• Registered: 19-05-2010
  • Posts: 4

Topic: nan at free dofs

I am trying to Analise a one bay one storey frame fixed at both ends and loaded at storey level by a lateral force.
But every time I am getting the nodal displacements as 0 and 'nan'. The analysis is nonlinear static.
The input file is :

psh.out
job description: Pushover analysis - nonlinear static
#NonLinearStatic nsteps 10 stepLength 0.1  minStepLength 0.1 rtolv 0.001 Psi 0.0 MaxIter 30
NonLinearStatic nsteps 100 renumber 0 nonlinform 1 stepLength 0.1 Psi 0
#LinearStatic nsteps 3
domain 2dBeam
OutputManager tstep_all dofman_all element_all
ndofman 4 nelem 3 ncrossSect 1 nmat 1 nbc 3 nic 0 nltf 1
node 1 coords 3 0. 0. 0. bc 3 1 1 2
node 2 coords 3 0. 0. 3. bc 3 0 0 2 load 1 3
node 3 coords 3 3. 0. 3. bc 3 0 0 2
node 4 coords 3 3. 0. 0. bc 3 1 1 2
Beam2d 1 nodes 2 1 2 mat 1 crossSect 1
Beam2d 2 nodes 2 2 3 mat 1 crossSect 1
Beam2d 3 nodes 2 3 4 mat 1 crossSect 1
SimpleCS 1 thick 1. width 1.
IsoLE 1 d 7.8e3 E 250.0e9 n 0.25 talpha 1.0e-6
BoundaryCondition 1 loadTimeFunction 1 prescribedvalue 0.
BoundaryCondition 2 loadTimeFunction 1 prescribedvalue 0.
NodalLoad 3 loadTimeFunction 1 Components 3 10000. 0. 0. cstype 0
ConstantFunction 1 f(t) 1.0

########################################################


and the output is : (part)
############################################################## www.oofem.org ###
       ####    ####   ######  ######  #    #
     #    #  #    #  #       #       ##  ##
    #    #  #    #  #####   #####   # ## #
   #    #  #    #  #       #       #    #
  #    #  #    #  #       #       #    #   OOFEM ver. 2.0.dev
  ####    ####   #       ######  #    #    Copyright (C) 1994-2009 Borek Patzak
################################################################################


Starting analysis on: Wed May 19 17:13:53 2010

job
Domain type: 2dbeam, default ndofs per node is 3, per side is 0




Output for time  0.000e+00, solution step number 1
Reached load level :                  nan in 1 iterations



DofManager output:
------------------
Node           1 (       1):
  dof 1   d  0.00000000e+00
  dof 2   d  0.00000000e+00
  dof 3   d  0.00000000e+00
Node           2 (       2):
  dof 1   d  nan
  dof 2   d  nan
  dof 3   d  0.00000000e+00
Node           3 (       3):
  dof 1   d  nan
  dof 2   d  nan
  dof 3   d  0.00000000e+00
Node           4 (       4):
  dof 1   d  0.00000000e+00
  dof 2   d  0.00000000e+00
  dof 3   d  0.00000000e+00




Element output:
---------------
beam element 1 :
  local displacements   nan  nan  nan  nan  nan  nan
  local end forces      nan  nan  nan  nan  nan  nan
beam element 2 :
  local displacements   nan  nan  nan  nan  nan  nan
  local end forces      nan  nan  nan  nan  nan  nan
beam element 3 :
  local displacements   nan  nan  nan  nan  nan  nan
  local end forces      nan  nan  nan  nan  nan  nan




    R E A C T I O N S  O U T P U T:
    _______________________________


    Node        1 iDof  1 reaction  nan    [bc-id: 1]
    Node        1 iDof  2 reaction  nan    [bc-id: 1]
    Node        1 iDof  3 reaction  nan    [bc-id: 2]
    Node        2 iDof  3 reaction  nan    [bc-id: 2]
    Node        3 iDof  3 reaction  nan    [bc-id: 2]
    Node        4 iDof  1 reaction  nan    [bc-id: 1]
    Node        4 iDof  2 reaction  nan    [bc-id: 1]
    Node        4 iDof  3 reaction  nan    [bc-id: 2]

User time consumed by solution step 1: 0.004 [s]



Output for time  1.000e+00, solution step number 2
Reached load level :                  nan in 1 iterations



DofManager output:
------------------
Node           1 (       1):
  dof 1   d  0.00000000e+00
  dof 2   d  0.00000000e+00
  dof 3   d  0.00000000e+00
Node           2 (       2):
  dof 1   d  nan
  dof 2   d  nan
  dof 3   d  0.00000000e+00
Node           3 (       3):
  dof 1   d  nan
  dof 2   d  nan
  dof 3   d  0.00000000e+00
Node           4 (       4):
  dof 1   d  0.00000000e+00
  dof 2   d  0.00000000e+00
  dof 3   d  0.00000000e+00




Element output:
---------------
beam element 1 :
  local displacements   nan  nan  nan  nan  nan  nan
  local end forces      nan  nan  nan  nan  nan  nan
beam element 2 :
  local displacements   nan  nan  nan  nan  nan  nan
  local end forces      nan  nan  nan  nan  nan  nan
beam element 3 :
  local displacements   nan  nan  nan  nan  nan  nan
  local end forces      nan  nan  nan  nan  nan  nan




    R E A C T I O N S  O U T P U T:
    _______________________________


    Node        1 iDof  1 reaction  nan    [bc-id: 1]
    Node        1 iDof  2 reaction  nan    [bc-id: 1]
    Node        1 iDof  3 reaction  nan    [bc-id: 2]
    Node        2 iDof  3 reaction  nan    [bc-id: 2]
    Node        3 iDof  3 reaction  nan    [bc-id: 2]
    Node        4 iDof  1 reaction  nan    [bc-id: 1]
    Node        4 iDof  2 reaction  nan    [bc-id: 1]
    Node        4 iDof  3 reaction  nan    [bc-id: 2]

User time consumed by solution step 2: 0.000 [s]



Output for time  2.000e+00, solution step number 3
Reached load level :                  nan in 1 iterations

....
.....
.....
.....
.....
#######################################


If you see, the values at the free dofs are 'nan'. So I am confused about why such thing happening.

Kindly help me.

2 Reply by bp

  • bp
  • Administrator
  • Offline
  • From: Prague, Czech Rep.
  • Registered: 02-03-2007
  • Posts: 1,047

Re: nan at free dofs

Hi,

looks like you are missing some cross section properties: moment of inertia and shear correction factor.
I also do not understand, why are you using nonlinear analysis as the model is linear (element behavior and material).
Anyway, you should add missing cross section properties, so the cross section record should, for example, look like this:

SimpleCS 1 thick 1. width 1. Iy 0.08333333 beamShearCoeff 1.e18

Borek

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