Corotational doesnot work for 3D beam column element

[J.Zhang]

Hi there,

I tried to do 3D analysis with dispbeamclolumn element. A cantilever with point load at the end, comparing the results of Linear and Corotational transformation. Because the displacement is small, the rusulsts should be very close. But they are very different indeed.

Linear Corotational
disp 0.00791664 0.00197916
rotation 0.000123697 0.000247395


The script is following:

=========================
wipe;
model BasicBuilder -ndm 3 -ndf 6;
set dataDir Data;
file mkdir $dataDir;

node 1 0 0 0;
node 2 1 0 0;

fix 1 1 1 1 1 1 1;

set Fy 4.55e8; # STEEL yield stress
set Es 2.1e11; # modulus of steel
set Bs 0.002; # strain-hardening ratio
set matTag 1;
uniaxialMaterial Steel02 $matTag $Fy $Es $Bs ;

set secTag 1;
set secFiberTag 2;
section Fiber $secFiberTag {
patch quadr $matTag 8 16 -0.1 0.05 -0.1 -0.05 0.1 -0.05 0.1 0.05;
}

set SecTagTorsion 20;
set AUbig 10; # a very large value;
uniaxialMaterial Elastic $SecTagTorsion $AUbig;
section Aggregator $secTag $SecTagTorsion T -section $secFiberTag


set IDBeamTransf 1;
#geomTransf Linear $IDBeamTransf 0 0 1;
geomTransf Corotational $IDBeamTransf 0 0 1;


set np 3;
element dispBeamColumn 1 1 2 $np $secTag $IDBeamTransf;

recorder Node -file $dataDir/DFree.out -time -node 2 -dof 1 2 3 4 5 6 disp;

pattern Plain 101 Linear {

#eleLoad -ele 1 -type -beamUniform 1e5 0 0 ;
load 2 0 0 0 0 0 3.45e3;

}


constraints Plain ;
numberer Plain;
system BandGeneral ;

test NormDispIncr 1e-8 6 ;
algorithm Newton;
integrator LoadControl 0.1;
analysis Static;
analyze 10;

==========================================

Your help is apprecate

Thanks

Jian

[seu]

I just ran your codes and got alomst the same answer of node 2's displacement:
Linear Disps: -7.65053e-009 0.000123697 -1.78644e-020 -5.99713e-018 3.25271e-020 0.000247395
Corotational Disps: -9.2533e-022 0.000123697 -1.48497e-020 0 3.15684e-020 0.000247395

[J.Zhang]

Thank you.

you are right.

but if the load type is changed to element load, there will be some errors. Probably because corotational can not be used to transfer elemental loads.

However, I also found PDelt is not working for the elemental loads too. And this notice can not be found on OpenSees Wiki.

thanks again

Jian