Robot Results errors?- Need help Please

[khanz4]

Dear Team,

Currently, I am working on building project and have modelled the structure in robot. There isn’t any problem with the model in terms of meshing or results. Having said that, results from model don’t match up with hands calculations and mirror columns-(Please the attach file  (SC-1) and you will notice that loads are identical on the structure and column are on exact similar position on plan; however, the (Fx) force in the column varies-?). For instance, the columns highlighted in the attach file-it clearly shows that (Fx) forces varies under live loading. As you go down to storey No. 1/2 where there is a transfer beam (SC-2) - you will notice that column in opposite direction has a varied (Fx) force than in column on Transfer beam. I don’t seem to understand how the load distribution is calculated in the model and what material properties might have influence the results. Any advice and solution to this problem would be greatly appreciated. If you need further information please let me know.

Thanks

Zeshan

 http://www.filemail.com/d/agdpeiluxgfbgui?&showconfirmation=true

Click the link below to download the model

[Pawel.Pulak]

It may be related to the effects observed when applying self-weight simultaneously to all stories in high-rise building.

See this forum post related to Load sequencing/construction stages and using phase structures in Robot:

http://forums.autodesk.com/t5/Robot-Structural-Analysis/Load-sequencing-construction-stages/m-p/4570...

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Regards,

[khanz4]

Hi,

Thank you for your reply. After looking the link you sent earlier, I am not sure if I can utilise this technique and to make things simple I modelled another simple (Trial) structure with same height and I don’t get any problem in term of results. The results are identical and load distribution is ok too. If applying SW load simultaneously was such the case then I would have achieved the similar results for trial model. Please provide more details as I am finding it difficult to figure out how to solve this issue. I am not certain if it is the modelling problem or any other issues. My concern is that at top storey in figure (SC-1), the axial (Fx) force should be similar. Is it something to do with release not applied to column correctly? Any thoughts would be greatly appreciated. And thank you for looking at this problem.

Thanks

Zeshan

[khanz4]

Just to add anothe point- do you think cladding panel incoporated in the model might have influenced the results. cladding panel adjacent to tranfer beam side- you will notice that cladding distribution of panel no correct. i will amend the model by removing caldding panel and check if i get right results.

[Pawel.Pulak]

I don't think that it is related to cladding because these unexpected values of forces in columns were observed in live load case 4 where no loads  on claddings were defined.

I am afraid that it is related to 3D deformation effects caused by supporting one chain of columns not directly on some support but on some transfer beam - see the screen capture below:

It is somehow confirmed by the fact that when I have defined some additional test load case where I have applied the same loads as in load case 4 but only to slabs of the top story then I have obtained relatively close compression forces in the top columns mentioned by you. While in load case 4 they were 20.30 and 0.59 kN in the additional test case they were 26.58 and 27.22 kN respectively.

As concerns other remarks related to this model I recommmend correcting it to reduce the number of warnings reported during verification and analysis - avoiding incoherent mesh and kinematic constraints, load distribution errors, eliminating type 2 instabilities during analysis.

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Best regards,

[khanz4]

Dear Pawel,

Thank you for your reply. you are right about cladding- only wind load is applied on cladding. as for the othe comments about meshing and error i will look into it and try reduce the number of errors in the model. Thank you very much for wise advice.

Good wishes

Zeshan