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Design of Base Plates (was RE: base plate software)

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absolutely they are warranted. if a condition such as what you are briefly
describing exists and the structure is properly laid out than it means you
are either working on an extremely architectural high-rise building or a
heavy industrial structure. Either one of them warrant extreme measures.

I like to emphasize that I am not advocating not using thicker plates, I am
merely saying that every structural element has its own place and
application. And that if they are to be used in design they should be
carefully specified. I am specially concerned of those designs where the
bottom of column is under biaxial bending. Surely not both moments can be
critical at the same time, though I know we can deliberately design
something that is loaded in such complicated manner!. On the other hand the
simplest thing to do is to relieve the bottom of the column from carrying
moment in its weak axis, no?

Ghassem.

-----Original Message-----
From: Keith Fix [mailto:kefix(--nospam--at)yahoo.com]
Sent: Tuesday, June 13, 2000 11:01 AM
To: seaint(--nospam--at)seaint.org
Subject: RE: base plate software


I have base plates on a project with t > 2", due to bending moments.  Plate
thickness is governed mostly by distance of edge of plate to column edge.

Are base plate stiffeners warranted due to assumption of uniform stress
under
base plate?

Keith Fix
Cromwell Architects Engineers

--- "Khosrownia, Ghassem SPK" <GKhosrownia(--nospam--at)spk.usace.army.mil> wrote:
> Yes: be aware of the software that advertise finite element analysis of
> steel base plates complete with nice looking color coded stress
> distribution. All of this is fine, but to me it indicates that the
> developers may have no idea what an engineer needs to perform practical
> work. And that might result in other shortfalls down the road. We should
> never need to analyze the heck out of a base plate. We should never
transfer
> bending moment from a steel column to foundation via flexible steel base
> plate. If moment transfer is required the best way is to transfer directly
> through the flanges of the column via anchor bolts. Base plates should be
> designed for vertical loads only. We have enough to worry about without
> having to consider the flexibility of a base plate in the load path. At
> least this is what my practice is. Design of base plates starts from using
a
> 3/4" steel plate (for various reasons not necessarily related to load),
then
> should be checked for stresses using the two or three simple AISC
published
> formulas. Stay away from using 2" plates (or thicker) if you have any
choice
> at all. Use thick plates with caution. They require special milling and
> welding procedures. Try to stay within 1" to 1 1/2" plates if at all
> possible.
> 
> Ghassem.
> 


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