Bolt Group Moment of Inertia
Bolt Group Moment of Inertia
(OP)
Can anyone give a basic explanation of how to calculate the Moment of Inertia of a Bolt Group?
I need to determine the size of the rebar in an anchor bolt cage that is to be embedded in concrete.
Thank you.
I need to determine the size of the rebar in an anchor bolt cage that is to be embedded in concrete.
Thank you.






RE: Bolt Group Moment of Inertia
One about the centerline of the bolt pattern
and the other about the furthest bolt in the
bolt pattern.
RE: Bolt Group Moment of Inertia
Thanks.
RE: Bolt Group Moment of Inertia
Iy=x^2
Ip=Ix+Iy
For a bolt group, the Ip is the sum of all individual Ip of each bolt that makes up a group.
Ipgroup=sum(Ix)+sum(Iy)
The force due to moment that acts on each bolt then becomes:
Fx=M*y/Ip
Fy=M*x/Ip
Fres=sqrt(Fx^2+Fy^2)
RE: Bolt Group Moment of Inertia
I believe what you are showing is for a torsional moment (or an eccentric shear) on a bolt group. I believe the OP was asking a true MOI of the bolt group.
Transmissioneng-
Is that true? Which are you looking for? For the MOI used for calc'ing tension in a bolt, find the sum of Ab*(d^2) for the bolt group about the axis in question. d is the distance from the line of bolts to the centroid of the bolt group. This is the parallel axis theorem that you talk about. The actual I of the bolt is ignored. Do not add Ix and Iy.
RE: Bolt Group Moment of Inertia
RE: Bolt Group Moment of Inertia
Thanks.