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Re: Fixed or pinned support

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Alex:

Without more detailed information, I would assume that it is pinned. To
have column fixity, you need to restrict:

Footing rotation
Anchor Bolt elongation
Base Plate flexibility

There is a way to theoretically calculate the amount of fixity that you
have. I could help you calculate it, if you contact me off line. The
data that I would need is :

Footing        width, length and modulus of subgrade

Column          Depth, Moment of Inertia, Height, load eccentricity

Base Plate     width, length, thickness

Anchor Bolts  quantity, diameter, embedment, projection, edge distance

Of course, another question comes to mind........was it actually built
that way?

>From a practical standpoint, the way I would try to achieve column
fixity is to:

    1) use a foundation wall or grade beam to increase rotational
resistance by tieing footings together. A large rectangular footing
(oriented in the strong direction of the frame)  may
also be a good option, if there are no other footings nearby to tie to.
    2) use large anchor bolts at large moment arms and
    3) use a thick base plate or one that is stiffened.

I hope this helps.

Jim Kestner, P.E.
Green Bay, Wi.







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