The OpenSees Community

vesna wrote:
> If this rigid element connects to nonlinear beam-column elements such as
> forceBeamColumn and displacmenetBeamColumn your approach with modeling it
> using very stiff elastic element seems right to me. Otherwise, rigid link
> can be used as well.

vesna,
but using stiff elastic element might make period of the model unrealistic, right? would rigidLink change period of the model also? thx

basharfarah wrote:
> Exactly , but i still have problem with applying the (ZeroLengthSection
> Element +Bond SP01 ), Did you try it before ,
> i will be grateful if you can provide any help ,

yeah, it works, but i haven't verified it yet, and in fact I haven't come up with how I should verify it.

basharfarah wrote:
> hi , actually i got the same results with and without using the
> orientation , any way you can read the description of the orientation in
> the manual "Geometric Transformation Command and the zero length
> element command " . you should read both of these commands .

yes you can have the same results if the local orientation is coincidentally the same with the global orientation. as what said in
the note of the zerolength element command.

fmk wrote:
> as for the 1 1 0 and -1 1 0 .. they are 2 vectors draw them in a 2d vector
> space to see the local 1 and 2 vectors. the 3 dirn for the element is the
> cross product. (along z axis)
>
> you have 2 vectors {9144 3962 0} and {-3962 9144 0}. Taking the cross
> product results in a 3'rd vector. The 1'st vector and 3'rd vecor are 1 and
> 3 directions. The 2 vector is in the 1-2 plane given by the second vector.

Dear fmk,
I have two zerolength element connecting two nodes 1 and 101. zeroLengthSection element 100 (using fiber section) to model RC column bar-slip effect
and zeroLength element 200 modeling shear behavior. Both of them have its local x in Global Y and local y in Global -X. here is the script:

element zeroLengthSection 100 1 101 $IDColSec_zeroBSSec -orient 0 1 0 -1 0 0 -doRayleigh 0 ;
element zeroLength 200 1 101 -mat $IDShearMat -dir 2 -doRayleigh 0 -orient 0 1 0 -1 0 0 ;

So why in this case it's not working in opensees it has the warning:

WARNING BandGenLinLapackSolver::solve() -LAPACK routine returned 4
WARNING NewtonRaphson::solveCurrentStep() -the LinearSysOfEqn failed in solve()
StaticAnalysis::analyze() - the Algorithm failed at iteration: 0 with domain at
load factor 0.1
OpenSees > analyze failed, returned: -3 error flag

Thankyouooo!

Hi fmk
I found the problem is I used tansformation constraint, when I use penalty it is running fine? I have equalDOF in my model,
so do you think that would be the reason? thx

mhscott wrote:
> Try using an elastic section instead of the fiber section. This will tell
> you if it's a constraints problem or a section problem.

Hi,
can you explain the note on the zero-length section element:

The section force-deformation response represented by section string P acts along the element local x-axis, and the response for code Vy along the local y-axis. The other modes of section response follow from this orientation.

I didn't see any string used in the example, how should we assign the section orientation for the element? thanks

Hi,
In the command manual for ZeroLengthSection Element, in the note 2, it says:

The section force-deformation response represented by section string P acts along the element local x-axis, and the response for code Vy along the local y-axis. The other modes of section response follow from this orientation.

I wanna know where shall I input the section string, like P, Vy, and Mz? Assume I establish the section with fiberSec command. Thanks

fmk wrote:
> you need to provide some mass to the nodes before you issue the eigen
> command!

Right, fmk, I missed that.
I have another confusion, if I build the model in 2D domain (-ndm 2 -ndf 3), and I used truss element in this domain.
for truss element, each node has 2 dofs, no rotational dof. So in the constraints, I need to assign the rotatioanl dof
for the nodes on truss elements, right? in my model I used fix 0 0 1 for that, but there are some other alternative
options can be used, like equalDOF (assign the rotational dof of truss to be equal with other node's dof) or just connect
those nodes with other elements which would have 3 dofs on the nodes, or what I can do is I can build those nodes
connect truss element in 2D domain, but with only 2dof on each node (i.e., -ndm 2 -ndf 2). By the way, in other programs
like Drian2D or something else, when come across this issue, user do not need to worry about it, program itself will
handle it, so i don't know how exactly those programs would do for it, also.

So my question is does that matter how you assign the dof for the rotaional dof for the truss element? I don't quite
understand this part, thank you.

AND, for the writing sequence, take this as an example:
if i used
equalDOF 2 12 1 3; works OK!

Then instead, I rewrite it in 2 lines as:
equalDOF 2 12 1;
equalDOF 2 12 3; It's not working!

So does equalDOF command do not allow it be split by 2 commands? cause in rayleigh damping command, I kind
assign M-proportional damping and K-proportional damping separately?

Hi all,
I have some problems with the constraints options in OpenSees.

The model is simple, you can find the sketch in this link below:
https://www.dropbox.com/s/44ni4bs0m5ta5 ... raints.jpg

The tcl script is:
###################################
wipe;
model BasicBuilder -ndm 2 -ndf 3;
set dataDir Output;
file mkdir $dataDir;

node 1 0.0 0.0;
node 2 0.0 12.5;
node 3 0.0 25.0;

node 11 -17.0 0.0;
node 12 -17.0 12.5;
node 13 -17.0 25.0;

node 21 30.0 0.0;
node 22 30.0 12.5;
node 23 30.0 25.0;

geomTransf Linear 1;

element elasticBeamColumn 1 1 2 100. 200. 500. 1 ;
element elasticBeamColumn 2 2 3 100. 200. 500. 1 ;

element elasticBeamColumn 11 11 12 100. 200. 500. 1 ;
element elasticBeamColumn 12 12 13 100. 200. 500. 1 ;

element elasticBeamColumn 21 21 22 100. 200. 500. 1 ;
element elasticBeamColumn 22 22 23 100. 200. 500. 1 ;

fix 1 1 1 1;
fix 11 1 1 1;
fix 21 1 1 0;

fix 12 0 0 1; # truss dof3

equalDOF 2 22 1 ;
equalDOF 3 23 1 ;

equalDOF 2 12 1;

rigidLink beam 3 13 ;

timeSeries Linear 1 -factor 1.0;

pattern Plain 1 1 {
load 3 10. -10. 0.;
}

# constraints Plain;
# constraints Lagrange;
# constraints Transformation;
constraints Penalty 1.0e14 1.0e14;
numberer RCM;
system BandGeneral;
test NormDispIncr 1.0e-8 20 2;
algorithm Newton;
integrator LoadControl 0.1;
analysis Static;
analyze 10;
loadConst -time 0.0;
###################################

My problem is for the eigenvalue analysis, the error is:
OpenSees > eigen 3
ArpackSolver::Error with _saupd info = -9
Starting vector is zero.
WARNING StaticAnalysis::eigen() - EigenSOE failed in solve()

I have tried different constraints handler, but seems not working. so plz help me with it, thx.

fmk wrote:
> yes. it requires a bit of work using the printA (as printA will only print
> the contents of the A matrix and if transient analysis, this is some
> combination of K and M, so you would either have to know M, the factors and
> determine K or you might be able to switch analysis from transient to
> static and back again)
>
> http://opensees.berkeley.edu/wiki/index.php/PrintA

Hi fmk
Why nothing happened when I do printA -file $dataDir/AMatrix.out;

Hello all,

To model rebar in a RC section normally we use steel02 or Reinforcing steel material model in OpenSees. When the RC section undergoes large flexural deformation, in reality rebar may fracture at certain value(fracture stain), but as far as I know, few people would consider this fracture strain in rebar fiber material modeling. One alternative way to model the fracture of rebar is using MinMax material in OpenSees to assign a maximum/minimum strain, e.g. 10% for the original rebar material to include this effect. This may give dramatically different results when the structure/component goes large deformation like collapse level ground motion intensity.

So I was wondering is there any more practical way so far that I can use to include this effect in OpenSees modeling? Can any people share some clue or literature to handle this issue? Many thanks.

Georgia wrote:
> Hi,
> As far as I know, we can improve the accuracy of solution for FBE by
> increasing the NIPs, while in DBE this goal can not be achieved in a same
> way. And it is recommended that if you want to enrich the response, you
> should use "mesh refinement" in DBE. Could you tell me plz how
> can we refine the mesh in opensees? thanks for any help you could provide.

use more DBE elements.

ssami wrote:
> HI
> How can I get analysis time? Is there any script in opensees do this?
> Thanks a lot.

you can capture the time at any analysis step by using getTime command, e.g. set currentTime [getTime]

mhscott wrote:
> Make sure you are using the latest version of OpenSees. I recently fixed a
> bug related to this issue.

YES, I used the version 2.4.3<rev 5645>. And the analysis stopped at time 3.260800. By the way, when I compiled the
source code just updated this morning, there are 13 failed to get built. Thanks.

vesna wrote:
> Here it is:
> m.r.azadi AT ut.ac.ir

Hi vesna, the example does not give converged result for the dynamic case. For pushover and cyclic it is fine.

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.