modal and masses

[Anonymous]

Hi, I have some trouble with the following model.

http://www.mediafire.com/view/emb064kx5mn9uh6/Tesis-Robot-06.rtd

1. I need too many modes to get the mass participation. The model is for 4 storys but it's regular and typical I think it should need 12 max.
2. The mass fot each story is diferente en Stories 2 and 3 bot the distribution and loads are the same.
3. The program takes too much time to analyze the model.

I define the spectral case with local code, and only for  "x" and "y" diretions.

Please, I'm sure that is a trouble with the dynamic analysis but I can't find it.

[Rafal.Gaweda]

Time of calculations (from the caclulation note for 9 modes ; multithreaded solver) : 8sec

Time of calculations (from the caclulation note for 30 modes ; multithreaded solver) : 20sec

You need 9 modes in X direction and 30 modes in Y direction to obtain 90+% of masses in each direction

[Anonymous]

well, in my case take more time, but my cuestion is for the quantity of modes required for "y" direction, It should be no more than 12 modes and If the trouble is no in the modal options I think is in the mass because the model has diferent mass per story in stories that are the same for example stories 2y3. How calculates robot the mass per story? or what coud be the reason of this trouble? thanks

[Rafal.Gaweda]

I would start with checking loads:

Sum of reactions for case 1 for only story 4 = 2012 kN

Sum of reactions for case 1 for only story 3 = 1995,67 kN

Sum of reactions for sw only for only story 4 = 1541 kN

Sum of reactions for sw only for only story 3 = 1530 kN

[Anonymous]

I can't find the error in the model,but maybe it's in geometryor loads aply

[Rafal.Gaweda]

Check beams - without beams the sw is the same on stories 3 and 4

[Anonymous]

story 4 is different to story 3, but story 3 and 2 are the same. Story 1 is different in high. I think ithe sotories 2 and 3 would be checked.. The loads for case 1 applied on beams of story 4 are different.

[Anonymous]

I found two aspects that may can solve the trouble. I want to know if I'm correct.

• I was comparing Robot with ETABS and the modal mass participation are different, other aspects of the seismic analysis are similar, like story forces. The method of calculation of Robot is different than etabs, I think this affect the results of mass participation.
• The calculate of SW for each story is different too, but the total SW are the same. I think there are differences in the consideration of forces of the joints of vertical elements to each story