Hello, i had modeled a steel beam of dimensions as Length = 4000 mm, Cross section = 250 x 150 mm, E=2E+11 N/m^2, Density = 7850 kg/m^3.
Boundary conditions:
Left support is applied using Remote Displacement option with X=Y=Z= 0 & RX=RY = 0 and RZ = Free
Right support is applied using Displacement option with X=Z= Free & Y=0
Please note, beam is along X-Axis.
There is a difference of theoretical and FEM results. First two bending natural frequencies are almost comparable as you can see below while in higher modes like 3rd and 4th there is significant difference in results.
Mode Theoretical FEM Results Error Diff.
1 21.46 21.458 0.002
2 85.84 85.273 0.568
3 193.14 189.84 3.303
4 343.37 332.68 10.686
I am confused, how it would be done, so that i can get all FE results according to theoretical values? I guess there is something wrong with the boundary condition.
With same boundary conditions, if a more slender beam is considered like 1044 mm length and 23x5 mm cross section then all theoretical and FEM results comes almost equal for each natural frequency.
Looking forward for the solution if someone could help in this matter.
Thanks
Absolutely a difference between analytical and numerical (FE) result must be existed
In above message the table values are not clear, so now attaching the image file.
you are solving a beam with hinged and roller supports on either ends. One thing you can try by increasing number of elements i.e. number of nodes. So the mode which are disappeared may appear.
Absolutely a difference between analytical and numerical (FE) result must be existed
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