...girder modelled by shell elements

[SKJoe]

Hi,

i am modelling simply suppoted girder (it is not main goal, it is only in order to verify use
of shell element for another problem )by shell elements shell 181 in ansys subjected to uniform pressure on the top flange 5N/mm2( cross-cection is an I-shape, thickness of this flanges and web is 50mm, width of web is 700mm, width of flanges 200mm,lenght of girder is 3800mm )

i want to get normal stesses in the bottom flange (bottom layer of shell - along the path), but there is level of stress 177N/mm2,analytical solution is 188N/mm2...i realy dont know what to say - am i overworked, or stupid ?

there are some discontinuity in normal stesses on the interface flange - web as well - probably effect of shear locking, but how to obtain correct value (it is needed for the another problem...)

i hope there will be someone able to help me...thanx

 

[alleak]

I couldn't imagine what is your model.would you describe it more clear.is it a beam.what do you mean from flange

 

[SKJoe]

yes, it is a beam, could you imagine an I-shape cross section ? flange means bottom sheet, which is perpendicular welded to web...

 

[SKJoe]

in the help file for shell181 is also said :

"Bilinear elements, when fully integrated, are too stiff in in-plane bending.SHELL181 uses the method of incompatible modes to enhance the accuracy in bending-dominated problems."

it seems this increase of accuracy is not enough...

i also dont know what this expression "Bilinear elements" means...