For more information on the Linear Perturbation procedure for rotating structures, see Considerations for Rotating Structures.
To generate the Campbell diagram of a prestressed structure,
multiple static and perturbed modal solutions are calculated alternately. The Campbell
action (Action on the CAMPBELL command)
must be set to the results file name extension of the perturbed solution (RSTP) in the
first static analysis. Issue the command CORIOLIS,ON,,,ON in the
static prestress portion of the analysis to include the Coriolis effect.
The results of the modal analyses are appended to the Jobname.rstp file to accommodate a subsequent Campbell diagram analysis – see Campbell Diagram.
The example snippet below shows the commands used for a Campbell analysis of a prestressed structure.
Example 5.1: Commands used in a Campbell Diagram Analysis of a Prestressed Structure
! *** Define the rotational velocity array parameter ‘spins’ nbstep = 5 ! number of steps dspin = spin/(nbstep-1) ! increment *dim,spins,,nbstep *vfill,spins,ramp,0.,dspin spins(1) = 0.1 ! nonzero to ease the Campbell diagram sorting !*** Perform the multiple prestress modal analyses in a *do loop *do,iloop,1,nbstep /solu antype,static rescontrol,linear ! enable file writing for a subsequent linear perturbation coriolis,off ! de-activate Coriolis effect if needed (centrifugal force) omega,,,spins(iloop) ! set rotational velocity f,… ! define static loads campbell,rstp ! enable file handling for Campbell analysis solve fini /solu antype,static, restart,,,perturb perturb, modal coriolis,on,,,on ! activate Coriolis effect in stationary reference frame solve, elform modopt,… ! specify the eigensolver – only DAMP and QRDAMP are supported mxpand solve fini *enddo ! *** Post-process the Campbell diagram /post1 file,,rstp ! define the results file to be used plcamp finish