ERROR 153 - Suspension Bridge Model, how to improve?
Hello Everyone,
I am struggling with quite a simple question today and I hope that maybe someone of you could perhaps check my model to see what the issue is.
For a university project I am currently writing a FE-script which shall calculate the displacement of a suspension bridge. Natually, I want to validate my work. For this I am using the HyperWorks Student Edition to build a very simple model of said bridge, with only lines and shells.
The bridge I modelled before had a PSHELL for its roadway and PBEAM for its main and suspension cables. This worked fine, but I thought displacement might be more accurately modelled by using ROD-Elements.
However when I replaced the Line Elements, I keep getting the following error message when running OptiStruct:
*** ERROR # 153 ***
Exactly zero pivoting encountered during Numerical Factorization;
the model may have rigid body mode.
Solver error no. = -514
spc set id = 1
index = 1
Possible reasons are:
1) insufficiently constrained model,
2) having rigid body mechanisms within the model,
3) extremely ill-conditioned rigid element sets,
4) extremely thin shells (as used for skinning) that have MID2/MID3,
5) gap elements with extremely high stiffness (KA, especially KT or MU).
6) extremely high Poisson's ratio in hyperelasticity material definition.
Check the model and rerun the problem.
(MECHCHECK may be used to find the rigid body modes. To do so,
change the input to be an eigenvalue analysis and add MECHCHECK.)
(WARNING: results obtained with MECHCHECK cannot be used because
the model is changed internally.) This error was detected in subroutine bcsmtxfct.
And to be honest, I really do not understand much of what is suggested there. I have attached the very simple model, it would be fantastic if someone could have a quick look at it and tell me how to make it work. Thank you already in advance, this community has helped me time and again. /emoticons/default_smile.png' srcset='/emoticons/smile@2x.png 2x' title=':)' width='20' />
Best Regards,
Lennart