Non-Linear SLS Analysis and Design for Concrete Slabs

I am trying to design a basic concrete slab that includes a SLS Non-Linear Analysis task as well. My question is regarding the the design results that are stored in different design cases. Based on what I could understand from the various manuals this is what I have been doing.

  1. The linear load combinations for ULS are run in ASE.
  2. Task Design Parameters for Area Elements: Design Parameters for Area elements are set with min and max reinforcement. Crack width is specified
  3. Task Design ULS for Area elements: Reinforcement is calculated for ULS design combinations (Type D) and reinforcement results are stored in Design Case 1. (This already includes the minimum reinforcement from Step 1)
  4. Task Non-Linear Analysis in SLS: Using the base reinforcement of Design Case 1 (in step 3 above), a non linear analysis for a Quasi Permanent Combination (Type P) is carried out with appropriate creep and shrinkage factors. Any reinforcement, if increased to adjust stress levels is stored in Design Case 99. I am assuming that reinforcement values given here are the reinforcements combining that from both Step 3 and Step 4.
  5. Task Design SLS for Area Elements: The Non Linear Load combination from Step 4 is used for this task and the base design case or minimum design case is 99 from Step 4 above. The results from this design task are then stored in Design Case 2.
  6. Reinforcement values are then read in WinGraf for Design Case 2 as final values.

I would like to know if the procedure is correct or do I still need to insert this following code at the end for enveloping all the design cases.

+PROG BEMESS urs:52.1
CTRL LCRI 1,2,99
LCR 11

I hope, I have been able to explain my question properly.

Thanks in advance,

@JFH Do you have any suggestions?

Hi pinaki18,

your explanations are correct. You don’t need to envelope all the design cases in the end. Although I would first run Task Design SLS Area elements and after that Task Non-linear Analysis in SLS. Reinforcement distribution 99 is usually only stored for graphical checks, unless steel stresses are checked with CHKR. So I would use it as the “final” reinforcement distribution and calculate the nonlinear analysis with the reinforcement distribution 2 from the SLS design. Nevertheless, it is also possible the other way round.

By the way: There’s a new tutorial available on our website, that deals with the analysis of cracked slabs and might be helpful as well:

Best regards,



I had a chance to go through the tutorial mentioned by you which is well explained and quite detailed. However I have a conceptual question. As per the tutorial one must

  1. Do a ULS design using “Uncracked” forces and store the reinforcement in DC10.
  2. Do a SLS Design using “Uncracked” forces and DC10 and store it in DC15.
  3. Do a Cracked SLS Analysis using DC15 and store in DC35.

I would like to ask if the following steps still makes sense.

  1. Do a ULS design using “Uncracked” forces and store the reinforcement in DC10.
  2. Do a Cracked SLS Analysis using DC10 and store in DC35.
  3. Do a SLS Design using “Cracked” forces (from 2) and DC35 and store it in DC15.

And then read DC 15 as the final value.

I would assume that doing first the non-linear cracked analysis will give us the “actual” stress values which should then be used for doing the SLS design.

Thanks again for your answers.



The tutorial order makes more sense.

  1. ULS uncracked:
    Start off with this to get a quick estimate of actual reinforcement content.
    The design calculations are straightforward and the assumed reinforcement does not influence results (too much).
  2. SLS uncracked:
    Iterative design calculations and the result is more heavily affected by the assumed reinforcement content.
    The sectional forces are previously calculated in a linear analysis and the design reinforcement is calculated using ULS uncracked as a base line/first guess.
    Under the hood the design calculations are iterative, since reinforcement content is an input to crack width calculations
  3. SLS cracked
    The entire analysis is non-linear and you want the first guess of the reinforcement content to be as correct as possible.
    The calculations are theoretically more correct/complete, since you are considering the stiffness variations due to reinforcement content when calculating sectional forces/stresses.

Basically you want a good first guess for reinforcement content in SLS design either way, but:

  • SLS uncracked:
    System calculation and design calculation are separate processes and only the design calculation is dependent on reinforcement content.
  • SLS cracked:
    All calculations are non-linear and dependant on reinforcement content
    → More time consuming, i.e. you want a better starting guess here.

Thanks for the detailed explanation!