Bolting is convenient in cold-formed construction. Bolts, nuts, and washers should generally conform to the requirements of the ASTM specifications listed in Table 8.7. The maximum sizes of bolt holes are given in Table 8.8. Standard holes should be used in bolted connections when possible. If slotted holes are used, the length of the holes should be normal to the direction of the shear load. Washers should be installed atop oversized or slotted holes.
8.18.1 Spacing of Bolts
The distance e, in, measured in the direction of applied force, from the center of a standard hole to the nearest edge of an adjacent hole or to the end of the connected part toward which the force is directed should not be less than emin.
In addition, the minimum distance between centers of bolt holes should provide sufficient clearance for bolt heads, nuts, washers, and wrench but be at least 3 times the nominal diameter d, in. The distance from the center of any standard hole to the end or boundary of the connecting member should be at least 11⁄2d.
Bolted Cold-Formed Members in Tension
Calculation of the allowable tension force on the net section of a bolted connection depends on the thickness t, in, of the thinnest connected part. When t exceeds 3⁄16 in, design of the connection is governed by the AISC ‘‘Specification for Structural Steel Buildings, Allowable Stress Design and Plastic Design,’’ American Institute of Steel Construction, One East Wacker Drive, Chicago, IL 60601. When t does not exceed 3⁄16 in and washers are provided under the bolt head and nut, the following is applicable:
Table 8.9 lists nominal bearing stresses for bolted connections.
Table 8.10 lists nominal shear and tension stresses for various grades of bolts.
The bolt force resulting in shear, tension, or combinations of shear and tension should not exceed the allowable force Pa, kips, calculated from Eq. (8.48).
Example—Tension Joints with Two Bolts
Assume that the bolted tension joints of Fig. 8.11 comprise two sheets of 3⁄16-inthick,
A611, Grade C steel. For this steel, Fsy 33 ksi and Fu 48 ksi. The sheets
in each joint are 4 in wide and are connected by two 5⁄8-in-diameter, A325 bolts,
with washers under both bolt head and nut.