How Sofistik interpret nonliear temperature on circular section?

I have a circular section with D=1000 mm The nonlinear temperature is shown in the pic

I assume that the nonlinear temperature on the section will be like the red portion in the pic

I can calculate the equivalent axial force and moment based on the equation in Sofiload manual:

Hand calculation:

Axial force N=2061.7kN, moment=557.8kNxm

While Sofistik give me,
Axial force N=793.3kN, moment=313.2kNxm.

Teddy dats are attached.
Nonl Temp on Circular Section.dat (83 Bytes)
Aqua.dat (252 Bytes)
SofimshC.dat (175 Bytes)
SofiLoad.dat (624 Bytes)
ASE.dat (146 Bytes)