Hi Mateen Ali
Are you treating vehicles as a static or moving load?
The contribution of vehicle mass to the overall response depends on the mass ratio of the vehicle to the bridge which is usually is very small.
If the vehicle is modelled as a dynamic load, then it will give an impact load to the structure. If the bridge span is short and light, the impact load will affect the dynamic response of the bridge in higher frequency than the natural frequency of the bridge.
I assume that you are reading a time history data of a bridge and conducting FFT to find the natural frequency of the bridge. Because the vehicle is modeled as a moving load, and if the vehicle speed is quite large, it will create 'impact load effect' to the bridge, causing higher frequency response modes that may affect the FFT analysis. Try reading data after the time when the vehicle passed the bridge, in this case the 'impact load effect' already damped and the bridge will vibrate freely in its natural frequency.
Today I have found repetitions of your problem in five questions or discussions. You should stop these repetitions because I do not know where to answer. My answer including the effect on stiffness is given at your discussion https://www.researchgate.net/post/Effect_of_mass_on_the_frequency
Do you still remember all your many postings?
- Badges
- Science topic