Typically, a shear lug(s) is used to transfer large shear forces between a column base and the foundation (See Figure). Anchor rods are generally used to position, level and secure the column base plate. They may be used to transfer smaller shear. Use of standard hole size for bolts, or 1/16” hole clearance, is not practical as larger holes are necessary to accommodate anchor rod installation tolerances. In that case, appropriately designed washers with standard holes are field-welded to the base plate in the erected position to transfer the shear forces. It has been reported in research studies that these anchor rods are subjected to bending as well as shear, and any tension where present.
For additional information on shear transfer mechanisms at the base of a column, see Clause 25.3.3 of CSA S16-14. Clause 25 of CSA S16 covers design requirements for column bases in situations where anchor rods transfer end moments, uplift and horizontal forces due to lateral loads, etc. Furthermore, AISC Design Guide No. 1, Base Plate and Anchor Rod Design, offers supplementary background information on the subject.
