Masonry Magazine February 1985 Page. 34
REANCHORING
continued
The second project, an 18-story concrete dormitory in Lowell, Massachusetts, had a brick facade and required a different resupport system. The fastener designed for this application was adapted from a stud anchor (see Figure 2). This dowel stud provided load support in two directions: away from and toward the main structure. The modified stud anchor end expanded in the concrete wall and the other in the brick facade.
MODIFIED STUD ANCHOR
Figure 2
The anchor, made from stainless steel material, was inch in diameter and fit in the mortar joints of the brick facade. The dowel stud end that expanded into the concrete was modified for the application. The part of the dowel stud that expanded in the brick also is a modification of the stud anchor's expansion, and a specially designed stainless plug was used in the brick facade.
This facade anchoring system could support approximately 3,000 pounds while rigidly reconnecting the brick facade wall to the concrete dormitory structure. An added benefit to the contractor was an installation time of 90 seconds per stud.
The third project involved two 15-story brick apartment buildings in Newark, New Jersey, requiring resupport of brick facades to a primary structure of both concrete and masonry block units. The method of fastening utilizes the Pronto Anchor and an expandable, proprietary PVC element. This combination system anchors to a hollow masonry wall (sub-surface material) and ties back a brick wall facade (see Figure 3).
COMBINATION ANCHOR
Figure 3
34 MASONRY-JANUARY/FEBRUARY, 1985
The Pronto Anchor was designed for use in masonry units. A specially designed rod both activates the anchor and attaches the outer wall to the rear masonry structure. The PVC, when expanded, swells the drilled hole in the brick facade. It is attached to the special activation rod used with the anchor.
Each of the three facade resupport problems required a careful evaluation of the anchoring application. The effect of load direction on the original structure had to be considered so the new facade resupport anchoring would hold.
Criteria
In solving each problem of retrofitting a building with a facade that had a decaying anchoring system, the engineers used the following criteria:
Identify the cause. The problem may be absence of a portion or all required wall ties, or the wall ties originally used may be eroded to 50 percent of their capacity. This information will assist in material selection, and in determining the number of anchor support ties required. Proper selection of anchor type, material, and quantity is necessary to avoid a recurrence of the problem.
TYPICAL RE-SUPPORT MATERIAL COMBINATIONS
Figure 4
Examine existing structural integrity. Can the exterior wall, or facade, be repaired safely without further destroying the integrity of the building? Determine the degree of facade rigidity and the capabilities of the anchor materials. Be sure that the expansion stresses developed with the mechanical anchoring devices do not exceed working limits of the material. Consider stress for both the facade and the substructure, or cracking and further building support material degradation may occur. On-site testing can verify working limits of the materials.
Budget. There are usually constraints on money budgeted for building repairs. When developing a budget for a specific problem consider that the problem will not occur again for another 15 years using proper materials and installation procedures. The rehabilitation shouldn't cost more than the original buidling.
Working environment. Determine whether repair work done from a floating scaffold is necessary, and whether it will endanger occupants or pedestrians. These factors will influence the complexity of installation procedures and anchor selections.