EXPLOSION DESIGN
EXPLOSION DESIGN
(OP)
Can anyone advice how to consider/evaluate explosion loads against buildings. This is required for the design of a Power plant to be built inside a LNG Gas Station Facility. What are the regulatory codes, typical values.






RE: EXPLOSION DESIGN
RE: EXPLOSION DESIGN
THnaks for your support
RE: EXPLOSION DESIGN
www.aisc.org/blast
http://www.nibs.org/Apr03.pdf
www.SlideRuleEra.net
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Both documents that you mentioned are not available to the public any more!
Regards,
Lutfi
www.cdeco.com
RE: EXPLOSION DESIGN
As mentioned by AUCE98, the owner has to provide you with the threat level, i.e. bomb size. In addition, THE OWNER has to determine what is an acceptable level of damage for the given threat level. The location of the threat in relation to the facility also comes into play.
Blast analysis IS NOT simple. It requires a lot of FEM analysis and experience in order to mitigate the effects. Most important, and with all due respect, if you don't have the experience get someone who does.
RE: EXPLOSION DESIGN
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By the way, seems like I have seen info like this on ASCE's site- check there, also. And with terrorist bombing being an issue, seems like this info would need to be MORE available, rather than less.
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http://users.rcn.com/harwood.ma.ultranet/t17.html
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Thanks for the great support. The information we have received from our client is that the we shall consider an overpressure due to a blast of 4Kpa. On top of that our client require the buildings to be EMP- Protected
RE: EXPLOSION DESIGN
RE: EXPLOSION DESIGN
PBA:
You are right I've checked once again the spec and calls for an overpressure of 20KPA. Hope you can advice
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I'll bow to other peoples experience if they wish to contribute...
Previously I've done similar design as follows:
The overburden pressure (OP) is treated as an exceptional imposed load and as such it is applied with a low partial safety factor. It is not usual to consider the OP with either wind, or seizmic effects. The force can be considered to act in the worst possible direction. Generally vertically down for rafters, floor beams etc. and Horizontal for walls. It's worth considering both for columns. Non-structural parts of the building may well be allowed to fail during the explosion and as such transfer lower forces, equal to their failure load. Your client should define what has to remain working after the explosion. Dynamic effects of the explosion are usually incorporated into the magnitude of the OP, so normally you're looking at static analysis only.
Normal imposed floor loads are typically 5kPa and there is a partial safety factor of 1.6 under the cods I use giving 8kPa. The OP of 20 would have a partial safety factor of 1.05 giving 21kPa. As you can see the OP will govern the design of the elements exposed to the force (wich is usually most of them).
One other thing to remember - Actual explosions consist of a positive force wave (acting outwards) followed by a negative force wave (acting inwards) as the air rushes back to fill the vacuum created at the centre of the explosion. - So you can't neglect to consider the reversal case.
I only have experience of once actual explosion and there the windows on the far side of the building were blown out but the windows facing the explosion wre left mostly intact.
Good Luck
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And I would also reiterate the point that a positive blast pressure is followed by a negative one, so slabs and beams have to be resistant to upward pressures as well as downward ones.
richard
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You are of course absolutely correct.
I have personally designed four significant structures using the approach I outline above. These were not small insignificant projects but large complex buildings and process platforms for serious and knowledgeable clients. The process of establishing the blast overburden pressure should include some consideration of the type of structure to which it will be applied. Coupled to the uncertainty of predicting how explosions actually impact on buildings the concept of an equivalent static load is surely not unreasonable?
I had the fortune some years ago to work along side (note not with) an engineer who modelled explosions and such like as his full time job. I didn't understand any of what he did but I do know that the sofisticated analytical models were all calibrated to empirical evidence gained from phorensic examination of actual explosion sites.
The end result of this work was loading data supplied to simple engineers such as myself and so called peak stress contour plots for elements such as blast walls
RE: EXPLOSION DESIGN
A couple of firms that our company has used as consultants are Baker Engineering and Risk Consultants, Inc. and Applied Research Associates. Both are well known and well versed in designing hardened structures for blast and progressive collapse.
Regards,
AUCE98
RE: EXPLOSION DESIGN
I'm not a blast expert but I am managing the design of a structure that will be blast hardened; it's not being designed by empirical methods. You need to be careful because the empirical methods are typically based on open-air blast for a particular threat level and standoff distance.
If there are buried components that need to be protected, these methods may not work.
Again, you need to discuss with your client the acceptable level of damage to the facility and, sorry to say, potential loss of life.
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Yes - I may not have made my meaning clear - using an equivalent static load is fine if you have the skill to assess it in relation to the dynamic response of the member you are designing. As bridgebuster says, the acceptable level of damage is another component of the calculation. My concern was that civinco01 and his/her client may not have that level of experience.
Knowing when you are outside your own level of competence, and when therefore to call on specialist help is the mark of a professional.
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To All:
Thanks once again for the advice. I'm certainly looking for a specialist but before doing so I wanted to get a first impression of this complicated discipline. I think that there are alot more variable one should take care for, such as: refraction, far field explosion, near field explosion, allowable extent of damage, flying objects, etc.
All the above require professional knowledge & care
Thank you all
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design an automatic shutoff switch for the entire electrical/electronic systems - that is the only thing that is going to realistically provide EMP protection. unless you really mean TEMPEST protected.
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What I meant with EMP protected is Electromagnetic Pulse Protection. Has anyone anything to say about this?
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sorry to seem skeptical but case hardened installations requiring EMP protection usually fall under National Security and i am doubtful we are talking about such an installation as you describe on this board.
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Our client spec is rather confusing, in some parts is calling for EMP Protection and in others for EMI shielding. Can you please advice what is the difference and what are the impacts to the civil works construction of the building.
According to what you mentioned before,what sense does it make to ask for such special requirements when the structure will not even withstand the blast!!
The project I'm talking about is in Norway at the Statoil Gas facility in Karstoe.
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EMP/EMI description
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