HYBDAMP

Bulk Data Entry Defines the application of modal damping to the residual structure in a Direct Transient or Frequency Response analysis.

Format

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
HYBDAMP SID METHOD SDAMP KDAMP          

Definitions

Field Contents SI Unit Example
HYBDAMP Keyword for applying modal damping on a direct analysis  
SID Unique hybrid damping SID (Refer to HYBDAMP I/O Option).  
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
-1/YES
Modal damping is entered into the complex stiffness matrix as material damping, instead of viscous damping.
1/NO (Default)
Enter the damping as viscous damping.

(Integer)

 

Comments

  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:
    If KDAMP is set to 1/NO (Default), then:(1)
    B H = [ M ] [ ϕ 1 ϕ 2 ϕ n ] [ b ( ω 1 ) b ( ω 2 ) b ( ω n ) ] [ ϕ 1 T ϕ 2 T ϕ n T ] [ M ]
    If KDAMP is set to -1/YES, then:(2)
    K H = [ M ] [ ϕ 1 ϕ 2 ϕ n ] [ g ( ω 1 ) g ( ω 2 ) g ( ω n ) ] [ ϕ 1 T ϕ 2 T ϕ n T ] [ M ]
    Where,
    ϕ i
    Modes of the structure
    [M]
    Structural mass matrix
    b( ω i)
    Modal damping values (b( ω i) = g( ω i) ω imi)
    b( ω i)
    Are equal to twice the critical damping ratios calculated from the TABDMP1 entry
    ω i
    Natural frequency of mode ϕ i
    mi
    Generalized mass of mode ϕ i