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taking different loads together?

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I (we) have been asked to make a 3D calculation model. I only have to model the geometry, the loads, combinations,.... The actual calculation and the optimalisation will be done by someone else.

The project consists of :

- 2 buildings with each 4 office levels + 8 levels with 4 appartment on each level 

- "bridge" between them

Each building has a center concrete core, concrete outer/inter load-bearing walls and concrete floor slabs.

(footprint of the building is +- 22m x 22m)

The model itself isn't very difficult.


But I have a question about combining the variabel loads on the floor.

Each level has 4 "units" (office or appartement) and there are 12 levels.

Should I make

1) 1 loadcase for each unit? So I have 12 x 4 loadcases = 48 loadcases of variabel loads to make combinations of?

2) or 1 loadcase for each level = 12 loadcases to combine?

3) of 1 loadcase for each unit (all levels together) = 4 loadcases


I would think in theory, I need to make 48 loadcases. But this will give a lot of combinations.

How would you handel this?

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I would probably make 48 load cases which would be arranged in load groups as per imposed load categories (for example, A category for apartments and B for offices) and then I would make the software to produce critical load combinations taking each load group as leading imposed action (for examples all A category loads would be the leading ones and all B category loads accompanying), although I would require the software to ignore load cases in particular load group which are favorable for the effect under consideration. 



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First, some extra info:

*calculations should be made according the eurocodes

*calculations are made by Scia Engineer software


Some levels have 6 appartements.

I made 1 loadcase for each unit.

In total I have 

- 54 loadcases (var load) for the floors + 1 var loadcase for the roof (split in office, appartement and roof cases)

- snowload on the roof

- windload for each direction

- 1 fixed loadcase for fixed floor and roof load


In theory, every loadcase (= load for a unit) should/could be combined with any other loadcase.

For a normal (linear) calculation, this isn't a big problem. The calculation doesn't take to long.


But the building has also masonry wall (load bearing). I should model these as non-lineair "only pressure" wall-panels in the scia software.

For this I should also make non-lineair load combinations. I have done this before: explode the lineair combinations (ULS and SLS) and use these exploded combis for the non-lineair calculation-combination. But this was for a smaller project.

For this project, when I want to explode the lineair combinations, I got the message I will have some 100.000 combinations. And this will take a very long time the create the combination. It still was'nt ready after 30 minutes. So, When I should start a non-lineair calculation with all these combiniations, I will take forever to calculate.


Is there something I can do to speed this up?

Taking loadcases together? Lets say: taking together all "unit xx1" loadcases for each level. Were xx is the levelnumber.

For the creation of the non-lineair combinations, I could also illiminate the non-critical combis but then I have to look for these.


Anyone have suggestions?

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