i am trying to run a sol105 linear buckling on an unconstrained structure - usually in sol 101 i would have used a param inrel -2 , but here i read i have to use a param inrel -1 and a suport1 case control command + a suport1 bulk data card.
but....it simply does not work, the model setup check requires to ""add a constraint"", and when i remove the model setup check, i get fatal error message like
*** SYSTEM FATAL MESSAGE 7340 (LNNRIGL)
REPEATED SINGULAR MATRIX -- PROBABLY ILL-POSED PROBLEM.
question 1 : is it possible to run sol 105 on unconstrained structures
question 2: if yes, how?
i would really appreciate to get a small sample input file
thanks for your help
thanks for your answer,
yes i had found this note, and i tried to implement it, but with no success
i put a suport1 card in the case control of the static subcase, and a corresponding suport1 bulk data card with a grid point and its 6 dof.
in the bulk i also put a param inrel -1
what is missing ?
the f06 behaves like there was no param inrel at all and says the model has mechanisms:
^^^ USER FATAL MESSAGE 9137 (SEKRRS)
^^^ RUN TERMINATED DUE TO EXCESSIVE PIVOT RATIOS IN MATRIX KLL.
^^^ USER ACTION: CONSTRAIN MECHANISMS WITH SPCI OR SUPORTI ENTRIES OR SPECIFY PARAM,BAILOUT,-1 TO
^^^ CONTINUE THE RUN WITH MECHANISMS.
Typically, SUPORT/SUPORT1 dof are not all specified on a single grid. If the grid is on solid elements, this definitely will not work as solids only provide stiffness in 3 DOF.