A simple truss problem 1

[burtek]

Hi,
I made a simple truss model but I got an error(a small negative equation solver pivot term............Check for an insuffuciently constrained model). Can anybody please give me a tip to solve?

Thanks

/PREP7
!Element type
ET,1,LINK8
!real constant
R,1,1.343e-4, ,

!Material properties
MPTEMP,,,,,,,,
MPTEMP,1,0
MPDATA,EX,1,,2e11
MPDATA,PRXY,1,,0.3

!Keyponits
K,1,0,0,0,
K,2,1,0,0,
K,3,1,1,0,
K,4,0,1,0,
K,5,0,0,1,
K,6,1,0,1,
K,7,0,1,1,
K,8,1,1,1,

!Lines
LSTR, 5, 6
LSTR, 6, 8
LSTR, 8, 7
LSTR, 7, 5
LSTR, 1, 5
LSTR, 2, 6
LSTR, 3, 8
LSTR, 4, 7
LSTR, 5, 8
LSTR, 7, 6

!Meshing
LESIZE,ALL, , ,1, ,1, , ,1,
FLST,2,10,4,ORDE,2
FITEM,2,1
FITEM,2,-10
LMESH,P51X

FINISH
/SOL

!Fixed supports
FLST,2,4,3,ORDE,2
FITEM,2,1
FITEM,2,-4
!*
/GO
DK,P51X, ,0, ,0,ALL, , , , , ,

!Forces
FLST,2,2,3,ORDE,2
FITEM,2,5
FITEM,2,7
FK,P51X,FX,10

!Solution
/STATUS,SOLU
SOLVE

 

[TERIO]

Make sure it is actually a truss (all triangles). Glancing at it there does not appear to be enough lines for the number of keypoints you have.

 

[burtek]

Thanks TERIO

i found it you are right, it is not completely truss.