Traffic Load (Ambient traffic) Simulation

[Shz713]

Hi all,

Does anyone know how to simulate ambient traffic/load(any sort of loading which are random in time and space)?

Should I use time history? I'm interested to get response in terms of acceleration and frequencies of vibration.

Peace

 

[robyengIT]

hope it can help

 

[Shz713]

Hi robyengIT,


thanks mate for the link provided but what I meant something else.

I want to simulate ambient loading condition on bridge. Let's say in the field I record the response of bridge via set of sensors for specific duration (7 min). The measured response could be in terms of acceleration, displacement and alike. In my case, I want to mimic such recording in software by placing random load (which resembles traffic loading which are random in time and values) on bridge and recording response at certain location.

I reckon I need to use Time History Analysis, but not sure how to define the function and loading condition. Any suggestion is deeply appreciated.

Cheers

 

[JJIako]

The operational modal analysis is based on unknown input and known output. The latter means that the environmental and operational conditions are not known during testing, and the aim of the test is the accelerations. Secondly, the accelerations (time-series) transformed to spectral densities, in the frequency domain, by Fourier Transform. The latter show the distribution of the acceleration in each frequency. From the latter usually the singular value decomposition matrix generated and the picking method employed (simplest method). In all this procedure you do not know anything about the external excitation.

I suggest you use both mathematical regression and FE modeling to probable capture correlation between frequency and traffic load.

 

[Shz713]

Dear JJIako

Thanks for your critical comment. Surely I will consider that.

I have defined a random function in MATLAB and want to use it as random input for Time History Analysis to record the response of bridge to it in terms of acceleration. Then I will use MATLAB ToolBox/ARTeMIS for signal processing either using Frequency Domain methods (such as Peak Picking and Frequency Domain Decomposition) and Time Domain methods (such as Stochastic Subspace Identification) to extract modal parameters.

 

[JJIako]

The only concern about time history analysis is that the input (random function) introduced as ground vibration in the system. Hard assumption to make e?? Different types of excitation activates different modal frequencies and mode shapes. There is no direct link with ambient.

However, there is Fast Non-linear Analysis available in both Bridge and SAP. The latter is a discrete modal analysis.I have never use it but I probably use it in the near future.

 

[Shz713]

Dear JJIako

as yo mentioned it's quite complicated to simulate such loading condition. I've heard of Fast NL analysis available within CSI software but never used. (Here's the link to how to perform this loading in software

https://wiki.csiamerica.com/display/kb/FNA+application+process)

I'm interested to find out how to relate Fast NL analysis feature to ambient loading.

 

[koukyzala]

Hello, Mohandes2018 I work on the same subject so I need your help to tell me about the procedures you did to define the random process of traffic loads on MATLAB and is it possible to do so with other types of loads like the wind and earthqhake, finally without sensors signal how to simulate such loads, I hope that I find ansewers of my questions on this forum thanks a lot

 

[Shz713]

in the literature, for traffic load simulation you need to make sure it is stochastic, meaning it is random and time-invariant. From This definition and following previous works, you may use randn matlab command to generate gaussian white noise with zero mean and standard deviation of 1. you can do same for any type pf load, since later you can change it in the software. Lets say I want to see how it effects by 40 t truck, then when I apply generated noise in Matlab to CSiBridge, I multiply by an integer to get values around 40 and then run on the bridge to get response.
peace

Shoot for the Moon, even if U miss, U still land among Stars!

 

[koukyzala]

Thanks a lot