Hot Dip Galvanizing Draining/Venting

[ToadJones]

Does anyone know of a good reference for how to detail vent/drain holes for galvanizing closed shapes like HSS or dodecagonal poles?
Is this something I might consult the galvanizer on?

 

[ToadJones]

So, they could seal weld the backing bar to the Base PL prior to welding the pole to the plate?
a 12 sided backing bar might be tough to fab, no?

 

[ToadJones]

Tranny-
since you seem to be knowledgeable in this area, can you answer me this...why do most of the allowable stresses in ASCE 48 go all the way up to yield?
Even in the baseplate design it ASCE 48 appears to let you set fb=FY.

 

[transmissiontowers]

Went to the In-Laws for a long weekend, so couldn't reply till now. The back up bar is tacked to the shaft and BP so when the full pen weld is done from the outside, it penetrates into the back up bar. The backing tape is better if the pole shop can do it right. If the backing bars are used, you seal them with a fillet weld after the BP to shaft weld is done, but you need a big enough hole in the BP for the welder to get his head and arm into.

AFA ASCE 48, I know most of the people on the committee and Utility work is an entire sub-industry unto itself. Although the transfer of electrons from power plant to the home is very necessary, it is not a life threatening function like a bridge that must withstand all natural events or a building which houses human life. The Bridge and building industries pile overloads up and take stress reductions on the materials. In our industry we must balance the need to transfer electricity at a reasonable cost. Can we design the poles and towers to withstand a 10,000 year event? Yes, if you don't mind paying 4 to 10 times the cost you currently pay for electricity.

It mostly stems from the NESC which specifies the minimum overload factors to apply to the loads. Even the hurricane wind loads are for a 50 year MRI storm and we usually apply an OLF on top of that. So we apply loads with OLF and design up to the yield of the material. We recognize that the material will go beyond yield before the structure collapses. Our industry is one of the few that accepts structure failure when the load condition is exceeded. We design them for a 50 year MRI storm and when they fall down in a rare extreme event, we go out and restore the structure or build a temporary one to put the lines back up.

A transmission pole line is a distributed structure that can run for hundreds of miles. An extreme wind event may encompass one or 2 poles out of a 10 mile line and we may lose 1 pole because the wind front does not act on the entire span of conductor which are mostly stranded aluminum and a steel core wire that are up to 2 inches in diameter.

Sorry for the long dissertation but I can't help myself once I get going.

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I have been called "A storehouse of worthless information" many times.