MATERIALS AND SYSTEMS

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PART 2 MATERIALS AND SYSTEMS Steel tube Leveling bolt Leveling nut welded to tube Bearing plate Spandrel beam (a) Detail section showing bearing support of panel (c) Steel tube embedment viewed from the top Leveling nut welded to the bottom of tube (b) Steel tube embedment viewed from the bottom FIGURE 26.43 Leveling nut in a steel tube used for bearing support. (Photo by MM at a precast plant.) BEARING SUPPORTS A commonly used bearing support for the floor-to-floor panels is provided through a section of steel tube, a part of which is embedded in the panel and a part of which projects out of the panel. The projecting part rests on the (steel angle) bearing plate embedded at the edge of the spandrel beam. Dimensional irregularities, both in the panel and in the structure, require the use of leveling shims (or bolts) under bearing supports during erection. After the panels have been leveled, the bearing supports are welded to the bearing plate. The bearing support system is designed to allow the panel to move within its own plane so that the panel is not subjected to stresses induced by temperature, shrinkage, and creep effects. In place of leveling shims in a bearing support, a leveling bolt is often used, Figure 26.43. The choice between the Bearing support using W-section shims and the bolt is generally left to the preference of the precast manufacturer and the erector. Alternatives to the use of steel tube for bearing supports are steel angles or a wide-flange (I-) section, Figure 26.44. Shims under support Spandrel beam Tie back connection FIGURE 26.44 Wide-flange section used as bearing support in a PC panel. (Photo by MM.) TIEBACKS A lateral load connection (tieback) is designed to resist horizontal forces on the panel from wind and/or earthquake and due to the eccentricity of panel bearing. Therefore, it must be able to resist tension and compression perpendicular to the plane of the panel. A tieback is designed to allow movement within the plane of the panel. The connection must, however, permit 734
CHAPTER 26 EXTERIOR WALL CLADDING Steel tube embedded into panel for bearing support Leveling shims Coiled ferrule Steel angle bearing plate embedded in beam Coiled ferrule embedded in beam Spandrel beam Threaded rod and nut Anchor embedded in panel Clip angle with slotted holes FIGURE 26.45 A typical tieback connection that allows three-way field adjustment during panel erection in addition to in-service vertical deflection of spandrel beam and thermal expansion/contraction of panel. adjustment in all three principal directions during erection. A typical tieback is shown in Figure 26.45 (see also Figure 26.44). SUPPORT SYSTEMS FOR SPANDREL PANELS AND INFILL PANELS Support systems for a curtain wall consisting of spandrel and infill panels are shown in Figure 26.46; see also Figure 26.41(c). PANELS AND STEEL FRAME STRUCTURE PC wall panels, which create eccentric loading on the spandrel beams, create torsion in the beams. Due to the lower torsional resistance of wide-flange steel beams, PC panels used with a steel frame structure are generally designed to span from column to column and made to bear directly on them. Tiebacks, however, are connected to the spandrel beams. (Note that the rotation of the spandrel beam caused by the eccentricity of panel bearing is partially balanced by reverse rotation caused by the the floor’s gravity load on the spandrel beam.) CLEARANCE OF PANELS FROM THE STRUCTURAL FRAME The Precast/Prestressed Concrete Institute (PCI) recommends a minimum horizontal clearance of 2 in. of precast panels from the building’s structural frame. 26.8 BRICK AND STONE-FACED PC CURTAIN WALL PC curtain wall panels may be faced with thin (clay) bricks at the time of casting the panels. Generally, 4 - to 1-in-thick bricks are used. They are available in various shapes, Fig- 3 ure 26.47. The bricks are placed in the desired pattern in the form, and the concrete is 735
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Page 12 and 13: (a) Mortar capturing device, as ins
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Page 18 and 19: Anchor connects veneer to CMU back-
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Page 32 and 33: FIGURE 26.40 (a) Lightly abrasive b
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Page 42 and 43: Flex anchor Bonding pad, see Figure
Page 44 and 45: FIGURE 26.58 (a) Spraying GFRC mix
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Page 48 and 49: Panel with brick spandrel and soffi
Page 50: REVIEW QUESTIONS 1. Using sketches

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