Manual Verification of Rib Moments

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Hello everyone,

I am currently creating a design aid for reinforced concrete beams as the topic of my bachelor's thesis and am trying to better understand how RFEM 6, in the Concrete Design Add-On, handles the rib bars together with a surface, i.e., a slab.

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This is my model with a slab 24 cm high and the beams, which are modeled as ribs with a width of 20 cm and a height of 35 cm. My loads are the self-weight of the concrete, as well as a finishing load of 1.5 kN/m² and a live load of 3.5 kN/m².

Regarding my questions:

  1. I am trying to manually check the moments of the two middle ribs (267.78 kNm, -415.12 kNm, 95.56 kNm), but using the formulas for a three-span beam from Schneider, I don't really get the results of RFEM, especially not the large span moment. How exactly can these RFEM results be verified?
  2. Is there a way to activate that RFEM calculates the deflections in condition 2, or does it only work for condition 1?

Thank you very much in advance!

Best regards,
Moana Herdt

3

Hello moana.herdt,

Welcome to our community. :tada:

Regarding your questions:

  1. The linked technical article below describes the determination of internal forces for the ribs. It may help to first simplify the model and compare only a single beam with the associated area using manual calculations.

https://www.dlubal.com/en/support-and-training/support/knowledge-base/001411

  1. The deformations in state II can be determined in RFEM 6 by two different methods.
    1. Using the Concrete Design add-on – In the course of concrete design, the deformations in state II are calculated for the deformation verification using the effective stiffness method. The procedure and an example model are shown in the following technical article: https://www.dlubal.com/en/support-and-training/support/knowledge-base/001935.
    2. Using Nonlinear Analysis – Alternatively, the deformations in state II can be calculated by means of a physically nonlinear reinforced concrete analysis. The procedure is described in the subsequently linked technical article: https://www.dlubal.com/en/support-and-training/support/knowledge-base/001999.
    3. The following technical article deals with the differences between the two methods mentioned above. (Although the article is formulated for RFEM 5, the comparison of the two approaches is still valid.) https://www.dlubal.com/en/support-and-training/support/knowledge-base/001574

Best regards,

Juliane