Geostar STOP 1-Singular Matrix.

[JamboTron]

I have recently began a model in Geostar using the beam element function. Early simple models e.g fixed cantilever have worked fine. The problem now is that I'm modeling part of a oil platform, this requires 3 different Real Constant sets for different beams.
When I got to run the freq, analysis I get the following error message. STOP 1-SINGULAR MATRIX

What does this mean and where have I made the mistake?

I have kept all beam element sizes approx. the same size for all sections when meshing. I had a few early problems with the '3rd node' setting when selecting a beam section,but I feel comfortable this is not the problem as it usually has it's own type of error message.

Any assistance would be greatly appreciated.

 

[kellnerp]

It means your model probably has not been constrained sufficiently to prevent free body motion.

http://www.engtran.com

http://www.niswug.org

 

[JamboTron]

Thanks Kellnerp, managed to solve the problem not long after I posted. Didn't realise you had to identify each individual beam on a long section. e.g, instead of meshing 1x10m, it should be 4x2.5m sections. Took quite a while to redraw all the relevant the curves!