This option defines thermal loads acting on structure bars. Open the Thermal Load dialog by clicking 
on the Bar tab in the Load Definition dialog.
You can define a thermal load applied to a structure bar, acting in the X, Y, or X direction of the local bar coordinate system in this dialog.
dTy and dTz values refer to the differences in temperature between the extreme fibers of a cross-section through an element (in the direction of the Y or Z axis of the local coordinate system, respectively). The dTx value (or dT, the 2 symbols are equivalent) denotes uniform temperature distribution (heating or cooling down) of an entire element.
Example:
Load:
1 to 3, dTx =-27
Means that bars 1, 2 and 3 are cooled down in a uniform way by 27° (in the current units set in the Robot).
Load:
4 dTy =30
The difference between the temperature of the upper and the lower surface of the cross-section of bar 4 has a value equal to 30.