PBUSHFX

Bulk Data Entry Defines the various nominal property values for a generalized spring-damper-mass structural element. This property is not affected by translational and rotational stiffness limits specified using PARAM, BUSHSTIF.

Format

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
PBUSHFX PID K K K K K K K
B B B B B B B
GE GE1 GE2 GE3 GE4 GE5 GE6
M M1 M2 M3 M4 M5 M6

Example 1

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
PBUSHFX 35 K 4.35 2.4 RIGID 3.1
GE 0.02

Example 2

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
PBUSHFX 35 B 4.35
M 1.2 7.1

Definitions

Field Contents SI Unit Example
PID Property identification number.

No default (Integer > 0)
K Flag indicating that the next 1 to 6 fields are stiffness values.

No default (Character)
Ki Nominal stiffness values in directions 1 through 6. 3 5
RIGID
A very high relative stiffness (relative to the surrounding structure) is selected for that degree-of-freedom simulating a rigid connection.

Default = 0.0 (Real or RIGID)
B Flag indicating that the next 1 to 6 fields are force-per-velocity damping.

No default (Character)
Bi Nominal damping coefficients in directions 1 through 6 in units of force per unit velocity.

Default = 0.0 (Real)
GE Flag indicating that the next 1 to 6 fields are the structural damping constants.

No default (Character)
GEi Nominal structural damping constants in directions 1 through 6.

GEi is ignored in transient analysis, if PARAM, W4 is not specified. 3 5

Default = 0.0 (Real)
M Flag indicating that the next 1 to 6 fields are directional masses.
Mi Nominal mass values in directions 1 through 6. The Mi fields do not contribute to mass and inertia properties. Their contributions to gravity and/or centrifugal loading are also not included.

Default = 0.0 (Real)

Comments

  1. All generalized spring-damper-mass property entries must have unique ID numbers.
  2. The K, B, GE, and M lines may be specified in any order.
  3. Ki, Bi, GEi, or Mi may be made frequency dependent for both direct and modal frequency response by use of the PBUSHT entry.

    The nominal values are used for all analysis types except frequency response. For modal frequency response, the normal modes are computed using the nominal Ki values. The frequency-dependent values are used at every excitation frequency.

  4. To obtain the damping coefficient GE, multiply the critical damping ratio C / C 0 MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaam4qaiaac+ cacaWGdbWaaSbaaSqaaiaaicdaaeqaaaaa@391F@ by 2.0.
  5. For backward compatibility with Nastran, if ONLY GE1 is specified on a PBUSH entry and GEi, i = 2 to 6 are blank on that PBUSH entry, then a single structural damping is assumed and applied to all Ki of that PBUSH. If a PBUSH entry has a GEi, i = 2 to 6 specified, then the GEi fields are considered variable for that PBUSH entry.
  6. The keyword RIGID may be used in place of a stiffness value for Ki entries. When RIGID is defined, a very high relative stiffness (relative to the surrounding structure) is selected for that degree-of-freedom simulating a rigid connection.
  7. Rotational stiffness values are input based on rotations defined in Radians.
  8. This card is represented as a property in HyperMesh.