Traffic signal steel structure 2

[Ramezsayed EIT]

i am designing a traffic signal steel structure ( Pole height = 26 ft and the cantliever is 12 ft)

the client is concerned about the vibration since they will install cameras on those cantlievers


I am not sure what are the procedures to design such thing ? can anyone provide me an example or specific references

 

[r13]

I see everywhere the cameras are mounted on top of the pole without problem (been issued a few tickets for photo imposed section, real nice shot I guess the camera itself have self-balance function. Check the manufacturer for that aspect, and the client for criteria other than strength concerns.

 

[dauwerda]

Take a look at AASHTO's, "LRFD Specifications for Structural Supports for Highway Signs, Luminaires, and Traffic Signals, 1st Edition"
I believe it gives some information on vortex shedding issues that cause vibration.

https://store.transportation.org/Item/CollectionDetail?ID=144

 

[STrctPono]

When you say you are responsible for designing the traffic signal steel structure, are you sure you mean that you are not responsible for laying out the arrangement for the traffic signal structure (height, length, signal head arrangement, plus designing the foundation?) It is not typical for consultants with the DOT to design the steel structure itself. This is usually left to the traffic signal structure manufacturer.... think someone like Ameron Pole. It is normally your responsibility to provide them with all the loading parameters related to your specific wind criteria. Also, don't reinvent the wheel, most DOT's will have standard details for different types of structures with varying lengths and signal head arrangement. 26ft is pretty tall. Is there a luminaire arm above the traffic signal arm? Also, 12ft is relatively short for the cantilever arm so I wouldn't think that galloping or vortex shedding would cause a lot of vibration. FL does have some pretty significant wind loads though.

Follow dauwerda's advice. You are going to need to pick up a copy of AASHTO for this. If your state DOT has approved the 1st edition LRFD, then you are going to want to look at chapter 10, 10.4.3 - Vibration for the discussion on this. Unfortunately, it may not answer your question entirely.

 

[Ramezsayed EIT]

I may have explained this in a wrong way (to be honest I did not know what exactly needs to be done )

It is actually a CCTV Camera pole with double arm (Height is 26ft and each arm is 12ft)

when the client did performance test on the pole itself the vibration was too much on the arms and the camera was shaking. the deflection after applying wind pressure was too much as well compared to other poles performance tests