Frictional Resistance and Transmitting of Shear Force into Anchors

6 FRICTIONAL RESISTANCE AND TRANSMITTING OF SHEAR FORCE INTO ANCHORS 

Anchors need not be designed for shear if it can be shown that the factored shear loads are transmitted through frictional resistance developed between the bottom of the base plate and grout at the top of the concrete foundation. If there is moment on a base plate, the moment may produce a downward load that will develop frictional resistance even if the eolumn or vertical vessel is in uplift, and this downward load ean be eonsideied in calculating frictional resistance. Care should be taken to assure that the downward load that produces frictional resistance occurs simultaneously with the shear load. 

If the assumption of paragraph 2 does not yield sufficient shear capacity to transfer the shear from the base plate through bearing on the anchors, then the anchor diameters, material, or edge distances could be increased to achieve sufficient shear capacity. If it is not practical or economically feasible to increase anchor diameters, material, or edge distances sufficiently, then the use of a shear lug could be considered. Shear lugs are recommended only where a more cost-effective solution is not possible or practical. 

The frictional resistance can be used in combination with shear lugs to resist the factored shear load, but should not be used in combination with the shear resistance of anchors unless a mechanism exists to keep the base plate from slipping before the anchors can resist the load. One mechanism to prevent base plate slippage is to install plate washers between the base plate and the anchor nut. Plate washers with holes 1/16 in. (1.6 mm) larger than the anchor rods can be field welded to the base plate to assure minimal slip between the 

Note Field welding is something that is typicalfy avoided due to time, cost and problems associated with field welding galvanized steel (that is, prep for welding and increased corrosion potential). 

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