### Nodal forces in non-linear analysis

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### Nodal forces in non-linear analysis#2300

vom ingvast
#2300
Hi
I am new to Z88aurora but have earlier run Z88 v13 with good results.

I use it now for non-linear calculations and have run into a small problem.
I like to calculate the nodal forces for each loadstep and can not figure out how to do that in a structured way.
It does not seem as the program computes the nodal forces, what is the workaround?

/johan

### Re: Nodal forces in non-linear analysis#2301

vom mz15
#2301
Hello ingvast,

from the GUI it is not possible to get the nodal forces, because they are not calculated. A workaround is to create a file with the name "z88nli7.txt" in the project directory. There you have to put the following infomations for example:
4
9 5 -1
9 7 -1
9 8 -1
10 -1 -1

4 ist the number of the following lines
9 is the flag to calculate the nodal force for the node number 5. So you have to do this for all node numbers you are interested in. If you want more than 3 nodes, you have to increase the first number.
The ending 10 explains that die forces will be summed.
Than you get an output file with the name z88ohnl.txt.

### Re: Nodal forces in non-linear analysis#2303

vom ingvast
#2303
Thanks a lot. That works and is pretty straight forward.

I used the file z88sets.txt to find the node numbers, and then just solved again.

Is there any way of calculating the nodal forces after solving?

thanks again and I must say a great program

/johan

### Re: Nodal forces in non-linear analysis#2306

vom wehmann
#2306
Dear Johan,

for calculating the nodal forces there is the procedure described by mz15. The output file z88ohnl.txt contains the nodal forces. The first part of the file repeats z88nli7.txt. Next, every section begins with a header line, for example 9 45 -1 which means that nodal forces (9) of node no. 45 are following. Then for every load step the x-, y- and z-components of the force are written. If you have further questions, don't hesitate to ask!

Best Regards

Christoph Wehmann

### Re: Nodal forces in non-linear analysis#2314

vom ingvast
#2314
Yes, I managed to calculate as described by mz15. However my question was how to do that when the system is already solved.
I have systems that take a few hours to solve but I did not write the z888nli7.txt file before starting the solver. I want to get the forces now without rerunning the solver. That should just take a few seconds so there is lots to gain.
/johan

### Re: Nodal forces in non-linear analysis#2315

vom wehmann
#2315
Dear Johan,

unfortunately, there is no possibility at the moment to run the solver to calculate nodal forces from given nodal displacements. If you want to, you can program a "post-solver" by implementing the formula for the inner forces given on page 155 in the book "Finite Elemente Analyse für Ingenieure" (4th edition). This edition is written in german, but there will come up an english edition in the near future. But I think, programing such a post-solver will take more than a few hours and therefore, the best will be to rerun the solver.

Best Regards

Christoph Wehmann

### Re: Nodal forces in non-linear analysis#2317

vom ingvast
#2317
Hi Christof,
thanks for the clarification
Maybe I will program that algorithm. Then I publish it here.
/johan

### Re: Nodal forces in non-linear analysis#2319

vom wehmann
#2319
Dear Johan,

in that case, it would be great if you publish the algorithm here! Thank you!

Best Regards

Christoph Wehmann
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