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*Damping Ratio

Purpose

To specify stiffness damping coefficients as a function of a damping ratio and a damping period.

Theory

Refer to Damping Ratio for further information on this feature.

Keyword Format

A block of lines which define the damping parameters as a function of element set. The block of lines can be repeated as often as necessary.

Block defining damping ratio data:

SET=Set Name

Damping Ratio [, Damping Period]

The specification of damping for an element set using *DAMPING precludes the specification of damping for the same element set using *DAMPING RATIO, and vice versa. The Damping Ratio must be between 0 and 1. The Damping Period is optional in the case of a single regular wave analysis and defaults to the regular wave period. Otherwise it is a mandatory input.

Table Input

Notes

(a)Rather than explicitly defining a coefficient (or coefficients), stiffness proportional damping may alternatively be defined as a function of a damping ratio and a damping period in a time domain dynamic analysis. Refer to Damping Ratio for further details.

(b)The damping ratio ξ must be between 0 and 1. If the excitation in your dynamic analysis is a single regular wave, then the specification of damping period T is optional. If omitted, T defaults to the regular wave period. If the excitation is of any other type, then the period input is required.

(c)If damping ratios and periods are assigned to an element set in this table, the same element set may not be referenced in the Damping or Damping - Deformation tables.