Recorder for zeroLength element with Elastic-perfectly plast

[zsherliza]

Dear Vesna,

I need a little advice on recording forces for zeroLength element with ElasticPPGap material. I am assuming a finger joint type of expansion joint, and have used these element and material to model internal expansion joint to observe forces, which would be transmitted in these directions. The aim is to determine if there is a need to introduce restrainers in the bridge I am studying. I have tried my best to follow the manual, have assumed material in compression only in both directions. I then used the element recorder to view the forces in the zeroLength element, but am getting zeros in the element. Why is this? . I am posting the script I have used, and I hope you can help me understand what is it that I am doing wrong.

For your information, I have modeled the elastomeric bearings supporting both reinforced concrete beams (or girder) as free to move in the longitudinal direction, the gap between these beams are 150 mm. For you to understand the model, I will give an example by taking on expansion joint. Let's take zeroLength element 276, which connects nodes 210 and 211 (having the same coordinates). The beams on either side of the expansion joint are mounted on elastomeric bearings, which are modeled by zeroLength elements 29 and 203 (free to move in the longitudinal direction and rotation is allowed).

Thank you for your time.

#elastomeric bearing
# translational
uniaxialMaterial Elastic 9 [expr (8*1000.0*$N/$mm)]; # shear stiffness (translation) for free column - without expansion joints (assume bearing pad to behave linear);
uniaxialMaterial Elastic 10 [expr (8*1000.0*$N/$mm)]; # shear stiffness (translation) for abutment
uniaxialMaterial ElasticPPGap 29 [expr 200000.0*$N/$mm] [expr -3000000.0*$N] [expr -150.0*$mm]
uniaxialMaterial ElasticPPGap 30 [expr 100000000.0*$N/$mm] [expr -15000000000.0*$N] [expr -10.0*$mm]

# rotational
uniaxialMaterial Elastic 13 [expr (8*2.6e11*$N/$mm)]; # for free column, rotational stiffness (for ; originally used [expr 1.0e5*$Ubig]
uniaxialMaterial Elastic 14 [expr (8*8.65e9*$N/$mm)]; # rotation stiffness at abutment is twice as much as that in girder, original value=0.5*8*7200
uniaxialMaterial Elastic 15 [expr (8*1.0e11*$N/$mm)]; # for fixed column, rotational stiffness


equalDOF 1 2 2 3 4 5 6
equalDOF 6 5 2 3 4 5 6
equalDOF 11 10 1 2 3 4 5 6
equalDOF 16 15 2 3 4 5 6
#equalDOF 20 21 2 3 4 5 6
equalDOF 144 145 1 2 3 4 5 6
equalDOF 146 147 2 3 4 5 6
equalDOF 26 25 2 3 4 5 6
equalDOF 31 30 1 2 3 4 5 6
equalDOF 36 35 2 3 4 5 6
#equalDOF 41 40 2 3 4 5 6
equalDOF 148 149 1 2 3 4 5 6
equalDOF 150 151 2 3 4 5 6
equalDOF 46 45 2 3 4 5 6
equalDOF 51 50 1 2 3 4 5 6
equalDOF 56 55 2 3 4 5 6
#equalDOF 60 61 2 3 4 5 6
equalDOF 152 153 1 2 3 4 5 6
equalDOF 154 155 2 3 4 5 6
equalDOF 66 65 2 3 4 5 6
equalDOF 71 70 1 2 3 4 5 6
equalDOF 76 75 2 3 4 5 6
#equalDOF 80 81 2 3 4 5 6
equalDOF 156 157 1 2 3 4 5 6
equalDOF 158 159 2 3 4 5 6
equalDOF 86 85 2 3 4 5 6
equalDOF 91 90 1 2 3 4 5 6
equalDOF 96 95 2 3 4 5 6
#equalDOF 100 101 2 3 4 5 6
equalDOF 160 161 1 2 3 4 5 6
equalDOF 162 163 2 3 4 5 6
equalDOF 106 105 2 3 4 5 6
equalDOF 111 110 1 2 3 4 5 6
equalDOF 116 115 2 3 4 5 6
#equalDOF 120 121 2 3 4 5 6
equalDOF 164 165 1 2 3 4 5 6
equalDOF 166 167 2 3 4 5 6
equalDOF 126 125 2 3 4 5 6
equalDOF 131 130 1 2 3 4 5 6
equalDOF 136 135 2 3 4 5 6
equalDOF 141 140 2 4 5 6
equalDOF 211 210 2 4 5 6
equalDOF 213 212 2 4 5 6
equalDOF 215 214 2 4 5 6
equalDOF 217 216 2 4 5 6
equalDOF 219 218 2 4 5 6
equalDOF 221 220 2 4 5 6

#------------------------------------------------------------------------------------------------------------
# Generate elements - Define zero-length element (top of cap beam to bottom of girder - elastomeric bearing)
#------------------------------------------------------------------------------------------------------------

#create zero-length at bearing

# tag ndI ndJ matID dir orientation

element zeroLength 1 1 2 -mat 10 14 -dir 1 4 ;#-orient 1 0 0 0 0 -1; #abut
element zeroLength 8 6 5 -mat 9 13 -dir 1 4 ;#-orient 1 0 0 0 0 -1;# p1
element zeroLength 15 11 10 -mat 15 -dir 4 ;#-orient 0 1 0 -1 0 0 ;# p2
element zeroLength 22 16 15 -mat 9 13 -dir 1 4 ;#-orient 1 0 0 0 0 -1
#element zeroLength 29 21 20 -mat 9 13 -dir 1 4 ;#-orient 1 0 0 0 0 -1
element zeroLength 29 145 144 -mat 9 13 -dir 1 4 ;#-orient 1 0 0 0 0 -1
element zeroLength 203 147 146 -mat 9 13 -dir 1 4 ;#-orient 1 0 0 0 0 -1
element zeroLength 36 26 25 -mat 9 13 -dir 1 4 ;#-orient 1 0 0 0 0 -1
element zeroLength 43 31 30 -mat 15 -dir 4 ;#-orient 0 1 0 -1 0 0
element zeroLength 50 36 35 -mat 9 13 -dir 1 4 ;#-orient 1 0 0 0 0 -1
#element zeroLength 57 41 40 -mat 9 13 -dir 1 4 ;#-orient 1 0 0 0 0 -1
element zeroLength 57 149 148 -mat 9 13 -dir 1 4 ;#-orient 1 0 0 0 0 -1
element zeroLength 204 151 150 -mat 9 13 -dir 1 4 ;#-orient 1 0 0 0 0 -1
element zeroLength 64 46 45 -mat 9 13 -dir 1 4 ;#-orient 1 0 0 0 0 -1
element zeroLength 71 51 50 -mat 15 -dir 4 ;#-orient 0 1 0 -1 0 0
element zeroLength 78 56 55 -mat 9 13 -dir 1 4 ;#-orient 1 0 0 0 0 -1
#element zeroLength 85 61 60 -mat 9 13 -dir 1 4 ;#-orient 1 0 0 0 0 -1
element zeroLength 85 153 152 -mat 9 13 -dir 1 4 ;#-orient 1 0 0 0 0 -1
element zeroLength 205 155 154 -mat 9 13 -dir 1 4 ;#-orient 1 0 0 0 0 -1
element zeroLength 92 66 65 -mat 9 13 -dir 1 4 ;#-orient 1 0 0 0 0 -1
element zeroLength 99 71 70 -mat 15 -dir 4 ;#-orient 0 1 0 -1 0 0
element zeroLength 106 76 75 -mat 9 13 -dir 1 4 ;#-orient 1 0 0 0 0 -1
#element zeroLength 113 81 80 -mat 9 13 -dir 1 4 ;#-orient 1 0 0 0 0 -1
element zeroLength 113 157 156 -mat 9 13 -dir 1 4 ;#-orient 1 0 0 0 0 -1
element zeroLength 206 159 158 -mat 9 13 -dir 1 4 ;#-orient 1 0 0 0 0 -1
element zeroLength 120 86 85 -mat 9 13 -dir 1 4 ;#-orient 1 0 0 0 0 -1
element zeroLength 127 91 90 -mat 15 -dir 4 ;#-orient 0 1 0 -1 0 0
element zeroLength 134 96 95 -mat 9 13 -dir 1 4 ;#-orient 1 0 0 0 0 -1
#element zeroLength 141 101 100 -mat 9 13 -dir 1 4 ;#-orient 1 0 0 0 0 -1
element zeroLength 141 161 160 -mat 9 13 -dir 1 4 ;#-orient 1 0 0 0 0 -1
element zeroLength 207 163 162 -mat 9 13 -dir 1 4 ;#-orient 1 0 0 0 0 -1
element zeroLength 148 106 105 -mat 9 13 -dir 1 4 ;#-orient 1 0 0 0 0 -1
element zeroLength 155 111 110 -mat 15 -dir 4 ;#-orient 0 1 0 -1 0 0
element zeroLength 162 116 115 -mat 9 13 -dir 1 4 ;#-orient 1 0 0 0 0 -1
#element zeroLength 169 121 120 -mat 9 13 -dir 1 4 ;#-orient 1 0 0 0 0 -1
element zeroLength 169 165 164 -mat 9 13 -dir 1 4 ;#-orient 1 0 0 0 0 -1
element zeroLength 208 167 166 -mat 9 13 -dir 1 4 ;#-orient 1 0 0 0 0 -1
element zeroLength 176 126 125 -mat 9 13 -dir 1 4 ;#-orient 1 0 0 0 0 -1
element zeroLength 183 131 130 -mat 15 -dir 4 ;#-orient 0 1 0 -1 0 0
element zeroLength 190 136 135 -mat 9 13 -dir 1 4 ;#-orient 1 0 0 0 0 -1
element zeroLength 197 141 140 -mat 10 14 -dir 1 4 ;#-orient 1 0 0 0 0 -1

#----------------------------------------------------------------------------
# Expansion joints
#----------------------------------------------------------------------------
element zeroLength 276 210 211 -mat 29 30 -dir 1 3
element zeroLength 277 212 213 -mat 29 30 -dir 1 3
element zeroLength 278 214 215 -mat 29 30 -dir 1 3
element zeroLength 279 216 217 -mat 29 30 -dir 1 3
element zeroLength 280 218 219 -mat 29 30 -dir 1 3
element zeroLength 281 220 221 -mat 29 30 -dir 1 3

puts "All elements for elastomeric bearings have been generated"

#---------------------------------------------------------------------------------------
# recorder
#-------------------------------------------------------------------------------------
recorder Element -xml Data6e1/ZeroLengthEle276.xml -time -ele 276 force
recorder Element -xml Data6e1/ZeroLengthEle277.xml -time -ele 277 force
recorder Element -xml Data6e1/ZeroLengthEle278.xml -time -ele 278 force
recorder Element -xml Data6e1/ZeroLengthEle279.xml -time -ele 279 force
recorder Element -xml Data6e1/ZeroLengthEle280.xml -time -ele 280 force
recorder Element -xml Data6e1/ZeroLengthEle281.xml -time -ele 281 force

[vesna]

What load are you applying on your model? If you want to see some forces in the expansion joint make sure to apply load in the right direction and big enough to close the gap and to start compressing the other end.

[zsherliza]

Dear Vesna,
This is a 3-D model of an entire bridge. I have gravity load and the Kobe earthquake load applied bidirectionally (longitudinal and transverse) at the base. I believe that the loads in the longitudinal direction are large enough to record something. Anything else I did not do? Please help.

Thank you.

[zsherliza]

Dear Vesna,

I forgot to tell you that, although the recorder for forces gave all zeros, I observe that there are values for deformations (as high as 50 mm), and if I am right, I can use these values to find forces by multiplying deformation with stiffness, can't I? Also, when I record deformations, I can only see values in the longitudinal direction, even though I have defined the zerolength element in both the longitudinal and transverse directions. Why is this? Can you help clarify this?

Thanks again for your time

[vesna]

Your gap is 10 mm. If you have compression deformation in your zeroLength elements as high as 50mm you should see some forces. If you do not see them, there is a bug in your model.

I would suggest you to make a small structure (two elastic beams separated with the expansion joints and seating on the elastomeric bearings). Test it first in one direction and then in the other to make sure that your zeroLength elements work the way they should.