What is the maximum unreinforced hole in a steel light pole

[Gasma]

Hi,

We have a light pole 70' feet tall and 30 inch in diameter. I need to make a 2'' hole, is there any rule for what is the maximum hole size without reinforcement that is permited ?

I don't see it in the AASHTO

Thx

 

[centondollar]

AASHTO governs bridge design, not design of poles.

An approximately 21 meter high, 70cm diameter pole sounds unusual to me. What is the wall thickness? What is the loading? Where is the hole to be located: at the root (fixed into a concrete block?) or at the tip (free end) of the pole? A 5cm diameter hole doesn´t seem large at first glance, but you´ll need to provide more information to verify that. Can the pole resist bending and shear (and possibly buckling (stiffness = stiffness at cross-section with hole if you want to be conservative), if loaded axially) at critical sections with a part of its cross-section removed?

 

[bridgebuster]

Check the AASHTO Specifications for "Sign Structures and Luminaires". It has provisions for hand holes. 2" in a 30" diameter hole doesn't seem excessive. You could also check DOT standard sheets to see what individual states do.

 

[BridgeSmith]

The AASHTO sign spec. doesn't have prescribed limits; it's based on the design and fatigue stresses of the pole at the hole location. If the cross section is reduced enough to push the stresses in the pole wall over the design or fatigue stress limits, the section modulus would need to be increased by adding reinforcement.

I just completed a design for our high mast light towers, which will be 80', with a 24" base diameter, and 8" wide unreinforced handholes. Our pole designs are exclusively controlled by the fatigue stress limits, and the stress limits are considerably higher for unreinforced handholes, so with 8" wide holes on an approximately 22" diameter pole (at the handhole location), the fatigue stress ratio (stress limit / applied stress) was considerably better with the handhole unreinforced.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[dik]

Rod... do you have a publication that shows the methodology? I'm curious... thanks, Dik

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Do you feel any better?

-Dik

 

[BridgeSmith]

Rod... do you have a publication that shows the methodology? I'm curious... thanks, Dik

Not really, other than what's in the AASHTO sign spec. We use the analysis methods, tools, and design limits in the spec, along with the calculated (net) section properties, to design poles.

Rod Smith, P.E., The artist formerly known as HotRod10