Structural Steel

Screw Connections

Screws are frequently used for connections in cold-formed steel because they can be driven with a hand-held drill, usually without punching a hole. The AISI Specification gives provisions for calculating nominal strength for self-tapping screws with 0.08

The distance between the centers of fasteners, and the distance from the center of a fastener to the edge of any part, must not be less than 3d. However, if the connection is subjected to shear force in one direction only, the minimum edge distance in the direction perpendicular to the force is 1.5d. Nominal strength equations are given for shear and for tension using the following notation:
Pns = nominal shear strength per screw
Pnt = nominal tension strength per screw
Pnot = nominal pull-out strength per screw
Pnov = nominal pull-over strength per screw
t1 = thickness of member in contact with the screw head

t2  thickness of member not in contact with the screw head
Fu1  tensile strength of member in contact with the screw head
Fu2  tensile strength of member not in contact with the screw head



For screws that carry tension the diameter of the head of the screw, or of the washer if one is used, must be at least 5⁄16 in (7.94 mm). Washers must be at least 0.05 in (1.27 mm) thick.
Two conditions must be checked: (1) pull-out of the screw and (2) pull-over of the sheet. In


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