In heavy industrial construction, steel is expensive and heavy. Over-designing a hundred anchor bolt chairs on a massive tank farm wastes thousands of dollars. The AISI formulas allow you to find the ideal thickness for the chair's top plate, vertical stiffeners, and the vessel shell itself. 3. Prevents Localized Shell Buckling
To help tailor this design information to your specific project, tell me: What is the you are using? What is the thickness of the bottom tank shell course ?
Without a chair assembly, the base plate acts as a simple cantilever. Under high tensile loads (uplift), the plate can deform, causing the nut to lose contact or the grout to crack. An is essentially a structural assembly—often consisting of a horizontal plate (cap plate), vertical stiffeners (webs), and occasionally side plates—that encases the anchor bolt. It moves the reaction point of the bolt closer to the column flange, drastically reducing the bending moment on the base plate. aisi e 1 volume ii part vii anchor bolt chairs better
: Instead of isolated chairs, a continuous ring is welded at the top of the vertical plates. This ring acts as a single structural unit that distributes the anchor bolt load more uniformly around the entire circumference of the shell.
Standard gusset designs often fail to account for the complex local stresses where a bolt attaches to a shell. The AISI method is widely considered better for several technical and practical reasons: In heavy industrial construction, steel is expensive and
An anchor bolt chair is a structural bracket welded to the tank's shell wall. It provides a seat for the anchor bolt, which is embedded in the concrete foundation. The primary challenge lies in the of the load—the anchor bolt is located away from the tank shell, creating a significant bending moment that must be managed by the chair and the shell itself. The AISI standard provides a rigorous, validated method to ensure this connection is robust enough to handle these complex forces.
While it requires a rigorous look at algebra and stress distribution, passing your design through the crucible of AISI standards guarantees two things: structural integrity and material efficiency. For any high-stakes industrial project, that is a combination you cannot afford to ignore. Without a chair assembly, the base plate acts
When an industrial structure experiences high wind, seismic activity, or internal pressure, it generates an uplift force. Anchor bolts secure the base to the concrete foundation. However, because these bolts sit slightly outside the tank shell, they create an eccentric load path.
Ensure that the hole in the top plate of the chair provides adequate clearance for the anchor bolts. Standard practice usually requires the hole to be
A key advantage of this standard is its "capacity design" philosophy. It provides formulas ensuring the anchor bolt yields before the tank shell or the chair itself fails. This ductile behavior is essential for safety during extreme events like earthquakes.
Determining the required throat thickness for the welds connecting the chair components to each other and to the shell. Why the AISI Part VII Approach is Better