LinearSysofEqn failed

[majid-OS]

Hi,

I am modeling a very simple continuum system under dynamic load. very simple cubic shape with fixed base and uniform excitation.
It works fine when my ndof is 3 but it gives error in ndof=6 saying
"ProfileSPDLinDirectSolver::solve() - aii (0, (i, aii): (54,0)
WARNING NewtonRaphson::solveCurrentStep() -the LinearSysOfEqn failed in solve()"

I am using following analysis commands,

integrator Newmark $gamma [expr pow($gamma+0.5, 2)/4]
constraints Penalty 1.e18 1.e18 ;
test NormDispIncr 1.0e-3 30 1 ;
algorithm ModifiedNewton ;
system ProfileSPD ;
numberer RCM
analysis VariableTransient ;

I appreciate any idea where the problem would be.

[vesna]

The message says that your system is unstable. Check your boundary conditions and connectivity between your elements. You may use recorder display command to visualize your model: http://opensees.berkeley.edu/wiki/index ... ode_shapes

[majid-OS]

Thanks,
I think I found the problem. The Brick elements can't have 6DOF.
Can I have to model builder for example one for a 3DOF system and one for 6DOF system in one script?

[fmk]

yes .. issue the modelbuilder command twice, after the command is evaluated the nodes added will have the specified dof's .. you will need to use different
node numbers .. when done tie the two models together with the equalDOF command.