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RE: Deletion of ASTM F1642 Airblast Testing from USGS Specs

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David,
This is a timely question.  The UFGS revision was kind of an interim.  There is a more well crafted revision in the works.  There has been no small amount of confusion with this.  Some Corps districts (like Louisville) have developed their own specification which has enhanced the ambiguity. 
 
I am getting a schedule of the next sanctioned revision of the specification and I will post it.  Keep in mind that the UFGS is a guide specification.  If you want to offer the airblast test per ASTM F1642, that is your call as the designer.  If you do, I would encourage you to add more guidance about the airblast test if you feel it to be appropriate.  They are supposed to be clear in the connection requirements.  If the submittal is in doubt, whomever is doing the compliance determination should reject it. 

Regards, Harold Sprague






Subject: Deletion of ASTM F1642 Airblast Testing from USGS Specs
Date: Thu, 4 Dec 2008 10:16:35 -0500
From: David.Dickey(--nospam--at)masonandhanger.com
To: seaint(--nospam--at)seaint.org


The option to use Airblast test results per ASTM F1642 to verify a window’s adequacy for meeting UFC 4-010-01 antiterrorism requirements has been deleted from the latest versions of USGS window guide specifications.  The only option now is to perform a design analysis with calculations.  Why has the airblast paragraph been deleted?

 

There were many problems associated with using the airblast tests to approve a window system.  For example, the size of the tested window had to be within +10%/-25% of the window size used on the project, or additional testing was required.  The tested charge weight and standoff rarely matched project requirements.  The pressure may have met the spec but impulse did not.  Often the test results were not clear as to what type of connections to the supporting structure and their spacings were used.  Clearing effects occur around a test apparatus that do not occur on a window installed in an actual building wall. 

 

Were any of these problems the reason that the airblast option was eliminated, or is there a different reason?

 

Thanks,

David Dickey, PE

Lexington, KY

 

 



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