i am recording the vibrations from accelerometer while vehicles are passing from the bridge. i recorded the vibrations produced from vehicles. now the problem is how can i address the effect of vehicle mass on the fundamental frequency. how can i find the solution of this problem. the frequency is increasing when vehicle is present. but its agaist the physics because when mass increase the frequency decrease because they are inversely propotional to each other. the frequency is decreasing when vehicle is not present at the bridge. so this is the actual problem i am facing right now for my research. is it possible to find natural frequency while vehicle is present on the bridge or is there any way to find natural frequency. i read your suggestion about find the frequency when vehicel leave the bridge it sounds valid but is there any other method to address this problem
in case of bridge there is no tension developed in the bridge so tell me why frequency is increasing
Might it happen that the two portions of the bridge (ahead of the vehicle, behind the vehicle) start vibrating as if they were separate bodies?
(just a naive remark, though)
The researcher has asked the same question already on March 1, 2021and I have given a detailed answer of moving contribution to mass and stiffness already at https://www.researchgate.net/post/Effect_of_mass_on_the_frequency
This year the researcher has asked the same in slightly different form already 6 times. I hope that this will stop because a discussion could take place if the researcher participates instead of starting the discussion over and over again.
with due respect Manfred Staat you can ignore if you finding again and again if you dont want to add answer and i think there is no limit for anyone to post any question for once or twice.
Dear Mr. Faran Ali, you are free to start the same discussion as often as you like. But then you separate the contributors and the contributions. Your question is now discussed in already 6 places with different participants who each discusses without reflecting what has been said in the other places. Is this what you want to achieve?
i want answer to my problem and it is more likely to get more answers. but my intention was not that because i was not recieving answers so thats why i posted again and again to get answers and i think its not a bad thing for exploring the researchers
We are not answering to be explored. The community wants to learn from questions and (!) answers. The quality - not the number - of answers and discussions matters. Your strategy hinders the exchange between the discussing scientists.
Dear Faran,
More information is required how you measure the natural frequency of the bridge in both cases.
I am assuming, when vehicle is moving you record the acceleration data then take FFT of it an identify the natural frequency. If this is the case, then what is the speed of the vehicle? Is it constant or changing?
How about the case when there is no vehicle? How do you excite the bridge?
If you explain those then it may be possible identify the discrepancy between both results.
Ender Cigeroglu Sir i am recording the vibrations by smart phone throu android application. accelerometer in installed in the smartphone so i am using that. i am recording vibrations at the mid span of the bridge. after taking the vibrations i am processing the data in matlab fo this i am applying windowed fourier transform with 30 windows
Dear Faran,
You did not answer the question I've asked. What is the excitation you have applied for both cases? It seems like my assumption is correct. Moving vehicle is the source of excitation for on of the cases. For that case, what is the speed of the vehicle? This information is important. Is there any other car moving on the bridge or stationary on the bridge?
For the other case, i.e. when there is no vehicle on the bridge, how do you excite the bridge? Are there any other cars stationary on the bridge?
These questions need to be answered correctly in order to comment on the question? Unfortunately, you've only mentioned about how data is collected and processed (it can be discussed later), but no information regarding these questions is given.
Ender Cigeroglu sorry for that
actually the spped of vehicle is not constant it is normally passing vehicle at the bridge i think from 50 to 60 km/h approximately. because the idea of this study is to use normal traffic condition rather using a model vehicle. so the speed, mass, suspension properties and loading in the vehicle is not constant its varrying with vehicle to vehicle. i think thats why i am not able to calculate actual frequency of the bridge. but i have to find one value of the frequency from the data by keeping in mind these factors. when there is no heavy vehicle on the bridge the vehicle dont vibrate prominently its a normal thing. so for excitation of the bridge i am considering random traffic and specifically heavy truck. heavy truk produce prominent vibartions while passing the span. so the problem is that i am not well aware with the factor for effect of vehicle mass to the fundamental frequency
Dear Faran,
Your approach is not correct. You need to arrange testing in such a way that you can control what is going on. Vibrations for a moving vehicle occur at frequencies related to the vehicle speed and damped natural frequencies of the bridge. You need to differentiate these from each other to identify the damped natural frequency. To identify and eliminate the frequency related to speed of the vehicle, you need to know the vehicle speed. As far as I understood from your explanation you do not have a way of exciting the bridge. In both cases, the excitation is due to moving vehicle. Also you cannot control the vehicles on the bridge during these two tests. I would suggest you to do the test at specific time (late night) with a vehicle which you can make sure that the speed is constant (hire a vehicle and let someone drive it with a constant speed. you can repeat the test with different constant speeds.). Late night will also eliminate unknown vehicles present on the bridge, which will eliminate all of the problems.
- Badges
- Science topic