HYBDAMP

Bulk Data Entry

HYBDAMP – Apply Hybrid Damping in a Direct Transient or Direct Frequency Response Analysis

This bulk data entry defines the application of modal damping to the residual structure in a Direct Transient or Frequency Response analysis.

Format

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HYBDAMP	SID	METHOD	SDAMP	KDAMP

Field	Contents
HYBDAMP	Keyword for applying modal damping on a direct analysis
SID	Unique hybrid damping SID (Referred to by the HYBDAMP I/O section data).
METHOD	EIGRL/EIGRA data identification number. Hybrid damping is applied on the modes determined by the eigenvalue analysis. No default (Integer > 0)
SDAMP	A TABDMP1 entry identification number for modal damping. No default (Integer > 0)
KDAMP	If KDAMP is set to -1/YES, modal damping is entered into the complex stiffness matrix as material damping, instead of viscous damping. The default is 1/NO to enter the damping as viscous damping. Default = 1 (Integer)

1.	HYBDAMP SID can be set by the HYBDAMP I/O Options Entry in the I/O section of the input data.

2.	Hybrid damping can be defined as shown below:

If KDAMP is set to 1/NO (Default), then:

kdamp_no

If KDAMP is set to -1/YES, then:

kdamp_yes

Where,

are the modes of the structure

[M] is the structural mass matrix

b() are the modal damping values

g () are equal to twice the critical damping ratios calculated from the TABDMP1 entry

is the natural frequency of mode

mi is the generalized mass of mode