US3891731A - Method of pre-stressing form tie systems - Google Patents

Method of pre-stressing form tie systems Download PDF

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Publication number
US3891731A
US3891731A US867508A US86750869A US3891731A US 3891731 A US3891731 A US 3891731A US 867508 A US867508 A US 867508A US 86750869 A US86750869 A US 86750869A US 3891731 A US3891731 A US 3891731A
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United States
Prior art keywords
bolt
stress
concrete
shebolt
dummy
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Expired - Lifetime
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US867508A
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English (en)
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Chester I Williams
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Individual
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Individual
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Priority to US867508A priority Critical patent/US3891731A/en
Priority to GB48702/70A priority patent/GB1278926A/en
Priority to CA095801A priority patent/CA918388A/en
Priority to JP9168370A priority patent/JPS5311786B1/ja
Application granted granted Critical
Publication of US3891731A publication Critical patent/US3891731A/en
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    • E—FIXED CONSTRUCTIONS
    • E04—BUILDING
    • E04G—SCAFFOLDING; FORMS; SHUTTERING; BUILDING IMPLEMENTS OR AIDS, OR THEIR USE; HANDLING BUILDING MATERIALS ON THE SITE; REPAIRING, BREAKING-UP OR OTHER WORK ON EXISTING BUILDINGS
    • E04G11/00—Forms, shutterings, or falsework for making walls, floors, ceilings, or roofs
    • E04G11/06—Forms, shutterings, or falsework for making walls, floors, ceilings, or roofs for walls, e.g. curved end panels for wall shutterings; filler elements for wall shutterings; shutterings for vertical ducts
    • E04G11/20—Movable forms; Movable forms for moulding cylindrical, conical or hyperbolical structures; Templates serving as forms for positioning blocks or the like
    • E04G11/28—Climbing forms, i.e. forms which are not in contact with the poured concrete during lifting from layer to layer and which are anchored in the hardened concrete

Definitions

  • ABSTRACT A form anchor embedded in concrete is pre-stressed exclusively with respect to a connecting shebolt and the surrounding concrete to a substantial portion of the working load prior to the securing of the form to the shebolt.
  • a vertical or near-vertical face of a concrete structure is developed through repeated use of forms that confine the poured concrete to the plane of the face. It is common practice to secure anchor rods in the newly-poured concrete for use later in tying the forms in position to confine the succeeding pour.
  • the anchors are preferably in the form of undulated rods threaded at the end nearest the formed face, and this threading is engaged by internal threading in the end ofa bolt that transfers the loading to reinforcing beams of the form structure.
  • the anchors are placed in position for engagement with the newly-poured concrete through the use of dummy bolts mounted at the upper portion of the form, and it is the usual practice to use a dummy bolt configuration such that a tapered socket is formed in the concrete exposing the threaded end of the anchor at a position set back somewhat from the plane of the face.
  • the stress bolt has essentially the same configuration as the socket, the purpose of the arrangement being to provide an enlarged bearing area against the concrete for the transmission of the vertical loads representing the weight of the form structure.
  • This invention provides for a system of pre-stressing that eliminates the axial movement of the stressed shebolt with respect to the concrete. Pre-stressing is developed prior to the application of securing forces to the form.
  • the procedure for the connection of the tie systern involves a preliminary pre-stressing operation in which the shebolt is forcibly rotated in its threaded engagement with the anchor to the point that the pre stress loading is developed by a pulling action resisted by the pressure of the tapered end of the shebolt in the concrete socket.
  • the anchor is pulled until it develops its predetermined loading. which may be approxi mately determined by the amount of torque applied to the shebolt (allowance being made for the frictional resistance against the rotation in the concrete socket).
  • FIG. 1 is a sectional elevation showing a typical steel form structure modified to the extent necessary to accommodate it to the present invention.
  • FIG. 2 is a fragmentary sectional elevation on an enlarged scale over FIG. 1 showing a preliminary stage in the attachment of the tie system.
  • FIG. 3 is a fragmentary sectional elevation similar to FIG. 2, and showing the completed attachment of the tie system.
  • FIG. 4 is a sectional elevation on an enlarged scale over FIGS. 2 and 3, showing the interengagement of an anchor rod with a dummy shebolt.
  • FIG. 5 illustrates the subsequent interengagement of the anchor with the stress-carrying shebolt in the prestressed condition.
  • FIG. 6 illustrates a different form structure and tie arrangement that can utilize the present invention.
  • the mass of concrete 10 has been developed through successive pours, the last two of which are indicated at 11 and 12.
  • the formed face 13 is developed by the panel 14 of the form structure 15, which includes (in addition to the panel 14) the horizontal beams 16-19, spaced vertical beams 20, and the cantilever beams 21.
  • the latter are normally installed in pairs, with the space between them being traversed by the tie systems.
  • the cantilever beams 21 may be pivotally connected to the beams 20 by the pins 22, with the upper extremity of the form structure being adjustable with respect to the cantilever beam 21 by a jack system (not shown).
  • the abutment beam 23 at the lower extremity of the cantilever beam 21 acts in conjunction with the tie systems to maintain the vertical orientation of the cantilever beam 21, to maintain the erect position of the form structure.
  • an chor rods 25 are supported in position to be surrounded by concrete through the use of dummy shebolts 26 slipped through appropriate holes in the form structure, and positioned axially by the pins 27 traversing a flange of the angle 28 mounted on the cantilever beams 21.
  • the conical inner extremity 29 of the dummy shebolt 26 forms a socket extending inwardly from the formed face 13 for receiving the similarlyshaped end 30 of the stress-carrying shebolt 31.
  • the anchor rod 32 shown in FIG. 1 was initially supported and placed in position in the same manner as the anchor 25.
  • the threaded bore 33 in the inner end of the dummy shebolt 26 is provided with a stop plug 34 limiting the penetration of the threaded end 35 of the anchor rod 25.
  • the counterbore 36 at the entrance of the threaded bore 33 is optional, but is desirable as means for facilitating the threaded engagement between the anchor and the dummy shebolt.
  • the seal ring 37 Prior to the engagement of the anchor with the dummy shebolt, the seal ring 37 is slipped into place to close off the opening at the entrance of the counterbore 36 to prevent the inflow of concrete.
  • the bolt 31 When the stress-carrying shebolt 31 is attached to the anchor 32, and prior to the application of securing forces to the form structure, the bolt 31 is rotated down against the threaded end of the anchor 32 with a sufficient intensity of torque to pull the anchor 32 sufficiently to develop the desired degree of pre-stress.
  • the resulting axial movement of the anchor 32 with respect to the concrete results in a movement of the unthreaded portion of the anchor rod 32 into the counter bore 38 in the bolt 31.
  • the bolt 31 is not provided with the stop plug, thus permitting the end of the anchor rod to move axially into the threaded bore 39 to whatever extent is necessary to develop the desired degree of pre-stress.
  • the successive stages of completely coupling the tie systems are shown in FIGS. 2 and 3, together with the preferred mechanism for accomplishing these procedures.
  • the stress-carrying shebolt 31 has a square section 40 slidably received in a similarly-shaped opening in the drive hub of the conventional reversible gear motor 41 secured to the flange 42 of the beam 21. Torque delivered by the gear motor will generate the pre-stress condition illustrated in FIG. 5, accompanied by a slipping of the square section 40 through the drive opening of the gear motor 41.
  • This operation is performed while the form structure is suspended either from a conventional overhead crane. or possibly by a lifting mechanism of a climbing form system. In either case.
  • the complete form structure will be brought close to or lightly against the formed face 13, and the presence of the light spring 43 acting against the nut 44 will permit the bolt 31 to back off resiliently and apply a gentle force facilitating threaded interengagement with the anchor rod as the gear motor 41 begins its operation.
  • the shebolt changes from the FIG. 2 position to the FIG. 3 position, when full pre-stress may be considered to have been developed.
  • the nut 45 is preferably backed off to provide substantial clearance over the bridge plate 46 spanning between the beams 21 for transferring the forces ultimately securing the form structure in position.
  • the similar gear motor 47 induces rotation of the shaft 48 on which the axially elongated gear 49 is supported. Operation of the gear motor 47 will shift the nut 45 down into bearing position, as shown in FIG. 3. The extended axial length of the gear 49 will permit the axial movement of the nut 45 from the clearance position required by the pre-stressing operation down into the bearing condition shown in FIG. 3.
  • the conical surface 29 In order to provide a solid and positive vertical placement of the form structure, it is preferable to either extend the conical surface 29 to a sufficient degree to provide bearing for the flanges 50, or a cylindrical portion 51 may be provided as an intermediate surface between the conical portion and the square cross-section 40.
  • the latter arrangement has the advantage of providing a more distributed bearing for the weight of the form structure.
  • the solid pre-stressing of the anchor rod with respect to the surrounding concrete permits the shebolt 31 to provide a firm positioning function.
  • the pre-stressing operation outlined above can be performed manually with the aid of a torque wrench, if desired.
  • the gear nut 45 can also be replaced by a standard nut set by a wrench.
  • An arrangement such as this is shown associated with a conventional wooden form structure in FIG. 6.
  • the form structure generally indicated at 52 includes the plywood panel 53, the horizontal studs 54-59, and the vertical walers 60.
  • the abutment block 61 stabilizes the lower extremity of the walers to provide a cantilever wooden form structure of generally standard design.
  • the vertical walers are secured to the horizontal studs by the use of L bolts 62 and 63.
  • the placement of the anchors 64 for the new pour is handled in exactly the same manner as that illustrated in FIG. 1.
  • the dummy shebolts 65 are supported by the form structure in the position shown at 66.
  • the stress shebolt 67 differs from standard in the provision of the square or hex section 68. lf the circumscribed diameter of the section 68 is larger than that of the threaded portion 69, the shebolt 67 can be tightened on the anchor 66 through the use of a socket wrench slipped in between the waler pairs 60.
  • the pre-stressing operation of the shebolt 67 on the anchor 66 be accomplished prior to placement of the form structure 52 on the shebolt, so that there will be clearance for the application of a wrench to the portion 68 from the side.
  • the section 68 can extend outwardly beyond the plane of the walers 60, accompanied by the use of a bearing plate 70 which is sufficiently deep (in the direction of the axis of the bolt 67) to assure that the wing nut 71 will have sufficient axial threading to secure the form structure.
  • disengagement of the form after the new pour of concrete has set involves the release of the form structure from the concrete mass.
  • this is done by the removal of the nut 71, the bearing plate 70, and the pin 72.
  • the form structure can be moved horizontally outward to a position free of the stress shebolt and the dummy shebolt.
  • the shebolt remains associated with the form, and the disengagement is accompanied by back-rotation ofthe reversible gear motor 41, possibly preceded by removing the load on the nut 45 by back rotation of the gear motor 47.
  • the dummy shebolt 26 would also be provided with a power-actuated arrangement utilizing a reversible gear motor functioning in the manner of the motor 41.
  • a spring arrangement similar to the spring 43 would be desirable to assure the proper axial placement of the dummy shebolt through the gear motor.
  • a fully automated arrangement of this type can make possible a very efficient operation. as it may be controlled from remote positions with a high degree of accuracy, the torque applied to the shebolts being easily determinable by notation of the power being consumed by the gear motors as determined by standard metering arrangements.
  • predetermined pre-stress in said anchor rod at least to the extent of the working load to be applied thereto by tightening the threaded engagement of said stress bolt therewith prior to the securing of said form panel to said stress bolt, said stress bolt remaining in axially substantially fixed position with respect to said concrete mass during said generation of pre-stress.

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  • Engineering & Computer Science (AREA)
  • Architecture (AREA)
  • Mechanical Engineering (AREA)
  • Civil Engineering (AREA)
  • Structural Engineering (AREA)
  • Forms Removed On Construction Sites Or Auxiliary Members Thereof (AREA)
  • On-Site Construction Work That Accompanies The Preparation And Application Of Concrete (AREA)
US867508A 1969-10-20 1969-10-20 Method of pre-stressing form tie systems Expired - Lifetime US3891731A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
US867508A US3891731A (en) 1969-10-20 1969-10-20 Method of pre-stressing form tie systems
GB48702/70A GB1278926A (en) 1969-10-20 1970-10-13 Method of securing a form structure to concrete
CA095801A CA918388A (en) 1969-10-20 1970-10-16 Method of securing a form structure in concrete
JP9168370A JPS5311786B1 (enrdf_load_stackoverflow) 1969-10-20 1970-10-20

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US867508A US3891731A (en) 1969-10-20 1969-10-20 Method of pre-stressing form tie systems

Publications (1)

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US3891731A true US3891731A (en) 1975-06-24

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US867508A Expired - Lifetime US3891731A (en) 1969-10-20 1969-10-20 Method of pre-stressing form tie systems

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US (1) US3891731A (enrdf_load_stackoverflow)
JP (1) JPS5311786B1 (enrdf_load_stackoverflow)
CA (1) CA918388A (enrdf_load_stackoverflow)
GB (1) GB1278926A (enrdf_load_stackoverflow)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4564316A (en) * 1982-11-08 1986-01-14 Hunziker Kenneth J Face panel system
US4758393A (en) * 1982-01-21 1988-07-19 Societe Anonyme De Traverses En Beton Arme Systeme Vagneux Process for casting elements in reinforced concrete
WO1990007410A1 (en) * 1988-12-27 1990-07-12 Varitech Industries, Inc. Method of encapsulating a tendon tensioning anchor
US5072558A (en) * 1988-04-21 1991-12-17 Varitech Industries, Inc. Post-tension anchor system
CN107292052A (zh) * 2017-07-10 2017-10-24 河南理工大学 一种锚杆施加预应力的数值模拟方法

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2918283C2 (de) * 1979-05-07 1983-04-21 Carl Baasel, Lasertechnik KG, 8000 München Gerät zur Substratbehandlung mit einem Drehspiegel od. dgl.

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2967343A (en) * 1952-12-02 1961-01-10 Chester I Williams Cantilever form
US3355529A (en) * 1965-06-24 1967-11-28 Joan L Easterday Method of forming post tensioned concrete liners in conduits

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2967343A (en) * 1952-12-02 1961-01-10 Chester I Williams Cantilever form
US3355529A (en) * 1965-06-24 1967-11-28 Joan L Easterday Method of forming post tensioned concrete liners in conduits

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4758393A (en) * 1982-01-21 1988-07-19 Societe Anonyme De Traverses En Beton Arme Systeme Vagneux Process for casting elements in reinforced concrete
US4564316A (en) * 1982-11-08 1986-01-14 Hunziker Kenneth J Face panel system
US5072558A (en) * 1988-04-21 1991-12-17 Varitech Industries, Inc. Post-tension anchor system
WO1990007410A1 (en) * 1988-12-27 1990-07-12 Varitech Industries, Inc. Method of encapsulating a tendon tensioning anchor
CN107292052A (zh) * 2017-07-10 2017-10-24 河南理工大学 一种锚杆施加预应力的数值模拟方法
CN107292052B (zh) * 2017-07-10 2020-06-19 河南理工大学 一种锚杆施加预应力的数值模拟方法

Also Published As

Publication number Publication date
GB1278926A (en) 1972-06-21
JPS5311786B1 (enrdf_load_stackoverflow) 1978-04-24
CA918388A (en) 1973-01-09

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