ASCE 113 Substation Structure Design Guide 1

[budynek]

thread608-259312

The ASCE website seems to be down. Doen anyone know if there is only one version of this manual (ASCE113 substation structure desing guide) ?

I'm specifically interested in the following comment in this manual: "1/3 increase in the allowable stress for wind loading is not recommended for substation structures..." We're reviewing existing 40 year old structures and wanted to find out when the 1st version of this manual was published and if it contained this recommendations. Many thanks.

 

[transmissiontowers]

I am the vice-chair of this committee and helped the Chair edit the document. The 113 Guide is the first edition. We started the committee because there was nothing in one place to document the design of electrical substation structures. ASCE 10 and ASCE 48 are there for towers and poles, but there was nothing for substations, so we started writing the guide several years ago.

It is very difficult to get 25 structural engineers from all over the country to agree on anything. I'm from the Gulf Coast and really care about hurricanes but I don't have earthquakes. The California members wanted seismic in the guide and didn't care much about wind.

The guide (it is still a guide and not a standard and it probably never will be a standard) has been in circulation for a couple of years and we get a few questions now and then. We need to reform a new revision committee and tackle a revision. I am scheduled to be the Chair this time but have been too busy to get much accomplished.

The 1/3 stress increase statement is for people that still use ASD for steel design. The problem with ASD in designing structures is the NESC code specifies the overloads you must use but the ASD uses unfactored loads and reduces the allowable stress. Trying to use ASD on factored loads is very confusing.

IIRC the 1/3 stress increase when combined with the 0.75 x Fy for weak axis bending allowable will give a safety factor of 1.0 and we didn't feel that was prudent. (I don't do ASD so forgive my poor memory if I am off on the numbers).

ASCE 113 is not alone in not allowing the 1/3 increase. I believe the latest EIA antenna standard does not allow the 1/3 increase when they went with the ASCE 7 wind maps in Rev G.

Sorry for the long winded explanation.

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

 

[msquared48]

"Sorry for the long winded explanation."

Since you are from the Gulf Coast, I'm not surprised.

Mike McCann
MMC Engineering