lapack solver failed - Modeling a truss problem

[assimi]

Hi, I tried to model this benchmark truss but it failed and returned some errors, would you mind helping me to solve this issue?
Benchamrk:
[img]http://uploads.im/uwU2Z.png[/img]

Error: WARNING BandSPDLinLapackSolver::solve() - the LAPACK routines returned 1
WARNING NewtonRaphson::solveCurrentStep() -the LinearSysOfEqn failed in solve()
StaticAnalysis::analyze() - the Algorithm failed at iteration: 0 with domain at load factor 1
OpenSees > analyze failed, returned: -3 error flag
-3
Code:
[Code]model BasicBuilder -ndm 2 -ndf 2
node 1 0.0000 0.0000
node 2 360.0000 0.0000
node 3 720.0000 0.0000
node 4 0.0000 360.0000
node 5 360.0000 360.0000
node 6 720.0000 360.0000
fix 1 1 1
fix 4 1 1
uniaxialMaterial Elastic 1 10000
element Truss 1 1 2 5.219 1
element Truss 2 1 5 20.310 1
element Truss 3 1 3 14.593 1
element Truss 4 2 4 7.772 1
element Truss 5 4 5 28.187 1
element Truss 6 3 5 20.650 1
timeSeries Linear 1
pattern Plain 1 1 {
load 2 0 -100
load 3 0 -100
}
system BandSPD
numberer RCM
constraints Plain
integrator LoadControl 1.0
algorithm Linear
analysis Static
recorder Node -file NodeDispX.out -time -node -dof 1 disp
recorder Node -file NodeDispY.out -time -node -dof 2 disp
recorder Element -file AxialForces.out -time -eleRange 1 6 basicForces
analyze 1
wipe[/code]

[emjac]

Take a look at your nodes. The node 6 is unnecessary. Comment out this line and the code works fine. Otherwise you need to restrain it.

[assimi]

Thank you so much, I didn't know that I have to eliminate it. By the way, would you let me know when I should consider degree of freedom (dof) as three in two dimension problems?

[fmk]

3 when you have beam-ccolumn elements .. trusses only have 2 dof.