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Re: Precast concrete barrier wall (spandrel) design againstvehicle  impact load.

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I suppose you might have to use energy equations to do this design "precisely," but I think a simple "equivalent static" analysis is appropriate.  He seems to have doubled the moment.  Simple span moment for a single concentrated load at midspan is Pl/4, whereas he has used Pl/2.  This might help.

Ralph Hueston Kratz, S.E.
Richmond CA USA

In a message dated 2/27/06 2:22:23 PM, rgarner(--nospam--at)moffattnichol.com writes:
Let's see if my memory is right.  Yield line theory applies to two way slabs, with the yield lines projecting at approximate 45 degree lines from the corners to the centerline of the slab.  I think you have to consider one way slab action.  If you are considering impact from a moving vehicle, you can consider that some of the energy of the vehicle is expended in just overcoming the inertia of the barrier wall.  I think you have to use energy equations to do this accurately.
 
From: Wontae Kim [mailto:Wontae.Kim(--nospam--at)unistresscorp.com]
Sent: Monday, February 27, 2006 2:07 PM
To: seaint(--nospam--at)seaint.org.
Subject: Precast concrete barrier wall (spandrel) design againstvehicle impact load.

 
Hi!
 
I would like to hear your opinions about precast concrete barrier wall design.
 
Here are conditions:
           H=50in, L=60ft (between two columns), THK=12in
           Car impact load= 10kips (Factored) in the mid of section
 (25in from the bottom of barrier wall.)
Both top and bottom of the wall are free end (horizontal sides).
Only vertical sides at both ends can have connections to column:
 
           Bearing and tieback connections are possible only to the column at both ends.
When I assumed this wall as one-way action wall like a simple beam, its bending moment is 10k*30ft, which
 requires unrealistically high flexural reinforcement. (Is this high reinf ratio correct?)
 
I heard some books and engineers use yield line theory.
According to this theory, where and how can I assume the yield line locations?
If I assume three vertical yield lines, this may bring the same results as one-way action wall.
 
How can I design this concrete barrier wall with respect to the car impact load?
 
 
 
Thanks for your advice!
 
 
****Wontae Kim****
Unistress Corp.
Pittsfield, MA 01201
(Tel) 413-629-2031
(Fax) 413-499-0824

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