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BOLTS, WELDS, AND CONNECTED ELEMENTS
ANCHOR RODS OR THREADED RODS
Cast-in-place anchor rods, illustrated in Figure 8-14, are generally made from unheaded rod material or headed bolt material. Drilled-in anchor rods, illustrated in Figure 8-15, are not normally used; their design is governed by manufacturer’s specifications. Refer also to Cannon, Godfrey, and Moreadith (1981). LRFD Specification Section A3.4 permits the use of unheaded rod material from the following ASTM specifications as anchor rods or threaded rods: A36, A193, A354, A449, A572, A588, and A687. Additionally, LRFD Specification Section A3.4 permits the use of headed bolts conforming to the provisions of LRFD Specification Section A3.3 for use as anchor rods. Headed bolts, however, are generally available only in lengths up to about eight inches. Furthermore, designations such as ASTM A325, A490, and A307 apply only to bolts manufactured with a head and it is, therefore, improper to specify unheaded anchor rods or other similar threaded devices as ASTM A325, A490, or A307. The availability and strength of the aforementioned ASTM specifications for unheaded rod material and headed bolt material are summarized in Table 8-26. Suitable nuts may be selected from ASTM A563 or ASTM A194 grade 7. Because base plates typically have holes larger than oversized holes to allow for tolerances on the location of the anchor rod, washers are usually furnished from ASTM A36 steel plate; they may be round, square, or rectangular, are generally about 1⁄2-in. thick, and generally have holes which are 1⁄16-in. larger than the anchor rod diameter. Minimum Edge Distance and Embedment Length
The recommendations of Shipp and Haninger (1983) for minimum anchor-rod (concrete) edge distance and embedment length for tensile forces, adopted from ACI 349, are summarized in Table 8-26. The edge distance requirement is intended to prevent blow-out of the side of the concrete foundation and is based on concrete with fc′ = 3,000 psi. For edge distance requirements for shear, refer to Shipp and Haninger (1983). In addition to providing the recommended minimum embedment length, anchor rods must extend a distance above the foundation that is sufficient to permit full thread engagement of the nut; from RCSC Specification Section 2(b), “…the end of the [anchor rod] will be flush with or outside the face of the nut when properly installed.”
Lh
(a) Hooked
(b) Headed
(c) Threaded with Nut
Fig. 8-14. Typical cast-in-place anchor rods. AMERICAN INSTITUTE OF STEEL CONSTRUCTION