ENCAPSULATION SYSTEM FOR POST TENSION ANCHORS AND TENDONS

Description

CROSS REFERENCE TO RELATED APPLICATIONS

Priority is claimed from U.S. Provisional Application No. 63/733,604 filed on Dec. 13, 2024.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT

Not Applicable.

BACKGROUND

This disclosure relates to the field of post tension concrete reinforcing systems. More particularly, the disclosure relates to encapsulation for such systems to exclude moisture, which enhances the life of the reinforcing system.

Reinforced concrete is able to withstand certain loads when it is used in pre-stressed or post-tensioned members. Spans as great as 100 feet can be attained in members as deep as three feet for roof loads, for example. The basic principle of reinforcing concrete is simple. In prestressing, reinforcing rods of high tensile strength material, e.g., steel, are stretched to a certain determined limit and then high-strength concrete is placed around them. When the concrete has set, it holds the steel in a tight grip, preventing slippage or sagging.

Post-tensioning follows the same principle, but the reinforcing, e.g., multiple strand tendon, is held loosely in place while the concrete is placed around it. The reinforcing tendon is then stretched by hydraulic jacks and securely anchored into place. Prestressing is done with individual members in the shop and post-tensioning is done as part of the structure on the construction site.

In a typical tendon tensioning anchor assembly in such post-tensioning operations, there is provided a pair of anchors for anchoring the ends of the tendons suspended therebetween. In the course of installing the tendon tensioning anchor assembly in a concrete structure, a hydraulic jack or the like is releasably attached to one of the exposed ends of the tendon for applying a predetermined amount of tension to the tendon. When the desired amount of tension is applied to the tendon, wedges, threaded nuts, or the like, are used to capture the tendon and, as the jack is removed from the tendon, to prevent its relaxation and hold it in its stressed condition.

Metallic components within concrete structures may become exposed to many corrosive elements, such as de-icing chemicals, sea water, brackish water, or spray from these sources, as well as salt water. If this occurs, and the exposed portions of the anchor suffer corrosion, then the anchor may become weakened due to this corrosion. The deterioration of the anchor can cause the tendons to slip, thereby losing the compressive effects on the structure, or the anchor can fracture. In addition, the large volume of by-products from the corrosive reaction is often sufficient to fracture the surrounding structure. These elements and problems can be sufficient so as to cause a premature failure of the post-tensioning system and a deterioration of the structure.

U.S. Pat. No. 7,424,792 issued to Sorkin discloses an encapsulated post tension reinforcing system, an anchor assembly for a post tension system that comprises an anchor member having an end surface, a polymeric encapsulation covering the anchor member, a rigid ring affixed within a tubular section of the polymeric encapsulation, and a cap having a generally tubular body with an open end and a closed end. The rigid ring has a notch formed on inner wall thereof. The cap has a flanged end adjacent the open end thereof. The flanged end has an outer periphery engaged within the notch of the rigid ring. The flanged end has an end surface and an outer wall extending outwardly therefrom. The outer wall has a lip formed at an end thereof opposite the end surface of the anchor member. The lip is the outer periphery that is engaged with the notch. The outer wall has a groove formed therein. An elastomeric seal is received within this groove and extends around the cap. The elastomeric seal is in generally liquid-tight engagement with the inner wall of the rigid ring.

There continues to be a need for improved encapsulated post tension reinforcing systems.

SUMMARY

One aspect of the present disclosure relates to an encapsulated anchor system. An anchor for a post-tension system has an anchor body having an end surface. Encapsulation covers the anchor body; the encapsulation extends outwardly from the end surface and has a retaining groove on an exterior surface of the encapsulation on an end of the encapsulation opposed to the end surface. A cap has a generally tubular body with an open end and a closed end; the cap has a flange adjacent the open end. The flange has a plurality of circumferentially spaced apart locking features, or a circumferentially continuous locking feature, extendable over the end of the encapsulation and engageable within the retaining groove.

Some implementations further comprise a rigid ring disposed in the end of the encapsulation opposed to the end surface and proximate to a longitudinal end of a wedge receiving bore in the anchor body.

In some implementations, the rigid ring comprises a groove on an exterior surface thereof to engage the encapsulation, wherein the rigid ring is secured within the encapsulation.

In some implementations, the rigid ring comprises steel.

In some implementations, the part of the encapsulation extending outwardly from the end surface comprises a tubular section attached thereto.

Some implementations further comprise a flexible tube coupled to the part of the encapsulation extending outwardly from the end surface.

An anchor for a post-tension system according to another aspect of the present disclosure includes an anchor body having an end surface. Encapsulation covers said anchor body; said encapsulation comprises a tubular section extending outwardly from said end surface. The encapsulation includes retaining groove on an exterior surface of the encapsulation on an end of the encapsulation opposed to the end surface. A cap has a generally tubular body with a first open end and a second open end. The cap has a flange adjacent to said first open end, and the flange has a plurality of circumferentially spaced apart locking features, or a circumferentially continuous locking feature, extendable over the end of the encapsulation opposed to the tubular section. The locking features are engageable within said groove. The cap has a locking feature on the second open end to retain a first flexible tube attached to the cap proximate the second open end.

Some implementations further comprise a rigid ring disposed in the end of the encapsulation proximate to a longitudinal end of a wedge receiving bore in the anchor body.

In some implementations, the rigid ring comprises a groove on an exterior surface thereof to engage the encapsulation, wherein the rigid ring is secured within the encapsulation.

In some implementations, the rigid ring comprises steel.

Some implementations further comprise a first flexible tube connected to the second open end of the cap.

Some implementations further comprise a second flexible tube coupled to the tubular section of the encapsulation.

In some implementations, the second flexible tube engages an exterior of the tubular section of the encapsulation.

Another aspect of this disclosure relates to an anchor for a post-tension system. An anchor according to this aspect comprises an anchor body having an end surface. Encapsulation covers the anchor body, and extends outwardly from the end surface. A rigid ring is disposed inside the encapsulation on the side opposed to the end surface. The rigid ring comprises a groove on its exterior surface to engage a locking feature on the encapsulation.

Some implementations further comprise a cap having a generally tubular body with an open end and a closed end. The cap has a flange adjacent the open end. The flange has a plurality of circumferentially spaced apart locking features, or a circumferentially continuous locking feature, extendable over or into the encapsulation on a side opposed to the end surface.

In some implementations, the locking feature on the flange engages a groove on an exterior of the encapsulation.

Other aspects and possible advantages will be apparent from the description and claims that follow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a top view of an encapsulated anchor with a cap according to the present disclosure.

FIG. 2 shows a cross sectional view of the anchor and cap of FIG. 1, further showing a flexible tube coupled to the anchor encapsulation on a side of the anchor opposed to the cap.

FIG. 3 shows a side view of the encapsulated anchor, cap and flexible tube.

FIG. 4 shows an oblique view of the encapsulated anchor, cap and flexible tube.

FIG. 5 shows an enlarged view of the anchor, encapsulation and cap portion of FIG. 2.

FIG. 6 shows an oblique view of an encapsulated anchor system as in FIG. 4, wherein the cap is substituted by an intermediate cap and tube assembly used with intermediate anchors.

FIG. 7 shows a cross sectional view of the encapsulated anchor system of FIG. 6 to show details of the intermediate cap and tube assembly.

DETAILED DESCRIPTION

FIG. 1 shows a top view of an example implementation of an encapsulated post tension reinforcing anchor (hereinafter “anchor” for convenience) 10 with a cap 12 according to the present disclosure. The specific features of the anchor 10 do not limit the scope of the present disclosure, nor does the material from which the encapsulation is made; any known encapsulation material, e.g., polymeric plastic, may be used in accordance with the present disclosure. Likewise, the material from which the anchor 10 is made is not a limitation on the scope of the present disclosure. The cap 12 may be generally tubular in shape, having an open end (see 12D in FIG. 2) and a closed end 12C. The tubular portion of the cap 12 may be surrounded on its perimeter by a generally flange shaped area 12B. The generally flange shaped area 12B (or simply, “flange”) may comprise features (explained below with reference to FIGS. 2 and 5) for extending over the longitudinal end of, engaging with and locking to the encapsulation (see 10B in FIG. 2) on the anchor 10.

FIG. 2 shows a cross sectional view of the anchor 10 and the cap 12 described above with reference to FIG. 1. The anchor 10 may comprise an anchor body 10A enclosed within encapsulation 10B over the surface of the anchor body 10A other than in a tapered wedge receiving bore 10A2, to be explained further below. The anchor body 10A may be made from metal such as ductile iron, although as explained above the anchor material is not a limitation on the scope of the present disclosure. The anchor 10 may in some example implementations further comprises an attachment extension 10D in the load bearing side of the encapsulation for attaching a first flexible tube 14 to the anchor encapsulation 10B on a side of the anchor opposed to the cap 12. The open end 12D of the cap 12 engages the anchor 10, in particular the encapsulation 10B, on a side opposed to the load bearing side 10A1. The encapsulation 10B may comprise a rigid ring 10C such as a steel ring on its interior surface, disposed on a side of the anchor 10 opposed to the load bearing side 10A1 and proximate the end of the wedge receiving bore 10A2; such rings are known in the art to reduce the chance of damage to the encapsulation 10B when a tendon (not shown in FIG. 2) is cut after being locked in the anchor 10. Cutting in such cases often is performed using a cutting torch; the rigid ring 10C protects the interior surface of the encapsulation 10B from heat damage. The first flexible tube 14 may be attached to and secured in place on the encapsulation 10B by a locking feature or tab 14A disposed on the interior surface of a tube attachment 14B, e.g., a swaged or otherwise enlarged diameter part of the first flexible tube 14, that is moved over the exterior of the encapsulation 10B. The encapsulation 10B may also comprise a locking feature 10D1 on the attachment extension 10D to better secure the first flexible tube 14.

FIG. 3 shows a side view of the anchor 10, cap 12 and the first flexible tube 14; FIG. 4 shows an oblique view of the anchor 10, cap 12 and first flexible tube 14. In the present example implementation, the cap 12 may be attached to the first encapsulation 12 by a plurality of circumferentially spaced apart locking tabs 12A. The locking tabs 12A engage the exterior surface of the encapsulation 10B, e.g., in a groove 10B1 (see FIG. 5) to hold the cap 12 in place on the anchor 10. While the views in FIGS. 3 and 4 show the locking tabs 12A covering substantially the full circumference of the cap 12, in other implementations, the locking tabs 12A may traverse less of the circumference and may be fewer in number, e.g., as few as two.

FIG. 5 shows an enlarged view of a portion of the anchor 10, the encapsulation 10B and the cap 12 to better illustrate the manner of attachment of the cap 12 to the anchor 10 (on the side of the anchor 10 opposed to the load bearing side). As previously explained, the encapsulation 10B may comprise an internally disposed rigid ring 10C, such as a steel ring, engaged with the interior surface of the encapsulation 10B. The rigid ring 10C may comprise a circumferential groove 10C1 on its exterior surface in order to engage the encapsulation 10B and better retain the rigid ring 10C within the encapsulation 10B. The encapsulation 10B may comprise a circumferential groove 10B1 on its exterior surface to engage a protrusion 12A1 on each of the locking tabs 12A. In this way, the cap 12 may be locked in place on the anchor 10. By having a plurality of circumferentially spaced locking tabs (as shown at 12A in FIGS. 3 and 4), attachment of the cap 12 to the anchor 10 is facilitated. A seal 16 such as an O-ring may be disposed in the space between the cap 12 and the rigid ring 10C to better exclude moisture from the assembled anchor 10 and cap 12. In other implementations, the locking tabs 12A may be substituted by a single locking ring, i.e., a circumferentially continuous locking feature extending over the end of the encapsulation 10B and having a single, circumferentially continuous locking tab 12 engaging the circumferential groove 10B1. “Circumferentially continuous” as used herein includes an implementation where there is a single gap in the locking feature, wherein the rest of the locking feature is circumferentially continuous apart from the single gap.

FIG. 6 shows an oblique view of an encapsulated anchor system as in FIG. 4, wherein the cap (12 in FIG. 4) is substituted by an intermediate cap and tube assembly when the encapsulated anchor system is used for intermediate anchors. Intermediate anchors are used in a concrete slab that is poured in multiple sections. The cap 32 is open at both longitudinal ends to enable pass through of a tendon 20. A second flexible tube 22 is attached to one longitudinal end of the cap 32 to enclose an exposed part 20A of the tendon 20. The exposed part 20A of the tendon 20 is provided by removing a selected length of a sheath or jacket 20B that surrounds the tendon strands so as to prevent entry of moisture and contaminants as is known in the art. The exposed part 20A is where the tendon 20 is secured in the anchor 10. The cap 32 may comprise circumferentially spaced apart locking features 32C that may be configured substantially as explained with reference to FIGS. 2 and 5. The locking features 32C may engage a groove (10B1 in FIG. 7) on the exterior of the encapsulation (10B in FIG. 7) to retain the cap 32 onto the encapsulation 10B substantially as explained with reference to FIGS. 2 and 5.

FIG. 7 shows a cross sectional view of the encapsulated anchor system of FIG. 6 to show details of the intermediate cap and tube assembly. The anchor 10 may comprise a metal part 10A and encapsulation, just as the anchor explained with reference to FIG. 5. The cap 32 may be in most respects the same as the cap shown at 12 in FIG. 5, the exception being the open longitudinal end 32B, and in some implementations, a circumferential locking ridge 32A to lock the second flexible tube 22 in place. The first flexible tube 14 may be attached to the encapsulation substantially as explained with reference to FIG. 2.

The exposed part 20A of the tendon 20 is held in place within a wedge receiving bore 10A2 part of the anchor 10 by wedges 11 affixed to the exterior of the exposed part 20A as is well known in the art of post tension concrete reinforcing.

It will be appreciated that a tendon and wedges may be affixed within the anchor as explained with reference to FIGS. 6 and 7, wherein the tendon is cut a short distance above the wedge receiving bore 10A2 to enable placing a cap as explained with reference to FIGS. 2 and 5. In such instances, the anchor 10 is disposed at the end of a concrete slab and may be referred to as a terminal anchor.

An anchor, encapsulation and cap system according to the present disclosure may provide improved exclusion of moisture and contaminants from assembled tendons and anchors, may facilitate manufacturing of the system and be easier to install at a construction site.

In light of the principles and example implementations described and illustrated herein, it will be recognized that the example implementations can be modified in arrangement and detail without departing from such principles. The foregoing discussion has focused on specific implementations, but other configurations are also contemplated. In particular, even though expressions such as in “an implementation,” or the like are used herein, these phrases are meant to generally reference implementation possibilities, and are not intended to limit the disclosure to particular implementation configurations. As used herein, these terms may reference the same or different implementations that are combinable into other implementations. As a rule, any implementation referenced herein is freely combinable with any one or more of the other implementations referenced herein, and any number of features of different implementations are combinable with one another, unless indicated otherwise. Although only a few examples have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible within the scope of the described examples. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims.