable and of its sheath according to a ?rst way of realization, the section being cut at a point located beyond the anchorage. Figure 2 is a partial longitudinal sectional

view of this cable. » Figure 3 is a longitudinal half sectional view

of the anchoring device and of the tensioning jack at one end of the construction. \Figure 4 is the front view of a group of 2 wires and of an anchoring jaw on the jack. Figure 5 is part of the front view of a slotted

washer perpendicular to the cable, the function of which is to separate the wires prior to their

. tensioning.

In the practical example represented on Fig ures 1 to 5, the cable to be tensioned and an chored comprises 2 layers of wires or strands 8 and! (having in all an even number of wires or strands, 32 for example) grouped around a core consisting of a long pitch helicoid spring I. It is enclosed in a sheath composed of, for example (Fig. 1) two metallic sheets ‘I, ‘la, hooked one to the other by bending back their edges. This sheath is put in place in the molds be fore the concrete of the construction is poured and serves to insulate the cable with regards to the concrete in order to allow the elastic elongation of this cable at the moment of ten sioning, even if at this moment the concrete has already set and hardened. ' As can be seen in Figure 3, the extremity

of the cable penetrates into a truncated steel member 6 provided with a funnel-shaped cavity and hooped by a hardened steel wire 3 having, for example, an elastic limit superior to 35 kg. per square millimeter. This part 6 and the coil 3 are embedded in the concrete 2 poured about them. A concrete tight junction ID, of tape for example. joins part 6 to sheath ‘I to prevent the concrete from penetrating into this part and into this sheath. At the end of the slab of con crete 2, there is a thick steel washer l2 the pur pose of which is to sustain the thrust of the ten sioning jack and to transmit it to the concrete. A slotted plate I3 a portion of which figures in - the front view ‘on Figure 5 and which is ?xed by bolts l5 embedded in the concrete is coupled to a hoop-iron washer M which maintains the wires of the cable by pairs in the slots of plate iii. A cone I6 of very hard mortar and con

:3

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40

50

2,270,240 siderably reenforced longitudinally is poured be tween a tube I‘! (the axis of which lies along that of the cable) and a conical casing of smooth and polished sheet steel I8 enclosed in another casing l9 made of brass or tin plate. A conic casing 20, also made of tin plate or brass, is inserted in member 6, the surface of contact ‘between member 8 an dcasing 20 being lubricated so as to obtain a coefficient offriction of the order of 5 to 10%. The piston 2| of a jack bears upon washer l2 and is provided with sixteen radial slots 2la which allow the wires of the cable to pass by pairs. This piston 2| contains an ‘auxiliary piston 22 bearing upon cone l8. Cylinder 23 of piston 2| has sixteen anchoring jaws 24 each one of these receiving two-wires of the cable which are separated by an intermedi ate wedge 21 (a front view of which is seen on Figure 4 between the projections 28 and 29 which make up the anchoring laws). The concrete slab 2 comprises moreover a

number of turns 25 of ordinary soft steel and a set of reenforcements 26 parallel to the cable. The cable with its sheath having been cor

rectly placed in the molds of the construction, the extremity of the cable having been passed through casing 20 which lines the inside of the hollow member 6, and ?nally the coils 3 and 25 being in place, the concrete 2 is poured. Once the concrete has hardened, the wires of

the cables are separated by pairs and made to pass between washers l2 and i4 and in the slots of plate I3, which fastened by bolts, holds in place the whole ?xture. Then, cone IS with its tube l1, its casing I8

and the second casing 19, are inserted into the central hollow of the cable, and fresh plastic mortar containing silicious sand or asbestos is packed into the interval between casing l9 and casing 20. By means of the jack, the piston 2i of which bears, through the medium of washer l2, on the concrete surrounding tube 6, the steel wires, held fast by pairs on the anchoring jaws 24 of the cylinder of this jack, are tensioned; the

. cylinder drawing away from the concrete when pressure is admitted into the cylinder. Then, the wires being kept under tension, pis

ton 22 is made to drive in cone IS, the metallic casing !3 then sliding on casing H! with a mod erate friction of metal against metal. The cone produces an intense compression of the mortar between casings i9 and 20 of the order of 400 kg. per square centimeter in the particular exam ple which the drawing illustrates. '

' The mortar loses its excess 'water and becomes very hard, and a high value is obtained for the friction angle of the mortar on itself and on the - steel; at the same time, the mortar takes up a minimum volume. When the pressure in the cylinder of the jack

is released the tension in the steel is entirely transferred to that part of the device composed of cone l6, casings i8 and I9, and the mortar between l9 and 20 and casing 20. This ensem ble attracted by the tension then slides along the lubrified surface between tube 6 and casing 20, which condition produces a very strong grip ping eifect of the mortar on the wires of an ap proximate value of 800 ‘to 1000 kg. per square ' centimeter. This gripping effect obtains a per fect bond between the mortar and the wires, the angle of friction between surfaces 6 and 20, in creased by the slope of the cone, being inferior to the inner friction of the wires on the mortar. The elastic swelling of tube 6 and of coil 3 com

2,270,240 presses the concrete which lies between coils 3 and 25 and so transmits the strains developed in the anchorage to the whole reenforced slab‘by means of reenforcements 25, 26. Jack 2|, 23 may then be removed and those parts of the wires which jut" out from the construction may be cut oil‘. Then, through the centrally located tube II, a substance protective against rust may be in jected such as liquid cement, a synthetic resin capable of setting, or any other ?ller; it is even possible by these means to establish a bond‘ be

' tween the wires and their sheath. A warm sub stance, easy to melt, such as bitumen or a resin, may be injected after having heated the interior ‘of the cables by injecting hot air or steam, The function of the core composed of the heli

coid spring I is to ensure the possibility of this injection and the regularity of the cable itself in the curves which. it assumes. My invention is not con?ned only to the case _

where the tensioning occurs “after hardening of the concrete. The concrete in which the reen forcements under tension are embedded can be poured after the tensioning of these reenforce ments, on condition that supports for the an— chorage heads are available during this tension ing; these supports can be on the molds or on a portion of the concrete slab in which the reen forcements are not embedded and which is vpoured in advance, and which has already hard ened at the time of the tensioning.

It is obvious that the embodiments which have just been described constitute only examples and

' that these can'be departed from without affect ing the scope of the invention. For example, in the case when the reenforce

ments are tensioned after the setting and hard

r

H)

3 struction at the place where ‘the said‘ extremity‘ is- located. the setting of the group of wires in this cavity, the spreading out of the wires against

. the inner surface of the said cavity, the tension~ - 'ing'of these‘wires by an external force, the em bedding of the tensioned wires in a pasty sub stance adhering to the wires and capable of hardening, then the compressing of this sub stance, after its hardening, against the inner surface of the cavity, after which the said ex ternal force is removed. ‘

3. The process for anchoring the extremity of a group of steel wires constituting a reenforce

» ment of a concrete construction or the like which

30

ening of the concrete, the sheath insulating the . reenforcement with respect to the concrete may consist merely of a plain coating of a greasy sub stance or of a plastic one of low melting point, basically composed of bitumen, pitch or rubber

' and which is applied to the wires and protected if need be by swathing with paper or other ?bres. This plastic substance of low melting point may be softened at the true of the tensioning by means, for example, of an electric current sent throughout the reenforcements. My invention is applicable‘to the case where

the elements of the cable to be tensioned are constituted by strands or groups of wires in lieu of single wires. The word "wire” in the follow ing claims is intended to cover as well as a sin gle wire properly speaking a strand or a group of wires. What I claim is: - l. The process for anchoring the extremity of

agroup of steel wires constituting a reenforce ment of a concrete construction or the like which comprises: the provision of a cavity in the con struction at the place where the said extremity is located, the setting of the group of wires in this cavity, the spreading out‘ of the wires against the ‘inner surface of the said cavity, the tensioning of these wires by an external force, then the‘ compressing of the tensioned wires against the surface of the said cavity by a com pression adapted to produce between the wires and the said surface a friction capable of with standing the tension of the wires, after which the said external force is removed.

2. The process for anchoring the extremity of a group of steel wires constituting a reenforce ment of a concrete construction or the like which comprises: the provision of a cavity in the con- '

40

comprises: the provision of a funnel-shaped cav ity, in the construction, at the place therein where the extremity of the group is located. the said funnel-shaped cavity having its larger opening facing the said extremity, the setting of ' the group of wires in this cavity, the spreading out of the wires against the inner surface of this cavity, the tensioning of these wires, by an external force, then the compressing ‘of these tensioned wires against the surface of the said cavity by a compression adapted to produce an elastic deformation of the wall of the cavity, after which the said external force is removed.

4. The process for anchoring the extremity of a group of steel wires constituting a reenforce ment of a concrete construction which com

‘ prises: the provision of a funnel-shaped cavity, in the concrete at the place therein where the said extremity is located, the said funnel-shaped cavity having its larger opening facing the said extremity, the reenforcing of vthe wall of this

,cavity by means of a reenforcement embedded in the concrete about this cavity, the setting of the group of wires in this cavity, the spreading out of the wires against the surface of the said cavity, the tensioning of these wires by an ex ternal force, then the compressing of the ten sioned wires against the surface of the said cav ity by a compression adapted to produce an elas tic expansion of the said embedded‘steel reen forcement, after which the-said external force is removed. '

5. The process for anchoring the extremity of a group of steel wires constituting a reenforce ment of a concrete construction which com prises: the provision of a funnel-shaped cavity, in the concrete at the‘place therein where the said extremity is located, the said funnel-shaped ‘cavity having its larger opening facing the said extremity, the reenforcing of the surface of this cavity by means of steel embedded in the con~ crete about this cavity, the setting of the group of wires in this cavity, the spreading out of the Wires against the surface of the said cavity, the tensioning of these wires by an external force, then the compressing‘ of the tensioned wires against the surface of this cavity by means of at least one wedge inserted in the cavity with a force adapted to produce an elastic expansion. of the said embedded steel after which the said external tensioned force is removed.

6. The process for anchoring the extremity of a group of wires constituting a reenforcement of a concrete construction which comprises: the provision of a funnel-shaped cavity in the con creteat the place wherein the said extremity is located, the said funnel-shaped cavity 'having its larger opening facing the said extremity, the reenforcing of the surface of this cavity by means of a steel coil embedded in the concrete about this cavity, the setting of a hollow funnel-shaped

4 part in the interior of the said cavity, the pro vision of a lubricant between the said part and the surface of the cavity, the setting of the group ' of wires in the ‘interior of the said hollow part. the spreading out of the wires against the inner surface of the said hollow part, the tensioning of these wires by an external force, the embed ding of the tensioned wires in a cement mortar adhering suitably to the wires and poured in the said hollow part, then the compressing of_'this

Cl

mortar after its hardening, against the surface - of the cavity, by means of at least one wedge inserted in the said mortar with a force adapted “to produce an elastic expansion of the said coil after which the said external force is removed.

7. A device for anchoring a group of tensioned wires constituting a reenforcement of a concrete construction, the said device comprising in com bination: a concrete part in which is provided ;a funnel-shaped cavity, the inner surface of which surrounds the extremity of the wires, the said cavity having its larger opening facing the exterior‘of the construction,‘ asteel reenforce ment embedded in the concrete about the said cavity and means in the said cavity adapted ‘ to compress the wiresagainst the, surface of the said cavity whereby the steel constituting the said embedded reenforcement is elastically ten sioned. . '

8. The process of simultaneous tensioning and anchoring of a group of steel wires constituting a reenforcement of a concrete construction which comprises the setting of a hollow, funnel-shaped, steel shell over the extremity of the said group, the larger opening of the said hollow shell fac ing the exterior of the ‘construction, the pouring of the concrete about the said hollow shell, the spreading out of. the wires against the inner sur face of the said shell, the setting of at least one Wedge in the said shell, the tensioning of the wires after the hardening of the concrete, by applying an external tension to the extremity which projects out from the concrete, using the said concrete as fulcrum, then while maintaining this external-tension, the driving in of the wedge towards the smaller opening of the said hollow shell by a force adapted to produce an expan sion of the said shell, after which the said ex ternal tension is removed. ,

9. In a concrete or similar structure, in combi nation, a mass of concrete or the like, a longitudi nally tensioned reinforcement passing there

40

through and comprising an elongated member _ having a divided end portion comprising a plu rality of strands, the mass of concrete adjacent . one surface being provided with a cavity sur rounding the stranded end of said reinforcement, sa"d end being ?ared by the spreading out of the strands and embedded in an adherent plastic material which prevents relative movement be tween the strands and which forms therewith a hollow body in contact with the walls of the cavity, and means exerting pressure in a direction generally radially of the axis of the member and forcing saidbody firmly against the walls of said cavity. .

10. In a concrete or similar structure, in com bination, a mass of concrete or the like, a longi tudinally tensioned reinforcement passing there through ,and comprising an elongated member ' having a divided end portion comprising a plu rality of strands, the mass of concrete adjacent one surface being provided with a conical out wardly ?ared cavity surrounding the stranded end of said reinforcement, said end being ?ared

> H 2,270,240 '

by the spreading out of the strands and embedded in an adherent plastic material which prevents relative movement between the strands and which forms therewith a hollow frusto-conical body in anti-frictional contact with the walls of the cav ity, and a conical wedge exerting pressure in a di-' rection generally radially of the axis of the mem ber, disposed in anti-frictional contact with said body and forcing said body firmly against the walls of said cavity. '

11. In a concrete or similar structure, in com bination, a mass of concrete or the like, a longi tudinally tensioned reinforcement passing there th'rough and comprising an elongated member having a divided end portion. comprising a plu rality of strands, the‘ mass of concrete adjacent one surface being provided with a conical out wardly ?ared cavity surrounding the stranded end of said reinforcement, reinforcement means for the wall of said cavity, said stranded end be ing ?ared by the spreading out of the strands and" embedded in an adherent plastic material which prevents relative movement between the strands and which forms therewith a hollow frusto-coni cal _body/ in contact with the walls of the cavity, and means exerting pressure in a direction gen erally radially of the‘ axisof the member and forcing said body ?rmly against the walls of said cavity.

12. In a concrete or similar structure, in com bination, a mass of concrete or the like, a longi tudinally tensioned reinforcement passing there through and comprising an elongated member at least an end portion of which is divided into a plurality of strands, the mass of concrete ad y'acent said end portion of the reinforcement be ing provided with a conical outwardly ?ared cav ity surrounding said end portion and with a metallic reinforcement embedded in said concrete near the wall of said cavity, said end-portion be ing ?ared by the spreading out of the strands, means disposed between the spread strands and which forms therewith a substantially rigid frusto-conical body, said body being pressed ?rm ly against the wall of the cavity and tending to produce an elastic expansion thereof.

13. In a concrete or similar structure, in com bination, a mass of concrete or the like, a longi iudinally tensioned reinforcement passing there through and comprising an elongated member having a divided end portion comprising a plu rality of strands, the mass of concrete adjacent one surface being provided with a conical out wardly flared cavity surrounding the stranded end of said reinforcement, said end being ?ared by the spreading out of the strands and embedded in an adherent plastic material which prevents relative movement between the strands and which forms therewith a hollow frusto-conical body in contact with the walls of the cavity. means exerting pressure in a direction generally radially of the axis of the member and forcing said body ?rmly against the walls of said cavity. and metal sheathing covering the walls of said cavity and both the inner and outer walls of said frusto-conical body. ‘

14. A device for anchoring a group of tensioned wires constituting a reinforcement of a concrete construction. the said device comprising incom bination, a concrete part in which is provided a funnel-shaped cavity, the inner surface of which surrounds the extremity of the wires, the said cavity having its larger opening facing the ex terior of the construction, a metallic reinforce ment embedded in the concrete about the said

2,270,240 , 5 cavity, means in, the said cavity adapted to com press the wires against the surface of the said cavity whereby the metal constituting the said embedded reinforcement is elastically tensioned, and a. second metallic reinforcement embedded in said concrete part, disposed about said first named reinforcement, and spaced radially there

from, whereby the annular portion of the mass of concrete between the 'two reinforcements is placed under greater compression than the rest of the concrete part when said ?rst named rein

5 forcement is tensioned.

EUGENE FREYSSINET.

March 20? 1945. 2,371,882 ~

TENSIONING AND ANCHORING 0F CABLES IN CONCRETE 0R SIMILAR STRÚCTURE '

E. FREYSSINET

Filed Feb. l, 1941

A _ _

_ E .ì ä

_.rlll lllllllll.; ."5

_ Patented Mar. ­20,­ 1945 2,371,882 '

UNITED STATES PÄTENT oFl-?icE TENSIONING AND ANCHORING 0F CABLES . 1N_ CONCRETE 0R SIMILAR, STRUCTURES Eugène Freyssinet, Neullly-sur~8eine, France:

vested in the Alien Property Custodian

application February 1, 1941, serais». :11,041 In France October Z8, 1940 '

s claims.' (ci. ‘za-5o) It is well known that the characteristics of re

enforced concrete constructions are vconsider ably improved by artificially submitting the re enforcements to preliminary tensile stresses sum ciently high in order that the concrete is subject ed to permanent compressive strains (see my U. S. Patent No. 2,080,074). The tension may be lm parted to the reenforcements either before the setting of the concrete, or after its setting and hardening, on condition that, in the latter case, provision be made for suitable means to prevent the adhesion of the steel to the concrete, in order to allow the elongation of this steel embedded in the set and hardened concrete. _ Such reenforcements are frequently constituted

by means of steel wire cables having a high elas tic limit. In general, the devices used for ten­ sioning and anchoring comprise projections exte rior to the concrete to be compressed, and do not allow the compressive stresses to be increased be-­ yond a certain maximum which is very much less than the resistance of the concrete to be com pressed. f ` ­

My invention has for its object a process and a device for tensioning and anchoring cables, said device being incorporated in the concrete to be compressed without requiring any projection or

v25

addition to the concrete for the purpose of con- , ' cealing the anchorings. This device allows more over the increasing of the preliminary stresses to the yielding point of the concrete. y This process is applicable in particular to pre

stressed concrete constructions in the case where the tension is imparted to the reenforcements after the setting of the concrete, although it can also be utilized in constructions other than­ con crete or in concrete constructions when the re

' enforcements are tensioned before the setting of the concrete. . ­

In what follows, only the application of the process to concrete will be considered for the sake of simplicity, it being understood that the other applications also fall within the scope of my in vention. According to one practical application of this

process, an anchoring member which can be em bedded >in the concrete to be , compressed and which presents a funnel-shaped orifice, the smaller base of which faces the length of cable to be tensioned, is utilized in combination with a set of wedges placed between the wires of the lcable which wires are pressed down against the wall of the said oriûce, s'o that after the tensioning of theV wires by means of a :lack or other instrumen tality, the pressing of the wedges between the

35

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wires and ñnally the releasing of the tension ex erted by the jack, the tension- of the wires is maintained bythe wedßing. in the female c'one. of the male cone composed of the wires and the wedgesl pressed one against the other.

'I'he anchoring arrangement comprises then es sentially a tunnel-shaped cavity, the inner Sur face of which is capable of withstanding the stresses of expansion imrted to it by the wedg- . ing of the male cone, and means for transferring to the concrete to be compressed that component of these stresses which is parallel ,to the cable.

It may be made up, for example, of an element of cast steel, embedded in the concrete, compris ing, in the first place, a funnel-shaped cavity the inside of which is machined to obtain the desired shape and, in the second place, one or more sur faces bearing on the concrete, of sumcient ares to subject the concrete to sustainable stresses. But the same results may be obtained more '

economically by having recourse to means proper to reenforced concrete. The truncated cone may be hollowed 'out in the concrete itself and the wall of this cavity rendered capable of resisting the stresses of expansion by embedding in the concrete a first reenforcement which may con sist in a truncated tube or in a. coil formed by helicoid turns of steel wire, having preferably a high elastic limit, or in a combination of both means. The transmission of the strains from this first reenforcement or coil to the concrete to be compressed may be ensured by a second trans verse reenforcement of the concrete in which it is embedded. This second reeniorcement con.­ sists, for example, of a coil of'steel wire helically wound and located at a certain distance from the ñrst one. ,

In order to ensure a better achievement of the truncated aperture or cavity, it is possible to pour in advance concrete slabs, each provided with a cavity and with the reenforcing coil or coils. These slabs may contain one or more anchoring ' cavities.

one­ or more of these anchoring members are embedded in >the concrete of the construction which concrete can, in the proximity of the an choring members, be additionally reenforced or subjected'to preliminary stresses, perpendicular ly to the anchoring to be obtained. The appended drawing, purely illustrative and

not inclusive of all cases, represents various em bodiments oi my invention. Figure 1 is an axial sectional view of a portion

of a concrete anchoring slab constructed in con formity with my invention. ' This ligure shows

2 also a sectional view of a part of an hydraulic jack utilized in tensioning a cable. Figures 2 to­ 4 are transverse sectional views

along axes II-II, III-III and IV-IV of Fig. 1. Figure 5 represents a fragmentary plan view

of the device utilized for the fixation of the wires to the ,i ack. Figure 6 shows a fragmentary sectional view

showing another embodiment of an anchoring block. Figure 7 shows diagrammatically in longitudi

nal section one extremity only of a pre-stressed concrete beam, provided with anchoring blocks constructed in accordance with my invention. Figure 8 represents a sectional view of a pre

stressed concrete beam provided with these an choring blocks.

10

2,371,882 spread out and pressed against the inner wall a-b of the truncated cone and between these wires steel wedges 8 are set. The sides of these wedges are provided with cylindrical grooves la corresponding to the shape of the wires, so that these wedges, inserted between the wires are maintained by the latter and ‘form together with them a sort of male cone which comes to bear against the inner wall af--b of the female cone. For the operation of tensioning, in the case un

der consideration, an hydraulic Jack is utilized, the piston 9 of which can bear against head 2. This piston is provided with slots l0 equal in

_ number to that of the wires of the cable and

In the example illustrated by the drawing, the _ application of the anchoring device to the ten# sionlng of the reenforcements of a concrete con struction has been presumed to occur after the setting and hardening of the concrete. Each re enforcexnent. composed of a cable. is set in a sheath I which is set in place in the molds be fore the pouring of the concrete and serves to in sulate the said reenforcement from the concrete in order to allow the elongation of the reenforce ment. ' l

This sheath may consist of a tube of steel or of other material, preferably thin sheet steel rolled into a cylindrical shape, and clasped by bending back the edges. It may even consist merely of a plain coating of a greasy substance or of a plastic one of low melting point, basically com

. posed of bitumen, pitch or rubber which is ap plied to the wires. This coating can be protected by swathing with paper or other fibres impreg nated with substances of the same nature.

20

Each extremity of a reenforcement or only one , of the extremities, if the other be securely fas tened to the concrete by any well known anchor ing system, is inserted in the anchoring slab or block, which is going to be described with respect to Figures 1 to 5. This slab or block comprises a high-resistance

concrete mass 2, having therein an aperture or cavity the contour of which is generated by a complete revolution of the straight line af-b about the axis :Iz-_x, which forms with line a-b an angle having a tangent of approximately 5’5, the said straight line being joined to the gener ant of tube I parallel to axis :c-œ by a curve b-c. About the wall of the ori?ce so formed, a steel

reenforcemcnt 3 is embedded in the concrete 2. This reenforcement may be composed of heli cold­ turns of asteel wire having a high elastic limit so that the coil thus formed can resist the strains to which the wall of the cavity is subject ed in operation. In the example described, the slab or block has the form of a solid of revolu tion composed of a head 2a and of a prolonga tion 2b having the shape of a. truncated cone which is joined to the extremity of sheath I by a junction Ia of tissue or of paper impregnated with a plastic substance, such as tape. About the head 2a, the concrete is reenforced by a sec ond coil 4 which may be of soft steel. The concrete 5 of the construction or of the

piece to be built is poured about tube I and about the block taking care to allow provision for a hole 6 through which it will be possible to have access to the extremity of the cable (passing through head 2) from the exterior of the con struction. The wires 1 composing this cable are

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u

used for the passage of the wires, whereas the cylinder II comprises devices for the fastening of these wires. These devices consist in trape zoidal slots I2 provided on a rim I3 of the cylin der I_I and of wedges I4 which are inserted in these slots between two wires of the cable; the number of slots is consequently equal to half the number of wires, which condition requires, in this embodiment, the use of cables having an even number of wires. In the interior of piston 9, a second piston

I5 may displace itself and come to bear on the extremity of wedges 8 by means of a small plate I6 provided with slots for the passage of the wires. Piston 9 is provided with a hollow Il the diameter of which corresponds to that of the small plate. The jack being disposed as shown in Fig. 1

and pressure being admitted in cylinder II,­ this cylinder draws away from piston 9 and tensions wires l. The wedges follow the movement of the wires at the start until they run against plate I6, they then leave between themselves suillcient clearance to allow the wires, pulled by cylinder I I, to slide freely. In zone b-c of the anchoring head, the wires

press against the concrete of this head and to limit their friction, this zone is lined -by a casing I8 of tinplate for example. ì When the tension stress, which can be de

termined from the pressure in cylinder II, at tains the desired value, the pressure is maintained _ in the cylinder, and piston I5 is put under pres sure. The latter obtains a compression of the wedges between the wires by expanding the male cone and by compressing it against the inner wall of the female cone. The pressure in the two jacks may then be

released, the wires withdrawn from slots I2 of the jack and the latter removed; the anchoring thus being finished. The tensioned cable. sub jected no longer to any external force, wedges the male cone composed of the Wires and of the wedges in the female cone. The wires could, as a matter of fact, slip between the wedges only if the angle of friction between wedges anf‘ wires fell below a value ß such that tan.

a being the value of 1%; the angle at the top of the cone and n the number of wires.` Butl this angle ß is chosen much smaller than the angle of friction which renders slipping impossible regardless of the condition of the surfaces of the Wires and of the wedges and even if these sur faces were abundantly greased. The pressures between wedges and wires are, besides, of such magnitude that the grease, if there were any, would be completely driven away. In order that the anchoring may resist it_

2,371,882 is therefore sufficient that the wall of the female cone withstand the tension of the cable and b able totransmit it to the concrete. . '

It is at ̀ this point that the purpose of the hard steel coil 3 appears. It must bear the stresses which make with the axis of the cone an angle which is the sum of the angle at the top ’of the cone and of the angle of friction steel on concrete. Under the action of the tensioned cable, there

results, finally, an equilibrium between the de formations of coils 3 and l, of the concrete 2 and that of the underlying concrete 5, an equilib rium which allows a relatively large deforma tion of coil 3, a relativelyv much smaller de formation of coil 4 and a triple compression stress accompanied by a plastic deformation of the concrete 2 with the production of isostatic lines such as UV, XY. In that portion of the concrete where the head

bears on the concrete 5 of the construction, this concrete may be profitably reenforced by rectan guiar reenforcements.

It is to be noted that nothing prevents the jack from being set in place for operation a second time; the wires may be tensioned again by means of the jack, the wedges loosened, the initial tension increased (or even reduced, if a means for preventing the wedges from jamming by themselves be provided). So the tensioning operations may be effected in a progressive man ner, they may be rectified, in case of error, etc. Once‘the tensioning has been completed, hole

t may' be stopped up by concrete, and the ex tremities of projecting wires embedded in con crete which ñils up a small recess provided for- in the mass subjected to preliminary stresses, which process oñers the advantage of an additional security by opposing the vslipping of the wires against the wedging means. Figure 6 shows a cast steel anchoring block 2a

provided with a female >cone 2b, the surface 2c, 2d of which block bears on the concrete and transmits the strains developed by the tensioned cable. This _anchoring block» is utilized in the same manner as that described for the concrete slab.

Figure ‘7 shows the extremity of a beam pro 4vided with reenforcements d set in sheaths, the reenforcements being tensioned and anchored as has just been described. The anchoring heads e are located at the extremities of the reenforce ments in the housings provided for, prior to the pouring of the concrete. The block may have also a square or rectangu­`

lar cross-section and comprise anchoring devices for several cables. In this case, coils ‘i may be

, replaced by rectangular. reenforcements perpen­ dicular to the cable. In the case where the cables are embedded in

a plastic substance of low melting point, this sub stance may be softened at the time of the ten sioning by means, for example, of an electric cur rent sent throughout the reenforcements.

It can be seen, in the process described, that the jack which tensions the wires uses, as a ful crum, the concrete which constitutes the final anchoring, so that the temporary tension (dur~

A ing the tensioning operation) and the final ten sion are both directed along the same axis and act on the same substance, which conditions al low the compressing of the entire surface of the concrete to a maximum stress consistent with its resistance. The invention is not limited to the case where

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the tensioning is effected after hardening of the concrete. The concrete in which the tensioned reenforce

ments are embedded may be poured only after the tensioning of these reenforcements, on con dition that fulcrums for the anchoring blocks be available while the tensioning is in process; these fulcrums can be chosen on the molds or on a por tion of the concrete of the construction in which the reenforcements are not embedded, which concrete is poured in advance and has already hardened prior to the tensioning. For example, in the case of a beam having a

cross-section as represented on Figure 8, it is possible, after setting in place reenforcements d and the anchoring blocks, to pour first the con crete represented by the hatchings in which con crete the reenforcements are embedded only at the extremities of the beam. When this concrete has hardened, those reenforcements, the an‘èhor ing blocks e of which utilize the said concrete, as fulcrum, may then be tensioned. Once the ten sion and anchoring operations are completed, the rest of the concrete (see the dotted lines in Fig. 8) may be poured about the tensioned reenforce ments d. y

The device for tensioning and anchoring con structed according Ato my invention also odors a

_ practical means of obtaining, by tensioned re

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enforcements, a uniting into a single structure of distinct concrete pieces laid out end to end for example. The tensioning of the reenforcements which will be placed for example in the holes provided in these pieces, will result in their com pression one against the other.

it is obvious that the embodiments which have just been described constitute only examples and that these can be departed from without affect ing the scope of the invention. The invention is applicable not only to the case where the ele ments of the cable to be tensioned consist in sim ple wires, but also to the case where these ele ments consist of strands or of groups of wires. In the claims hereunder, the word “wire” must be understood as designing not only a single wire properly speaking, but also a group of wires or a strand. What I claim is: l. A process for anchoring an end of an elon- _

gated reinforcement for a structural member, which reinforcement includes a group of wires, said process ‘comprislng, providing a funnel-` shaped cavity in said structural member with its larger end facing outwardly away from the mem ber, inserting said reinforcement wires within said member with portions adjacent the ends thereof Within said cavity, spreading out the wires in spaced relationship against the wall of the cavity, tensioning the wires by the applica tion of an external force, and forcing wedges be tween each pair of adjacent wires, the force ap plied to the wedges being sufficient to produce enough friction between the wires and the wedges l to withstand the ,tension in the wires, after which v said external force is discontinued.

2. A process for anchoring an end of an elon- , gated reinforcement for a concrete member, which reinforcement includes a bundle of wires, said process comprising, providing a funnel shaped cavity in said concrete member with its larger end facing outwardly away from the mem ber, lining the wall of the larger end of the cav ity with reinforcing metal inserting said rein forcement wires within said member with por tions adjacent to the ends thereof disposed within

4 aaneen the larger end of said cavity, spreading out the wires in spaced relationship against lining of the larger end of the cavity, tensioning the wires by the application of an external force, and apply ing wedges between each pair of adjacent wires, with 'sufficient force to produce an elastic expan sion in the metal lining and sufiicient friction be tween the wedges and wires to anchor them in place, after which said external force is discon tinued. .

3. A process for anchoring an end of an elon gated reinforcement for a concrete member. which reinforcement includes a bundle of wires, said process comprising: enclosing said wires ad 'jacent their ends within a hollow funnel-shaped steel member, said hollow member having its larger opening facing in the direction of said ends, pouring concrete about said hollow mem ber, spreading out the wires in spaced relation ship against the inner surface of the hollow member, placing wedges between eacn pair of adjacent wires, tensioning the wires after the' hardening of the concrete by exerting a tensile stress on their extremities which project out from the concrete using said concrete as a fulcrum, then while maintaining the tensile stress, apply ing the wedges toward the smaller end of said hollow member between adjacent wires with suf ncient force to produce an elastic expansion of said hollow member and suincient friction be tween the wedges and wires to anchor them in place', after which said external tensile stress is discontinued.

4. In a concrete or similar structure, in com bination, a mass of concrete or the like, a longi tudinally tensioned reinforcement passing there through and comprising an elongated member having a divided end portion comprising a plu rality of strands, the mass of concrete being pro vided with a conical outwardly flared cavity sur rounding said strands, said strands being spread to engage the wall of the cavity in circumferen tially spaced relationship, and wedges forced be tween each adjacent pair of strands in a, manner to hold the strands tofrictionally engage with the wall of the cavity. \

5. A concrete or similar structure having means for anchoring the end portions of a bundle of tensioned wires constituting reinforcement of said structure, said means comprising, in com bination, a concrete part having a funnel

f shaped cavity therein, the wall of which sur rounds said bundle of wires adjacent the said end portions, said cavity having its larger end facing in the direction of said end portions and away from said concrete structure, a tubular metal reinforcement embedded in said concrete part and spacedly encircling said cavity, said rein forcement being tapered oppositely to and sur rounding the larger end of the cavity, said wires

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being spread against the surface of said larger end of the cavity, and wedges forced between each pair of adjacent wires in a manner to ten sion the wires around the wall of the cavity.

6. A concrete or similar structure, according to claim 5, wherein said tubular metal reinforce ment consists of a helically wound hard steel wire.

7. A concrete or similar structure having means for anchoring the extremity of a bundle of tensioned wires constituting reinforcement of said structure, said means comprising, in com binatìon, a concrete block embedded in said struc ture and provided with a funnel-shaped cavity serving as a housing for a portion of said bundle of wires adjacent to the extremity thereof, said cavity having its larger end facing in the direc tion of said extremity and away from said struc ture, a steel reinforcement lining the wall of the larger end of said cavity, a second steel rein forcement embedded in the block and spacedly surrounding said lining and located adjacent to the outer periphery of said block, bearing sur faces on said block facing said structure in a direction away from said extremity of the bundle of tensioned wires and arranged to transmit com pressive strains to the structure under the in-' iìuence of the tension in said wires, said wires being deñected to lie along the lining( in circum ferentially spaced relation, and wedges forced between each pair of adjacent wires in a manner to tension said lining.

8. A, concrete or similar structure having means for anchoring the extremity of a bundle of tensioned wires constituting reinforcement of said structure, said means comprising, in com bination, a concrete block embedded in said structure and provided with a funnel-shaped cavity serving as a housing for a portion of said bundle of wires adjacent to the extremity thereof, said cavity having its larger end facing in the direction of said extremity and away from said structure, a steel reinforcement lining the wall of the larger end of said cavity, a second steel reinforcement embedded in the block and spacedly surrounding said lining and located ad jacent to the outer periphery of said block, bear ing surfaces on said block facing said structure in a direction away from said extremity of the bundle of tensioned wires and arranged to trans mit compressive strains to the structure under the influence of the tension in said wires, said wires being deflected to lie along the lining in circumferentially spaced relation, and wedges

, forced between each pair of adjacent wires and forcing the wires against said lining with suf ficient pressure to place said lining and the sur rounding concrete .under tension.

EUGÉNE magasiner.

2,618,147 E. FREYSSINET Nov. 1s, `195.2 MEANS ANCHORING TENSIONED CABLE FOR PRESTRESSED CONCRETE

Filed June 8, 1945

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UNITED STATES

2,618,147

il . f . TENT OFFICE

2,618,147

MEANS ANCHORING TENSIONED CABLE FOR PRESTRESSED CONCRETE

Eugène Freyssinet, Neuilly-sur-Seine, France

Application June 8, 1945, Serial No. 598,313 In France September 30, 1941

Section 1, Public Law 690, August 8, 1946 Patent expires September 30, 1961

(Cl. 72-50) 5 Claims. l

In my prior U. S. Patent No. 2,270,240, I have described means for anchoring tensioned cables passing through concrete masses to which they do not adhere. The cable to be anchored is passed through a Very strong tube embedded in concrete and strongly adherent thereto, then the cable is tensioned by extraneous means, and a soft substance capable of hardening, such as ce ment mortar, is compressed very tightly between the cable component wires and the inner wall of the tube; in the case where the tube provides a generally frusto-conical or ñaring recess, com pression is obtained for instance by means of a wedge forced into the recess along the axis there of. The purpose of cement mortar was to provide for an even action on the various wires in spite of fortuitous diameter dilferences; however, I have found that the mortar is not altogether nec essary to serve the purpose aimed at.

It is an object of my invention to provide im provements in or modifications of my aforesaid anchoring means. Instead of being lined by a steel tube as dis

closed in my aforesaid patent, the wall of the frusto-conical or flaring recess in concrete may merely be lined with a hoop of hard steel having a high tensile strength, the hoop being made of contacting coils. The conical wedge forced along the recess axis may be a mass of concrete pro vided with an outer hard steel hoop or steel sheet; such outer coatings providing for regu larization or even distribution of compressional forces from the wires on concrete in the wall of the recess and the wall of the wedge so as to pre vent damage to said concrete but they allow an amount of plastic deformation of the combina tion of parts, which secures an even action on the various Wires as a hydraulic distribution would do.

It is possible to manufacture a separate an chorage unit or block made of concrete having a frusto-conical recess lined with a hoop embedded in said concrete and a second hoop of soft steel proximate to the periphery of the concrete mass; the blocks may be positioned at proper location in the planking when the cables are placed be fore pouring concrete. The following description with reference to

the appended drawings given solely by way of example will show how this invention may be carried out.

Fig. 1 is an axial section taken along the axis of a cable and showing an anchoring device in accordance with my invention.

Fig. 2 is a diagrammatic development drawn

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on a smaller scale, of a hoop disposed around the anchorage block.

Fig. 3 is a longitudinal section of a wedge. Fig. 4 is a cross section of a modified wedge. Referring to Fig. 1, the reference character l

designates cable wires accommodated in a sheath 2 positioned before pouring concrete 3, as dis closed in my prior patent. At either end of the cable or, at one end thereof should the other end be provided with usual anchoring means, an an choring unit or block manufactured beforehand, and to be presently described is secured. The block includes a substantially cylindrical mass 4 of high grade concrete having a soft steel hoop 5 near its periphery, and a substantially frusto conical recess 6 along­ the axis of the cable to be tensioned, through which the cable wires pass. The inner wall of the recess is lined with a hoop 'I consisting of contacting coils of hard steel hav ing a high tensile strength, around which con crete ll is poured. The block thus constituted is threaded on the cable end before pouring con crete 3 and secured to the planking. Around the block is disposed a hoop connsistingI of a wire 8 which is festooned in zig-zag fashion, and a few coils 9 as shown in development on a smaller scale on Fig. 2.

Concrete 3 is then poured. When said con crete has set and hardened, the planking is taken away and a wedge I0 is forced into the recess along its axis; the wedge I0 (Fig. 3) may be made of high strength concrete II cast into the annular space between a central tubular steel core I 2 and a frusto-conical hoop I3 having con tacting coils of hard steel. By means of a, jack device as described in my prior patent, the outer ends Ia of wires I are drawn to be tensioned as required, after which the wedge I0 is driven into the recess so as to squeeze the cable wires be tween the wedge and the recess wall. Owing to the squeezing action, hoop ‘I is sub

jected to a high stress causing a resilient de formation thereof, and concrete 4 of the anchor ing block is compressed between said hoop 'I and hoop 5 which is also stressed although to a less degree. Hoop 8, 9 acts to distribute through concrete 3, the forces transferred to the outer hoop 5 of the anchoring block. Anchoring is thus performed; the jack device

may be removed and the ends Ia of wires I cut away. Through the central core I2 in Wedge I0, a

rustprooñng material may be injected into sheath 2 for instance cement, synthetic resin or any other ñlling. material.

2,618,147 3

In the modiñed wedge shown on Fig. 4, a steel sheet I4 is substituted for hoop I3; sheet I4 may be provided with corrugations Ida located along generating lines of the cone, for accommodation of the cable Wires. The plasticity of the outer conical Wall and of

the wires (of the cable) themselves are sufficient -to provide for anchorage of all Wires in spite of any small difference in diameter thatY they may

p exhibit.

An advantage of my process is that the Wires can be tensioned by degrees or steps; after ar first tensioning, the jack may be mounted again, the wires drawn, the Wedge removed and then reset after increasing or decreasing tension. In the latter case, it is only necessary to hold the Wedge apart from its ñnal position by any suitable device. f »

While I have described; What I deem to be an eñ‘lcient and reliable embodiment of my inven tion, I do not Wish to be limited thereto as many alterations may be brought therein without de parting from the spirit of the appended claims. What I claim is: l. In combination With an open-centered bun

dle ofV stretchedA steel Wires, a pair of cooperating gripping units for maintaining said wires in stretched condition, which comprises an annular concrete structure through which said wires ex tend, having a daring, inner, Wire-contacting Wall providing a backing for said wires, said inner, wire-contacting Wall being faced with mutually contacting coils of Wire, and a ñaring wedge hav ing an outer peripheral surfaceA of mutually con tacting coils of. wire providing a Wire-contacting Wall, said wedge being held in> compressed condi

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4 tion within said bundle to nip said steel wires between said Wire-contacting walls and having its outer surface conformed to the general shape of the inner surface of said Wire bundle, at least one of said­ uni-tsy comprising a­ plastical‘lyV deformable concrete portion in ring formation adjacent said Wire-contacting wall thereof.

2. The structure of claim 1, said Wedge having . a core of plastically deformable concrete confined in said. Wire-contacting Wall thereof.

3. The structure of claim 1, the coils of Wire forming the wire-contacting Wall of said Wedge comprising> a spiral.

4. The structure of claim 1, including a metal tube positioned axially in said wedgeand periph erally spaced apart from said wall thereof, and a. body of concrete confined between said wall and said metal tube.

5`. The structure of claim 1, said annular struc ture being reinforced in its outer portion to resist bulging. ` `

EUGENE FREYSSINET.

REFERENCES CITED

The following> references are of record in the file of this patent:

UNITED STATES' PATENTS

Number Name Date 453,286 Lieb _____________ __ June 2, 1891

2,173,698 Schenk _________ __ Sept. 19, 1939~ 2,264,035 Birkhofe-r ________ __ Nov. 25,1941 2,270,240 Freyssinet ________ -_ Jan. 20, 1942

FOREIGN PATENTS Number Country Date

5451,43? Great' Britain ____ __ Nov.Y 26, 1941

Aug- 24, 1954 - E. FREYSSINETV _ 2,686,963

METHOD OF ANCHORING REINFORCEMENTS

Filed Sept. 15, 1948

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Patented Aug. 24, 1954‘ 2,686,963

UNITED STATES PATENT OFFICE 2,686,963

METHOD OF AN CHORING REINFO'RCEMEN TS

Eugene Freyssinet, Neuilly-sur-Seine, France Application September 15, 1948, Serial No. 49,377 Claims priority, application France April 27, 1948

(Cl. 29-525) 2 Claims. 1

I have already described in my prior Patents No. 2,270,240 and No. 2,618,147 an arrangement for anchoring previously stressed reinforcements, more particularly suitable for cable reinforce ments. ‘

This arrangement includes, in register with the . end of the cable,‘ a frusto-conical wall operatively connected to the mass to which a preliminary stress is to be given and against which the strands of the reinforcing cable to be anchored are strongly fastened by a frusto-conical wedge en gaging it under high pressure. This wedge may be constituted by a casing of sheet metal or by a hoop of hard steel ?lled with concrete and it may include an axial tube allowing the injection under pressure of the protecting cement into the

‘ recess provided for the reinforcement in the mass submitted to a preliminary stressing. My invention has for its object improvements

in the anchoring means wherein the wedge is con stituted by concrete without any outer casing enclosing it, the fastening of the reinforcing strands being performed through direct contact with the concrete of the wedge so as to bene?t to a maximum by the plastic deformation of the concrete obtained by pressure, so as to secure a uniform tightening of the various reinforcing strands even if the diameters of these strands show substantial differences.

This improvement provides an important ad vantage inasmuch as it is possible to use for the constitution of reinforcing strands not only drawn Wire of comparatively regular diameter but also ?laments obtained through extrusion or rolling at high temperature or at room temperature and the variations in gauge of which may be fairly large.

Preferably the concrete wedge is provided with recesses of a substantially cylindrical shape in tended for the housing of the reinforcing strands to be anchored and matching substantially the shape of these strands. The following description and accompanying

drawings which are employed by way of exempli ?cation and by no means in a limiting sense, will show how the invention may be executed and the various features appearing both in the drawings and in the speci?cation form of course part of the invention. In said drawings:

Fig.‘ 1 is a perspective view of an embodiment of the wedge according to my invention.

Fig. 2 is a longitudinal section thereof. Fig. 3 is a longitudinal section of a complete

anchoring system incorporating my improved wedge. ‘

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2 Fig. 4 is a transversal cross-section of this

arrangement including the tightening wedge. Fig. 5 is a transversal cross-sectional view at

a larger scale of one of the recesses provided in the wedge for the armature strands. Figure 5a is a view similar to Figure 5 illustrating the ideal condition existing after the wedge has ben plas tically deformed. The wedge illustrated in ‘the drawings is con

stituted by a frusto-conical body I of molded con crete showing a high resistance to compression, the granular structure and the composition of the concrete. being carefully chosen in order to achieve this result while the molding may be carried out, as well known per se, under vibratory conditions and under compression. The frusto conical surface of the wedge thus obtained is left bare, in other words it is not enclosed in a sheath or binding or hoop of steel as described in my prior patents referred to hereinabove. In said frusto-conical wall of the wedge, it is sometimes desirable ‘to provide, in the casting, recesses 2 directed substantially along generating lines of the wedge and the number of which corresponds to that of the strands of the reinforcement to! be anchored, each recess showing cross-sectionally the shape of a half-cylinder a—-b—-c the diameter of which is substantially equal to that of the strands or slightly greater, sa‘id half cylinder ex tending laterally under the form of ?aring sur faces aa', cc’ to further the introduction of the reinforcing strands (Fig. 5). The wedge may be provided with an inner tubu

lar metal core 3 that may serve for the subse quent injection of cement or of another substance into the channel containing the reinforcement. The reinforcement being inserted in each chan~

nel 4 provided inside the mass that is to be re inforced (Fig. 3) and the different strands of said reinforcement 5 opening into contacting relation ship with the wall of the frusto-conical opening 6 forming an extension of said channel at the end thereof, the wedge is urged axially into said open ing whereby the strands are housed in the various. recesses 2 of the Wedge. This introduction of the wedge may be executed by means of a jack already described in my prior patents, said jack allowing a preliminary stress to be given to the reinforcing strands and keeping them stretched during the wedging operation while an extremely high pres sure is exerted on the wedge the reaction of which pressure is absorbed by the reinforcement itself. The contacting surface between the wedge and

each strand is considerable as it is formed by the entire half surface of the strand. The pressure

2,686,963 3

exerted on the wedge is generally higher than the rate of resistance of the concrete to compres sion so that the latter is plastically deformed and ?lls up all the open spaces, as shown in Figure 5a, that is the spaces remaining open by reason of an uneven gauge of the reinforcing wires or else those constituted by the spaces ‘I required for the correct positioning of the strands with reference to the wedge. The wedge concrete is longitudinally bound by

reinforcements 8 that may be constituted by mere nails. The member inside which a frusto-conical opening 6 is provided, the shape of which matches that of the wedge, may be a previously cast con crete member that is then provided with a hoop wound in tight convolutions over the inner wall of the opening and the outer wall of the member. The member considered may also be constituted by a cast steel body.

This latter case has been illustrated in Fig. 3: the tubular steel body de?ning the opening 6 is provided outwardly with projecting flanges 9 adapted to bear against the concrete it of the reinforced part. The tubular body may include striations, regular or otherwise, as illustrated at 911 in Fig. 3. In Figure 3, the curvature of the sleeve 6 has ben exaggerated for ready visibility. The purpose of the curvature is to avoid having a sharp bend or angular elbow in the reinforce ment wires 5, being conventional and having nothing to do with the invention. The wedge, when deformed, does not completely ?ll the sleeve 9 (unless its size has been accurately determined for that purpose, but in practice the wedge is very roughly designed). When the wedge is in serted into the sleeve, contact between the wires 5 and the surfaces of 5 and I occurs along a rela tively short distance somewhat along the wedge.‘ As the latter is forced in and undergoes plastic distortion, the contacting zone progressively ex

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4 tends. Eventually, a part of the length of the sleeve is ?lled.

Obviously, many modi?cations may be made in the arrangement that has just been described, in particular by substituting technically equivalent means for those disclosed, without departing from the scope of the invention as de?ned in the accom panying claims. What I claim is: 1. A method for anchoring reinforcement wires

in a member having an inwardly tapering cavity along the wall of which portions of said wires are spread, said method comprising the steps of in~ serting between said portions and in contact therewith a bare-surfaced wedge of hardened concrete the general shape of which is that of said cavity, for engaging said portions between said wall and the bare concrete surface of said wedge, and forcing said wedge inwardly of said member with a pressure suf?cient for causing plastic deformation of the hardened concrete‘ of said wedge to the extent that empty space around said portions is filled with plastically deformed hardened concrete.

2. A method as recited in claim 1 and further comprising the step of positioning said wires in recesses in the hard surface of said wedge.

References Cited in the ?le of this patent

UNITED STATES PATENTS

Number Name Date 985,915 Marchand, Jr ______ __ Mar. '7, 1911

2,371,882 Freyssinet ________ __ Mar. 20, 1945

FOREIGN PATENTS Number Country Date

424,006 Great Britain _____ __ Feb. 13, 1935 541,160 Great Britain _______ __'___ of 194-1 541,437 Great Britain _____ __ Nov. 26, 1941 561,716 Great Britain _____ __ ‘June 1, 1944