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# RE: Bolt force in round column

• To: seaint(--nospam--at)seaint.org
• Subject: RE: Bolt force in round column
• From: TJ Fu <tzujfu(--nospam--at)yahoo.com>
• Date: Thu, 12 Jan 2006 06:22:59 -0800 (PST)

Here is another simple equation for that situation: It is from ?Ateel Plate Engineering Data ? Vol. 1, Steel Tank for Liguid Storage ?82? by AISI.

Design tension load per bolt = 4M/ND ? W/N

Where: M = overturning moment (K-Ft)
N = number of anchor bolts
W = total weight (Kips)
D = diameter of anchor bolt circle (Ft)

T.J. Fu
Louisville, KY

"M. David Finley, P.E., P.A." <davidfinley(--nospam--at)bizsea.rr.com> wrote:
Rich,

T = P/A + MC/I.  You can use that to find the forces in every bolt.

If you are looking for the maximum tension or compression, then it simplifies to

Bolt_Group_Inertia = (Number of Bolts /  8) x (Bolt_Circle_Diameter)^2

Section_Modulus = (Bolt_Group_Inertia) / (Bolt_Circle_Diameter / 2)

Bolt_Force = (Moment / Section_Modulus) + (Axial Load / Number of Bolts)      Use correct signs for loads.

I forget the minimum number of bolts for which this is applicable ( 4? ), but from your description, it should be applicable.

David Finley
M. David Finley, P.E., P.A.
2086 SW Main Boulevard - Suite 111
Lake City, FL  32025
386-752-6400
-----Original Message-----
From: Rich Lewis [mailto:seaint03(--nospam--at)lewisengineering.com]
Sent: Tuesday, January 10, 2006 5:53 PM
To: seaint(--nospam--at)seaint.org
Subject: Bolt force in round column

I have a large diameter round column with bolts at about 6 inches on center around the perimeter of the base.  I know the axial load and the bending moment.  The bending moment is large.  The virtual eccentricity is larger than the column diameter so I know I have tension in some of the bolts.  Can someone direct me to a reference, or give me a formula, to calculate the maximum tension in the individual bolts?

Thanks.

Rich

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