Application of thermal load on a slab

[Anonymous]

Hello, I am designing a railway slab which is posed on the deck of a super rigid bridge. 

Among all the loads applied, 4 thermal loads are applied to this slab. 

1. Uniform variation of temperature +25°C on the whole slab

2. Uniform variation of temperature -25°C on the whole slab.

3. Heat gradient +80°C/m

4. Heat gradient -80°C/m

I would like to know how to fill the definition window of the thermal load for each loading case above. In fact, I have filled this window as follows: 

                   1st case:                                                                    2nd case

                       

                3rd case:                                                                    4th case

                 

I would like to especially know the definition of thermal grandient  (case 3 and 4) because these two thermal loading cases are dominating in my project. On knowing that the thickness of my slab is 20 cm, I filled the window with 80 and -80. Is it correct? or it is necessary to fill with a value 80*0.2=16 and (- 80) *0.2=-16 as the heat gradient?

Thank you in advance.

Yan

[Rafal.Gaweda · Accepted solution]

I would like to especially know the definition of thermal grandient  (case 3 and 4) because these two thermal loading cases are dominating in my project. On knowing that the thickness of my slab is 20 cm, I filled the window with 80 and -80. Is it correct? or it is necessary to fill with a value 80*0.2=16 and (- 80) *0.2=-16 as the heat gradient?

This is correct :   value 80*0.2=16 and (- 80) *0.2=-16 as the heat gradient

(in this case you assume initial temp = 0) Full explanation here:

http://forums.autodesk.com/t5/Autodesk-Robot-Structural/Thermal-Load/td-p/3806569

Case 1 and 2 are correct if you assume initial temp = 0