eigenvalue analysis

[mrathore]

I have modeled a 3D geometry in openSees with beams pinned at the ends. The geometry also has rigid diphragm effect. Thus there is sequential slaving for nodes.

If I remove the pinned beam slaving, I get first two modes in X and Z direction but when I use pinned beam slaving, I get both two modes in X direction only. I think this is because the constraint handler which is being used for eigenvalue analysis is Transformation instead of Lagrange.

In eigenvalue analysis, is there any way to change the constraint handler?

If this is not possible, then is there any way to make the ends of a nonlinearbeamcolumn element as pinned? (I just want to make the Mz as zero)

[fmk]

not at the moment .. you can of course go into the code and make the change in OpenSees/SRC/tcl/commands.cpp

[mrathore]

Sir,
If I change the constraint handler to Lagrange, the system of equation does not remain symmetric positive definite. Is the equation solver used by default is for non-SPD equations, or do I need to change the equation solver also.

Thanks

[fmk]

no A just must be symmetric .. if it doesn't work try the BandGenArpack option. if that fails you could always try using the Penalty constraint handler.

[mrathore]

Thanks a lot for your kind guidance.

I think the changes are to be made in following commands:

Code: Select all

    // create the rest of components of an eigen analysis
    EigenIntegrator  *theEigenIntegrator = new EigenIntegrator();    
    RCM *theRCM = new RCM(false);	
    DOF_Numberer *theEigenNumberer = new DOF_Numberer(*theRCM);    	
    ConstraintHandler *theEigenHandler = new TransformationConstraintHandler();


    // create the eigen analysis
    theEigenAnalysis = new EigenAnalysis(theDomain,
					 *theEigenHandler,
					 *theEigenNumberer,
					 *theEigenModel,
					 *theEigenAlgo,
					 *theEigenSOE,
					 *theEigenIntegrator);

As per my understanding, we need to change the line:-

Code: Select all

    ConstraintHandler *theEigenHandler = new TransformationConstraintHandler();

with the line

Code: Select all

    ConstraintHandler *theEigenHandler = new PenaltyConstraintHandler();

Is it correct.

Also I want to ask, do I need to recompile the Opensees code in order to get these changes in final result or will it work by just modifying the file??

Thanks again.

[fmk]

should be and yes you need to recompile the .exe