Abstract:
Structural wall reinforcement method and apparatus for reinforcing a wall comprising a plurality of post-tensioned cable assemblies and wire mesh embedded in a layer of concrete-like material for applying compressive forces to the wall.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to structural wall reinforcing apparatus and methods in general and in particular to an apparatus and method for reinforcing brick and block walls. 
     2. Description of the Prior Art 
     In years past many buildings and other structures were constructed using brick and blocks as structural wall members but without any interior steel reinforcing rods, bars, or the like, being used for reinforcement as is the current practice. 
     In the course of powerful seismic activity, e.g. earthquakes, many such unreinforced structures suffer extensive dislocations and damage, if not total destruction. 
     To preserve such structures and eliminate or significantly reduce the threat of their being damaged during earthquakes, it is necessary to reinforce such structures in a manner which makes them substantially equivalent in strength and soundness to modern-day structures and at a reasonable cost. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing, principal objects of the present invention are a method and apparatus for reinforcing a brick and/or block wall structure. 
     In accordance with the above objects, there is provided a plurality of post-tensioned cable assemblies which are located at selected positions along and attached to the. Each of the cable assemblies is anchored at the base and to the top of the wall and comprises a tendon which runs through a cable duct or grout tube. After the cable assemblies are installed, reinforcing wire mesh is laid across the assemblies and anchored to the wall at selected points by steel dowels embedded in the wall. The cable assemblies and wire mesh are then embedded in a layer of Gunnite or Shotcrete which attaches to the wall by itself or is attached to the wall as by a bonding agent or doweling. After the Gunnite or Shotcrete is cured, the tendons are tensioned and the cable ducts filled with grout. The tensioning of the tendons results in compressive forces being transferred to the wall in such a manner that the resulting composite wall structure is as strong as or stronger than walls constructed originally using current building techniques. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects, features and advantages of the present invention will become apparent from the following detailed description of the accompanying drawings, in which: 
     FIG. 1 is a front elevation view of a brick wall reinforced with cable assemblies according to the present invention; 
     FIG. 2 is a side elevation view of a section of the wall of FIG. 1; 
     FIG. 3 is a side elevation view showing the installation of an upper anchor plate and wire mesh according to the present invention; 
     FIG. 4 is a front elevation view of FIG. 3 with the wire mesh omitted for clarity; 
     FIG. 5 is a side elevation view of a lower anchor plate, i.e. footing anchor, showing the manner in which the lower anchor plate of the cable assemblies are anchored to a wall foundation using footing anchor dowels according to the present invention; 
     FIG. 6 is a top plan view of FIG. 5; and 
     FIG. 7 is an alternative view of the footing anchor comprising a spiral rebar cage tied to the footing anchor dowels according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1, there is shown an elevation view of an unreinforced brick wall designated generally as 1 which is built on a foundation 2. Attached at selected locations across the face of the wall 1 there is provided a plurality of cable assemblies 3. 
     Referring to FIGS. 2-6, there is provided in each of the cable assemblies 3 an upper anchor plate 5 and a lower anchor plate 6. Extending between the upper anchor plate 5 and lower anchor plate 6 there is provided a cable duct 7, also called a grout tube, comprising an upper duct section 8 and a lower duct section 9 which are joined by a coupling 10. The duct 7 is provided for enclosing a tendon 11, as shown in FIGS. 5 and 6. The upper end of the tendon 11 is anchored in the anchor plate 5 and the lower end of the tendon 11 is anchored in the anchor plate 6 by means of clamping wedges (not shown). The clamping wedges grasp the tendon in a well known manner so as to maintain the tendon under tension, as will be further described below. 
     Referring in particular to FIGS. 3 and 4, the upper anchor plate 5 and the upper section 8 of the cable duct 7 are embedded in a square block of concrete 15. For added strength a plurality of reinforcing bars 16, which are joined at their intersecting points, are also embedded in the concrete block 15, as shown more clearly in FIG. 4. During its construction, the block 15 is rigidly attached to at least a portion of the top of the wall 1 so as to impart compressive forces thereto, as will be further described below. 
     Referring to FIGS. 5 and 6, the lower anchor plate 6 is mounted on the foundation 2 which extends beneath the wall 1. If a foundation similar to foundation 2 does not exist in the original construction of the wall 1, a foundation 2 is poured and a rigid connection made in any suitable manner with the original foundation. 
     To secure the lower anchor plate 6 to the foundation 2 there is provided a plurality of segments of reinforcing bar 17 and 18. Reinforcing bar segments 17 and 18 comprise a lower section 19 and an upper horizontal section 20. The lower sections 19 are embedded in the foundation 2 and rigidly affixed thereto by means of an adhesive epoxy, or the like. 
     In practice, the segments 17 and 18 are arranged to extend over the anchor plate 6 so as to capture the anchor plate 6 between the segments 17 and 18 and the foundation 2. 
     Referring again to FIGS. 2 and 3, after the cable assemblies 3 are anchored to the top and bottom of the wall 1, wire mesh 21 is placed across the face of the wall 1 and attached thereto as by a plurality of dowels 22 which are rigidly attached, as by epoxy or the like, in holes provided therefor in the wall 1. 
     After the cable assemblies 3 and wire mesh 21 are mounted to the wall 1 and foundation 2, the adjacent surface of the wall 1 is sandblasted and coated with an adhesive, such as an epoxy. Thereafter, a concrete-like material, typically known under the trade name Gunnite or Shotcrete, is applied over the wall between the lower surface of the concrete block 15 and the upper surface of the foundation 2 for embedding the exposed portion of the cable assemblies 3 and the wire mesh 21. As is well known, Gunnite or the like has substantially the same or greater compressive strength as does the brick typically used in the wall 1. 
     After the Gunnite is cured, a jack 25 is coupled to the upper end of the tendon 11 for applying tensile force to the tendon 11. After a desired amount of tensile force is applied to the tendon 11, e.g. 6,000 pounds, a relaxation of the tensile force will cause the wedge-shaped clamping members in the upper anchor plate 5 to grasp the upper end of the tendon 11, maintaining the tendon 11 under tension. This tension is then transmitted via the block 15 to the wall 1, placing the wall 1 under compression. 
     Referring to FIG. 7, there is provided in an alternative embodiment of the present invention a spiral rebar cage designated generally as 30. Cage 30 is placed around the footing anchor rebar 17 and 18 and tied thereto in a conventional manner before being embedded in the Gunnite 26. 
     In a typical embodiment of the present invention, the dowels 21, the rebar sections 16, 17 and 18, typically comprise No. 4 or No. 5 rebar. The layer of Gunnite 26 is typically 4-6 inches thick and the block 15 is typically an 8-10 inch square block. After the tendon is tensioned, grout is forced into the duct 7 in a conventional manner so as to protect the tendon 11 from corrosion. 
     While a preferred embodiment of the present invention is described above, it is contemplated that various modifications may be made thereto without departing from the spirit and scope of the present invention. Accordingly, it is intended that the embodiment described be considered only as an illustration of the present invention and that the scope thereof should not be limited thereto but be determined by reference to the claims hereinafter provided and their equivalents.