What is the minimum size of the anchor bolt that can be used in seismic category D or less?

• A. 1/4 inch
• B. 3/8 inch
• C. 1/2 inch
• D. 5/8 inch

Answer: (C)

Anchor bolts must be sized to carry the expected seismic forces, and the required minimum diameter increases with seismic risk. For seismic category D or less, the standard minimum is 1/2 inch. This size provides enough withdrawal and shear capacity for typical connections without being unnecessarily large. A smaller bolt, like 1/4 inch or 3/8 inch, wouldn’t meet the required strength for seismic loads in category D or less. A larger bolt, such as 5/8 inch, is specified for higher seismic categories where greater strength is needed.