Temperature gradients

[Luciano Jacinto]

Hello,
I have a question regarding temperature gradient loads.
For example, consider a doble-fixed beam with a rectangular cross-section 0.20*0.60, and a “C25/30” concrete material. According to NextFEM database E = 31.476 GPa, alphaT = 0.00001.
The beam (see Attached NXF file) is subjected to two thermal loads:
– uniform gradient of 15ºC (load case “vut”)
– linear gradient in y-local direction of 10ºC (load case “vdt”)
The first load case generates an axial force of:
N = (10^-5)(15)(31.476*10^6)(0.20*0.60) = 566.568 kN.
NextFEM gives the same result (although compression).
Regarding the linear gradient, it generates the following moment:
Mz = (10^-5)(10/0.60)(31.476*10^6)(0.20*0.60^3/12) = 18.8856 kNm.
NextFEM gives Mz = -56.657 kNm, which is much different.
Any help will be greatly appreciated.
Thanks for the free basic version of the program.
Kind regards,
Luciano Jacinto
(PS: Thermal loads in the model were assigned via GUI, because apparently there is no API method to add thermal loads via Python, which I would prefer. Do you consider implementing this method in the future?)

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[Luciano Jacinto]

In the case of uniform gradient the result given by NextFEM (compression) is obviously correct. The doubt is only about linear gradient.

[NextFEM Admin]

Dear Luciano,
thanks for your inquiry, please wait the next minor patch for having this solved. We’ll also try to add an API method for adding temperature loads.

Regarding the sign of temperature gradient: starting from a user’s dT, the gradient is applied to the section as to have -dT/2 on the positive Y+ face of the section, and dT/2 on the negative Y- face of the section. We’re evaluating to invert this sign as to have positive temperature on Y+.

[NextFEM Admin]

Dear Luciano,
update is out, please see API https://www.nextfem.it/api/html/M_NextFEMapi_API_addThermalDistLoad.htm

Let us know, regards

[Luciano Jacinto]

Thank you very much for the update. I’ve just tested the method addThermalDistLoad() in several beams (doble-fixed, fixed-supported and continuous) and everything worked as expected, both uniform gradient and linear gradient. Congratulations!

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