 # What does "ADDF" do in CSM?

According to CSM → CTRL → ADDF: ADDF =1 add optimization factor to the last one

1. What deos ADDF do in CSM?
2. “last one” of what?

Hello

In order to understand the optimisation workflow in CSM open the TEDDY example

TEDDY > File > Examples > csm >english > optimize > csm20_opti_intro_finalstage.dat

In this example you see that you need different steps to calculate the optimal prestressing forces of the cables. The basic ideas of the optimisation workflow is also described in the CSM manual (chapter 2.10.1 Optimization on ﬁnal system without construction stages).

1. Step: Formfinding with estimated prestressing forces. This run only gives a first estimation of the structural behaviour and does not show any optimised pressing forces.
ASE → SYST PROB TH3 → LC 91
2. Step: Freeze the stiffness the structure (calculated in Step 1) and calculate the structural behaviour due to the four prestressing loadcases 101 → 104 of the cables.
ASE → SYST PROB LINE
3. Step: Optimisation of the prestressing forces so that the vertical displacements (or in other cases the inner forces (e.g. bending moments)) are 0. This CSM run calculates factors for each prestressing load case. These factors are saved within the TEDDY file “csm20_opti_intro_finalstage_csm.dat”.
CSM → Optimisation of Loadcase 91 and (101, 102, 103)
4. Step: Formfinding of the first iteration (geometric nonlinear system → cable elements)
ASE → SYST PROB TH3 → LC 92
5. Step: Optimisation of the prestressing forces in a second CSM run.
CSM → Optimisation of Loadcase 92 and (101, 102, 103)
6. Step: Formfinding of the second, final iteration, consideration of the caluclated factors
ASE → SYST PROB TH3 → LC 93

Now I explained the basics of the optimisation process, you can understand what the comand `CTRL ADDF 1` does.
The steps 3 and 5 calculate factors for the prestressing load cases. Because you have different iteration steps and different primary load cases (ECLC 91 and EQLC 92), you get two sets of factors. If you don’t add the factors of the second CSM run to the first CSM run you only consider the change of the factor between iteration 1 and 2.

Calculated factors after the first csm optimisation run:

Calculated factors after the second csm optimisation run (`CTRL ADDF 0`)

Calculated factors after the second csm optimisation run (`CTRL ADDF 1`)

As you see in the screenshots, the command `CTRL ADDF 1` adds the new factors of the second CSM optimisation run to the factors of the first CSM optimisation run.

I hope you can understand my explanations and now understand how the command works.

Best regards
Frederik Höller
Your SOFiSTiK Support Team

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