Blast proof Wall 2

[Engr ZANIA]

Hi!
I have to design BLAST PROOF BRICK MASONRY WALL, required height is 4 ft.
Please suggest or share design code and how to investigate the strength of brick wall and its joint

 

[WARose]

Blast loads and masonry really don't mix. But if you want a (general) blast load reference, get:

'Design of Blast Resistant Buildings in Petrochemical Facilities' by ASCE

EDIT: Checking the mentioned reference, there are (a few) details for a masonry structure. However it notes that economical masonry design is typically limited to blast pressures of about 3 psi.

 

[Engr ZANIA]

thanks,
May I have a source for 3psi pressure or any relevant guide of pressure resistance of different types of walls

 

[robyengIT]

some literature attached. Then Google "blast resistant structures"

 

[WARose]

May I have a source for 3psi pressure or any relevant guide of pressure resistance of different types of walls

It's in the reference I mentioned.

 

[masonrygeek]

I'm not sure about the comment that blast resistance and masonry don't mix. Reinforced masonry works well for blast resistance. Some of the negative comments about masonry are in regard to unreinforced masonry which is not common in new construction. If you want to pursue blast resistant masonry structures, here is some information from the National Concrete Masonry Association (NCMA):

http://ncma-br.org/pdfs/68/TEK 14-21A.pdf.

 

[WARose]

I'm not sure about the comment that blast resistance and masonry don't mix. Reinforced masonry works well for blast resistance.

Not in my experience. It's a QC issue as much as anything......mainly with the horizontal reinforcement.

 

[ThomasH]

Hi
When you say you want to design a brick masonry wall for blast, what does that mean?

What is the overpressure and what is the load duration? Is the wall part of a building or is it standing alone?

Masonry is typically not good when it comes to blast loading, as already said. The thing is, you want something ductile to absorb the impulse loading. It is not just a matter of strength but also a questing of how it fails. A free-standing wall can just tip over regardless of the horisontal reinforcement .

One question is, how will it fail?

Thomas

 

[jittles]

Since I see some other opinions being shared here, I'm going to add that I agree with masonrygeek - reinforced masonry works well for blast resistance. Any further comments on why folks think it's not good?

In my experience, a wall with heavier mass has better response under the short term impulse loading of blast design.

 

[WARose]

It just really depends on what you are trying to do and what the load is. If we are talking a room with blowout panels (or far away from the source of the explosion), masonry is as good a choice as any. But for most blast loading (close by) I am use to seeing stuff in the neighborhood of 6 psi. In that case, you are going to get more bang for your buck (no pun intended) with reinforced concrete (or a ductile steel system). To start with, one of the big issues you will have is shear strength. With the options available for the placement of reinforcement (in masonry vs. RC) you are going to be much better off with RC.

So there are a lot of reasons. Not that it’s a bad choice…….but (like I said) it depends on the circumstances.

 

[ThomasH]

Hi again

Just to clarify my statement.

If given a choice I would not recommend masonry but it depends on the circumstances.
If it is a wall in a building it may work due to horizontal reinforcement. I am not sure if you can get any vertical reinforcement. I guess it depends on the bricks.
But I am uncertain regarding the ductility and the possibility to use plastic response. Using elastic response only is possible but often not very economic.

The same applies for precast concrete. The limiting factor can be the connections between the elements.

Regarding the mass, it can be very positive. But I once made an analysis for a steel wall, very lightweight and very ductile. I could withstand a significant explosion, there were huge deformations but it did not collapse.

If the assignment was the check an existing masonry wall for blast loading, then I would deal with it.

I would also assume that the mentioned 3 psi pressure should be accompanied with a load duration .

Thomas

 

[bones206]

For a clay brick wall designed for blast, I might do something like this:

- Two wythes of brick with a central cavity, tied together laterally with brick ties.
- Install a curtain of vertical and horizontal rebar in the cavity and grout solid.
- Design the central reinforced grout wall to take the blast for flexure and shear. Let the reinforced grout provide the ductile resistance and only consider the brick wythes as additional attached mass with no structural capacity.

Allowable damage level is up to the designer, so your max ductility ratio and rotation at the support will depend on how much damage is acceptable.

Blast debris could be an issue of concern with a brick wall, depending on location and magnitude of the blast. You could provide some kind of coating/membrane or some other mitigation for blast debris.

 

[masonrygeek]

I think Bones206 has it right. There were some fallout shelter tests back in the 1950s when they were doing atomic testing and they used the "grouted double wythe brick wall" with brick on both sides and reinforced and grouted center. If you want to see a 'blast' from the past check out this video from Operation Upshot-Knothole from 1953:

https://www.youtube.com/watch?v=PZSjZfAyYB4.

Start at 28:18 for the part about structures. It says the unreinforced brick wall performed well, but it looks like it got blown apart to me.

 

[JoshPlumSE]

I'd say that a CMU wall is fine for blast resistance.... Though we have to be careful what we're talking about here. Where I've seen this is for the process control centers for petrochemical plants. Someone told me that some plant will have a "sacrificial" CMU wall in some areas as well. One that is meant to fail, but which protects workers or valuable equipment from the primary effects of the blast wave.

 

[JLNJ]

The OP has it as just 4' high. Maybe he thinks you can duck down behind a kneewall and be protected.

 

[bones206]

I was thinking the height would make it tricky to develop any ductility before shear failure at the base. Might be better to provide pilasters or counterforts and span the reinforcement horizontally.

 

[Engr ZANIA]

Thanks everyone,
Its quite clear that RCC and concrete masonry wall has more blast resistance; also shear, as compared to brick masonry un-reinforced walls. But the question is do we really need to go for concrete wall when I have to design 4 ft high brick masonry wall for the catastrophic failure pressure of 4.4KPa(0.63psig). My query was how to make sure form any code or standard or design procedure that brick wall will remain integrated and will continue to perform its function and what thickness should I opt.

 

[ThomasH]

Hi
What is the walls function? I don't think you answered that question.

Thomas

 

[Engr ZANIA]

Purpose of wall is to protect; from blast impact; inhabitants living on other side of wall

 

[ThomasH]

A wall that is 4 feet high, how does that work? Does it include a roof or any other type of cover?

If you have just the wall the over pressure will probably be side-on instead of reflected but it will not disappear. Assuming that you want it to disappear.

Thomas