Sensitivity of the section area

[yecry]

Hi,

We can calculate the sensitivity of the material by using this available example:
http://opensees.berkeley.edu/wiki/index ... excitation

In order to obtain the sensitivity of the section area to the response, eg. area (say A) to the displacement (say disp); I use a elastic section to instead of section 3 (which is defined as a fiber section in the available example). The result of sensitivity of area (say A) is always 0 in this time history analysis. The results of sensitivities of other parameters (eg. fc) are available. No warning or error occurs.

The code I changed to calculate the sensitivity of the section area to the displacement is as following:

# ---------------------------------------------------------------------------------------------------------
#define the beam as the elastic section
section Elastic 3 $E $A $Iz $Iy

# define the element 7 [Beams]
# Columns tag ndI ndJ nPts secID transf
element dispBeamColumnWithSensitivity 7 2 5 $nP 3 1

#add the sensitivity of A
parameter 1 -element 7 A

#record the sensitivity of A to displacement
recorder Node -file sensA.txt -time -node 6 -dof 1 "sensitivity 1"
# ---------------------------------------------------------------------------------------------------------

What I did then to try to solve this problem:
1) I used the E or I to run this file, but the results of this two runs were 0 as well.
2) When I use the fiber section commands to calculate the sensitivity of section depth, base or cover, it seems cannot recognize these fiber section commands.
3) It is possible to calculate the section area/depth/base analysis when the lateral static load are applied instead of the ground motion.

Question:
What should I do to modify the posted commands if I want to perform the section area/depth/base sensitivity analysis? Thanks in advance!