Load to mass conversion and reactions

[Anonymous]

Hello everyone,

I made a simple model of multistorey building. In load to mass conversion I checked 100% of Dead load and 30% of Live load to be converted to mass that will be oscillating in horizontal directions for modal and afterward for seismic cases.

However, i cant get matching the values of total mass from dynamic analysis results and those from vertical reactions of dead and live loads. I tried a few variations of input parameters that i saw in similar topics with load to mass conversion issues (like not to check dead load to be converted assuming that would be converted by default).

Anyway, here are some screenshots and thank you for help. 

[Anonymous]

Here's the model as well

[adrian_ricinschi · Accepted solution]

Hello,

I think that you converted the self weight mass twice.

If you check Disregard density option in the modal analysis or take out the self weight case from load mass conversion it should be fine.

[Anonymous]

Thank you for fast reply. It seems that Robot converting self weight by default and additional dead loads do not. So, we either have to make two separated cases for DL (one for self weight and one for additional DL) or check this 'disregard density' option. In second case, the question is - does this 'disregard density' option have any other consequences except excluding self weight from dynamic analysis ?

[Artur.Kosakowski]

Hi @Anonymous

It will have the effect only on these load cases which are 'dependent' on the modal one it is set for. In other words self-weight load case if defined in the model will be used for the static analysis.

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