Hello 
I work on a model with concrete slab with ribs (members with type rib and eccentricity).
In the Concrete Design extension, I encountered a situation that raises my doubts.
I compared uz for Surface and Member through "Design Checks > On Members / On Surfaces > Serviceability Limit State > Serviceability > SE0400 | uz"
I know results depend on Displacement reference parameter but there I have Undeformed system for both (and as you can see results are same in "support point").
Shouldn't the displacement values at the same point coincide for member and surface in general? 
Hi r.sajdak,
thanks for your message!
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Best regards
Hedi Boukraa
Thank you for message.
I attach my model.
MODEL_3D_6.12.rf6 (1.4 MB)
Thank you for sending the model.
I suggest working with member sets and also defining design support in your rib. With both functionality I obtain the same displacement in the surface and in the rib:
Here you can finde more to the design supports and member sets:
https://www.dlubal.com/en/support-and-learning/support/knowledge-base/001684
https://www.dlubal.com/en/downloads-and-information/documents/online-manuals/rfem-6/000044
Best regards
Hedi
Thank you for your answer.
Is sugested by you solution with Design Supports and Member Sets necessary for correct calculation of RC slab with ribs ?
I did some benchmark and got similar results for exact slab+rib with and without this aaproach.
On the other hand I checked calcualtions one more time after changing "Life Cycle of Results" parameter and got same deflection for slab and beam (the slab deflection changed).
Also on this topic I found in Extranet > Development > Fixed bud this:
Is this maybe related to my problem? There is no description to this bug in extranet.. How can I find some details on this reported fixed bugs ?
In the subject of Member Sets - i have some doubts about difficulties in assigning longitudinal reinforcement, e.g. if there are different diameters of bars on the segments, especially in the case of any geometry corrections in the model (beam elongation, etc.) so I am reluctant to use it on regular basis.
Hi @r.sajdak,
The bug ID 488497 is about a problem of not calculating the deflection of surfaces/beams that you activate in the addon after you have run the addon calculation. So no, it is not related.
Yes, design supports are very important as they give exact supporting condition of the beam. The approach with design supports and member set is optimal for continuous beam.
When using member set, it possible define segments for the reinforcement and each segment has its own porperties:
More can be found here under ''Span Location'':
Thanks for reply 
I still have some doubts tho 
Concerning my issue with results differing for slab and member: I still have no explanation why I had wrong results in my model and why changing some settings helped.. I emphasize that I did not assign Design Supports and still receive correct results after just recalculating model...
Concerning Design Supports strictly: I did some comparison for same beams with and without and got same deflections.. so I still don't fully understand how this affects deflection calculation...
Concerning working with Member Set: I am aware of assigning longitudinal reinforcement in spans. In some cases I can image and have in my projects it will still work less efficient than working no members (e.g. when I modify geometry by moving nodes in this example of three span beam) Maybe if there were an option to set reinforcement with reference to intermediate points when working with Member Sets (like it is possible in case of Members and nodes type On Member)
Hi @r.sajdak, thanks for the feedback.
I’d like to clarify the effect of design supports just one more time, as my previous explanation may not have been clear enough regarding how they work and how they influence the deflection design check.
When using a member set, it is necessary to define design supports so that the continuous beam is divided into individual segments. This ensures that the reference lengths are determined correctly and that the deflection limits are applied to each segment separately. If no design supports are defined for a member set, the entire length of the member set is taken as the reference length for the deflection check, which leads to unrealistic design check ratio. (This is for single members not relevant).
Furthermore, for information, design supports are required if you want to consider (optional):
•Reduction of the moments or dimensioning for the moments at the face of a monolithic support according to 5.3.2.2
•Reduction of the shear forces in the support face and distance d acc. to 6.2.1(8)
Concerning the issue of obtaining different results: I have tested the model once again and observed that the results change when certain settings are modified, even though these settings are not expected to affect the deflection results. As you suggested, it is possible that the life cycle option is related to this behaviour. We will need to perform further internal tests to better document it and test it.
