The “chair” elevates the CFS member slightly above the concrete to prevent moisture wicking and accommodate bolt tolerances.
Result: During a moderate wind uplift event (85 mph), the mezzanine column experienced only 60% of its design load. Yet the anchor bolt chair legs buckled, the weld fractured, and the bolt pulled out of the concrete. The non-compliant chairs had no leg bearing check (Point 1 above) and used mild steel fillet welds too small for the applied load.
: Required to be thick enough to prevent buckling, typically at least Welding : Standardizes minimum aisi e 1 volume ii part vii anchor bolt chairs better
Why AISI E-1 Volume II Part VII Anchor Bolt Chairs are Superior
The critical stress in the top plate occurs between the bolt hole and the free edge. It is modeled as a beam with partially fixed ends. Formula snippet: is the design load and is the plate thickness. Chair Height ( The “chair” elevates the CFS member slightly above
The horizontal plate that sits on top of the chair. It features a hole for the anchor bolt and directly takes the compressive load from the washer and nut.
Traditional, non-standardized design methods frequently overcompensate for uncertainty by mandating excessively thick top plates and massive gussets. AISI’s formulas optimize component geometry based on actual stress fields. By applying AISI Part VII, fabricators can safely utilize thinner plates and smaller weld sizes. Across a large-diameter storage tank requiring dozens of anchor chairs, this optimization translates directly into significant material cost savings and reduced structural weight. 4. Simplified Fabrication and Welding Guidelines The non-compliant chairs had no leg bearing check
In AISI E-1, Volume II, Part VII, one of the most interesting and critical design features for anchor bolt chairs is the use of as an alternative to individual chairs for high-load applications.
The difficulty in designing this connection lies in the inherent eccentricity. Because the anchor bolt is not in line with the tank shell, it creates a bending moment that the anchor chair must withstand without overstressing the shell wall. The primary purpose of the chair is to minimize this secondary bending.