can't use non-numeric floating-point value as operand of "/"

[zemiki]

I'm trying to do an analysis considering soil. I used Gid+Opensees to visualize my model and then get the tcl code. I get the following error.

#==================================================
can't use non-numeric floating-point value as operand of "/"
while executing
"expr 6.283185/sqrt($lam)"
("foreach" body line 2)
invoked from within
"foreach lam $lambda {
lappend T [expr 6.283185/sqrt($lam)]
}"
#==================================================