Masonry Magazine April 1988 Page. 21
Re-anchoring systems are relatively new and commonly used to: 1) provide ties in areas where ties were not installed during original construction, 2) replace existing ties, 3) replace failed masonry bonding units, 4) upgrade older wall systems to current code levels, or 5) attach new veneers over existing facades.
As stated, re-anchoring systems are relatively new and many designers and contractors may not be fully familiar with their installation or limitations. For this reason, consultation with the system manufacturer is essential to assure proper application, detailing, installation, inspection, and performance.
TIE SELECTION
Strength and Deformation
The strength and deformation characteristics of tie systems are not generally analyzed nor investigated during the project design or specification phase. Building codes and standards have typically required minimum tie size (diameter or gage) and maximum tie spacing limits to control tie loading and deformation. Present tie size and spacing requirements have been derived from some testing and from the past performance of traditional tie systems (rectangular ties, "Z" ties and standard joint reinforcement).
The growing use of adjustable tie systems has caused some concerns in regard to tie strength and deformation. Most adjustable ties permit vertical adjustment up to approximately one-half the height of a standard brick unit, some permit greater adjustments. Depending on the tie configuration, the deflections of adjustable ties can become quite large as vertical adjustment eccentricities are increased. This deflection is further increased if mechanical play is present in the tie system.
Analytical and experimental investigations of cavity wall and veneer wall systems have shown that tie loads and deformations are a function of: 1) the relative stiffness between facing and backup materials, 2) tie spacing, 3) tie stiffness, 4) support conditions of the facing and backup systems, 5) location of openings, 6) cavity width and 7) applied loads.
Estimating tie loads based on tributary area can lead to large errors, depending on the geometry and properties of the wall system. Fig. 11 shows tie loads and deflections calculated from a simplified model of a cavity wall
5/8 IN. MIN OR
T/2 MAX
SECTION
A) LADDER TYPES
B) TRUSS TYPES
Adjustable Joint Reinforcement Assemblies
FIG. 8
5/8 IN. MIN OR
T/2 MAX
A) LADDER TYPE
B) TRUSS TYPE
Adjustable Assembly Details
FIG. 9