section Aggregator

[wuhaoshrek]

Hi,
I use "Aggregator" to build a section for force-based element, like this

section Aggregator 111 1 P 2 Mz ; # Section 111 with material 1 and 2 represent section axial and moment(z) relationship
element forceBeamColumn 1 1 2 4 111 1; # section 111
this is OK.

but when I want include shear by using a new "Aggregator" in this way:
section Aggregator 111 1 P 2 Mz ; # Section 111 with material 1 and 2 represent section axial and moment(z) relationship
section Aggregator 112 3 Vy -section 111; # Section 112 with material 3 represent section shear(y) relationship added to existing section 111
element forceBeamColumn 1 1 2 4 112 1; # section 112
in this case, OpenSees prompts error, seems like stiffness matrix is singular

AND, if I don't build section 112 by using a new "Aggregator", rather in this way:
section Aggregator 112 1 P 2 Mz 3 Vy; # Section 112 with material 1 2 and 3 represent section axial, moment(z) and shear(y) relationship
element forceBeamColumn 1 1 2 4 112 1; # section 112
this is OK, TOO.

So I don't understand why it's not working in the second case. Thanks all.

By the way, for displacement based element, it won't have any effect in the 3rd case above with shear component, it will
only use material 1 and 2 which are for axial and moment component, just have the same result as in case 1. So for DBE
it is not able to include shear in the element, am I right?

[mhscott]

Right, dispBeamColumn will ignore the section shear force-deformation.

Not sure why the second case gives an error. You need to provide more information, i.e., your entire script.

[wuhaoshrek]

mhscott wrote:
> Right, dispBeamColumn will ignore the section shear force-deformation.
>
> Not sure why the second case gives an error. You need to provide more
> information, i.e., your entire script.

Hi, here is the test script:
###############################################
wipe;
model basic -ndm 2 -ndf 3;
set dataDir Output;
file mkdir $dataDir;

node 1 0.0 0.0;
node 2 0.0 2.0;

fix 1 1 1 1;

geomTransf Linear 1;

# $eleTag $iNode $jNode $A $E $Iz $transfTag <-mass $massDens>
# element elasticBeamColumn 1 1 2 1.0 1.0 8.0 1;

uniaxialMaterial Elastic 1 [expr 1.0*1.0]; # axial
uniaxialMaterial Elastic 2 [expr 1.0*8.0]; # flexural
uniaxialMaterial Elastic 3 [expr 6.0*1.0]; # shear

section Aggregator 111 1 P 2 Mz;
# section Aggregator 112 1 P 2 Mz 3 Vy;
section Aggregator 112 3 Vy -section 111;

element forceBeamColumn 1 1 2 4 112 1;

recorder Node -file $dataDir/A1_DispNode.out -time -node 2 -dof 1 disp;
recorder Node -file $dataDir/A2_ForceNode.out -time -node 1 -dof 1 reaction;


timeSeries Linear 1 -factor 1.0; # lambda=factor*t

pattern Plain 1 1 {
load 2 3. 0. 0.;
}

constraints Plain;
numberer Plain;
system BandGeneral;
test NormDispIncr 1.0e-8 20 2;
algorithm Newton;
integrator LoadControl 0.1;
analysis Static;
analyze 10;
loadConst -time 0.0;
###############################################
two nodes, have horizontal force = 3.0 at node 2, should have 1.0 disp. at node 2 w/o shear, and 2.0 disp. w/ shear.
1. elastic beam element, w/o shear, d=1.0, OK!
2. FBE, w/o shear, case 1, d=1.0, OK!
3. FBE, w/ shear, case 3, d=2.0, OK!
4. FBE, w/ shear, case 2, NOT OK! OpenSees prompts error.

[mhscott]

Thanks for posting your script! There is a problem with recursive definitions of section aggregators because they are writing in to a common block of memory. In the mean time, you can use section Elastic for P and Mz instead of aggregator.

[paperairplane]

mhscott wrote:
> Thanks for posting your script! There is a problem with recursive
> definitions of section aggregators because they are writing in to a common
> block of memory. In the mean time, you can use section Elastic for P and
> Mz instead of aggregator.
dear mhscott, did the problem sloved? i try to simulate a beam with corrugated steel webs.
For bending ，the fiber section is good
for shearing ，GA of corrugated steel webs was arranged to the whole section, which could be Elastic Constitutive.
The second case ~~!