Linemesh and DiscretizeMember command

[kolebron]

Hello, everyone. Recently, when I used the Linemesh command and DiscretizeMember command, I found that when I used the linemesh command discrete component for gravity analysis, there seemed to be some problems with the direction of the last element. Please see the picture for details. I show an example here as a verification. Does anyone know what is going on here?





code：

• import openseespy.opensees as ops
  import openseespy.preprocessing.DiscretizeMember as dm
  import opsvis as opsv
  import matplotlib.pyplot as plt
  
  H = 360
  L = 144
  
  ops.wipe()
  ops.model('basic','-ndm',2,'-ndf',3)
  
  ops.node(1,0,0); ops.fix(1,1,1,1)
  ops.node(2,0,L)
  ops.node(3,H,L)
  ops.node(4,H,0); ops.fix(4,1,1,1)
  
  E = 29000
  
  # W14x90
  ops.section('Elastic',1,E,26.5,999)
  ops.beamIntegration('Legendre',1,1,2)
  
  # W18x76
  ops.section('Elastic',2,E,22.3,1330)
  ops.beamIntegration('Legendre',2,2,2)
  
  # Corotational transformation
  ops.geomTransf('Corotational',1)
  
  # Number of elements/member
  Nele = 4
  
  # Columns
  dm.DiscretizeMember(1,2,Nele,'dispBeamColumn',1,1,10,10)
  dm.DiscretizeMember(3,4,Nele,'dispBeamColumn',1,1,30,30)
  # Beam - storing and printing the return values for demonstration
  elems,nodes = dm.DiscretizeMember(2,3,Nele,'dispBeamColumn',2,1,50,20)
  # ops.mesh('line', 2, 2, *[2, 3], 0, 3, 90, 'dispBeamColumn', 1, 1)
  opsv.plot_model()
  plt.figure()
  plt.show()
  print(f'Beam nodes: {nodes}')
  print(f'Beam elements: {elems}')
  ops.timeSeries('Linear', 1)
  # define Load Pattern
  ops.pattern('Plain', 1, 1)
  QdlBeam = 10.
  # elems = [38, 39, 40, 41]
  ops.eleLoad('-ele', *elems, '-type', '-beamUniform', -QdlBeam)
  Tol = 1.0e-4
  NstepGravity = 10
  DGravity = 1. / NstepGravity
  ops.wipeAnalysis()
  ops.constraints('Plain')
  ops.numberer('Plain')
  ops.system('BandGeneral')
  ops.test('EnergyIncr', Tol, 200)
  ops.algorithm('KrylovNewton')
  ops.integrator('LoadControl', DGravity)
  ops.analysis('Static')
  ops.analyze(NstepGravity)
  
  opsv.plot_supports_and_loads_2d()
  plt.show()
  sfac = 1

[mhscott]

What versions of openseespy and opsvis are you using?

[kolebron]

What versions of openseespy and opsvis are you using?

hello, prof. here is the program version I use:
openseespywin-3.4.0.1.1
opsvis-0.96.7

[mhscott]

Upgrade to the latest version of opsvis and try again.

[kolebron]

Upgrade to the latest version of opsvis and try again.

Hey, Professor, after testing, I found that it is not the problem of image display. When you manually reverse the load of the last element of the component divided by the linemesh command, you can get the correct result similar to the discretizemember command.

[mhscott]

Please post an updated script that is consistent with the plots you show. For example, the script has fix 1 1 1 for the supports but plot_model shows pins. I know this is not the issue, but I'm not assured I'm working with the most up to date script.

[kolebron]

Please post an updated script that is consistent with the plots you show. For example, the script has fix 1 1 1 for the supports but plot_model shows pins. I know this is not the issue, but I'm not assured I'm working with the most up to date script.

Only beam members are used to compare the two division methods. If "-QdlBeam" in "ops.eleload ('-ele', 315,'-type','-beamuniform', QdlBeam)" is changed to "QdlBeam", a seemingly reasonable result will be obtained.

• import openseespy.opensees as ops
  import openseespy.preprocessing.DiscretizeMember as dm
  import opsvis as opsv
  import matplotlib.pyplot as plt
  
  H = 360
  L = 144
  
  ops.wipe()
  ops.model('basic','-ndm',2,'-ndf',3)
  
  ops.node(1,0,0)
  ops.node(2,0,L)
  ops.node(3,H,L)
  ops.node(4,H,0)
  ops.fix(1,1,1,0)
  ops.fix(4,1,1,0)
  
  E = 29000
  
  # W14x90
  ops.section('Elastic',1,E,26.5,999)
  ops.beamIntegration('Lobatto',1,1,3)
  
  # W18x76
  ops.section('Elastic',2,E,22.3,1330)
  ops.beamIntegration('Lobatto',2,2,3)
  
  # Corotational transformation
  ops.geomTransf('Corotational',1)
  
  # Number of elements/member
  Nele = 8
  
  
  
  # Columns
  # DiscretizeMember(ndI,ndJ,numEle,eleType,integrTag,transfTag,nodeTag,eleTag)
  dm.DiscretizeMember(1,2,Nele,'forceBeamColumn',1,1,100,100)
  dm.DiscretizeMember(3,4,Nele,'forceBeamColumn',1,1,300,300)
  
  # Beams
  # --------if DiscretizeMember--------
  # elems,nodes = dm.DiscretizeMember(2,3,Nele,'forceBeamColumn',2,1,500,200)
  
  #--------if linemesh--------
  # ("mesh",tag Npts nodes type dofs size eleType transfTag beamIntTag)
  ops.mesh('line', 2, 2, *[2, 3], 1, 3, 45, 'forceBeamColumn', 1, 1)
  
  ops.timeSeries('Linear', 1)
  # define Load Pattern
  ops.pattern('Plain', 1, 1)
  QdlBeam = 20.
  
  #--------if linemesh--------
  elems = [308, 309, 310, 311, 312, 313, 314]
  ops.eleLoad('-ele', *elems, '-type', '-beamUniform', -QdlBeam)
  ops.eleLoad('-ele', 315, '-type', '-beamUniform', -QdlBeam)
  
  # --------if DiscretizeMember--------
  # ops.eleLoad('-ele', *elems, '-type', '-beamUniform', -QdlBeam)
  
  Tol = 1.0e-4
  NstepGravity = 10
  DGravity = 1. / NstepGravity
  ops.wipeAnalysis()
  ops.constraints('Plain')
  ops.numberer('Plain')
  ops.system('BandGeneral')
  ops.test('EnergyIncr', Tol, 200)
  ops.algorithm('KrylovNewton')
  ops.integrator('LoadControl', DGravity)
  ops.analysis('Static')
  ops.analyze(NstepGravity)
  
  sfacN, sfacV, sfacM = 5.e-5, 5.e-5, 5.e-5
  opsv.plot_model(node_supports=True)
  plt.title('model')
  opsv.plot_loads_2d()
  plt.title('load')
  opsv.section_force_diagram_2d('N', sfacN)
  plt.title('Axial force distribution')
  opsv.section_force_diagram_2d('M', sfacM)
  plt.title('Bending moment distribution')
  
  plt.show()
  ops.wipe()