The primary function of an anchor bolt chair is to transfer the massive uplift and overturning forces generated by wind or seismic loads from the anchor bolts into the vessel shell.
The "better" aspect of the AISI approach lies in its detailed analysis of load paths. The standard accounts for the interaction between the chair components and the cylindrical shell. It recognizes that the stiffness of the chair plates distributes the localized point load of the bolt over a larger area of the shell, reducing the risk of localized buckling or yielding. By following Part VII, engineers can verify that the stress induced in the shell remains within allowable limits, preventing catastrophic failure at the skirt-to-shell junction.
An anchor bolt chair is a fabricated steel bracket, typically made from cold-formed C-sections or angles, that:
The “chair” elevates the CFS member slightly above the concrete to prevent moisture wicking and accommodate bolt tolerances. aisi e 1 volume ii part vii anchor bolt chairs better
In the realm of industrial construction and heavy engineering, the interface between a steel superstructure and its concrete foundation is arguably the most critical stress point in the entire system. While the steel frame is designed to flex and sway under wind or seismic loads, the foundation is rigid and unforgiving. Bridging this gap requires precision engineering, specifically regarding the anchorage system.
For decades, the AISE (Association of Iron and Steel Engineers) Standard No. 1 has served as the "steel bible" for the design and construction of mill buildings and heavy industrial structures. Within this comprehensive document, Volume II, Part VII, addresses a specific, often overlooked, yet vital component: Anchor Bolt Chairs.
This long-form analysis explores why the methodologies outlined in AISE 1 Volume II Part VII for anchor bolt chairs represent a "better" engineering approach—prioritizing structural integrity, load transfer, and longevity over cheaper, generic alternatives. The primary function of an anchor bolt chair
Volume II Part VII requires the use of cold-formed steel with specific ductility (minimum elongation of 10-12% in 2 inches). This is critical because brittle fracture of an anchor bolt chair during a seismic event can lead to catastrophic failure. The standard also demands material certification (mill test reports).
Generic chairs often use mystery metal—recycled bar stock with unknown yield strength. AISI-compliant chairs use known, traceable steel. That traceability is a legal and safety game-changer.
Common issue: The anchor bolt is centered in the CFS column’s web hole, but the line of action for tension is offset from the column’s centroid → prying action. The “chair” elevates the CFS member slightly above
Better approach:
While a pre-fabricated steel chair has a higher unit cost than a loose bolt, the "better" metric here is Total Installed Cost.
A standard chair detailed in Part VII typically consists of: