Load Case Code: Manual ULS

[XXalessio.amodioXX]

Hi all,

I have 7 load case and It will generate 26 ULS combinations.

I would like to generate the most disantavantages one.

How can I?

[Krzysztof_Wasik]

Hi @XXalessio.amodioXX 

If you are able to define critical combination criteria before design you can use Simplified code combination procedure

criteria can be defined on  Simplified tab

then on Selection tab elements for which critical combination are defined can be chosen

It is difficult to choose critical combination manually. Different combination can matter for different objects.

Usually we create more combinations than necessary. Critical combinations are determined while design.

If I managed to answer your question(s) press the Accept as Solution button please. This will help other users to find solution(s) much faster. Thank you.

[XXalessio.amodioXX]

Hi,

Thanks for your clear answear.

I am triying to generete ULS+ and SLS+ as you said using the function "Simplified Combination".

But none of that combinations load appear in my model, whilst if I do the same using "Manual Combinations" it works properly. What am I doing wrong?

I enclose a short video.

[Krzysztof_Wasik · Accepted solution]

Hi @XXalessio.amodioXX 

Once you are using "Full automatic combinations" or "Simplified automatic combinations"

you create one load case consisting of all combination created (SLS and ULS). Combinations are not displayed on load case list. Only one "superloadcase" consisting all of them is visible

Created combinations can be controlled in combination table

choosing in graphical results presentation

• ULS  you can see results for each combination individually - select them by case component icon
• ULS+,ULS-,ULS combinations you see in diagrams results envelope (the same view for all ULS+,ULS-,ULS combination)

choosing in results table

• ULS  you can see results for each combination individually 
• ULS+you see maximal results envelope
• ULS-you see minimal and maximal results envelope

Once you are generating combinations with manual combination generate option each combination is saved as separate load case in load case lists

Simplified and full automatic combinations cannot be used for nonlinear structures (manual can be used). This is main reason why those methods creates combinations in different way.

See attached film for structure similar to your example

Combinations

 If I managed to answer your question(s) press the Accept as Solution button please. This will help other users to find solution(s) much faster. Thank you.

[XXalessio.amodioXX]

You were clear as the water many thanks.

[XXalessio.amodioXX]

Hi,

Your explaination was eccellent.

I do have troubles in creating proper ULS cobinations.

I do have in sample, 3 loads : Dead,Live,Snow.

I want Live and Snow cannot be in same load case (e.g. Roof), same for wind load in cases (X+ X- Y+ Y-) they cannot coesist in same load case.

Plus I did not understand plenty the logic of ULS+(-), It sould give me the worste combination possible?

[Krzysztof_Wasik]

Hi @XXalessio.amodioXX 

Each load case type should be defined in separate load case (wind snow live dead). Program is prepared for it

If you use simplified combination you define criteria in simplified tab

In your case you defined creation of combination with maximal and minimal forces for the following conditions

1. reactions (program will create only combinations which results in maximal and minimal values (extreme values) of FZ and FX reaction - other code combinations required by code and created with full automatic option or manual

• Beam internal forces (MY and MZ verified in 15 points -internal bar division)- program additionally to combinations for reactions will create combinations results in extreme values of beam My and Fz force- other combinations required by code will not be created.

Not always extreme forces are the most critical for structure. It is difficult to choose combinations which are critical while  static analysis. Maybe except of deflection.

In most cases the criteria (given in design procedure:stresses, buckling,lateral buckling etc,) are critical. So I would recommend to generate all combinations required by code. Then launch design for (steel RC or foundations), In design process Robot will choose critical combination for each designed element automatically.

ULS- and ULS - are filters used in result tables to display maximal or minimal values generated for all calculated combinations

[XXalessio.amodioXX]

Thanks for the advice.

In the current state (Building permit) I would like to give an overall view of the structure showing maximum reactions for the column (Fz) ,maximum internal moment (ULS) for beams and maximum deflection (SLS) for beams in order to find out if the pre-designed sections are proper.

For  now, i would prefer run simple combination and calculate the maximum moment (Local-per each section type) and max Fx using ULS+.

In future  maybe it is better to run the full combination and design the reinforcement element by element.

What do you think?

[XXalessio.amodioXX]

Hi,

Furthermore the ULS+ continues to change in combination as soon as I change visualization in ULS.

Is it just a graphical issue?

[Krzysztof_Wasik]

Hi @XXalessio.amodioXX 

If you want to have overview of extreme results simple combination will work.

[Krzysztof_Wasik]

Hi @XXalessio.amodioXX 

For ULS+ and ULS- envelope is presented in diagrams and there is no possibility to choose component as it is possible for ULS