Triangular Shell Elements

[brag006]

Hi,

I have a gate that has already been meshed using another structural analysis software and contains quadrilateral and triangular plate elements. In converting the input files from this software to OpenSees I have found that there appears to be no triangular shell elements. Are there any elements that I am unaware of that could assist me in modelling these triangular plates because it is not practical for me to re-mesh the gate using only quad-shell elements.

Regards,

[fmk]

you can try using the regular shell element just duplicate one node. this approach works for regular quad elements. as numerical integration is same for shell and regular quad ele (i.e. not ssp quad) it may work for your case. you should of course check by comparing eigenvalues of 2 software programs.

[brag006]

I tried that but I am getting singularity issues. Here's the error when I assign Mumps for sys_of_eqns

WARNING MumpsParallelSolver::solve(void)- Error -10 returned in substitution dmumps()
cause: Matrix is Singular Numerically

and when using BandGeneral:

WARNING BandGenLinLapackSolver::solve() -LAPACK routine returned 1

Any other ideas that I could try to make it work in OpenSees.

Regards

[brag006]

I only have the problem with a 778 triangular elements out of 9443 total elements. I thought it might be possible to create the triangular nodes and elements in a ndm 2 ndf 2 system and then constraint them using equalDOF in the 1 and 2 direction to duplicate nodes in the ndm 3 ndf 6 system which will have the shell elements in. Do you think that has a chance of working? I am also not sure if it makes much sense. I only need it to calculate the natural frequency of the structure.

[fmk]

that will work.