900

from shear planes from shear planes a For the LSD method, see appendix B of the AISI North American Specification [7]. Note: 1 in. = 25.4 mm, 1 ksi = 6.9 MPa = 70.3 kg/cm2.

For bolts subjected to the combination of shear and tension, the reduced nominal tension stress for the ASD and LRFD is given in Table 6.10. For the LSD method, refer to appendix B of the North American Specification.

6.7.3 Screw Connections

Screws can provide a rapid and effective means to fasten sheet metal siding and roofing to framing members and to connect individual siding and roofing panels. Design equations are presently given in the AISI Specification for determining the nominal shear strength and the nominal tensile strength of connected parts and screws. These design requirements should be used for self-tapping screws with diameters greater than or equal to 0.08 in. (2.03 mm) but not exceeding 1 in. (6.35 mm). The screw can be thread-forming or thread-cutting, with or without drilling point. The spacing between the centers of screws should not be less than 3d and the distance from the center of a screw to the edge of any part should not be less than 1.5d, where d is the diameter of screw. In the direction of applied force, the end distance is also limited by the shear strength of the connected part.

According to the AISI North American Specification, the nominal strength per screw is determined from Table 6.11. See Figure 6.37 and Figure 6.38 for t1, t2, Fu1, and Fu2.

For the convenience of designers, the following table gives the correlation between the common number designation and the nominal diameter for screws.

Number designation Nominal diameter, d (in.)a
0 0

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