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Re: modeling composite beams in SAP2000

[Subject Prev][Subject Next][Thread Prev][Thread Next] I think you need to have two models and use the principal of superposition to combine the initial stresses due to fresh concrete on bare steel + dead load and live load effect on composite beam. Since your model changes, keeping track of stress history in SAP 2000 is not possible. Therefore you need to run to independent analysis and combined the results manually.

I hope this helps.

Majid Sarraf
NaBRO


At 01:00 PM 6/14/00 +0000, you wrote:
Dear Majid:
Thank you very much for your attention. I have a new question:
The model we're talking about (two elements connected only by joint constraints between every pair of nodes) is very good for the composite section, but:

How do you compute the final strength on the steel beam as a contribution of the initial stresses (basicly a product of the steel beam, steel deck and concrete slab self weights loads) resisted by the bare beam section and the post-composite stresses (live loads, floor, etc.) resisted by the composite section.

We must first compute initial stresses on the bare beam section. Then we have to analize the composite section, acting only post-composite loads, wich do not include steel beam, stell deck and concrete slab self weights but live loads and any other post-composite applied loads.

How do you account for the contribution in stresses of the different construction stages?

I can only figure to make two models (one for the bare beam section and the other one for the composite section) and then make hand calculations in a spreadsheet. Although, if I have to do this, I think it will allways be less time consuming to use an equivalent section and go ahead.

What do you do?


From: Majid Sarraf <msarraf(--nospam--at)unl.edu>
Reply-To: seaint(--nospam--at)seaint.org
To: seaint(--nospam--at)seaint.org
Subject: Re: modeling composite beams in SAP2000
Date: Tue, 13 Jun 2000 18:17:47 -0700


I have had a good success in using SAP2000 to model composite girders. In
fact I verified the results by checking them against field measurements,
and they are in very good agreement.

The key issue in modeling composite action is to constraint only pair of
nodes with different labels, and not all concrete nodes to those of steel
top flange with one lable. So it would be a bit tedious to define different
constraint for every pair if you have too many nodes along the girder. The
best way then is to go to *.s2k file and use a pre-processor program to
compile constraint section of the input file.

Majid Sarraf

National Bridge Research Organization (NaBRO)
www.Nabro.unl.edu

At 10:14 AM 6/13/00 -0700, you wrote:
Dear Leopoldo,
As far as m experiences, an easy way is just define an
equivalent section and go ahead by that. Although to
model steel and concrete parts together, you can
define two element, but the output generated by SAP
design module won't be accurate enough. Because the
model doesn't have an accurate definition of a
composite beam.
Good luck,
Frank

--- Leopoldo Sanz <leopoldosea(--nospam--at)hotmail.com> wrote:
> Dear friends:
> Is it possible to model composite beams in SAP2000
> without doing hand
> calculations? May I simply specify effective width,
> slab concrete f'c, E,
> etc.? Where?
> Thank you very much
> Yours,
> Leopoldo Sanz
>

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