Damping Constant

[Anonymous]

Hi,

Wonder if anyone can help?

Is the "Damping" constant required in Harmonic Analysis refer to;

A) Logarithmic decrement, around 0.03 or 3% for steel structure,

or

B) (Logarithmic decrement)/(2 x 3.142), around 0.005 for steel structure.

Many thanks 🙂

[Pawel.Pulak · Accepted solution]

Hi,

it is relative damping, i.e. part of critical damping

Just to remind some relation between relative damping, logarithmic decrement of damping  and  viscous damping.

Relation between logarithmic decrement of damping D and relative damping e (both dimensionless):

D = 2*Pi*e/SQRT(1-e*e)

so e = D/SQRT(4*Pi*Pi+D*D)

Example:
D=0.015 corresponds to e=0.002387

Relation between viscous damping a [N*s/m] and relative damping e (dimensionless):

a = 2*e*SQRT(k*m)

where
k - stiffness
m - mass

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Regards,

[Anonymous]

Thank you so much