Non linear combination with starting case

[Anonymous]

Hello everybody,

i'm trying to understand how the nonlinear combination work with a starting case.

In fact, i have 3 load cases:

   1. "Dead load" (DL) with pretension in the cables (i use temperature variation with tension only members for modeling the cables)

   2. "Wind" (W)

   3. "Temperature variation" (T)

Now i have to make the non linear combinations in ULS and SLS and i'm so confusing beetween two options:

   1. 1.35DL + 1.5W + 0.9T with no starting case

   2. 1.35DL + 1.5W + 0.9T with starting case (DL) (i check the case in "Definition of a starting case for non-linear analyses")

So, which one is correct ? i think the 2nd is right one, but when i use the coefficient 1.35 for DL, i'll multiply the pretension of my cables by 1.35 too, how can i do to maintain the cable pretension value in ULS combination?

Thanks

[Artur.Kosakowski]

My personal choice would be to use cables instead of tension only bars with temperature but if so then I'd try the following:

1. DL1 - temperature + dead load as starting case

2. DL2 - dead load from DL1 that you would like to use ULS load factor for (no temperature load)

3. W

4. T

ULS: 1DL1 + 0.35DL2 + 1.5W + 0.9T + starting case switched on

but in addition I'd compare the results with 

1. DL1 - temperature + dead load as starting case

2. Other loads case being loads 0.35DL2 + 1.5W + 0.9T defined in a single simple load case + starting case switched on

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