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RE: Light Guage Inspection Questions

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Sandy,

I see that you have not had much response.  So here is my contribution.

I have only had exposure to hydrogen embrittlement on guyed structures.  The steels are improved plow steels, galvanized, high in carbon, and very hard.  The following is from a good corrosion web page:
http://www.clihouston.com/hec.html
If you want to see the figure, you will have to access the web page.

Hydrogen Embrittlement of Steels
One of the most significant limitations of the use of high strength steel components is hydrogen embrittlement cracking (HEC). Hydrogen, in the atomic form, can enter the materials from many sources (1) steel making, (2) welding, (3) corrosion and (4) cathodic protection. It can produce a range of deterioration resulting in reduced ductility to brittle fracture. 
The following figure shows the reduced ductility of steels as the hydrogen content increases. Its effect is particularly severe in steels with hardness values greater than HRC 35. This can cause difficulties with some grades of high strength bolting materials which can range in hardness from HRC 25 to 40. There can be particular concern for embrittlement of as carburized parts which can have surface hardnesses in the range of HRC 45-50. The problem is magnified further if the steel parts are coated with sacrificial coatings (e.g. Zn, Cd) which accelerate hydrogen charging.

Regards,
Harold Sprague, PE
Krawinkler, Luth & Assoc.
4412 W. Eisenhower
Loveland, CO 80537
970-667-2426 voice
970-667-2493 fax
hsprague(--nospam--at)klaalov.com

-----Original Message-----
From:	Sandy Pringle [SMTP:sandyp(--nospam--at)sic-inc.com]
Sent:	Monday, June 15, 1998 7:12 PM
To:	seaoc(--nospam--at)seaoc.org
Subject:	Light Guage Inspection Questions

I am Principal Inspector for a structural inspection firm in Southern
California, I am to inspect an overseas project in a monsoon climate and
moisture will be a significant issue.
Questions have arisen regarding light guage steel framing inspection.  I've
posted a question to the American Galvanizers Association and am still
awaiting an answer. 
 
When assembling a light guage steel framed wall panel, including drilling
and         screwing galvanized metal framing members, is it necessary to
treat the         penetrations with a paint or paste, as with epoxy coated
rebar, to seal the         metal and prevent rust?
 
Do the screw heads need any treatment after they have been installed?  
What if power driven pins or welding is used?  I have the AWS refernces.

What requirements are there for the anchors set in the concrete.    
The Field Guide from the Light Guage Steel Engineers Assoc 2.1.3 refers to
            "popped screw heads"?  What is this condition?

Additionally, the Field Guide 2.1.4 refers to possible problems within 48
hours         of screwed connection installation related to "hydrogen
embrittlement"?  What is        this, what are consequences and how may I
inspect for it?

Plywood is proposed to cover the diaphragms and walls.  Is there any
special            requirement to connect wood elements to the steel
framing for high moisture             conditions?


Thanks for your help and if anyone knows of additional references that
might help, please respond.


R. Sandy Pringle       STRUCTURAL INSPECTION CONSULTANTS Inc. 
sandyp(--nospam--at)sic-inc.com 	 (800)598-1970    Fax(310)376-5294 
http://www.sic-inc.com	 Hermosa Beach & Redondo Beach, CA
      
The trouble with the world is that the stupid are cocksure and the 
intelligent are full of doubt. -Bertrand Russell
   

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