DSUM

DSUM, SIGNIF, Label, TD, ForceType
Specifies the double sum mode combination method.

Valid Products: Pro | Premium | Enterprise | PrepPost | Solver | AS add-on

SIGNIF

Combine only those modes whose significance level exceeds the SIGNIF threshold. For single-point, multi-point, or DDAM response spectrum (Spectype = SPRS, MPRS, or DDAM on SPOPT), the significance level of a mode is defined as the mode coefficient divided by the maximum mode coefficient of all modes. Any mode whose significance level is less than SIGNIF is considered insignificant and is not contributed to the mode combinations. The higher the SIGNIF threshold, the fewer the number of modes combined. SIGNIF defaults to 0.001. If SIGNIF is specified as 0.0, it is taken as 0.0. (This mode combination method is not valid for SPOPT, PSD.)

Label

Label identifying the combined mode solution output.

DISP

 — 

Displacement solution (default). Displacements, stresses, forces, etc., are available.

VELO

 — 

Velocity solution. Velocities, "stress velocities," "force velocities," etc., are available.

ACEL

 — 

Acceleration solution. Accelerations, "stress accelerations," "force accelerations," etc., are available.

TD

Time duration for earthquake or shock spectrum. TD defaults to 10.

ForceType

Label identifying the forces to be combined:

STATIC

 — 

Combine the modal static forces (default).

TOTAL

 — 

Combine the modal static plus inertial forces.

Notes

Modes whose effective damping ratio defined in Equation 14–42 exceeds or equals 1.0 are not combined.

This command is also valid for PREP7.

Menu Paths

Main Menu>Preprocessor>Loads>Load Step Opts>Spectrum>Mode Combine>DSUM Method
Main Menu>Preprocessor>Loads>Load Step Opts>Spectrum>MultiPt>Mode Combine>DSUM Method
Main Menu>Preprocessor>Loads>Load Step Opts>Spectrum>SinglePt>Mode Combine>DSUM Method
Main Menu>Solution>Load Step Opts>Spectrum>Mode Combine>DSUM Method
Main Menu>Solution>Load Step Opts>Spectrum>MultiPt>Mode Combine>DSUM Method
Main Menu>Solution>Load Step Opts>Spectrum>SinglePt>Mode Combine>DSUM Method