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# Anchor Bolt Design for Vessel/Stack

• To: seaint-seaosc(--nospam--at)mail-list.com
• Subject: Anchor Bolt Design for Vessel/Stack
• From: Bill Polhemus <bill(--nospam--at)polhemus.cc>
• Date: Tue, 19 Mar 2013 15:08:59 -0500
• List-subscribe: <mailto:SEAINT-SEAOSC-on@mail-list.com>

```Been awhile since I looked at this topic, and especially not in light of
ACI 318 App. D.

Observations:

1. Pretensioning bolts is a good idea. The benefits include lessening the
possibility of bolt loosening and fatigue, and creating a sort of composite
behavior between the concrete foundation and the anchor bolts. This  is
commonly done for anchoring tall slender structures such as highway light
standards.

2. If pretension is sufficiently applied, the base ring will be in
continual compression against the concrete (or grout).

3. Pretension to 70% of Fu appears ideal for this purpose.

Questions raised:

- How does ACI 318-11 App. D apply? I can't seem to find anything there
regarding pretension of anchors. I assume the following:

- It seems like only the "net tension" from lateral loads would pertain as
far as concrete breakout is concerned, since the pretension is opposed by
the pressure on the base ring.

- Bear in mind it's a base RING. The concrete breakout "effective area" is
modeled with anchor boys in nice rows and columns. My thought is to look at
the circular arc of Anchors in net tension, and bound it by a parallel arc
inside and parallel arc outside the anchor arc, at the appropriate
distance (1.5*hef max.) The "sides" would be max. 1.5*hef from the "last"
anchor. The resultant tension c.g. and the geometric c.g. are calculated
from the anchor locations on the arc, and their difference is the value for
e-sub-Nc.

- Pullout would however be affected by the total tension (pretension +

- Anchor steel strength would also be calculated using total force
(pretension + tension from lateral loads).

I'd love some comments on my thinking.

Thanks.

William L. Polhemus, Jr. P.E.

5

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