Diagram (P,V,M) values partially discrepant with reactions [bug on diagrams when lateral distribut loads applied]

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skypass
Posts: 15
Joined: Thu May 27, 2021 9:37 am

Diagram (P,V,M) values partially discrepant with reactions [bug on diagrams when lateral distribut loads applied]

Post by skypass »

Reference is made to this screenshot coming from the python code written underneath
Image

The 'strange matter' can be seen trough next schedule. Looking at bending moment on soil support (1) the proper value should be 69.996 (also confirmed by other sowtware) and not 57.496 as plotted in the diagram. Nevertheless, the one of node (5) is in perfect harmony, 37.874 kN*m.

Could it be a bug? Replies are welcomed. Cheers

Code: Select all

ElasticBeam2d: 1
        Connected Nodes: 1 2
        End 1 Forces (P V M): -2.53668 9.70513  57.4958  <<<<<  discrepancy with reactions()

ElasticBeam2d: 4
        End 2 Forces (P V M): -2.53668 -5.29487 37.8739  <<<<<  in compliance with reactions()       
        
-----------------------------------------        
 Node 1              Moment=  69.996
 Node 1   Vertical reaction=  -2.537
 Node 1 Horizontal reaction= -17.205


 Node 5              Moment=  37.874
 Node 5   Vertical reaction=   2.537
 Node 5 Horizontal reaction=  -5.295
Here is the related code .py

Code: Select all

# --- ese2_forum.py ---  Jun.03, 2021 ----
#
import openseespy.opensees as ops
import openseespy.postprocessing.ops_vis as opsv

import matplotlib.pyplot as plt
import numpy as np

ops.wipe()
ops.model('basic', '-ndm', 2, '-ndf', 3)


# --- Gehler configuration ---
#  A= 1000 stands for infinity, no deformations due to compressed areas      
A = 1.e3
I = 1.
E = 1.
#

Ep = {1: [E, A, I],
      2: [E, A, I],
      3: [E, A, I],
      4: [E, A, I]}      

# Coord. nodes
ops.node(1,  0.,  0.)
ops.node(2,  0., 10.)
ops.node(3, 12., 15.)
ops.node(4, 24., 10.)
ops.node(5, 24.,  0.)

# Soil supports
ops.fix(1, 1, 1, 1)  # fixed
ops.fix(5, 1, 1, 1)  # fixed

ops.geomTransf('Linear',12)

# Elements (between nodes)
ops.element('elasticBeamColumn', 1, 1, 2, A, E, I, 12)
ops.element('elasticBeamColumn', 2, 2, 3, A, E, I, 12)
ops.element('elasticBeamColumn', 3, 3, 4, A, E, I, 12)
ops.element('elasticBeamColumn', 4, 4, 5, A, E, I, 12)

# External forces and couples 
H1=  7.50;  C1= -12.50 
H2= 11.25;  C2=   9.25 
H3=  3.75;  C3=   3.25

# --- Distributed loads ---
Wx= 0.
Wy= 0.
Ew = {3: ['-beamUniform', Wx, Wy]} # fictitious null load on beam 3 

ops.timeSeries('Constant', 23)

ops.pattern('Plain', 1, 23)
# concentrated loads and couples applied
ops.load(1, H1, 0., C1) 
ops.load(2, H2, 0., C2)
ops.load(3, H3, 0., C3)

for etag in Ew:
    ops.eleLoad('-ele', etag, '-type', Ew[etag][0], Ew[etag][1],
                Ew[etag][2])

ops.constraints('Transformation')
ops.numberer('RCM')
ops.system('BandGeneral')
ops.test('NormDispIncr', 1.0e-6, 6, 2)
ops.algorithm('Linear')
ops.integrator('LoadControl', 1)
ops.analysis('Static')
ops.analyze(1)

ops.printModel()

ops.reactions()


# plot model with tag labels

szer, wys = 16., 10.

fig = plt.figure(figsize=(szer/2.54, wys/2.54))
fig.subplots_adjust(left=.08, bottom=.08, right=.985, top=.94)
ax1 = plt.subplot(111)

opsv.plot_model()
sfacN, sfacV, sfacM = 5.e-1, 5.e-1, 5.e-1 

# plot deformed model
plt.figure()
# plot_defo with optional arguments
sfac = opsv.plot_defo() # 
print(f'sfac: {sfac}')  # return sfac if automatically calculated

opsv.plot_defo(sfac, fmt_interp='b.-')
opsv.plot_defo(sfac, 5, interpFlag=0, fmt_nodes='bo-')
opsv.plot_defo(sfac, 3, endDispFlag=0, fmt_interp='r.--')
opsv.plot_defo(sfac, 2, fmt_interp='g.-')


# plot N, V, M forces diagrams
#
plt.figure()
minVal, maxVal = opsv.section_force_diagram_2d('N', Ew, sfacN)
plt.title(f'Axial forces [kN], max = {maxVal:.3f}, min = {minVal:.3f}')

plt.figure()
minVal, maxVal = opsv.section_force_diagram_2d('T', Ew, sfacV)
plt.title(f'Shear forces [kN], max = {maxVal:.3f}, min = {minVal:.3f}')

plt.figure()
minVal, maxVal = opsv.section_force_diagram_2d('M', Ew, sfacM)
plt.title(f'Bending moments [kN*m], max = {maxVal:.3f}, min = {minVal:.3f}')
# ----------
plt.show()
# ----------
print('\n Units kN, kN*m')
print(' Node 1              Moment= {:>7.3f}'. format (ops.nodeReaction(1,3)))
print(' Node 1   Vertical reaction= {:>7.3f}'. format (ops.nodeReaction(1,2)))
print(' Node 1 Horizontal reaction= {:>7.3f}'. format (ops.nodeReaction(1,1)))
print('\n')
print(' Node 5              Moment= {:>7.3f}'. format (ops.nodeReaction(5,3)))
print(' Node 5   Vertical reaction= {:>7.3f}'. format (ops.nodeReaction(5,2)))
print(' Node 5 Horizontal reaction= {:>7.3f}'. format (ops.nodeReaction(5,1)))

exit()
# EOF: ese2_forum.py
'''

C:\Training>python ese2_forum.py
Current Domain Information
        Current Time: 1
tCommitted Time: 1
NODE DATA: NumNodes: 5

numComponents: 5
 Node: 1
        Coordinates  : 0 0
        Disps: 0 0 0
         unbalanced Load: 7.5 0 -12.5
        ID : -1 -1 -1


 Node: 2
        Coordinates  : 0 10
        Disps: 1257.27 0.0253668 -89.7014
         unbalanced Load: 11.25 0 9.25
        ID : 6 7 8


 Node: 3
        Coordinates  : 12 15
        Disps: 1134.29 295.157 56.2005
         unbalanced Load: 3.75 0 3.25
        ID : 3 4 5


 Node: 4
        Coordinates  : 24 10
        Disps: 1011.21 -0.0253668 -113.995
         unbalanced Load: 0 0 0
        ID : 0 1 2


 Node: 5
        Coordinates  : 24 0
        Disps: 0 0 0
         unbalanced Load: 0 0 0
        ID : -1 -1 -1

ELEMENT DATA: NumEle: 4

numComponents: 4
ElasticBeam2d: 1
        Connected Nodes: 1 2
        CoordTransf: 12
        mass density:  0, cMass: 0
        release code:  0
        End 1 Forces (P V M): -2.53668 9.70513 57.4958
        End 2 Forces (P V M): 2.53668 -9.70513 39.5555

ElasticBeam2d: 2
        Connected Nodes: 2 3
        CoordTransf: 12
        mass density:  0, cMass: 0
        release code:  0
        End 1 Forces (P V M): 0.45039 -2.93573 -30.3055
        End 2 Forces (P V M): -0.45039 2.93573 -7.85905

ElasticBeam2d: 3
        Connected Nodes: 3 4
        CoordTransf: 12
        mass density:  0, cMass: 0
        release code:  0
        End 1 Forces (P V M): 5.86322 -0.305063 11.1091
        End 2 Forces (P V M): -5.86322 0.305063 -15.0749

ElasticBeam2d: 4
        Connected Nodes: 4 5
        CoordTransf: 12
        mass density:  0, cMass: 0
        release code:  0
        End 1 Forces (P V M): 2.53668 5.29487 15.0749
        End 2 Forces (P V M): -2.53668 -5.29487 37.8739

SP_Constraints: numConstraints: 6

numComponents: 6SP_Constraint: 0         Node: 1 DOF: 1 ref value: 0 current value: 0
SP_Constraint: 1         Node: 1 DOF: 2 ref value: 0 current value: 0
SP_Constraint: 2         Node: 1 DOF: 3 ref value: 0 current value: 0
SP_Constraint: 3         Node: 5 DOF: 1 ref value: 0 current value: 0
SP_Constraint: 4         Node: 5 DOF: 2 ref value: 0 current value: 0
SP_Constraint: 5         Node: 5 DOF: 3 ref value: 0 current value: 0

Pressure_Constraints: numConstraints: 0

numComponents: 0
MP_Constraints: numConstraints: 0

numComponents: 0
LOAD PATTERNS: numPatterns: 1


numComponents: 1Load Pattern: 1
  Scale Factor: 1
Constant Series: factor: 1
  Nodal Loads:

numComponents: 3Nodal Load: 1 load : 7.5 0 -12.5
Nodal Load: 2 load : 11.25 0 9.25
Nodal Load: 3 load : 3.75 0 3.25

  Elemental Loads:

numComponents: 1Beam2dUniformLoad - tag 0
  Transverse: 0
  Axial:      0
  Element acted on: 3

  Single Point Constraints:

numComponents: 0
PARAMETERS: numParameters: 0


numComponents: sfac: 0.0019089017319445234

 Units kN, kN*m
 Node 1              Moment=  69.996
 Node 1   Vertical reaction=  -2.537
 Node 1 Horizontal reaction= -17.205


 Node 5              Moment=  37.874
 Node 5   Vertical reaction=   2.537
 Node 5 Horizontal reaction=  -5.295

'''
Last edited by skypass on Thu Jun 03, 2021 9:47 pm, edited 2 times in total.
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anuragiitg
Posts: 12
Joined: Mon Aug 26, 2013 7:52 pm
Location: The University of Utah
Contact:
Contact anuragiitg

Re: Diagram (P,V,M) values partially discrepant with reactions

Post by anuragiitg »

Could you please create a new issue here? This has to do with how "ops_vis" handles its calculation. --> https://github.com/zhuminjie/OpenSeesPy/issues

In general, I would only prefer OpenSees calculations and not ope_vis or Get_Rendering modules.
--
Anurag Upadhyay
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skypass
Posts: 15
Joined: Thu May 27, 2021 9:37 am

Re: Diagram (P,V,M) values partially discrepant with reactions

Post by skypass »

Thanks for your drift.
Nevertheless, some doubts arise on writing into a GitHub issue, are we sure that somebody replies?

In addition, what I believe (up to now) is the presence of a bug due to element loaded with force and couple
at the soil support (node #1), while all flows properly in the other support (node #5).

Cheers
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skypass
Posts: 15
Joined: Thu May 27, 2021 9:37 am

Re: Diagram (P,V,M) values partially discrepant with reactions

Post by skypass »

Yes, confirmed, openseespy 3.2.2.10 presents erroneous values on diagrams when external loads (forces,couples) are applied on supports nodes, that shortly means when lateral distributed loads (wind) act on the structure.

Screenshot and new .py code below. I'll be careful to use the module in such circumstances, until next openseespy release appears.

Thank you for the kind attention. I'm amending the post title with the prompt: 'bug on diagrams when lateral distributed loads applied'

Image

Code: Select all

ElasticBeam2d: 1
        Connected Nodes: 1 2
        End 1 Forces (P V M): -2.53668 9.70513 57.4958

ElasticBeam2d: 4
        Connected Nodes: 4 5
        End 2 Forces (P V M): -2.53668 -5.29487 37.8739        

 Units kN, kN*m
 Node 1              Moment=  57.496
 Node 1   Vertical reaction=  -2.537
 Node 1 Horizontal reaction=  -9.705

 Node 5              Moment=  37.874
 Node 5   Vertical reaction=   2.537
 Node 5 Horizontal reaction=  -5.295
File bis.py

Code: Select all

# --- bis.py ---  Jun.04, 2021 ----
#
import openseespy.opensees as ops
import openseespy.postprocessing.ops_vis as opsv

import matplotlib.pyplot as plt
import numpy as np

ops.wipe()
ops.model('basic', '-ndm', 2, '-ndf', 3)


# --- Gehler configuration ---
#  A= 1000 stands for infinity, no deformations due to compressed areas      
A = 1.e3
I = 1.
E = 1.
#

Ep = {1: [E, A, I],
      2: [E, A, I],
      3: [E, A, I],
      4: [E, A, I]}      

# Coord. nodes
ops.node(1,  0.,  0.)
ops.node(2,  0., 10.)
ops.node(3, 12., 15.)
ops.node(4, 24., 10.)
ops.node(5, 24.,  0.)

# Soil supports
ops.fix(1, 1, 1, 1)  # fixed
ops.fix(5, 1, 1, 1)  # fixed

ops.geomTransf('Linear',12)

# Elements (between nodes)
ops.element('elasticBeamColumn', 1, 1, 2, A, E, I, 12)
ops.element('elasticBeamColumn', 2, 2, 3, A, E, I, 12)
ops.element('elasticBeamColumn', 3, 3, 4, A, E, I, 12)
ops.element('elasticBeamColumn', 4, 4, 5, A, E, I, 12)

# External forces and couples 
#H1=  7.50;  C1= -12.50 
H2= 11.25;  C2=   9.25 
H3=  3.75;  C3=   3.25

# --- Distributed loads ---
Wx= 0.
Wy= 0.
Ew = {3: ['-beamUniform', Wx, Wy]} # fictitious null load on beam 3 

ops.timeSeries('Constant', 23)

ops.pattern('Plain', 1, 23)
# Command to be inserted after ops.pattern
# concentrated loads and couples applied
#ops.load(1, H1, 0., C1) 
ops.load(2, H2, 0., C2)
ops.load(3, H3, 0., C3)

for etag in Ew:
    ops.eleLoad('-ele', etag, '-type', Ew[etag][0], Ew[etag][1],
                Ew[etag][2])

ops.constraints('Transformation')
ops.numberer('RCM')
ops.system('BandGeneral')
ops.test('NormDispIncr', 1.0e-6, 6, 2)
ops.algorithm('Linear')
ops.integrator('LoadControl', 1)
ops.analysis('Static')
ops.analyze(1)

ops.printModel()

ops.reactions()


# plot model with tag labels

szer, wys = 16., 10.

fig = plt.figure(figsize=(szer/2.54, wys/2.54))
fig.subplots_adjust(left=.08, bottom=.08, right=.985, top=.94)
ax1 = plt.subplot(111)

opsv.plot_model()
sfacN, sfacV, sfacM = 5.e-1, 5.e-1, 5.e-1 

# plot deformed model
plt.figure()
# plot_defo with optional arguments
sfac = opsv.plot_defo() # 
print(f'sfac: {sfac}')  # return sfac if automatically calculated

opsv.plot_defo(sfac, fmt_interp='b.-')
opsv.plot_defo(sfac, 5, interpFlag=0, fmt_nodes='bo-')
opsv.plot_defo(sfac, 3, endDispFlag=0, fmt_interp='r.--')
opsv.plot_defo(sfac, 2, fmt_interp='g.-')


# plot N, V, M forces diagrams
#
plt.figure()
minVal, maxVal = opsv.section_force_diagram_2d('N', Ew, sfacN)
plt.title(f'Axial forces [kN], max = {maxVal:.3f}, min = {minVal:.3f}')

plt.figure()
minVal, maxVal = opsv.section_force_diagram_2d('T', Ew, sfacV)
plt.title(f'Shear forces [kN], max = {maxVal:.3f}, min = {minVal:.3f}')

plt.figure()
minVal, maxVal = opsv.section_force_diagram_2d('M', Ew, sfacM)
plt.title(f'Bending moments [kN*m], max = {maxVal:.3f}, min = {minVal:.3f}')
# ----------
plt.show()
# ----------
print('\n Units kN, kN*m')
print(' Node 1              Moment= {:>7.3f}'. format (ops.nodeReaction(1,3)))
print(' Node 1   Vertical reaction= {:>7.3f}'. format (ops.nodeReaction(1,2)))
print(' Node 1 Horizontal reaction= {:>7.3f}'. format (ops.nodeReaction(1,1)))
print('\n')
print(' Node 5              Moment= {:>7.3f}'. format (ops.nodeReaction(5,3)))
print(' Node 5   Vertical reaction= {:>7.3f}'. format (ops.nodeReaction(5,2)))
print(' Node 5 Horizontal reaction= {:>7.3f}'. format (ops.nodeReaction(5,1)))

exit()
# EOF: bis.py
'''

C:\Training>python bis.py
Current Domain Information
        Current Time: 1
tCommitted Time: 1
NODE DATA: NumNodes: 5

numComponents: 5
 Node: 1
        Coordinates  : 0 0
        Disps: 0 0 0
         unbalanced Load: 0 0 0
        ID : -1 -1 -1


 Node: 2
        Coordinates  : 0 10
        Disps: 1257.27 0.0253668 -89.7014
         unbalanced Load: 11.25 0 9.25
        ID : 6 7 8


 Node: 3
        Coordinates  : 12 15
        Disps: 1134.29 295.157 56.2005
         unbalanced Load: 3.75 0 3.25
        ID : 3 4 5


 Node: 4
        Coordinates  : 24 10
        Disps: 1011.21 -0.0253668 -113.995
         unbalanced Load: 0 0 0
        ID : 0 1 2


 Node: 5
        Coordinates  : 24 0
        Disps: 0 0 0
         unbalanced Load: 0 0 0
        ID : -1 -1 -1

ELEMENT DATA: NumEle: 4

numComponents: 4
ElasticBeam2d: 1
        Connected Nodes: 1 2
        CoordTransf: 12
        mass density:  0, cMass: 0
        release code:  0
        End 1 Forces (P V M): -2.53668 9.70513 57.4958
        End 2 Forces (P V M): 2.53668 -9.70513 39.5555

ElasticBeam2d: 2
        Connected Nodes: 2 3
        CoordTransf: 12
        mass density:  0, cMass: 0
        release code:  0
        End 1 Forces (P V M): 0.45039 -2.93573 -30.3055
        End 2 Forces (P V M): -0.45039 2.93573 -7.85905

ElasticBeam2d: 3
        Connected Nodes: 3 4
        CoordTransf: 12
        mass density:  0, cMass: 0
        release code:  0
        End 1 Forces (P V M): 5.86322 -0.305063 11.1091
        End 2 Forces (P V M): -5.86322 0.305063 -15.0749

ElasticBeam2d: 4
        Connected Nodes: 4 5
        CoordTransf: 12
        mass density:  0, cMass: 0
        release code:  0
        End 1 Forces (P V M): 2.53668 5.29487 15.0749
        End 2 Forces (P V M): -2.53668 -5.29487 37.8739

SP_Constraints: numConstraints: 6

numComponents: 6SP_Constraint: 0         Node: 1 DOF: 1 ref value: 0 current value: 0
SP_Constraint: 1         Node: 1 DOF: 2 ref value: 0 current value: 0
SP_Constraint: 2         Node: 1 DOF: 3 ref value: 0 current value: 0
SP_Constraint: 3         Node: 5 DOF: 1 ref value: 0 current value: 0
SP_Constraint: 4         Node: 5 DOF: 2 ref value: 0 current value: 0
SP_Constraint: 5         Node: 5 DOF: 3 ref value: 0 current value: 0

Pressure_Constraints: numConstraints: 0

numComponents: 0
MP_Constraints: numConstraints: 0

numComponents: 0
LOAD PATTERNS: numPatterns: 1


numComponents: 1Load Pattern: 1
  Scale Factor: 1
Constant Series: factor: 1
  Nodal Loads:

numComponents: 2Nodal Load: 2 load : 11.25 0 9.25
Nodal Load: 3 load : 3.75 0 3.25

  Elemental Loads:

numComponents: 1Beam2dUniformLoad - tag 0
  Transverse: 0
  Axial:      0
  Element acted on: 3

  Single Point Constraints:

numComponents: 0
PARAMETERS: numParameters: 0


numComponents: sfac: 0.0019089017319445234

 Units kN, kN*m
 Node 1              Moment=  57.496
 Node 1   Vertical reaction=  -2.537
 Node 1 Horizontal reaction=  -9.705


 Node 5              Moment=  37.874
 Node 5   Vertical reaction=   2.537
 Node 5 Horizontal reaction=  -5.295
'''
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skypass
Posts: 15
Joined: Thu May 27, 2021 9:37 am

Re: Diagram (P,V,M) values partially discrepant with reactions [bug on diagrams when lateral distribut loads applied]

Post by skypass »

With warm pleasure, I do post the following comparison (screenshot) with other software, where openseespy fully comply.
Here no loads involve soil supports. Cheers

Image
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