Distribute Overturning Moment to bolts?
Distribute Overturning Moment to bolts?
(OP)
Are there any rules of thumb for distributing overturning moment to a silo base-ring? When the moment is applied obviously half of the ring will be in compression and the anchor bolts in the other half of the ring will experience varying amounts of tension. The bolts furthest from the center of the tank will experience the greatest tension which will be the uplift case to design for. The question is, does any resource provide a formula or rule of thumb for distributing the tension force among the anchor bolts and determining how much tension the furthest bolt(s) experience (for a given moment and ring diameter)?






RE: Distribute Overturning Moment to bolts?
http://www.towernx.com/downloads/Technical_Manual_...
It's a bit long, but it goes over a number of different scenarios.
RE: Distribute Overturning Moment to bolts?
RE: Distribute Overturning Moment to bolts?
RE: Distribute Overturning Moment to bolts?
JStephen: You're right this is like a beam.
Upon re-inspection my situation is not a continuously ring but instead channels (with their webs flat against the foundation) at each anchor point. I'm assuming only the anchor bolts resist tension, not the channels. There for I'm using the (M*y)/I +/- P/N equation instead of Mc/I +/- P/A.
If given "envelop" or "not-to-exceed" loads from the tank manufacturer, what is an appropriate factor of safety for tension in these bolts?
RE: Distribute Overturning Moment to bolts?
This is simple, but "wrong" as the compression is better modelled as a triangular distribution (from the tension bolts to a peak at the free edge).
And then of course there's preload to consider, clamping the joint.
another day in paradise, or is paradise one day closer ?
RE: Distribute Overturning Moment to bolts?
If you need to calculate factored loads, ask for the wind/seismic/dead/pressure loads per bolt to be broken out. Or if they're using the beam-distribution assumption, just get the total moments and total dead/pressure loads and work off that.
The design standards for liquid tanks require that the embedment strength be adequate for the full yield strength of the bolt, and that can control some of the design if applicable.
For the liquid tank codes, seismic and wind are normally service-level loads, not strength-level loads, so check on that as well.
RE: Distribute Overturning Moment to bolts?
Thank you JStephen: The maximum moment for wind and seismic is given, for conservativeness I will assume they are service if I don't get feedback from the manufacturer.
On a per bolt basis; which is a less costly, moving from F1554 36ksi to 55ksi? or moving from 0.75"Ø to a 1"Ø 36ksi bolt?
RE: Distribute Overturning Moment to bolts?
and you civil guys use that concrete stuff, good in compression ... so you tend to make a section of the compression side and the tension fasteners.
The triangular distribution is an attempt to represent the "plane faces remain plane" assumption, that on the compression side the reaction is proportional to the distance from the pivot line.
another day in paradise, or is paradise one day closer ?