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RE: about blast design of structures[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: seaint <seaint(--nospam--at)seaint.org>
- Subject: RE: about blast design of structures
- From: Walt Sawruk <sawruk(--nospam--at)ix.netcom.com>
- Date: Mon, 14 Apr 2003 11:39:59 -0400
You have not specified the source of the blast load (e.g., accidental vapor cloud explosion/deflagration, pressure vessel rupture, HE detonation) which does not fundamentally change the problem you are faced with but it does focus the search for published information sources. Most readily available publications on blast load predictions deal with HE so I am going to assume this is your source. An excellent reference for prediction of blast loads for a wide range of blast sources is Baker .
If all you wish to accomplish is to take into account blast clearing effects, a simple procedure can be used to calculate simplified blast pressure time histories acting on the front wall, roof, rear wall and side walls. The procedure is illustrated in the ASCE design guide for blast resistant design of buildings at petrochem facilities  although it originated elsewhere. Net blast loads acting on an enclosed structure, assuming the exterior envelop remains intact, can then be readily determined once the blast loads acting on all exterior surfaces are known.
If you wish to take into account the failure of cladding systems, floor systems and interior partitions on the blast loads acting on the structural system of a multi-story building, it is not possible to obtain a solution using the standard 'blast curves' which have been widely published [1, 3 and 4]. The blast curve method assumes open field conditions and no fluid-structure interaction (i.e., effects of facade element failures), hence, net blast loads acting on a structure calculated using blast curves are only accurate when these conditions are satisfied. Technical papers have been published addressing the prediction of blast pressure infiltration through exterior openings (e.g., windows) but these studies usually involve specific ranges on parameters which might not cover your conditions.
To obtain accurate predictions of net blast loads for conditions involving nonlinear structural response and fluid-structure interaction, you will most likely have to employ numerical computational fluid dynamics (CFD) methods. Commercially available CFD codes have the capability to make such predictions but these codes tend to be very sophisticated in the modeling of the explosive event as well as fluid-structure interaction effects. Prediction of global structural damage does not usually require such high levels of sophistication. In many cases, a CFD method employing simple Pressure-Impluse (P-I) structural damage criteria in combination with the so-called 'reduced explosion model' approach which does not accurately predict close-in blast effects but still retains a high degree of accuracy for medium to long range blast load predictions is the best choice.
One final remark - if you are primarily interested in vapor cloud explosions and only wish to address general building types (i.e., without regard to specific construction details), you may be able to use the screening criteria given in Table 4 of API RP 752  to gain some insight. These screening criteria are based on experience data and thus inherently represent the net blast load effect on the overall building response.
1. W. E. Baker, et.al., EXPLOSION HAZARDS AND EVALUATION, Elseevier Scientific Publishing Co., Amsterdam, The Netherlands, 1983.
2. ASCE Task Committee on Blast Resistant Design, "Design of Blast Resistant Buildings in Petrochemical Facilities", American Society of Civil Engineers, NY, NY, 1997.
3. G. C. Mays and . D. Smith (eds.), BLAST EFFECTS ON BUILDINGS, Thomas Telford Publications, London, UK, 1995.
4. ASCE/SEI, "Structural Design for Physical Security - State of the Practice", American Society of Civil Engineers, Reston, VA, 1999.
5. API/CMA, "Management of Hazards Associated with Location of Process Plant Buildings", API Recommended Practice 752, American Petroleum Institute, Washington, D.C. USA, 1995.
I wish you good luck with your project.
Walter Sawruk, P.E.
From: seko [mailto:serkan_karapinar(--nospam--at)hotmail.com]
Sent: Monday, April 09, 2001 11:19 AM
Subject: about blast design of structures
To whom it may concerned!
I am a graduate student from Turkey,which is named Bogazici University.I have a thesis topic that is "Analysis and design of the structures under balst load".I collected some materials but I could not find enough information about blast load.I have some problems.
Can you tell me briefly about the analysis procedure and how can I calculate the blast load on the multi-storey frames with openings(I can't determined the net pressure load).Can it be possible for me to receive some information about these?
Department of Civil Engineering
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