SOFiSTiK FEA Extension - Bending Stiffness

[Anonymous]

Hello,

I am working with Revit and the FEA Extension of SOFiSTiK (SSD).

I need to modify the bending stiffness of walls while not modifing the normal stiffness.

I am aware of the commands QEMX and QUEA but when using the commans QEMX for modifing the bending stiffness the normal stiffness is also influenced.

Is there a way to modify the bending stiffness without influencing the normal stiffness of the walls? Maybe it can also be done in Revit itself. Either way would be great.

Thank you for your help.

Best wishes.

[NoelieBoeger]

Hello Julia,

It depends a bit what you would like to acheive by modifying the stiffness of your walls. With SOFiSTiK FEA Extension (now called SOFiSTiK Analysis + Design for Revit 2019 by the way 🙂 ), you have two possibilities to influence the behaviour of your wall in the 3D model.

1) You can modify the SOFiSTiK Property "Stiffness" to "Membrane forces". However you have to be carefull with this settings, because it can easily create instabilities in your model.

2) Most of the times, the user just would like to prevent the wall element to pick up the bending moment coming from the slabs. For this, the Edge Release function of SOFiSTiK Analysis + Design is available. With it you can create hinges on one or several Wall Edges at the same time. 

I hope this helps!

Regards,

Noëlie Magnière

Product Management & Consulting

SOFiSTiK AG

[Anonymous]

Unfortunately both methods do not help in this case. 

So I had to play around with the E-Modulus and find the right factors to get around the problem. But this leads to another problem. I have to model the same structure again but this time with construction stages and a non-linear analysis. 

But SOFiSTiK tells me that it is not possible to use the QUEA and QEMX commands with a nonlinear analysis in CSM. Then I tried to use the command GRP (Group of walls) VAL LIN to switch of the non linear analysis only for the walls. But I think that the CSM is not doing that. It is plotting the same error again. I am using SSD by the way and have to use the teddy files which SSD creates. Do you see a way where I can modify normal stiffness and bending stiffness in CSM while doing a non linear analysis.

Thank you.

[NoelieBoeger]

Hi Julia,

Non-linear analysis + CSM + modified stiffness properties points out a very very complex calculation.

So back the question: what is your goal? what are you actually trying to calculate at the end?

Are you sure your analysis requires all these levels of complexity? E.g. CSM calculations already account for some "non-linearity" in the sense that you can define creep and shrinkage for concrete elements over there. Moreover, usually modifying single material values (e.g. E-Modulus) is not sufficient for a material non-linear analysis as these types of analysis are using the complete strain-stress curves of the material and not the elastic properties...

Regards,

Noëlie Magnière

Product Management & Consulting

SOFiSTiK AG