mass partition in modal analysis < 90%

[Anonymous]

hi everyone,
i model a industrial structure but the modal analysis only reaches a 73% of participation, can you give me any suggested to increase this valua to 90%

link of model: https://drive.google.com/file/d/1Fzakac2NLJbV2_1t5zLFhAb72FcIeqB3/view?usp=sharing  

[Romanich]

Hi @Anonymous ,

Try this settings:

[Anonymous]

Hi @Romanich
if i use a mass matrix lumped then the total mass decreases from 236 (ton) to 178 (ton). If i keep a mass matrix lumped and add nodes in the concrete columns to increase the total mass the percent of participation modal decreases to approx 70%

[Simau]

Hi @Anonymous 

Using this parameters you'll get 90%

[Anonymous]

Hi @Simau 
Yes, but if i apply a mass matrix lumped without intermediate nodes, the mas of the analysis decreases a lot (the total weight of the structure is 243205 kg)

and if i add nodes the weight is increased to 243205kg but the % decreases to 71%

[Simau]

@Anonymous 

Mass are taken into account in nodes, so with columns we lose half of columns weight that goes tout support and then not taken into account.

So spliting your columns you'll get much total mass. (the much you split the higher mass you'll get)

Below spliting columns in 5 part you get

[Simau]

And if course you need to increase the number of mode in modal analysis to reach 90%.

[Anonymous]

ok, my intention was to avoid increase the number of mode for the analysis time (136 mode)