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


(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)


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)

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.



  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:

    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:

    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 ]

    ϕ i
    Modes of the structure
    Structural mass matrix
    b( ω i)
    Modal damping values (b( ω i) = g( ω i) ω imi)
    g( ω i)
    Are equal to twice the critical damping ratios calculated from the TABDMP1 entry
    ω i
    Natural frequency of mode ϕ i
    Generalized mass of mode ϕ i