US2449276A - Pretensioned reinforcement - Google Patents

Pretensioned reinforcement Download PDF

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Publication number
US2449276A
US2449276A US606116A US60611645A US2449276A US 2449276 A US2449276 A US 2449276A US 606116 A US606116 A US 606116A US 60611645 A US60611645 A US 60611645A US 2449276 A US2449276 A US 2449276A
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Prior art keywords
sheath
reinforcement
elements
core
anchorings
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Expired - Lifetime
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US606116A
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English (en)
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Chalos Marcel
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B28—WORKING CEMENT, CLAY, OR STONE
    • B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
    • B28B23/00—Arrangements specially adapted for the production of shaped articles with elements wholly or partly embedded in the moulding material; Production of reinforced objects
    • B28B23/02—Arrangements specially adapted for the production of shaped articles with elements wholly or partly embedded in the moulding material; Production of reinforced objects wherein the elements are reinforcing members
    • B28B23/04—Arrangements specially adapted for the production of shaped articles with elements wholly or partly embedded in the moulding material; Production of reinforced objects wherein the elements are reinforcing members the elements being stressed
    • B28B23/06—Arrangements specially adapted for the production of shaped articles with elements wholly or partly embedded in the moulding material; Production of reinforced objects wherein the elements are reinforcing members the elements being stressed for the production of elongated articles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B28—WORKING CEMENT, CLAY, OR STONE
    • B28B—SHAPING CLAY OR OTHER CERAMIC COMPOSITIONS; SHAPING SLAG; SHAPING MIXTURES CONTAINING CEMENTITIOUS MATERIAL, e.g. PLASTER
    • B28B23/00—Arrangements specially adapted for the production of shaped articles with elements wholly or partly embedded in the moulding material; Production of reinforced objects
    • B28B23/02—Arrangements specially adapted for the production of shaped articles with elements wholly or partly embedded in the moulding material; Production of reinforced objects wherein the elements are reinforcing members
    • B28B23/04—Arrangements specially adapted for the production of shaped articles with elements wholly or partly embedded in the moulding material; Production of reinforced objects wherein the elements are reinforcing members the elements being stressed
    • E—FIXED CONSTRUCTIONS
    • E04—BUILDING
    • E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
    • E04C5/00—Reinforcing elements, e.g. for concrete; Auxiliary elements therefor
    • E04C5/08—Members specially adapted to be used in prestressed constructions

Definitions

  • the reinforcement forming the subject-matter of the present invention is intended to be used for preconstrained constructions: it comprises two juxtaposed elements which are very long relatively to their cross section; one of said elements, of great tensile strength, is intended to be incorporated in the construction to be preconstrained; it is combined with the second element, of high resistance to longitudinal compression, so that it can be greatly tensioned by taking a bearing on the end of the latter and thus remain tensioned until the reactions balancing its tension are transferred from the second element to the construction in which the reinforcement is incorporated.
  • the present invention makes use of a compression member which possesses in the stable state, an internal potential of forces, capable of being transferred to the construction with which it will be combined.
  • a compression member always prepared beforehand (for instance in the workshop) can be manipulated, transported, shaped according to a certain curvature, then used at any moment as an ordinary reinforcement according to classical construction methods
  • the reinforcement can be constituted by the following elements, or by any other equivalent members:
  • a sheath having high mechanical features under traction (treated steel, glass thread, etc.).
  • a core of high resistance to compression (steel, hooped concrete, etc.).
  • End anchorings which, before using the reinforcement, transfer the reaction of the previously tensioned or pretensioned sheath to the core, and, when it is utilised, transfer the reaction of the sheath to the material to be placed under a preconstraint.
  • the sheath can on the contrary be compressed and the core tensioned, and the splices can be replaced, entirely or in part, by the very elements composing the sheath if the connection of the constituent parts is intimately ensured.
  • the tensioned elements of the accumulating member will preferably be constituted by very strong hard wires, twisted or braided; the sheath obtained thus advantageously presents an apparent modulus of elasticity lower than Youngs modulus of the metal used.
  • hard steel is only contem plated for an economical purpose function of the industrial possibilities and does not characterise the invention in any way, as it is possible to use the high mechanical features ofall rolled, wiredrawn or cold-drawn materials, such as natural whatever may be the system of static or dynamic loads and over-loads.
  • end anchorings the function of which is to ensure, under the marketable form of the reinforcement, the action of the internal forces of the system, can be of any nature and maintain the threads or ribbons of threads, either by locking wedges on a cap, or by beading a plastic metallic cone on a very strong olive-shaped member, or preferably by coating with a binding materiaLjfusible or not (cement mortar, various resins, metals, etc.) according to the art of capping metallic cables.
  • the anchorings forming part of the invention allow, when manufacturing the reinforcements, the immediate locking of the desired tensions by means of any suitable mechanical devices: flexible metallic lock, key-bolt, nut, wedges, welding, etc. They also provide the user with possibility of verifying the value of the accumulated tensions, as well as the means of modifying, if need be, said state of equilibrium, Finally,
  • saidanchorings ensure the diifusion of artificial constraints by the simultaneous, progressive and automatic unlocking of all the reinforcements used.
  • fluid-tightness to cement grout and cement injections of the sheath-core unit is ensured eitherby the sheath, or by the core, or by the sheath core unit.
  • the various twisted elements, highly tensioned, of the sheath come close together until they constitute a tubular system similar to closed or semi-closed cables. If' the elements are braided the fluid-tightness of the sheath is obtained by using for one of the sheets of threads, ribbons having a lenticular circumscribed profile the outer threads of which are, if necessary, coated, or constituted by any suitable plastic materials.
  • the core in fact transmit to the anchorings the important reactions of the sheath, have an extremely low inertia so as to conform to the curvatures, maintain in the curves a length equal to all its fibres, ensure the perfect centering" of the elements'composin'g the reinforcement and allow the core to be systematically removed from the framing whilst ensuring sufiicient fluid-tightness.
  • the core'c'an beconstituted by short metallic elements of suitable profile: spherical; cylindrical, bitrun cated, etc.
  • the elements present at the ends thereof either two coni exities or a concavity and a convexity of spherical or cylindrical shape superposed or fitting one in the other, and in order that they can be extracted, they are rendered rigid together by an-ysuit'able means or devices: wire or cable passing in a longitudinal channel, key having a flange or a dove tail, hooking spring-sleeve, outer spiral spring, resilient hooks. etc.
  • the expansible' device ensuring the centering and the unframin of the core can be independent or not from the resistant body and placed in position with or before the latter; it is constituted either" by balloon springs havin adjoining blades or not, flexible'hooks. etc.
  • Said expansibledevice is set in action by any shortening contrivances (mechanical drawing together, expansion, resilient contraction, etc.) of the elements of the chain constituting the resistant body, contrivances which cause an important transverse swelling of the order of 1/10.
  • Said shortenings are obtained either by resilient distortion of elementary arcs under increasing thrusts, or by the sliding movement of a wedge-system, or by any other means producing the sameeife'ct.
  • the expansible device can re'-' of allauxiliary'means ensuring the industrial eX-' ploitat'ion of theo'ore; for instance:- devices lim I to the possibility of its re use, as it is free when,
  • the manufacture'of the reinforcements comprises the twisting and braiding of the resistant elements constituting the sheath, the cutting of the latter into sections of sufficient length, the capping of the anchorings on the ends of said sections,the placing in position of the expansible device of the core before or after tensioning the section of sheath on a draw-bench, the compression of the resistant body by "acting or not on each anchoring, the locking of the constraints introduced into the system.
  • the pretensioned reinforcements:- can be wound on suitable drums without affecting the resilient properties thereof, and economically forwarded.
  • Fig. 1 is a-crosssection of an embodiment of the reinforcement,- such as it is prepared in order to be subsequently used;
  • Fig.1 shows, in perspective view on an enlarged'scale, an end anchoring.
  • Fig. 3 is a longitudinal section of the complete reinforcement with its two anchorings.
  • Fig. 4' illustrates the anchoring in longitudinal section on an enlarged scale.
  • Fig. 5 shows in perspective view a second embodiment, in the zone of the anchoring thereof.-
  • Fig. 6 diagrammatically illustrates details of theconstitution of the core'of said reinforcement.
  • I is the sheath, 2 the core, 3 a splice.
  • the cross section of the reinforcement can be of any nature: circular, square, fiat, etc.
  • the sheath is constituted by a tube or preferably by parallel elements adjoining or not, such.
  • the-sheath l is formed by steel wires such-as la. Figs. 2 to 4. r
  • the choice of the elements constituting the sheath is function of the general economy of the construction-and of the maximum adherence possible thereof with the preconstr'ained material.
  • the optimum shape of the core is solely related therea'ctions of the sheath have been transferred to the construction and it can then be extracted.
  • the splices can be constituted either by adjoining turns of wire, hoops, rings or washers sufficiently resilient to maintain the elements forming the reinforcement closely clamped together, or by a continuous coiled wire the spacing apart of the turns of which, as that of the other attaching members above defined, can be calculated in function of the desired curvatures and of the strength of the elements constituting the core.
  • the end anchorings satisfy the following conditions:
  • the anchorings can correspond to the device of Fig. 2.
  • the elements lb of the sheath I are flared and locked in a head 4 of any kind, solid or compound, made of hooped concrete or constituted by a metallic clamping hoop.
  • Hooks or lugs 5, rigid with head 4, arranged for instance in two pairs as seen in Fig. 2, allow a traction to be exerted on said head 4, that is to say on the sheath l, as indicated by the arrows '1', whereas a compression reaction is exerted on the core 2 by any means whatever (jack, etc.) according to the arrow C.
  • the desired internal system of forces is then stabilized by a key-bolt 6 which locks the core on the sheath through the medium of the lugs 5.
  • the line 6' indicates the axis according to which the keying is effected.
  • the placing under tension and pressure of the reinforcement can be effected by any mechanical or thermic means (jacks, screws, wedges, expansion, torsion, etc.) by acting indifferently on one or the other of the end anchorings, whereas the key-bolt previously locks the sheath and the core on the opposite anchoring.
  • any mechanical or thermic means jacks, screws, wedges, expansion, torsion, etc.
  • the reinforcement thus constituted and prepared encloses an invariable known potential of forces.
  • said reinforcement it is incorporated in the construction as an ordinary reinforcement, then when the concrete has hardened to the required degree for instance, said potential of forces is transferred to the material to be compressed, by driving the key-bolts out of both anchorings.
  • the core 2 can then be extracted as above stated.
  • the ends of the sheath ll constituted by strands or threads l2, twisted and braided, are sealed by means of a fusible material I8 in the annular space comprised between a. cap l4 and a cone [5.
  • the core I! the resistant body of which is composed of elements I8 fitted in each other and an expansible device l9 constituted by overlapping balloon springs having curved flexible blades I9, is placed within the sheath l I and compressed by the push-piece H) by the action of a dynamometric jack.
  • This operation produces the contact of all the elements l8 of the resistant body of the core and resiliently shortens them, by causing the transverse swelling of the expansible device I 9 by accentuating the sagging of the flexible arcs I9 and, consequently, the close centering of core I! in sheath II.
  • the sheath-core 6 unit is locked by the action of the nut 2
  • the reinforcement is placed in service, that is to say the forces accumulated are released by the action of a heating resistance 22 fitting over the cap M.
  • a reinforcement for use in preconstrained structures comprising a pair of flexible juxtaposed elements of substantial length as compared to their section, one of said elements having a high tensile strength and a high elongation coeflicient for being embedded in the structure to be pre-constrained, the other element having high resistance to longitudinal compression, the first-mentioned element being tensioned strongly, while using the ends of the second-mentioned element as a bearing and remaining thus tensioned until the reactions that balance the tensile stress are transferred from the second-mentioned element to the structure in which the reinforcement has meanwhile been embedded, none of said elements exhibiting any resistance to bending, while stability to buckling is ensured as a result of practically continuous radial reactions being exerted by each element upon the other,
  • a reinforcement for use in pre-constrained structures comprising a tubular transversally stable element of considerable length as compared to its section and having high tensile strength and high coefficient of elongation, and an inner flexible element composed of a series of short compression-resisting cores arranged end to end.
  • a reinforcement for use in pre-constrained structures as claimed in claim 3 in which the cores composing the inner element are fitted with imbricated arched spring strips connecting said cores by pairs and providing an elastic layer thereabout whose diameter, which is less than that of the tubular element in the released state of the springs so that the cores can be taken out, will increase as theinner element is more tightly compressed, for the purpose of providing for contact between the compressed element and the tensioned element in the pro-stressed reinforcement.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Chemical & Material Sciences (AREA)
  • Ceramic Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Architecture (AREA)
  • Civil Engineering (AREA)
  • Structural Engineering (AREA)
  • Reinforcement Elements For Buildings (AREA)
US606116A 1943-09-30 1945-07-20 Pretensioned reinforcement Expired - Lifetime US2449276A (en)

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Application Number Priority Date Filing Date Title
FR984471T 1943-09-30

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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2674115A (en) * 1949-06-23 1954-04-06 Grands Travaux De Marseille Sa Flexible pretensioned reinforcement for prestressed structures
US2675695A (en) * 1954-04-20 Composite structure of metal and concrete
US2677956A (en) * 1950-11-13 1954-05-11 Schorer Corp Prestressing and reinforcing apparatus for concrete structures
US2696040A (en) * 1950-09-15 1954-12-07 Preload Co Inc Method and apparatus for prestressing
US2934935A (en) * 1956-01-20 1960-05-03 Holzmann Philipp Ag Cast tensioning head for anchoring tensioning members, preferably for prestressed concrete
US3007284A (en) * 1954-04-13 1961-11-07 Southwest Structural Concrete Prestressed concrete slabs
US3516211A (en) * 1967-01-20 1970-06-23 Beton & Monierbau Ag Internally prestressed reinforcement rod
WO1985005394A1 (en) * 1984-05-17 1985-12-05 Friedrich Bodner Reinforcement element based on steel parts for prestressed concrete constructions and prefabricated prestressed concrete elements
US20050028477A1 (en) * 2003-07-28 2005-02-10 Freyssinet International (Stup) Method for strengthening a structure and associated anchorage unit

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE954195C (de) * 1952-12-10 1956-12-13 Bauunternehmung Sager & Woerne Aus Einzeldraehten mit radialen Beruehrungsflaechen zusammengesetztes Vorspannglied

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2270240A (en) * 1939-08-26 1942-01-20 Freyssinet Eugene Anchoring of tensioned cables in concrete constructions
US2303394A (en) * 1940-02-21 1942-12-01 Schorer Herman Prestressing reinforced concrete
US2328033A (en) * 1941-08-14 1943-08-31 Schorer Herman Prestressing reinforcing device for concrete
US2371882A (en) * 1940-10-28 1945-03-20 Freyssinet Eugene Tensioning and anchoring of cables in concrete or similar structures
US2378584A (en) * 1943-05-05 1945-06-19 Schorer Corp Prestressing reinforcing device for concrete

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2270240A (en) * 1939-08-26 1942-01-20 Freyssinet Eugene Anchoring of tensioned cables in concrete constructions
US2303394A (en) * 1940-02-21 1942-12-01 Schorer Herman Prestressing reinforced concrete
US2371882A (en) * 1940-10-28 1945-03-20 Freyssinet Eugene Tensioning and anchoring of cables in concrete or similar structures
US2328033A (en) * 1941-08-14 1943-08-31 Schorer Herman Prestressing reinforcing device for concrete
US2378584A (en) * 1943-05-05 1945-06-19 Schorer Corp Prestressing reinforcing device for concrete

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2675695A (en) * 1954-04-20 Composite structure of metal and concrete
US2674115A (en) * 1949-06-23 1954-04-06 Grands Travaux De Marseille Sa Flexible pretensioned reinforcement for prestressed structures
US2696040A (en) * 1950-09-15 1954-12-07 Preload Co Inc Method and apparatus for prestressing
US2677956A (en) * 1950-11-13 1954-05-11 Schorer Corp Prestressing and reinforcing apparatus for concrete structures
US3007284A (en) * 1954-04-13 1961-11-07 Southwest Structural Concrete Prestressed concrete slabs
US2934935A (en) * 1956-01-20 1960-05-03 Holzmann Philipp Ag Cast tensioning head for anchoring tensioning members, preferably for prestressed concrete
US3516211A (en) * 1967-01-20 1970-06-23 Beton & Monierbau Ag Internally prestressed reinforcement rod
WO1985005394A1 (en) * 1984-05-17 1985-12-05 Friedrich Bodner Reinforcement element based on steel parts for prestressed concrete constructions and prefabricated prestressed concrete elements
US20050028477A1 (en) * 2003-07-28 2005-02-10 Freyssinet International (Stup) Method for strengthening a structure and associated anchorage unit
US8104246B2 (en) * 2003-07-28 2012-01-31 Freyssinet International (Stup) Method for strengthening a structure and associated anchorage unit
US8333047B2 (en) 2003-07-28 2012-12-18 Freyssinet International (Stup) Method for strengthening a structure and associated anchorage unit

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NL61228C (en))
FR984471A (fr) 1951-07-06

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