Harmonic Dynamic Load

Hello,
I am working on applying harmonic dynamic loads in SOFiSTiK and I cannot match the results of a verified benchmark example from SCIA, where the solution is also confirmed by hand calculations.

Model description:

Simply supported beam with overhang, total length 4 m + 1.5 m + 1.5 m.

Cross-section: HEA240, material S235 (EC-EN) and for the simplicity of the example the self weight is 0.01 kN/m³ (else 0).

An electric motor of 500 kg is mounted at the middle of the overhang and the damping ratio is constant and equal to 10%.

Three harmonic load cases at different motor speeds:

Speed Frequency Force Amplitude
800 rpm 13.33 Hz 4.21 kN
1000 rpm 16.67 Hz 6.58 kN
1200 rpm 20.00 Hz 9.47 kN

Despite replicating the model with identical parameters, my displacements in SOFiSTiK do not match the expected results. I suspect the issue may be in how I am defining the harmonic load cases or the dynamic analysis settings (damping, frequency, load type), but I have not been able to identify it.

I am attaching my SOFiSTiK file. Any help or pointers would be very much appreciated.

Thank you!

example 2 2D.dwg (53.3 KB)

example 2 2D.sofistik (488.1 KB)

Hi,

If your problem is that you do not see the damping effects, this is due to your harmonic load definition. Your function covers the entire analysis duration of 5 seconds, which means it is not possible to observe damping effects.

I have changed this to only one period:

FUNC T 0.075 F 1 tmin 0   tmax 0.075

The accelerations are now decreasing: