Friday, May 23, 2008

RE: Was embedded timber post (80 Tons trailer impact on Structure)

If both the missile and the target behave in a linear fashion, the problem is relatively easy.  But when it comes to vehicular impact barriers, the math is incredibly complex.  The forcing function creating the demand is nonlinear because the vehicle is a deformable body and the the barrier itself and in the soil create a nonlinear response.  The Department of State has performed a lot of studies and has developed a rating system predicated on testing.  Barriers are rated with a ranking predicated by K.  They vary the velocity at impact. 
 
The old 10k at 18" came from the old BOCA code for parking garage barriers.  It was adopted in the UBC after a tragic accident in a California parking garage in the early 1990's.  It is not a definitive requirement regarding vehicular impact, and it does not accurately capture the real response.  It is better than nothing. 

Regards,
Harold Sprague


Date: Fri, 23 May 2008 11:12:36 -0700
From: d.topete73@gmail.com
To: seaint@seaint.org
Subject: Re: Was embedded timber post (80 Tons trailer impact on Structure)

Oh yeah, I forgot the other 3 zeros...  i had seen Joe's post about the embedded posts at K-rails to resist the 10kip force at 30" above road surface.  Thank you for checking my "fuzzy math."

On Fri, May 23, 2008 at 10:41 AM, Casey K. Hemmatyar <khemmatyar@gmail.com> wrote:
Great David;
 
Just to refresh your memory, it  has a 28,340 k-ft of Force but not Energy.
Applying Work-Kinetic Energy Theorem:
Wnet = Kf – Ki= ½*mv^2
W [Work]= ½*mv^2
m=mass; kg
v= Speed; meter/sec
W=(½) (80*1016)*(70*1.609*1000/3600)^2=39,779,275 Joules (This is "Work")
 
1 Joule≈0.73756 ft-lb
F [Force]=39,779,275*0.73756/1000=29,340 ft-k
 
Regards
Casey K. Hemmatyar, SE
___________________________________________________________ 
From: David Topete [mailto:d.topete73@gmail.com]
Sent: Friday, May 23, 2008 8:59 AM
To: SEAINT
Subject: Was embedded timber post
 
http://news.enquirer.com/apps/pbcs.dll/article?AID=/20080521/NEWS01/805210387
 
If my calcs are correct, an 80-ton trailer at 70 mph creates 26,200 ft-kips of energy.  (F = 1/2 mv^2 if my math serves me correctly... )  That is about 10k at 30".  Or am i way off?

--
David Topete, SE



--
David Topete, SE

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