Ram Concept - Slab Reinforcing

[kauaiboi04]

I am working on a project that includes a 5 story steel (moment frame) building over 2 levels of concrete parking. I have modeled the steel building in Ram and the concrete portion in Ram and then transferred to Concept. I designed my intermediate slab which is a typical 2 way concrete slab. I am now working on the 1st level which has concrete beams to resist the moments at the bases of the steel moment frames and a standard 2 way slab everywhere else. I was getting unusually high top and bottom steel requirements when looking at this level and started to troubleshoot. I found that when I ran the D+L combos the results were very typical, but the combos which include E seem to add 100 +/- top and bottom bars to each design strip. Has anyone ran into this problem? Any help would be appreciated. Thank you

Billy

 

[KootK]

What is bracing the concrete levels laterally? If there are no shear walls and the columns are doing the lateral bracing, the results probably make sense.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[Lion06]

The lateral steel frames are also throwing concentrated lateral forces into your concrete floor. Ram tracks the transfer forces from the Frame module into Concept. Did you look at ALL of the loading, including transfer forces. If you have fixed base moment columns on a concrete beam that will significantly change the steel requirements between gravity and lateral loading.

 

[JAE]

You might try posting this in a more appropriate forum - maybe get better results:

Bentley: RAM

http://www.eng-tips.com/threadminder.cfm?pid=1342

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faq731-376

 

[asixth]

I think it would be the cross-section that concept uses. You probably need to change the section trimming to "T or L beam". If you have it set to "slab rectangle" or something similar it would only be using the slab part of your cross-section and trying the design that section for the design actions.

You can get a visual on your cross-section by going into the perspective view in the design strips. You want it so that the beam web is heavily highlighted and the slab panel is outlined.

 

[kauaiboi04]

Wow... This was my first time posting and I am thrilled to see so many responses so quickly. Thank you all for your help.

To answer a few of the questions:
There are "shear walls" around the perimeter of the structure. I have also tried playing with the bases of the columns being labeled as pinned and fixed and got similar results in both situations.
Because of "nodes" not aligning between Ram and Concept the moments and axial forces from the steel structure were entered directly into concept. In all situations the columns (gravity and frame) beams and concrete columns. No shear forces were entered into concept because we have gotten weird answers in doing this before.
We are using the slab rectangle section because beams are only provided under columns and the majority of the deck is typical 2-way slab.

In looking at the loading diagram it seems as if a lot of the steel which is being added is because of axial forces in the deck, but cant figure out where the axial forces are coming from. We have an agreement with Bentley and will likely package up the model to send to them on Monday morning, but if anyone else has any other ideas that are greatly appreciated. Thanks