simple shear wall model... Help!

[omaramin]

Hi all,

I'm a beginner in OpenSees and I want to perform a pushover analysis on a simple two story shear wall model. I followed the procedure given in this post and am using zerolength element.
http://opensees.berkeley.edu/community/ ... 66#p100266

I'm getting this error " Element 1 has L=120 which is greater than the tolerance..."

Here is the model.

model Basic -ndm 1 -ndf 1

node 1 0.0
node 2 120.0 -mass 0.035
node 3 240.0 -mass 0.035

#Boundary Conditions
fix 1 1
#uniaxialMaterial SAWS 1 $F0 $FI $DU $S0 $R1 $R2 $R3 $R4 $alph $bet
uniaxialMaterial SAWS 1 24000 182 3 17000 0.05 -0.01 1 0.0165 0.75 1

## Define Model
element zeroLength 1 1 2 -mat 1 -dir 1
element zeroLength 2 2 3 -mat 1 -dir 1
## Recorder
recorder Node -file Disp.dat -node 3 -dof 1 disp
recorder Node -file Force.dat -node 1 -dof 1 reaction

Thanks!

[HassanF]

Hi Omaramin,

I see some problems in your script:
1- Why you've used -ndm 1 -ndf 1? (I think you should use -ndm 2 -ndf 3)
2- Why you use zero length elements? A zero length element should has real zero length! but here point you have a distance between successive points (120).

If you are beginner, I think it is more helpful to use one of ready examples in OpenSees manual.

Hassan

[fmk]

what you dd originally was fine except that zeroLength elements should really have zero Length .. yours have length 120. .. they spit out a warning (not an error) ..
you can ignore the message just be aware that the length is ignored in calculating strains in materials and tangent given the stress in material.

[Jeena]

Hi,

I have done some 2D wood shear wall models and used zero length elements ... I tried to modify ur model in the way I used to follow and is as follows ...

model Basic -ndm 1 -ndf 1

node 1 0.0
node 2 120.0 -mass 0
node 3 120.0 -mass 0.035 # two nodes with same nodal coordinates at floor level 1
node 4 240.0 -mass 0
node 5 240.0 -mass 0.035 # two nodes with same nodal coordinates at floor level 2

#Boundary Conditions
fix 1 1
equalDOF 1 2 1; # connect the degrees of freedom
equalDOF 3 4 1;


#uniaxialMaterial SAWS 1 $F0 $FI $DU $S0 $R1 $R2 $R3 $R4 $alph $bet
uniaxialMaterial SAWS 1 24000 182 3 17000 0.05 -0.01 1 0.0165 0.75 1

## Define Model

element zeroLength 1 2 3 -mat 1 -dir 1 -doRayleigh 1
element zeroLength 2 4 5 -mat 1 -dir 1 -doRayleigh 1


## Recorder
recorder Node -file Disp.dat -node 5 -dof 1 disp
recorder Node -file Force.dat -node 1 -dof 1 reaction

puts "Done"

I was able to run this model with out errors ...

U can verify the model accuracy by checking the time period or any other parameters ...

[fmk]

yes it would be good to check the accuracy of the model and looking at the period is usually a goof place to start as if building is simple enough you can estimate it by hand, if more complicated you will find that the period of certain type of buildings will fall within a certain range .. google is your best source, e.g. for moment frames

http://digitalcommons.calpoly.edu/cgi/v ... t=cenv_fac

[omaramin]

Hi Jeena,

I used the modified model you suggested and added the load pattern to perform the pushover analysis but I'm getting 0 values for node 1 reaction. Please let me know your thoughts on this! I can cope the source file if you think that will be helpful.

pattern Plain 2 Linear {
load 3 0.53
load 5 1.0
}

[afsoon]

hi
i am trying to model steel shear wall too.i want to know why you use zero length element?is it true to use it? and how you want evaluate the wall thickness?