How to achieve more mass participation in single mode? 2

[Aasutosh Gupta]

Hello everyone, I have ETABS model of G+14 Story Regular Residential Building of typical floor plan. In this, I am getting 74% mass participation in the First mode in the X direction and I want to increase mass participation more than 85% in the first mode only so how to achieve this. Help me!

 

[TLHS]

You would need to make that mode even more predominant. So it would presumably involve looking at your other modes and stiffening them in comparison, or making your primary mode more flexible.

Why are you trying to do this? Normally you're not trying to increase participation in a given mode, but rather to ensure that you're considering the effects of all the modes necessary to get a given amount of participation.

 

[JoshPlumSE]

This is a 14 story building? If so, 74% is pretty good mass participation for a single mode. Usually, the shorter / wider buildings are more likely to have a single totally dominant mode... not the taller ones.

Regardless, what's happening with the other higher order modes? If one of them is a torsional mode (or a mode with mass participation in both directions), then that tells you something. And, you can stiffen up some aspects of the structure to avoid torsion.

If, on the other hand, the other mode (or modes) are merely higher order flexural modes, then there may not be much you can do about it. A single mode just doesn't fully capture the dynamic behavior of a lot of buildings.

 

[Aasutosh Gupta]

Hello TLHS,
Thank you for your response,
I want to Increase it because my Client wants to do this. I tried it by removing of X-dir walls and I got 80% participation but I affected 2nd mode in which participation decreased from 67% to 64%. Also, the inter-story drift ratio reached beyond the limit. So now I convinced my client with 74% mass participation model.

 

[Aasutosh Gupta]

Hello JoshPlum,
Thank you for your response,

This Table of Modal Mass participation Ratio, and is looking good structural configuration and later I will improve more while the design is finalized.