Autodesk Robot Structural Analysis

[#1]

Hi,

I'm using tapered sections in my project and when i make the member verification i get the following warning:

Does it mean that the deflections of this members is calculated has if i had a constant cross-section with the midsection of my original one? I have made a comparison model with 3 cases:

1st - Structure made with constant section profiles.

2nd - Structure made with tapered section profiles with 5 division per element.

3rd - Structure made with tapered section profiles - Just 1 profile per element.

The results are the same for 2nd and 3rd models but in the first one i get diferent results. (6% more deflection)

In my understanding if the software uses the midsection moment of inercia, the results should be the same in the 1st and 2nd cases, right? 

Thanks in advance!

FR

[#2]

1st - Structure made with constant section profiles.

Such member is a little bit differently treated than tapered. In fact weighted average is considered (lenght of every member is taken into account for average calculations) for such profile so the small difference may appear - 6% - I think reasonable difference.