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mass participation factors in tall structures

mass participation factors in tall structures

mass participation factors in tall structures

(OP)
why is that the mass participation factor in first few modes of structures such as chimneys is zero.
infact the mass participation comes into picture only when we consider more than 50 modes or so.

RE: mass participation factors in tall structures

Either you have a lot of mass on restrained d.o.f. or the first modes are torsion ones (torsion modes have no participation factor)...

if none of this I dont know... :(

RE: mass participation factors in tall structures

(OP)
define  a  master joint at the geometric center of the floor plan then assign all  the  floor mas  to  the joint with rotational inertia also

RE: mass participation factors in tall structures

Your "lower" modes should be your primary modes and should have high mass participation. If your lower modes have small mass participation, they are probably local modes and not global modes. The lower modes may be local vibration such as a beam in a floor (low mass participation) with a lower frequency than the over all floor.

Check your model and the output. See if the mode involves only a localized motion.

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