Variable inertia - global cals and checking

[t.sautierr]

I have made this mdoel to test the calculations made with a variable inertia.

the question came to me when I noticed that in the design module, robot says the chekings are made with the average inertia so I start wonder if it is the same for displacements, reactions, moment ... and it seems not.

It also seems that you don't need to divide the bars in order to have more accurate results.

the question is : robot takes into aacount the variable inertia in the calculations but not in the chekings why? because it is made for the calcs then, there somewhere the properties of the bar for x points of calculations in the memory. Why is it not used for the checks?

Link to the test model : http://we.tl/9DnBgC1iVV

TS

[Artur.Kosakowski]

Try to run check of a bar with such section forcing the verification points at 0L ; 0.5L and 1L respectively and check cross sectional properties in these locations.

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[t.sautierr]

I'll do that.

Do you confirm that the properties are taken into account during the calcs and that there is no need to divide the bars in smaller part?

[Artur.Kosakowski]

The check in a given location is done for the cross section from this very location. The averaged value of inertia may be assumed if it is necessary to use such values as e.g. stiffendss of the entire element during the code checking.

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[t.sautierr]

No I meant to calculate displacement, moment etc .....

Because it quite different to calculate the model with all the bars average values or with the right properties along the bars.

By the way how can I set the number of points robot will use during the analysis (not the checkings)

[Artur.Kosakowski]

I have to say that I'm not sure if I understand you correctly. In your first message you wrote

I have made this mdoel to test the calculations made with a variable inertia.

the question came to me when I noticed that in the design module, robot says the chekings are made with the average inertia so I start wonder if it is the same for displacements, reactions, moment ... and it seems not.

It also seems that you don't need to divide the bars in order to have more accurate results.

and then you wrote:

No I meant to calculate displacement, moment etc .....

Because it quite different to calculate the model with all the bars average values or with the right properties along the bars.

Which you answered yourself in the first post ?

By the way how can I set the number of points robot will use during the analysis (not the checkings)

Robot doesn't use the number of point - you do not set the number of points in which you want to see the results - they can be checked in any location along a bar). The solution for linear static is exact. 

For the question below:

the question is : robot takes into aacount the variable inertia in the calculations but not in the chekings why? because it is made for the calcs then, there somewhere the properties of the bar for x points of calculations in the memory. Why is it not used for the checks?

I believe I provided the answer in my previous post.

Am I missing something?

[t.sautierr]

"Which you answered yourself in the first post ?"

I said : 

the question came to me when I noticed that in the design module, robot says the chekings are made with the average inertia so I start wonder if it is the same for displacements, reactions, moment ... and it seems not.

As you tell me that the solution for static linear is exact, I deduce that that for calculating moments; displacement etc .... robot takes into account exactly the inertia of the bars even when vairable and doesn't make an average.

so the question is answered! thanks.

I think this is nt true for modal, spectral seismic, non ilnear etc .... in this kind analysis the precision depends also if you divide or not the bars. 

[Artur.Kosakowski · Accepted solution]

I think this is nt true for modal, spectral seismic, non ilnear etc .... in this kind analysis the precision depends also if you divide or not the bars. 

Correct.

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.