Aisi E 1, Volume Ii, Part Vii Anchor Bolt Chairsl: Examples and Case Studies of Anchor Bolt Chairs for Different Types of Shells

Aisi E 1, Volume Ii, Part Vii Anchor Bolt Chairs

An anchor bolt chair is a device that supports and distributes the load of an anchor bolt to a shell or a column. Anchor bolt chairs are used when anchor bolts are required at supports for a shell, such as in tanks, silos, or other structures. They are made of carbon steel or alloy steel and consist of a top plate, vertical plates, and a bottom or base plate. The top plate has holes for the anchor bolts and may project radially beyond the vertical plates. The vertical plates are welded to the top plate and the shell or the column. The bottom or base plate is optional and may be used to increase the stability of the chair.

The design of anchor bolt chairs involves several considerations, such as the size and shape of the top plate, the height and thickness of the vertical plates, the location and diameter of the anchor bolts, the load and eccentricity of the anchor bolts, the stress in the top plate and the shell or the column, and the weld size and strength between the vertical plates and the shell or the column. The American Iron and Steel Institute (AISI) provides some guidelines and formulas for designing anchor bolt chairs in its publication "Aisi E 1, Volume Ii, Part Vii Anchor Bolt Chairs".

Aisi E 1, Volume Ii, Part Vii Anchor Bolt Chairsl

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The following are some of the main points from the AISI publication:

The critical stress in the top plate occurs between the hole and the free edge of the plate. The top plate width and length should be determined by using equations (7-1) or (7-2), which depend on the distance between vertical plates (g), the anchor bolt diameter (d), and the anchor bolt eccentricity (e).

The chair height should be high enough to distribute the anchor bolt load to the shell or the column without overstressing it. The maximum stress in the vertical direction is a combination of bending and direct stress. The chair height should be determined by using equation (7-3), which depends on the design load (P), the anchor bolt eccentricity (e), the vertical plate thickness (a), the vertical plate width (b), and a reduction factor (f).

The weld size between the vertical plates and the shell or the column should be sufficient to resist shear and bending stresses. The weld size should be determined by using equations (7-4) and (7-5), which depend on the total load on weld (W), the horizontal load on weld (WH), the vertical load on weld (WV), and a safety factor (S).

For more details and examples, please refer to the original publication.

References:

Part VII Anchor Bolt Chairs W - Apiexam.

Aisi E 1, Volume Ii, Part Vii Anchor Bolt Chairs.

AISI - Anchor Chair Design - [PDF Document].

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