The present disclosure relates generally to post-tensioned, pre-stressed concrete construction.
Many structures are built using concrete, including, for instance, buildings, parking structures, apartments, condominiums, hotels, mixed-use structures, casinos, hospitals, medical buildings, government buildings, research/academic institutions, industrial buildings, malls, roads, bridges, pavement, tanks, reservoirs, silos, sports courts, and other structures.
Prestressed concrete is structural concrete in which internal stresses are introduced to reduce potential tensile stresses in the concrete resulting from applied loads; prestressing may be accomplished by post-tensioned prestressing or pre-tensioned prestressing. In post-tensioned prestressing, a tension member is tensioned after the concrete has attained a desired strength by use of a post-tensioning tendon. The post-tensioning tendon may include for example and without limitation, anchor assemblies, the tension member, and sheaths.
Traditionally, a tension member is constructed of a material that can be elongated and may be a single or a multi-strand cable. The tension member may be formed from a metal, such as reinforced steel. The tension member is encapsulated within a polymeric sheath hot extruded thereabout to form an encapsulated tension member. The sheath may prevent or retard corrosion of the tension member by restricting exposure of the tension member to corrosive or reactive fluids. Further, the sheath may prevent or retard concrete from bonding to the tension member. The sheath may be filled with grease. Because the tension member and the polymeric sheath are formed from different materials, the thermal expansion and contraction rates of the tension member and polymeric sheath may differ. When the encapsulated tension members are coiled for transport and storage, uneven thermal contraction may occur as the tendon cools. When installed as part of the post-tensioning tendon in a pre-stressed concrete member, cooling of the sheath may cause separation of the sheath from an anchorage, potentially exposing the tension member to corrosive or reactive fluids.
The post-tensioning tendon traditionally includes an anchor assembly at each end. The tension member is fixedly coupled to a fixed anchor assembly positioned at one end of the post-tensioning tendon, the “fixed-end”, and stressed at the stressed anchor assembly positioned at the opposite end of the post-tensioning tendon, the “stressing-end” of the post-tensioning tendon.
When coupling the tension member to the stressed anchor assembly positioned at the stressing-end of the post-tensioning tendon, the sheath at the stressing-end is retained within the stressed anchor assembly, such as, for instance, by coupling the sheath within a sheathing retainer. Examples of sheathing retainers include a sheathing lock and a sheathing retention capsule. The sheathing retainer holds the sheathing in the stressed anchor assembly, such as through the use of wedges. During installation, the sheath may be decoupled from or improperly coupled to the sheathing retainer. For example, decoupling or improperly coupling to the sheathing retainer may be caused by: (1) cutting a portion of the sheathing to expose a portion of the strand, where the sheath is cut too short to couple with the sheathing retainer; (2) applying tension applied to the sheath, resulting in shrinkage of the length of the sheath over time; or (3) applying force applied to the sheath causing stretching of the sheath, or shortening of the sheath. During installation, tension may be applied to the sheath from stepping on the sheath or impact by tools or heavy equipment. Traditionally, solutions for a sheath that is too short or is otherwise decoupled from the sheathing retainer include applying tape about the unsheathed portion of the tension member, or splicing additional sheath onto the existing sheath.
The present disclosure provides for a sheathing puller. The sheathing puller includes a stationary coupler and a force applicator mechanically coupled to the stationary coupler. The sheathing puller also includes a sheathing gripper mechanically coupled to the force applicator.
The present disclosure also provides for a post-tensioning system comprising a fixed object and an encapsulated tension member, the encapsulated tension member including a tension member and a sheath. The tension member is encapsulated by the sheath. The post-tensioning system includes a sheathing puller, which in turn includes a stationary coupler that is mechanically coupled to the fixed object. The sheathing puller also includes a force applicator that is mechanically coupled to the stationary coupler and a sheathing gripper that is mechanically coupled to the force applicator and grips or engages the sheath.
The stationary coupler may comprise a coupling body configured to engage the at least one anchor. The force applicator may be a pulley, screw, ratchet, bar clamp, pipe clamp, or screw clamp or may comprise a linear actuator that is mechanically coupled to the stationary coupler and a sliding head that is coupled to the linear actuator and mechanically coupled to the sheathing gripper. The linear actuator may be a hydraulic linear actuator, a pneumatic linear actuator, an electro-mechanical linear actuator, or a linear motor or a mechanical linear actuator comprising a screw, chain drives, belt drives, rigid chains, and/or a rigid belt.
The sheathing gripper may include a cable-receiving channel and at least one gripping member that is pivotable into engagement with a cable that is positioned in the cable-receiving channel. Actuation of the force applicator may cause the sheathing gripper to grip the sheath and apply a longitudinal force thereto.
The present disclosure also provides for a method. The method includes providing an encapsulated tension member including a tension member and a sheath positioned about the tension member. In addition, the method includes providing an anchor that includes a sheathing retainer, a sheathing puller that includes a stationary coupler, and a force applicator that is mechanically coupled to the stationary coupler. The sheathing puller also includes a sheathing gripper that is mechanically coupled to the force applicator. The method also includes mechanically coupling the stationary coupler to a fixed object and mechanically coupling the sheathing gripper to the sheath. In addition, the method includes sliding the sheath along the tension member using the sheathing puller.
The method may further comprise coupling the sheathing retainer to the sheath. Actuating the force applicator may cause the sheathing gripper to grip the sheath and apply a longitudinal force thereto. The sheathing gripper may include a cable-receiving channel and at least one gripping member that is pivotable into engagement with a cable that is positioned in the cable-receiving channel. The force applicator may comprise a stationary head, a linear actuator mechanically coupled to the stationary head, and a sliding head slideably coupled to the linear actuator and wherein the step of sliding the sheath along the tension member using the sheathing puller comprises mechanically urging the sliding head towards the stationary head using the linear actuator.
The present disclosure is best understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.
It is to be understood that the following disclosure provides many different embodiments, or examples, for implementing different features of various embodiments. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.
In some embodiments, fixed end anchor 13 may include a fixed end anchor body 14 and a sheathing retainer 100″, which may be positioned within concrete form 21 such that fixed end anchor body 14 and sheathing retainer 100″ will be encased in concrete when concrete is poured into concrete form 21. In some embodiments, a fixed end cap 19 may be positioned at distal end 41 of fixed end anchor body 14. Fixed end cap 19 may, in certain embodiments, protect encapsulated tension member 27 from corrosion after concrete is poured by preventing or retarding corrosive fluids, reactive fluids, or concrete from contacting tension member 27.
Stressing end anchor 17 may be positioned within concrete form 21 and may include a stressing end anchor body 18. In certain embodiments, a pocket former 25 may be positioned between stressing end anchor body 18 and an end wall 22 of concrete form 21.
When installing tendon 28, in some embodiments, a length of sheath 29 may be removed from a first end 43 of tendon 28, exposing a portion of tension member 27. Tension member 27 may be inserted through fixed end anchor 13 until sheath 29 engages with sheathing retainer 100″. Sheathing retainer 100″ and sheathing retainer 100′, located proximate stressing end anchor 17, may each comprise any structure adapted to grip, hold, and/or retain sheath 29. In some embodiments, sheathing retainers 100′, 100″ may grip, hold, and/or retain sheath 29 via frictional force or pressure fit. For example and without limitation, sheathing retainer 100′, 100″ may be a sheathing retention capsule as described U.S. patent application Ser. No. 15/226,528, filed Aug. 2, 2016, a sheathing retention assembly as describe in U.S. patent application Ser. No. 15/226,594, filed Aug. 2, 2016, a wedge as described in U.S. Pat. No. 7,866,009, issued on Jan. 11, 2011, a sheathing lock as described in U.S. Pat. No. 8,065,845, issued on Nov. 29, 2011, or a fixing means as described in U.S. Pat. No. 7,841,140, issued on Nov. 30, 2010, each of which disclosures is hereby incorporated by reference in its entirety.
Although described hereinafter with respect to fixed end anchor 13 and sheathing retainer 100″, the present disclosure applies equally to stressing end anchor 17 and sheathing retainer 100′.
In some embodiments, sheathing retainer 100″ may be mechanically coupled to fixed end anchor 13. Sheathing retainer 100″ may mechanically couple to fixed end anchor 13 and stressing end anchor 17 by a retainer coupler, including but without limitation a thread, detent, press lock, tab-and-slot connection, or a combination thereof. In some embodiments, sheathing retainer 100″ may be a sheathing retention capsule including one of one or more holding wedges having an inner wall with a diameter corresponding with outer diameter 32 of sheath 29, such as the sheathing retention capsules described in U.S. patent application Ser. No. 15/226,528. In such embodiments, the inner wall of the holding wedges may form a press or friction fit when sheath 29 is inserted into sheathing retainer 100″. The press or friction fit may be formed by, for example and without limitation, surface features on the inner wall of such holding wedges that increase the static friction between sheath 29 and sheathing retainer 100″. The surface features may include grooves, protrusions, or teeth that may contact sheath 29 and, in some embodiments, press against or into sheath 29, thus increasing the retention force between sheathing retainer 100″ and sheath 29.
In some embodiments, sheathing retainer 100″ may include seals positioned to seal between sheath 29 and fixed end anchor 13. Such seals may be annular or generally annular and may fit into a recess formed in fixed end anchor 13. The seals may protect tension member 27 from corrosion after concrete 23 is poured and may prevent or restrict concrete 23 from ingressing into tension member 27. Although described herein as a separate component from fixed end anchor 13, sheathing retainer 100″ may alternatively be formed as a part of fixed end anchor 13.
In some installations, tension member 27 may be mechanically coupled to fixed end anchor 13, such as by the use of wedges, and positioned within concrete form 21. Tension member 27 may be cut to correspond with the length of concrete form 21. In some embodiments, a length of sheath 29 may be removed from tension member second end 44 of tension member 27, exposing tension member 27 at second end 44. Tension member 27 may be inserted through stressing end anchor 17.
As depicted in
In certain embodiments of the present disclosure, a sheathing puller 1000 may be employed to recouple sheath 29 to sheathing retainer 100′.
Fixed object 50 may be any object that is static with respect to sliding head 415. Examples of fixed object 50 include, but are not limited to, an anchor, such as fixed end anchor 13 or stressing end anchor 17, a portion of concrete form 21 such as a form board, rebar, or the ground. Stationary coupler 200 may be mechanically coupled to fixed object 50. Stationary coupler 200 may be any device configured to any structure, static or mechanical, configured to grab, grip, hold, mechanically couple with, and/or be affixed sheathing puller 1000 to fixed object 50, including, but not limited to, one or more clamps, straps, bolts, screws, stakes, brackets, or cables.
Still referring to
In certain embodiments, and as shown in
Likewise, linear actuator 410 may be any apparatus for mechanically urging sliding head 415 towards stationary head 225, as indicated by arrow 610. Linear actuator 410 may be, but is not limited to, a mechanical linear actuator, a hydraulic linear actuator, a pneumatic linear actuator, an electro-mechanical linear actuator, or a linear motor. Mechanical linear actuators include but are not limited to screws, such as leadscrews, screw jacks, ball screws, and roller screws; chain drives; belt drives; rigid chains; and rigid belts. Hydraulic linear actuators include but are not limited to hydraulic cylinders that may be controlled by hydraulic pumps. Pneumatic linear actuators include but are not limited to pneumatic cylinders that may be controlled by compressed gas. Electro-mechanical linear actuators may include mechanical linear actuators mechanically coupled to an electric motor. In the embodiment depicted in
Linear actuator 410 may be slideably coupled to sliding head 415. As described hereinabove, sliding head 415 is any mechanical apparatus configured to be mechanically urged by linear actuator 410 towards stationary head 225. As shown in
As further depicted in
During operation, stationary coupler 200 may be mechanically coupled to fixed object 50 and sheathing gripper 300 may be affixed to sheath 29. Sheathing puller 1000 may then be employed to slide sheath 29 along tension member 27 in direction 600. The sliding movement of sheath 29 along tension member 27 may be further facilitated by grease within sheath 29. In the embodiment shown in
By sliding sheath 29 along tension member 27, sheath 29 may be brought into proximity to and then coupled or recoupled with sheathing retainer 100′, as shown in
Referring now to
As further depicted in
Referring again briefly to
Sheathing gripper 300 may include a handle 350 mechanically coupled to the gripping members 340. Handle 350 may include a tab 352 mechanically coupled to handle a frame 354. Handle frame 354 may be mechanically coupled to gripping members 340, such as via one or more pins 356, which may be mechanically coupled to handle frame 354 and handle ends 344 of gripping members 340. Tab 352 may include a through-hole 358 for mechanically coupling to sheathing gripper coupler 520, described above. In operation, force applicator 400 may apply force, such as through force applicator coupler 500, to sheathing gripper 300 to pull tab 352 in direction 600. When tab 352 and frame 354 are pulled in direction 600, force may be transferred from handle 350 to gripping ends 342 of gripping members 340. This force may allow gripping members 340 to pivot about pins 345 and gripping ends 342 to pivot at least partially into channel 330. If sheath 29 is within channel 330 when tab 352 and frame 354 are pulled in direction 600, gripping ends 342 may pivot into contact with sheath 29 thereby gripping sheath 29 between channel cylindrical surface 325 and gripping members 340.
Embodiments of the present disclosure allow a cable sheath that has shrunk or otherwise pulled away from an anchor and sheathing retainer to be pulled and/or stretched so as to close the gap between the sheath and the sheathing retainer so that the sheathing retainer can grip the sheath and form a sealed system that prevents corrosion of the cable strand.
The foregoing outlines features of several embodiments so that a person of ordinary skill in the art may better understand the aspects of the present disclosure. Such features may be replaced by any one of numerous equivalent alternatives, only some of which are disclosed herein. One of ordinary skill in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. One of ordinary skill in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure. Unless explicitly stated otherwise, nothing herein is intended to be a definition of any word or term as generally used by a person of ordinary skill in the art, and nothing herein is a disavowal of any scope of any word or term as generally used by a person of ordinary skill in the art.
This application is a divisional application which claims priority from U.S. utility application Ser. No. 15/730,178, filed Oct. 11, 2017, with is itself a non-provisional application which claims priority from U.S. provisional application No. 62/407,612, filed Oct. 13, 2016, each of which is incorporated by reference herein in its entirety.
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Number | Date | Country | |
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Parent | 15730178 | Oct 2017 | US |
Child | 16591237 | US |