Accessing nodal degrees of freedom at previous time step

[hamza]

Dear Feap users,

I have a case with 3 nodal degrees of freedom and 8-noded elements. So the values of the 3x8 nodal degrees of freedom at current time step t_n+1 are stored in the ul array in 3 rows and first 8 columns. Now I want to access the third degree of freedom at all 8 nodes for the previous time step t_n. According to FEAP programmers manual, the dimensions of ul array are ul(ndf,nen,j). In my case ndf=3 and nen=8. The manual also states that when j=1, we have the nodal values at the current time step t_n+1 and when j=2, the ul array stores the increment u_n+1-u_n, the difference between the values at the current and previous time step. So in order to access the values of the third nodal dof at time t_n, I proceed as follows:

do i=1,8
value(i)=ul(3,i)-ul(3,i+nel)
enddo

However, by doing so I get the values of the required dof at the previous iteration of the current time step t_n+1 instead of converged value of the required dof at the previous time step t_n.

Any help here is greatly appreciated.

[Prof. S. Govindjee]

To get the value of the previous converged time step at dof=d and node=n use

Code: [Select]

ul(d,n,1)-ul(d,n,2)


[Prof. R.L. Taylor]

You need to add the include for cdata.h and dimension the ul array as

include 'cdata.h'

real (kind=8) :: ul(ndf,nen,*)

to do the step proposed by Professor Govindjee.  This should give the values you want unless you have somehow modified FEAP in a way that the values in the ul array are not correct.

[hamza]

Thank you very much