Anchorage System For Prestressing Non-Metallic Tendons

Abstract

An anchorage system for prestressing a non-metallic (e.g., FRP) tendon against a support member may include a dead-end assembly and a live-end assembly configured to be placed on opposite sides of the support member, each assembly having a support sleeve affixed to a support plate. The anchorage system may also include a tensioning rod coupled to an end of the support sleeve of the live-end assembly that is remote from the respective support plate, and a removable support box extending around the support sleeve of the live-end assembly, the tensioning rod extending through an opening defined in the removable support box, the support box configured to be an abutment structure against which a jack may be placed. The anchorage system may also include one or more slotted shim plates interposed between the support plate of the live-end assembly and a first confronting surface of the support member.

1 . An anchorage system for prestressing a non-metallic tendon against a support member, the anchorage system comprising:
 a dead-end assembly and a live-end assembly configured to be placed on opposite sides of the support member, each of the dead-end assembly and the live-end assembly having:
 a support sleeve affixed to a support plate, a longitudinal axis of the support sleeve being perpendicular to a planar surface of the support plate, the support sleeve having an interior that is configured to extend around a portion of the non-metallic tendon, the support sleeve being configured to be affixed to the non-metallic tendon using an expansive grout that extends therebetween, the support sleeve having one or more apertures extending into the interior that are configured to receive insertion of the grout therethrough; and 
 a hollow bolt removably coupled to an end of the support sleeve adjacent to the support plate, the hollow bolt having a lumen configured to slidably receive a portion of the tendon therethrough with a clearance that is sufficiently close to prevent the expansive grout from leaking out of the lumen when the non-metallic tendon extends therethrough; 
   a tensioning rod coupled to an end of the support sleeve of the live-end assembly that is remote from the respective support plate;   a removable support box extending around the support sleeve of the live-end assembly, the tensioning rod extending through an opening defined in the removable support box, the support box configured to be an abutment structure against which a jack may be placed; and   one or more slotted shim plates interposed between the support plate of the live-end assembly and a first confronting surface of the support member, the one or more slotted shim plates having a total width approximately equal to a length that the non-metallic tendon has been stretched from a relaxed state thereof.   
     
     
         2 . The anchorage system of  claim 1 , further comprising the non-metallic tendon and the expansive grout, the expansive grout affixing the non-metallic tendon to an inner surface of each of the support sleeves. 
     
     
         3 . The anchorage system of  claim 1 , wherein the end of the support sleeve of the live-end assembly is threadedly coupled to an end of the tensioning rod. 
     
     
         4 . The anchorage system of  claim 1 , further comprising the support member, the non-metallic tendon extending through each of the support sleeves and either: through a duct extending through the support member; or outside of and along an outer surface of the support member and coupled to the outer surface. 
     
     
         5 . The anchorage system of  claim 4 , wherein the support member has a recess extending into a second confronting surface thereof adjacent to the support sleeve of the dead-end assembly, the hollow bolt of the dead-end assembly positioned within the recess such that the support plate of the dead-end assembly is positioned flush with a second confronting surface of the support member. 
     
     
         6 . The anchorage system of  claim 1 , wherein the aperture of each support sleeve has internal threads, the anchorage system further comprising removable bolts configured to be threadedly coupled to respective ones of the apertures. 
     
     
         7 . The anchorage system of  claim 1 , wherein the one or more slotted shim plates is a plurality of shim plates each having a different thickness in a direction along the longitudinal axis of the support sleeve of the live-end assembly. 
     
     
         8 . A method of prestressing a non-metallic tendon against a support member, the method comprising:
 placing the non-metallic tendon extending either through a duct connecting opposite sides of the support member or outside of and along an outer surface of the support member and coupled to the outer surface;   positioning a dead-end assembly and a live-end assembly on the opposite sides of the support member, each of the dead-end assembly and the live-end assembly having a support sleeve affixed to a support plate, a longitudinal axis of each support sleeve being perpendicular to a planar surface of respective support plate;   feeding first and second ends of the non-metallic tendon into the support sleeve of the dead-end assembly and the support sleeve of the live-end assembly, respectively, so that an interior of each support sleeve extends around a portion of the non-metallic tendon;   coupling a tensioning rod coupled to an end of the support sleeve of the live-end assembly that is remote from the respective support plate;   pouring an expansive grout into apertures extending into an interior of each of the support sleeves, the expansive grout extending around exposed portions of the non-metallic tendon within the interior of each of the support sleeves;   curing the expansive grout so that the non-metallic tendon is affixed to the support sleeve of each of the live-end assembly and the dead-end assembly;   assembling a support box extending around the support sleeve of the live-end assembly, the tensioning rod extending through an opening defined in the removable support box;   coupling a jack to the tensioning rod, an end surface of the support box serving as an abutment structure against which the jack is placed;   a first pulling of the tensioning rod along the longitudinal axis of the support sleeve of the live-end assembly to stretch the non-metallic tendon by a first elongation length, the first pulling of the tensioning rod creating a first gap extending between the support plate of the live-end assembly and a first confronting surface of the support member; and   inserting one or more first slotted shim plates into the first gap, the one or more first shim plates having a first aggregate width approximately equal to the first elongation length that the non-metallic tendon has been stretched.   
     
     
         9 . The method of  claim 8 , further comprising:
 a second pulling of the tensioning rod along the longitudinal axis of the support sleeve of the live-end assembly to further stretch the non-metallic tendon by a second elongation length, the second pulling of the tensioning rod creating a second gap extending between the first slotted shim plate and either the support plate of the live-end assembly or the first confronting surface of the support member; and   inserting one or more second slotted shim plates into the second gap, the one or more second shim plates having a second aggregate width approximately equal to the second elongation length that the non-metallic tendon has been stretched.   
     
     
         10 . The method of  claim 9 , wherein the second aggregate width is less than the first aggregate width. 
     
     
         11 . The method of  claim 8 , wherein the end of the support sleeve of the live-end assembly is threadedly coupled to an end of the tensioning rod. 
     
     
         12 . The method of  claim 8 , wherein the aperture of each support sleeve has internal threads, the method further comprising threadedly coupling removable bolts to seal respective ones of the apertures after the pouring and before the curing. 
     
     
         13 . The method of  claim 12 , further comprising removing the removable bolts from the respective ones of the apertures after the curing. 
     
     
         14 . The method of  claim 8 , further comprising removably coupling a hollow bolt to an end of each support sleeve adjacent to the respective support plate, each hollow bolt having a lumen that slidably receives a portion of the non-metallic tendon therethrough with a clearance that is sufficiently close to prevent the expansive grout from leaking out of the lumen. 
     
     
         15 . The method of  claim 14 , wherein the support member has a recess extending into a second confronting surface thereof adjacent to the support sleeve of the dead-end assembly, the method further comprising positioning the hollow bolt of the dead-end assembly within the recess such that the support plate of the dead-end assembly is positioned flush with the second confronting surface of the support member. 
     
     
         16 . The method of  claim 8 , wherein during the inserting of the one or more first slotted shim plates into the first gap, the first shim plate is inserted into an open side of the support box, and a slot extending into each of the one or more first slotted shim plates is positioned around a portion of the non-metallic tendon. 
     
     
         17 . The method of  claim 8 , further comprising, after the inserting of the first slotted shim plate into the first gap, uncoupling the jack from the tensioning rod, uncoupling the tensioning rod from the end of the support sleeve of the live-end assembly, and removing the support box from the live-end assembly. 
     
     
         18 . The method of  claim 8 , wherein the non-metallic tendon is made of a fiber reinforced polymer. 
     
     
         19 . The method of  claim 8 , wherein the non-metallic tendon is a first non-metallic tendon, the method further comprising placing a second non-metallic tendon extending either through the duct or outside of and along the outer surface of the support member and coupled to the outer surface, the curing step affixes the second non-metallic tendon to the support sleeve of each of the live-end assembly and the dead-end assembly, and the first pulling of the tensioning rod stretches the second non-metallic tendon by the first length. 
     
     
         20 . The method of  claim 8 , wherein the support member is a concrete element.