Force vs Disp Plot

[grx]

I proposed to get the force versus displacement of the load node. I tried REACtion, Node and DISPlacement,Node by setting FORCe Node,0,-100,0(only applying x direction force). For the REACtion part, I noticed the load node has three values in three dof. What's the meaning of those values? For the Nodal displacement, the load node also has three different values. Does it mean I need to constrain the load node if I want it to move in x direction?
I also try to use BATCh->TPLOT->END->DISP LoadNode 1->SHOW. But I didn't get the F vs D plot as the manual described. Is there something missing in my code?
Otherwise, it seems I set a constant force here. How can I change the force and get the corresponding displacement?
I'm new to FEAP so that I would appreciate it if you can give me some guidance.

[Prof. R.L. Taylor]

Reaction at a node reports values for all degree of freedoms.  If the problem has converged then the residual for all degree-of-freedoms that had FORC apply should be a numerical zero (which due to round-off will not be exactly zero) and the value for all DISP degree of freedom will be the reaction force. 

[Prof. S. Govindjee]

See attached.  A simple example with a point force applied to a 2D plane strain square.  It uses TPLOt.  It generates two files Pld.dis and Pld.rea which contain the displacement of the node where the load is applied and the reaction force at that node.  To generate the plot cross-plot the second column in each file.  If you specify multiple locations with TPLOt, then you will get additional columns in the Pld.* files.

See also the Wiki Entry: http://feap.berkeley.edu/wiki/index.php?title=Tplot#TPLOT

[grx]

See attached.  A simple example with a point force applied to a 2D plane strain square.  It uses TPLOt.  It generates two files Pld.dis and Pld.rea which contain the displacement of the node where the load is applied and the reaction force at that node.  To generate the plot cross-plot the second column in each file.  If you specify multiple locations with TPLOt, then you will get additional columns in the Pld.* files.

See also the Wiki Entry: http://feap.berkeley.edu/wiki/index.php?title=Tplot#TPLOT

Thank you for your guidance. It helped a lot. But I'm a little confused about why those valued are written like 1.d0. What's the meaning of d0?
And can I delete TANG,,1 if I only want to get the plot?

[Prof. S. Govindjee]

1.d0 mean 1 to double  precision.  1.e0 or 1.0 or just 1 would work too.  I just wanted to differentiate what was an integer and what was not an integer.

You definitely need the TANG,,1 as you have to solve the problem to determine the load deflection curve.  TANG,,1 is equivalent to using the three commands FORM then TANG then SOLVe.

[grx]

1.d0 mean 1 to double  precision.  1.e0 or 1.0 or just 1 would work too.  I just wanted to differentiate what was an integer and what was not an integer.

You definitely need the TANG,,1 as you have to solve the problem to determine the load deflection curve.  TANG,,1 is equivalent to using the three commands FORM then TANG then SOLVe.

Thank you for your patience.
I can get those two .rea and .dis files by modifying my code. But the second columns of both file are zero. Could you please check my code?
I applied 100 Force to node 52 in -x direction. And I want to get F vs D of the node 52.

[Prof. R.L. Taylor]

You have set node 52 to have a specified displacement in the x- direction, not a force. 
Secondly, you have an extra "," in the set of the tplot variables.

NOTE: FEAP stores all nodal values between 1 and the maximum you specify for a COOR, thus your problem says it has 80 nodes.  It does not matter for small problems, however, as the problem size gets bigger it may.

I suggest you look at a plot of the problem you are solving it looks strange to me for a frame problem.

I changed the loading to displacement controlled -- probably much too big but you can change.  (file attached)

[grx]

You have set node 52 to have a specified displacement in the x- direction, not a force. 
Secondly, you have an extra "," in the set of the tplot variables.

NOTE: FEAP stores all nodal values between 1 and the maximum you specify for a COOR, thus your problem says it has 80 nodes.  It does not matter for small problems, however, as the problem size gets bigger it may.

I suggest you look at a plot of the problem you are solving it looks strange to me for a frame problem.

I changed the loading to displacement controlled -- probably much too big but you can change.  (file attached)

Thank you for your reply.
Somehow I can't run the file you attached. I rewritten the code for another structure and it worked. However, there's some difference between the output data and the experimental result. The F vs D plot based on the output data is always a linear straight line. However, I'm expecting to see a curve which becomes a flatter line after some point.

[Prof. R.L. Taylor]

Your input file uses a linear elastic, small strain model which means the displacement is linearly related to the force.  You need to get help from your supervisor to learn what needs to be added to the formulation to model the experimental results.