Anchor bolts are provided to stabilize the column during erection and to prevent
uplift for cases involving large moments. Anchor bolts can be cast-in-place
bolts or drilled-in bolts. The latter are placed after the concrete is set and
are not used often. Their design is governed by the manufacturer’s
specifications before the concrete is set. Anchor rods and threaded rods shall
conform to one of the following ASTM specifications: A36=A36M, A193=A193M, A354,
A572=A572M, A588=A588M, or F1554. Of the three types of cast-in-place anchors
shown in the figure, the hooked bars are recommended for use only in axially
loaded base plates. They are not normally relied upon to carry significant
tensile force.

Bolts and threaded rods with nuts can be used for both axially loaded base

plates or base plates with moments. Threaded rods with nuts are used when the
length and size required for the specific design exceed those of standard size
bolts.

Column base plate subjected to shear.

Base plate anchors.

Cone pull-out failure.Failure of bolts or threaded rods with nuts occurs when
the tensile capacities of the bolts are reached. Failure is also considered to
occur when a cone of concrete is pulled out from the pedestal. This cone
pull-out type of failure is depicted schematically as shown above. The failure
cone is assumed to radiate out from the bolt head or nut at an angle of 45 with
tensile failure occurring along the surface of the cone at an average stress of
4 SQRT (f’c) where f’c is the compressive strength of concrete in psi. The load
that will cause this cone pull-out failure is given by the product of this
average stress and the projected area of the cone Ap (Marsh and Burdette
1985a,b). The design of anchor bolts is thus governed by the limit states of
tensile fracture of the anchors and cone pull-out.