Simple supported beam with spring in the middle

[dcizmar]

Hi. I am trying to model simple spring in order to verify more complex models. However I cant get a force in the spring. I looked at the file 10x times and can't figure this.

So please if anyone can help!


model BasicBuilder -ndm 2 -ndf 3
set L 200
set A 20
set E 21000
set I 167

node 1 0.0 0.0
node 2 $L 0.0
node 3 $L 0.0
node 4 [expr 2*$L] 0.0

fix 1 1 1 0
#fix 2 1 1 1
fix 4 0 1 0

equalDOF 2 3 1 3

# Define force-deformation relationship for spring

uniaxialMaterial Elastic 1 1050

# id ndI ndJ mat dir

element zeroLength 1 2 3 -mat 1 -dir 2

# Geometric transformation

geomTransf Linear 1

# id ndI ndJ A E I transf

element elasticBeamColumn 2 1 2 $A $E $I 1
element elasticBeamColumn 3 3 4 $A $E $I 1

pattern Plain 1 Linear {

eleLoad -ele 2 -type -beamUniform -5
eleLoad -ele 3 -type -beamUniform -5

}

#recorder Node Z.out disp -time -node 2 -dof 2
recorder Node -file p.txt -time -node 2 3 -dof 2 disp
recorder Node -file px.txt -time -node 3 -dof 1 disp
recorder Element -file ele1.txt -time -ele 1 localForce
recorder Element -file ele2.txt -time -ele 2 3 localForce

constraints Plain
numberer RCM
test NormUnbalance 1.0e-2 250 0
integrator LoadControl 0.025 1 0.025 0.025
algorithm Newton
system ProfileSPD
analysis Static

integrator LoadControl 0.05 3 0.05 0.05
analyze 16

integrator LoadControl 0.02 3 0.02 0.02
analyze 10

[fmk]

your spring is in the middle and carrying the shear .. so ask yourself this, what does the shear force diagram look like for a simply supported beam with uniform load.

[dcizmar]

thanks for replay, I understand what I have done.

...but I am trying to model a kind of bearing in the middle of the beam. so when the axial stifness of the sping is very large it will become support which will "carry" vertical reaction.

How to model this with the zerolength element?

[fmk]

[code]
fix 2 1 1 1
element zeroLength 1 2 3 -mat 1 -dir 2
element elasticBeamColumn 2 1 3 $A $E $I 1
element elasticBeamColumn 3 3 4 $A $E $I 1
[/code][/code]

[dcizmar]

Working perfectly. Thanks very much.