Patent Description:
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 sheathes. Traditionally, a tension member is constructed of a material that can be elongated and may be a single or a multi-strand cable. Typically, the tension member may be formed from a metal or composite material, such as reinforced steel. The post-tensioning tendon conventionally includes an anchor assembly at each end. The post-tensioning tendon 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.

Post-tension members are conventionally formed from a strand and a sheath. The strand is conventionally formed as a single or multi-strand metal cable. The strand is conventionally encapsulated within a polymeric sheath extruded thereabout to, for example, prevent or retard corrosion of the metal strand by protecting the metal strand from exposure to corrosive or reactive fluids. Likewise, the sheath may prevent or retard concrete from bonding to the strand and preventing or restricting movement of the sheath during post-tensioning. The sheath may be filled with grease to further limit the exposure of the metal strand and allow for increased mobility. Because the metal strand and the polymeric sheath are formed from different materials, the thermal expansion and contraction rates of the metal strand and polymeric sheath may differ. During conventional manufacturing, the sheaths are formed by hot extrusion over the metal strand. When the tension members are coiled for transport and storage, uneven thermal contraction may occur as the tendon cools. When installed as a 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 metal strand to corrosive or reactive fluids. A conventional arrangement for use with an anchor for a concrete component is disclosed in <CIT>.

According to one aspect of the present invention, there is provided an anchor as defined in claim <NUM> hereinafter.

The present disclosure provides an anchor. The anchor includes an anchor body, the anchor body having an internal passage, and a lock nut, the lock nut having an internal tapered surface defining a forcing cone. The lock nut is coupled to the anchor body. The anchor also includes a spindle, the spindle positioned within the internal passage and threadedly coupled to the lock nut. The spindle has an expansion wedge.

The present disclosure also provides for a post-tensioning tendon as defined in claim <NUM>. The post-tensioning tendon includes a tension member including a strand and a sheath where the sheath is positioned about the strand. The post-tensioning tendon also includes a first anchor coupled to a first end of the tension member and a second anchor coupled to a second end of the tension member. Each of the anchors include an anchor body, the anchor body having an internal passage, and a lock nut, the lock nut having an internal tapered surface defining a forcing cone. The lock nut is coupled to the anchor body. The anchors also include a spindle, the spindle positioned within the internal passage and threadedly coupled to the lock nut. The spindle has an expansion wedge, and the sheath is gripped between the expansion wedge and the forcing cone.

In addition, the present disclosure provides for a method of coupling a tension member to an anchor for forming a post-tensioning tendon, that does not form part of the invention. The method includes providing a tension member including a strand and a sheath, where the sheath is positioned about the strand. The method also includes providing an anchor. The anchor includes an anchor body, where the anchor body has an internal passage and a lock nut, the lock nut having an internal tapered surface defining a forcing cone. The lock nut is coupled to the anchor body. The anchor also includes a spindle, the spindle positioned within the internal passage and threadedly coupled to the lock nut. The spindle has an expansion wedge, and the sheath is gripped between the expansion wedge and the forcing cone. The method also includes removing a portion of a first end of the sheath from a first end of the tension member exposing a first end of the strand and inserting the first end of the tension member into the anchor. In addition, the method includes inserting the first end of the strand through the spindle and inserting the sheath between the expansion wedge and the forcing cone. The method also includes tightening the lock nut onto the spindle such that the sheath is compressed between the expansion wedge and the forcing cone and coupling the strand to the anchor.

The present disclosure is best understood from the following detailed description when read with the accompanying figures.

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, the scope of protection being limited by the appended claims.

When stressing concrete member <NUM>, anchoring systems may be provided to hold the tension member before and after stressing. In some embodiments, as depicted in <FIG>, post-tensioning tendon <NUM> may be positioned within concrete form <NUM>. Concrete form <NUM> is a form into which concrete may be poured to form concrete member <NUM>. Post-tensioning tendon <NUM> may include for example and without limitation fixed end anchor <NUM>, tension member <NUM>, and stressing end anchor <NUM>. As depicted in <FIG>, in some embodiments, fixed end anchor <NUM> may include fixed end anchor body <NUM>. Fixed-end anchor body <NUM> may be positioned within concrete form <NUM> such that fixed-end anchor body <NUM> will be encased in concrete <NUM> after concrete is poured into concrete form <NUM>. In some embodiments, fixed end cap <NUM> may be positioned at distal end <NUM> of fixed end anchor body <NUM>. Fixed end cap <NUM> may, in certain embodiments, protect tension member <NUM> from corrosion after concrete <NUM> is poured by preventing or retarding corrosive or reactive fluids or concrete from contacting tension member <NUM>.

Stressing end anchor <NUM> may include stressing end anchor body <NUM>, positioned within concrete form <NUM> such that stressing end anchor body <NUM> is within concrete <NUM>. Pocket former <NUM> may be positioned between the end of stressing end anchor body <NUM> and end wall <NUM> of concrete form <NUM>. Pocket former <NUM> may prevent or retard concrete <NUM> from filling space between stressing end anchor body <NUM> and concrete form edge <NUM> of the resultant concrete member <NUM> formed by concrete <NUM> within concrete form <NUM>. Pocket former <NUM> may allow access to tension member <NUM> from outside concrete member <NUM> once concrete member <NUM> is hardened and concrete form <NUM> is removed.

As used herein, stressing end anchor <NUM> and fixed end anchor <NUM> may be referred to as "first anchor" and "second anchor," or vice versa.

In some embodiments, tension member <NUM> may include strand <NUM> and sheath <NUM>. Strand <NUM> may be a single or multi-strand metal cable. Sheath <NUM> may be tubular or generally tubular and may be positioned about strand <NUM>. In some embodiments, space between strand <NUM> and sheath <NUM> may be filled or partially filled with a filler such as grease. When installing tension member <NUM>, in some embodiments, a length of sheath <NUM> may be removed from first end <NUM> of tension member <NUM>, exposing strand <NUM>. Strand <NUM> may be inserted through fixed end anchor body <NUM> and secured thereto, for example and without limitation, by one or more wedges. After strand <NUM> is secured, fixed end anchor body <NUM> may be installed in concrete form <NUM>. Tension member <NUM> may be positioned within concrete form <NUM> and tension member <NUM> may be cut to correspond with the length of concrete form <NUM>. In some embodiments, a length of sheath <NUM> may be removed from second end <NUM> of tension member <NUM>, exposing strand <NUM>. Strand <NUM> may be inserted through stressing end anchor body <NUM>. After insertion of strand <NUM> through stressing end anchor body <NUM>, stressing end anchor <NUM> may be positioned within concrete form <NUM> such that pocket former <NUM> contacts end wall <NUM> of concrete form <NUM>. End wall <NUM> may include strand aperture <NUM> through which strand <NUM> may extend.

In some embodiments, as depicted in <FIG>, and <FIG>, when tension member <NUM> is inserted into stressing end anchor body <NUM> and fixed end anchor body <NUM>, sheath <NUM> may be coupled to stressing end anchor body <NUM> and fixed end anchor body <NUM> to, for example and without limitation, prevent or restrict sheath <NUM> from pulling away from the respective anchors and exposing strand <NUM> to concrete <NUM>.

The fixed end anchor <NUM> includes lock nut <NUM> and spindle <NUM>. Likewise, stressing end anchor <NUM> includes lock nut <NUM> and spindle <NUM>. Spindles <NUM>, <NUM> may be tubular or generally tubular members having cylindrical or generally cylindrical inner surfaces <NUM> defining spindle inner passages <NUM> through which strand <NUM> may pass. Spindles <NUM>, <NUM> are positioned within internal passage <NUM> of the corresponding anchor bodies <NUM>, <NUM>. The spindles <NUM>, <NUM> include threads <NUM> to threadedly couple spindles <NUM>, <NUM> to a respective lock nut <NUM>.

In some embodiments, lock nuts <NUM> and spindles <NUM>, <NUM> may grip first end <NUM> and second end <NUM> of sheath <NUM> when coupled. As depicted in <FIG>, spindles <NUM>, <NUM> include expansion wedge <NUM>. Expansion wedge <NUM> may be positioned within first end <NUM> and second end <NUM> of sheath <NUM> and expand first end <NUM> and second end <NUM> radially outward as expansion wedge <NUM> is inserted. Likewise, lock nuts <NUM> include internal tapered surface <NUM> defining forcing cone <NUM> corresponding to expansion wedges <NUM> such that, as lock nuts <NUM> are tightened, expansion portion <NUM> of sheath <NUM> into which expansion wedge <NUM> is gripped between forcing cone <NUM> and expansion wedge <NUM>. In some embodiments, one or both of expansion wedge <NUM> and forcing cone <NUM> may be smooth or may include a grip enhancing surface feature such as teeth, grooves, or any other grip enhancing surface features known in the art.

Spindles <NUM>, <NUM> couple to fixed end anchor body <NUM> or stressing end anchor body <NUM> by tensile forces applied when lock nuts <NUM> are tightened thereonto. Spindles <NUM>, <NUM> include a retention feature. The retention feature transferring the tensile force onto fixed end anchor body <NUM> or stressing end anchor body <NUM> and preventing or restricting spindles <NUM>, <NUM> from being pulled through fixed end anchor body <NUM> or stressing end anchor body <NUM>. The retention feature being an edge, detent, extension, or, as depicted in <FIG>, conical retaining profile <NUM>.

In some embodiments, one or more of spindles <NUM>, <NUM> may couple fixed end anchor body <NUM> or stressing end anchor body <NUM> to end wall <NUM> of concrete form <NUM>. As depicted in <FIG>, and <FIG>, spindle <NUM> includes spindle extension <NUM>; spindle extension <NUM> may thread through strand aperture <NUM> in end wall <NUM> through which strand <NUM> extends. In some embodiments, spindle extension <NUM> may include external threads <NUM>. External threads <NUM> may threadedly couple spindle extension <NUM> with spindle nut <NUM>. Spindle nut <NUM> may allow stressing end anchor body <NUM> to be retained to end wall <NUM> during concrete pouring.

In some embodiments, after concrete <NUM> is poured, spindles <NUM>, <NUM> may be left in fixed end anchor <NUM>. In some embodiments, after concrete <NUM> is poured and set as depicted in <FIG>, spindle <NUM> may be removed from stressing end anchor body <NUM> by unthreading spindle <NUM> from lock nut <NUM>. Although sheath <NUM> may no longer be retained between extended spindle <NUM> and lock nut <NUM> after concrete pouring, sheath <NUM> may be prevented from retracting from stressing end anchor body <NUM> by concrete <NUM>. As understood in the art, concrete <NUM> surrounding sheath <NUM> may conform to surface irregularities of sheath <NUM> and may adhere thereto, thus preventing or restricting any contraction of sheath <NUM>.

In some embodiments, one or more seals may be positioned to prevent or restrict concrete <NUM> from ingressing into tension member <NUM> that may prevent or retard the tensioning of strand <NUM>. In some embodiments, as depicted in <FIG>, gasket <NUM> may be positioned between lock nut <NUM> and stressing end anchor body <NUM>.

Although described specifically with respect to fixed end anchor <NUM> and stressing end anchor <NUM>, a spindle such as spindles <NUM>, <NUM> may be utilized with either a fixed end anchor or stressing end anchor. Furthermore, a spindle such as spindles <NUM>, <NUM> may be used with an intermediate anchor. An intermediate anchor, as understood in the art, may be an anchor used between adjacent concrete members which are poured and stressed sequentially utilizing the same tension member <NUM>.

Although fixed end anchor <NUM> and stressing end anchor <NUM> are depicted as unencapsulated or bare anchors, such as those formed from ductile iron, fixed end anchor <NUM> and stressing end anchor <NUM> may be encapsulated-type anchors without deviating from the scope of this disclosure and may be formed from any material. Non-limiting examples of encapsulated anchors are disclosed in <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; and <CIT>. In some embodiments, spindles <NUM>, <NUM> may be formed from a nonconductive material such as a polymer. In some such embodiments, spindles <NUM>, <NUM> may act to electrically insulate strand <NUM>, fixed end anchor <NUM>, and stressing end anchor <NUM>. This electric insulation may prevent or retard galvanic corrosion from occurring due to contact between strand <NUM>, fixed end anchor <NUM>, or stressing end anchor <NUM> when strand <NUM>, fixed end anchor <NUM>, and stressing end anchor <NUM> are formed from different metals.

Claim 1:
An anchor for a post-tensioning tendon comprising:
an anchor body, the anchor body (<NUM>, <NUM>) having an internal passage (<NUM>);
a lock nut (<NUM>), the lock nut (<NUM>) having an internal tapered surface (<NUM>) defining a forcing cone (<NUM>), the lock nut (<NUM>) coupled to the anchor body (<NUM>, <NUM>); and
a spindle (<NUM>, <NUM>), the spindle (<NUM>, <NUM>) positioned within the internal passage (<NUM>) and threadedly coupled to the lock nut (<NUM>), the spindle (<NUM>, <NUM>) having an expansion wedge (<NUM>) and a retention feature, wherein:
the forcing cone (<NUM>) corresponds to the expansion wedge (<NUM>) such that the lock nut (<NUM>) grips an expansion portion (<NUM>) of a sheath (<NUM>) between the forcing cone (<NUM>) and the expansion wedge (<NUM>) when the lock nut (<NUM>) is tightened;
the spindle (<NUM>, <NUM>) being coupled to the anchor body (<NUM>, <NUM>) by a tensile force applied when the lock nut (<NUM>) is tightened onto the spindle (<NUM>, <NUM>); and
the retention feature transfers the force from the spindle (<NUM>, <NUM>) to the anchor body (<NUM>, <NUM>) and prevents or restricts the spindle (<NUM>, <NUM>) from being pulled through the anchor body (<NUM>, <NUM>);
wherein the retention feature is an edge, detent, extension, or conical retaining profile (<NUM>).