Masonry Magazine October 1980 Page. 17
WIND
LOADING
ASSUMED
DEFLECTED
SHAPE
MOMENT SHEAR
(BRICK
(BRICK
WYTHE) WYTHE)
24"(600 mm)'
MAXIMUM
VERTICAL SPACING
2% SQ FT (0.25 m²)
MAXIMUM WALL
SURFACE AREA
PER TIE
24"(600 mm)
MAXIMUM
HORIZONTAL
SPACING
Spacing of Metal Ties
FIG. 7
Lateral Wind Loading
FIG. 6
flection of L/240 or L/360. Even using an L/360 deflection criteria for the backup may permit more deflection than the brick veneer is able to tolerate without cracking and distress.
Adequate Moment Resistance-In order to provide for full lateral support of the metal studs, and thus be able to use the full allowable stresses in the studs, there must be properly attached sheathing on both sides of the studs. If this is not clearly detailed and specified, or properly constructed, problems may arise. As an example, the practice of loading the scaffold from the inside of the building has often resulted in exterior sheathing being left out of the system in various locations. In addition, proper attachment of the backup system at the top and bottom is mandatory.
Recommendations
Support of Veneer. In order to alleviate the many problems associated with the use of shelf or relief angles at each floor, it is suggested that the brick veneer may be designed to support its own dead weight on the foundation, unless heights [in excess of 100 ft (30 m)] or number and location of openings in the veneer make it mandatory that the walls be vertically supported by the structural frame. This suggestion may be in conflict
Typical Ties
FIG. 8
with local building codes, so it is advisable to check before designing in this manner.
By following this suggestion, the veneer can be designed as a continuous, vertical member spanning over several supports, thus reducing the deflection and the tensile stresses induced by the flexural moments, as shown in Fig. 6.
Allowable Deflection. It should be noted that this wall system has not been tested as a complete system. Because of this lack of established data on the question of relative rigidities of brick veneer facing and metal stud backup, the recommended limitations on deflection criteria are based on analysis and engineering judgment. The Brick Institute of America suggests a maximum allowable deflection of the backup system, under full lateral load, of L/600 to L/720.
The Metal Lath/Steel Framing Association, which represents the manufacturers of metal studs, does not agree with this recommendation. Research is planned to study this question.
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