Load combination including the temperature

[chekre]

The effects of temperature in ACI318-11 are left to the engineer judgment where the load combinations does exclude the effect of T.
When dealing with temperature on a roof slab where temperarure is considered due to the external exposure of the slab, what is the load combination including the temperarure that you use? Using 1.2DL + 1.6LL combined with 1 x T is too conservative since it is unlikely to happen. So it would like what do you do in practise.
Thank you

 

[wannabeSE]

ASCE 7-10 has pushed the self-straining load combinations into the commentary with engineering "judgment" in the verbiage. ASCE 7-05 has 1.2(D + T) + 1.6L + 0.5Lr. It seems reasonable to use 0.5Lr if the roof isn't likely to be fully loaded during temperature extremes. But, I would also probably consider some portion of T with the full roof live load.

Is the bottom of the roof slab exposed to conditioned space?

 

[chekre]

Yes it is.
Personally i am thinking to 1.2DL + 1.0 LL + 1.0 T , to combine it in some non linear analysis in order to reduce the effects of restraint and temperature.

 

[BOCH]

The Eurocode is very clear about combination of temperature with other cases, the attached image is showing a eurocode developed load combination that we've done for one of your project (keep in mind that the factors used in the attached image, highlighted in yellow, are depending on the occupancy of the structure. Reference EC0 for ψ factors and combinations) ..
Yes for ACI and ASCE 7-10 it is kept to the engineering judgment, however you can still take some guidelines from different codes to have an idea.
Cheers ..