Autodesk Robot Structural Analysis

[#1]

Dear friends

Please check my conclusion about using Curtain walls in modal analysis. In first model I used Curtain wall and obtained the following results:

In second model I used equal loads and obtain different results:

Also, I made load to mass conversion with coefficient 1. Certainly, I checked model without any curtain walls and loads except self weight. The results coincided with the first model. My opinion is that we cannot use curtain walls in modal analysis, because they don’t taken into account. Maybe I'M wrong

[#2]

Two points:

1. Robot in order to be able to distribute load (including self weight) from curtain wall needs to detect supporting objects which can be either a panel edge or a beam. In your case the floor panels should be defined as starting/ending at the partition wall locations rather than as a single panels for the entire floor or you should add fake beams under the partition walls.

2. You may consider if the self weight of a partition wall should be modeled as a linear load at the location where the partition wall is 'now' as an owner of the building may change thits location (or add new) at some point in time ('later'). Perhaps you can think about adding some uniform load on the floor panel instead?

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.

[#3]

Ok Artur, I've tried use fake beams (simple steel bar with diameter 1 cm) and modal analysis results not changed.

You absolutely right, I'm always add some uniform load on the floor panel. 

[#4]

Let me give detailed answer.

First model - curtain walls with fake beams:

Second model - equal loads without any partition walls and fake beams:

As you can see, results from static analysis approximately the same. But results from Modal analysis is different. Maybe Robot have hidden ability to convert automatically generated forces in masses? I think the problem in this.

[#5]

It is hard for me to discuss a particular situation without looking at the corresponding model but in general (some restrictions may apply) :

1. Cladding load (load generated by triangular and trapezoidal distribution method) is taken into account for static analysis provided the load carrying object can be detected (see bending moment diagram for case 2 on the attached picture 2)

2. Such load can be converted into mass (and this is standard rather than hidden functionality of Robot) in the way shown on picture 1.

3. Such generated mass is taken into account for modal analysis (in my example this is the only mass as the disregard density option is switched on in the parameters of the modal analysis).

[#6]

Dear Artur

Please, check these two simple models.

[#7]

In Robot 2013 this problem still exist.

[#8 · Accepted solution]

Thank you, friends from Robot team! Service pack 1 for RSA 2013 solved this problem.

[#9]

I am running 2013 with SP1 and I'm getting the problem of curtain wall not being including in modal mass.  I will send file via large file transfer to Artur/Rafal if you are interested. 

Tony

[#10]

Save as under new name as rtd without results, then zip, then send.