Steel braced design may use the design methodology shown in AISI S211 or in AISI Committee on Specifications (COS) S100 “North American Specification for the Design of Cold-Formed Steel Structural Members.” AISI S211 Table B1-1 Maximum Axial Nominal Load Limited by Gypsum Sheathing-to-Wall Stud Connection Capacity The Designer should neglect the rotational restraint of the sheathing when determining the wall stud flexural strength and is limited by the AISI S100 Section C5.1 interaction equations for designing a wall stud under combined axial and flexural loading. In addition, the Designer is required to design the wall studs without the sheathing for the load combination 1.2D + (0.5L or 0.2S) + 0.2W as a consideration for construction loads of removed or ineffective sheathing. When the sheathing on either side is not identical, the Designer must assume the weaker of the two sheathings is attached to each side. Sheathing braced design requires that identical sheathing is used on each side of the wall stud, except the new AISI S240 standard Section B1.2.2.3 clarifies that for curtain wall studs it is permissible to have sheathing on one side and discrete bracing for the other flange not spaced further than 8 feet on center. The wall stud is connected to the top and bottom tracks or supporting members to provide lateral and torsional support and the construction drawings should note that the sheathing is a structural element. CFS Curtain Wall Stud Steel Clip and Bridging Bracing
#Cold formed steel framing joist details how to
AISI S211 Section B1 and the Commentary discuss the design method and assumptions and demonstrate how to determine the sheathing bracing strength. AISI S211 prescribes a maximum nominal stud axial load for gypsum board sheathing with fasteners spaced no more than 12 inches on center. Due to this limitation, the Designer has to use a steel braced design for most practical situations. This design method is based on an assumption that the sheathing connections to the stud are the bracing points and so it’s limited by the strength of the sheathing fastener to stud connection. Sheathing braced design has limitations, but it is a cost effective method of bracing studs since sheathing is typically attached to wall studs. One is sheathing braced design and the other is steel braced design. There are two methods for bracing CFS studs as prescribed by the American Iron and Steel Institute (AISI) Committee on Framing Standards (COFS) S211 “North American Standard for Cold-Formed Steel Framing – Wall Stud Design” Section B1. Bracing is required to resist buckling due to axial or out-of-plane lateral loads or a combination of the two. Without proper consideration of bracing, excessive buckling or even failure could occur. While consideration of bracing is important for any structural element, this is especially true for thin, singly symmetric cold-formed steel (CFS) framing members such as wall studs.
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