Lifting anchor for precast concrete structures

Abstract

A lifting anchor for a precast concrete structure is made from a single strand of metal bar stock. The anchor includes undulations or waves that ensure proper engagement of the anchor in a desired compressed concrete zone and also minimizes interference with the pre-stressed strands in the concrete structure. The anchor can be positioned in different orientations in the structures, depending on functional requirements of particular structures, and can be made from a single strand of bar stock of desired cross-sectional thickness and shape (e.g., round or square). Also, the undulations or waves in the legs of the anchor can extend in one or both directions from a plane defined by the anchor's legs.

1 . A lifting anchor configured to be embedded in a precast concrete structure, said lifting anchor comprising:
 a single strand of metal bar stock bent to include a pair of elongated legs and a central section that integrally interconnects the pair of elongated legs; and   wherein a lower end section of each of the pair of elongated legs includes undulations that are configured to engage in a compressed zone of a concrete structure resulting from prestressed strands cast in the concrete structure and configured to minimize interference with the prestressed strands.   
     
     
         2 . The lifting anchor of  claim 1 , wherein the pair of elongated legs extend from the central section in substantially parallel alignment with each other. 
     
     
         3 . The lifting anchor of  claim 1 , wherein the central section comprises an inverted V shape configured to engage a lifting chain. 
     
     
         4 . The lifting anchor of  claim 1 , wherein the central section separates the pair of elongated legs away from each other at a spaced distance configured to dispose the pair of elongated legs on opposing sides of a vertical arrangement of the prestressed strands in the concrete structure 
     
     
         5 . The lifting anchor of  claim 1 , wherein the central section and upper sections of the pair of elongated legs define a common plane, and wherein the undulations in the lower end sections of the pair of elongated legs extend from at least one side of the common plane. 
     
     
         6 . The lifting anchor of  claim 5 , wherein the undulations are defined by the lower end sections of the pair of elongated legs bent to a wave shape with at least two wavelengths that extends from a side of the common plane. 
     
     
         7 . The lifting anchor of  claim 1 , wherein the pair of elongated legs are configured to be disposed between the two vertical arrangements of the prestressed strands. 
     
     
         8 . The lifting anchor of  claim 1 , wherein the single strand comprises one of a generally square cross-sectional bar stock and a generally round cross-sectional bar stock. 
     
     
         9 . An apparatus comprising:
 a precast concrete structure including a surface-forming panel portion, a panel-reinforcing rib portion, and prestressed strands disposed within the rib portion;   a plurality of lifting anchors positioned within the rib portion;   wherein the plurality of lifting anchors each comprise a single strand of metal bar stock that includes a pair of parallel legs and a leg-connecting section; and   wherein a lower end section of each of the pair of parallel legs includes undulations shaped to engage in a compressed zone in the rib portion proximate the prestressed strands.   
     
     
         10 . The apparatus of  claim 9 , wherein the prestressed strands are disposed at spaced locations along a length of the rib portion, and wherein the leg-connecting section and upper sections of the pair of parallel legs extend generally in a common plane. 
     
     
         11 . The apparatus of  claim 10 , wherein the common plane extends parallel to the prestressed strands. 
     
     
         12 . The apparatus of  claim 10 , wherein the common plane extends perpendicular to the prestressed strands. 
     
     
         13 . The apparatus of  claim 10 , wherein the undulations extend from at least one side of the common plane, and wherein the undulations are configured to minimize interference with the prestressed strands. 
     
     
         14 . The apparatus of  claim 9 , wherein the leg-connecting section separates the pair of parallel legs away from each other at a spaced distance configured to dispose the pair of parallel legs on opposing sides of the prestressed strands. 
     
     
         15 . The apparatus of  claim 9 , wherein the undulations are defined by the lower end sections of the pair of parallel legs each bent to a wave shape with at least one wavelength. 
     
     
         16 . The apparatus of  claim 15 , wherein the pair of parallel legs are disposed between the two prestressed strands. 
     
     
         17 . The apparatus of  claim 9 , wherein the single strand comprises one of a generally square cross-sectional bar stock and a generally round cross-sectional bar stock. 
     
     
         18 . A method of forming a concrete structure, said method comprising:
 providing a plurality of lifting anchors that each comprise a single strand of metal bar stock that includes a pair of parallel legs and a leg-connecting section, wherein a lower end section of the legs includes undulations bent into the single strand;   casting concrete to form a precast concrete structure that includes a surface-forming panel portion, a panel-reinforcing rib portion, and prestressed strands that extend along a length of the rib portion; and   wherein, prior to hardening of the precast concrete structure, the plurality of lifting anchors are disposed within the rib portion with the undulations positioned to engage a compressed concrete zone in the precast concrete structure and to minimize interference with prestressed strands in the concrete structure.   
     
     
         19 . The method of  claim 18 , wherein the leg-connecting section and upper sections of the pair of parallel legs extend generally in a common plane. 
     
     
         20 . The method of  claim 19 , wherein each of the plurality of lifting anchors is positioned for its common plane to extend generally parallel or perpendicular to the prestressed strands.