three dimension truss analysis

[MahmoudRezaei]

Hi
I have modeled a simple 3D truss structure and when i run it, i receive this error:

WARNING BandGenLinLapackSolver::solve() -LAPACK routine returned 28
WARNING Linear::solveCurrentStep() -the LinearSOE failed in solve()
StaticAnalysis::analyze() - the Algorithm failed at iteration: 0 with domain at load factor 1
OpenSees > analyze failed, returned: -3 error flag

I have considered enough constraint and used Penalty method for constraints option but this error is still exist.
I appreciate if somebody helps me.
Here is the code:

wipe
wipeAnalysis

model BasicBuilder -ndm 3 -ndf 6

node 1 0 0 0
node 2 2 0 0
node 3 0 2 0
node 4 2 2 0
node 5 1 1 1

fix 1 1 1 1 1 1 1
fix 2 1 1 1 1 1 1
fix 3 1 1 1 1 1 1
fix 4 1 1 1 1 1 1


uniaxialMaterial Elastic 1 300

element truss 1 1 5 10.0 1
element truss 2 2 5 10.0 1
element truss 3 3 5 10.0 1
element truss 4 4 5 10.0 1


pattern Plain 1 "Linear" {
load 5 0.0 0.0 -5.0 0.0 0.0 0.0
}

recorder Node -file example.out -load -node 5 -dof 1 2 3 disp

integrator LoadControl 1
system BandGeneral
numberer Plain
constraints Penalty 1e17 1e17
algorithm Linear
analysis Static
analyze 1

[Jeena]

Hi,

Change the model definition to model BasicBuilder -ndm 3 -ndf 3 and change the load and fixity definition ....

Truss elements take only axial forces .... Since you have only truss elements, each node takes only three global translational degrees of freedom (in X, Y and Z directions ) , and no rotations ...

This modification as follows will work

model BasicBuilder -ndm 3 -ndf 3 # change number of degrees of freedom to 3

node 1 0 0 0
node 2 2 0 0
node 3 0 2 0
node 4 2 2 0
node 5 1 1 1

fix 1 1 1 1 # need to define fixity for three translational degrees of freedom
fix 2 1 1 1
fix 3 1 1 1
fix 4 1 1 1


uniaxialMaterial Elastic 1 300

element truss 1 1 5 10.0 1
element truss 2 2 5 10.0 1
element truss 3 3 5 10.0 1
element truss 4 4 5 10.0 1


pattern Plain 1 "Linear" {
load 5 0.0 0.0 -5.0 # needs to define loads only in three translational degrees of freedom
}

recorder Node -file example.out -load -node 5 -dof 1 2 3 disp

integrator LoadControl 1
system BandGeneral
numberer Plain
constraints Penalty 1e17 1e17
algorithm Linear
analysis Static
analyze 1

Thanks,
Jeena

[MahmoudRezaei]

thanks a lot geena, it works properly...

[MohsenShani]

or your can use -ndm 3 -ndf 6
and fix rotation start and end of node's truss element
example : fix 5 0 0 0 1 1 1

[LaundryService]

Thanks For All Reply