Load Combinations

[crasmussenGKDV6]

I am wondering if their is a way to reduce the number of automatic load definitions created.  I have dead loads, live loads, moving loads, wind loads, snow loads, and seismic loads.  I currently have over 25,000 different definitions of load combinations.  How can I reduce that number and still use the automatic load combinations.

[Artur.Kosakowski · Accepted solution]

Try to group live load cases together as much as possible.

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.

[Anonymous]

I am currently experiencing the same issue. I have a simple two span footbridge with live loads applied to different areas, 4 temperature cases and another 4 loads applied to the handrail. Besides that, I have the permanent loads, one wind case and one snow case.

I wonder If I am creating the groups properly as i still have 6000 combinations (only for ULS!).

My groups are:

LL1 which includes the live loads in the 4 different areas. Set as or(incl).

T1 which are the temperature cases (exluding)

LL2 which is the load on the rail. Also inclusive.

The permanent loads are grouped as (and).

Is there any possible way to get some sort of envolvents for the worst case combination of each group? It could be possible after to load these envolvents into de definitive combination effects.

Thanks! Best regards.

[haider.mumtaz]

Hello @Anonymous 
Kind of stuck here. I am trying to generate load combinations according to ASCE-LRFD for design of steel building but don't know how to proceed? Can someone please show me what is the correct way to generate load combinations so that it is also considered in design?
Previously, only gravity loads are being considered. 

[haider.mumtaz]

Hello @Anonymous 
Kind of stuck here. I am trying to generate load combinations according to ASCE-LRFD for design of steel building but don't know how to proceed? Can someone please show me what is the correct way to generate load combinations so that it is also considered in design?
Previously, only gravity loads are being considered. 

[Simau]

Hi @haider.mumtaz 

Tools>Job preferences>design code>Loads and select your code

To generate combinations

Loads>automatic combinations>

[haider.mumtaz]

Hello @Simau @Artur.Kosakowski 
Thank you so much for replying. It worked in the end. I have three questions.
1. I used ELF(Equivalent Lateral Force Method) procedure to calculate the seismic effects and generate the load combinations. Now, when I am designing my steel structure using the design module it is not considering the earthquake cases. This can be due to two reasons. In any case of ULS, earthquake is not the governing one or when used ELF procedure robot designs only based on dead, wind and live loads? Is my understanding correct?
2. Just came to know that client wants the reactions at the support on which foundations will be designed manually. Now that I need service loads what is the best approach?
Should I generate SLS combinations in Robot structural analysis or do this manually(I have wind loads, dead loads and live loads)?
3. Is the worst case of SLS suitable for designing the foundations? 
Thanks for your kind response. 

[Simau]

1. I used ELF(Equivalent Lateral Force Method) procedure to calculate the seismic effects and generate the load combinations. Now, when I am designing my steel structure using the design module it is not considering the earthquake cases. This can be due to two reasons. In any case of ULS, earthquake is not the governing one or when used ELF procedure robot designs only based on dead, wind and live loads? Is my understanding correct?

If you create correctly automatic combinations, you'll get also comb with earthquake cases. I made a small example and i get all combinations with DL LL Wind  and sismic

 Just came to know that client wants the reactions at the support on which foundations will be designed manually. Now that I need service loads what is the best approach?
Should I generate SLS combinations in Robot structural analysis or do this manually(I have wind loads, dead loads and live loads)?

If you look at the picture above you'll see that SLS combinations are already generated.

Is the worst case of SLS suitable for designing the foundations? 

It depends on the code you select in Job preferences

Example model attached