Plastic deflection of reinforced concrete under blast load. 1

[DDH75]

I'm trying to find a decent reference to calculate deflections in a reinforced concrete wall for an ultimate limit state (ie the building is a control room and just needs to remain standing up after the blast for safe shut-down of plant).

I have a bit of an example calc with elastic and plastic deflections in it, but no references or explanations. It includes;

Elastic and plastic resistance factors re and ru
Elastic stiffnes Ke
Elasto-plastic stiffness Kep
I of cracked section
Max elastic displacement Xe
Max plastic displacement Xp
Factors (from unattached tables) to determine vibrating mass participation factors

THEN,

According to ratio of length of blast impulse to structure's natural period, there is another unattached chart to look up which yields a tm value(?) and a value for Xp/Xe. It then concludes that because Xp < 3Xe, there is no cracking in the concrete pressure zone, and no spalling on either the tension or compression side(???!!!)

I am absolutely in the dark, no technical bookstores of note here in my part of the Carribean, and the net hasn't been much use. If you have some idea, a decent reference or a better example calc, I would be most appreciative.

DDH

 

[JWB46]

Hiya,

The best references are:
J.Biggs 'Intro to Structural Dynamics'

and P.D.Smith 'Blast and ballistic loading of structures'

I'm pretty sure these and the refs in Smith will answer all your questions.
Unfortunately both books are out of print (although the state of art hasn't really changed) but you should be able to get a copy from a library.

You could also look at two web sites and work from first principles, if you have the time -

http://www.app1.fema.gov

this has some good free software on blast loading

or look at

http://www.electronic-calculus.com

for the EC-DYABLO program which is for blast analysis of beam-like structures.

Sorry this is not the quick answer you were probably hoping for, but I hope it helps.

Good luck

 

[dbuzz]

Another very good book for blasts, although I think it may also be out of print, is:
Goshcy, B
Design of buildings to withstand abnormal loadings
Butterworths, 1990

I don't have any reference information for the deformation of concrete walls under such loads. I would have thought you would lose some concrete from the tension side though. One of our Clients, an undergroud mining company, had a significant ground movement event that applied a massive surcharge pressure to one wall of a reinforced concrete pit. This resulted in large plastic deformation of the wall and delamination and spalling of much of the concrete on the tension side.

 

[DDH75]

JWB46, found a book by PD Smith and GC Mays &quot;Blast Effects on Buildings&quot;. Very good reference that draws on the experience gained from IRA bombings. It considers a wide variety of &quot;beam cases&quot; and various loadtypes (impulse, quasi-static), although one shortcoming is that it only considers a rectangular section size, and not a T beam. It heavily references the book you mentioned (same author), and also a US Army Technical Manual.

DBUZZ, the reference I found allows you to specify whether or not spalling on the tension side is allowed (depending on whether it is acceptable to have flying debris on the tension side!).

Thanks

 

[akhalil66]

Try Blast Effects on buildings , edited by G C Mays and P D Smith ISBN : 0 7277 2030 9