how can fix this problem?!ArpackSolver::Maximum number of it

[MohsenShani]

hi

node 9, 10 , 11 , 12 is my roof Structure.

node 1000 is my Central node for my rigidDiaphragm

when i use mass like :

mass 9 [expr 15066.*0.25] [expr 14066.*0.25] [expr 15000.*0.25] 1.e-9 1.e-9 1.e-9
mass 10 [expr 15066.*0.25] [expr 14066.*0.25] [expr 15000.*0.25] 1.e-9 1.e-9 1.e-9
mass 11 [expr 15066.*0.25] [expr 14066.*0.25] [expr 15000.*0.25] 1.e-9 1.e-9 1.e-9
mass 12 [expr 15066.*0.25] [expr 14066.*0.25] [expr 15000.*0.25] 1.e-9 1.e-9 1.e-9

ArpackSolver::Maximum number of iteration reached.
ArpackSolver::Maximum number of iteration reached.
First Eigen Value is: 3.237859e-319
First Mode Period is: 1.104175430906306e+160
ArpackSolver::Maximum number of iteration reached.

when i use mass :
mass 1000 15066.3646 14066.3646 15066.3646 1.e-9 1.e-9 1.e-9
my period is fine!

how can i fix this problem???

[fmk]

you might try asking for more modes, Arpack can have issues with multiple modes with same eigenvalue.