Structures for Deflagration Venting

[Boiler106]

Does anyone have experience designing structures for deflagration venting that could point me to structural design resources?

Im looking into structure type, and to whether or not a steel ceiling structure with metal roof deck and cmu walls is appropriate or if i need to choose a CIP concrete structure for a 40ftx40ft room.

to complicate the problem, i have an existing hss column that will stand in the middle of the room we are enclosing and i need to know how to protect it.

your help is appreciated. thanks!

 

[Once20036]

My experience with blast / deflagration venting typically involves the following:
-Blast panels / blow out panels to limit forces within the room. Panels are tied back to the building so they wont fly across the site.
-Masonry or Precast walls. I can't put my finger on the source right now (NFPA? FM Global?) But I believe 12" masonry grouted solid the standard.
-Design for an equivalent static load, typically 100 psf on my projects.
-I wouldn't worry about a post in the center of the room - there's very little surface area for a blast to act against, compared to the walls.
-I haven't used any special details for the roofs.

Typically your walls will need several girts at a relative close spacing. Pay attention to weak axis bending for the posts that support these girts.

 

[ajh1]

Try looking at FM DS 1-44 for some guidance. FM takes a simplified approach that does not require full dynamic analysis and in lieu of that substitutes static loads of some magnitude depending upon the percentage of surface area available for venting. As I recall their recommendation is that masonry walls not be used as a load-bearing condition. Loads on the remainder of the building (exclusive of the vent panels) start at 100 psf (consistent with the IFC code provisions) and go up from there.

 

[azcats]

NFPA 68 is a resource as well.

 

[Boiler106]

good information, guys.

can i assume that my foundation will need to be designed for the uplift on the structural ceiling, resulting from the blast? or is their an exception?

 

[Once20036]

a) Blast will exert as much pressure up as down. If your slabs are tied into your columns and the roof is designed to take the load, you'd have no net force on the foundations.
b) I typically don't design the roof for the blast load, so there's no way to get the load into the columns or foundations - no uplift.

 

[Boiler106]

Once20036, i have a situation where i am building a structural ceiling and walls over a slab on grade within a single story building, and venting through the roof.

any upward force on the ceiling will get back to by supports and into the ground. i just wondered if there was some exception or reduction in the foundation design.

thanks for your responses.

 

[JStructsteel]

I did a blast room once, I remember there were special screws used for the roof deck. Would hold up to a certain capacity, then would fail and allow the room to vent. Cant remember the brand, but I am sure they are still out there. We did tilt up for the walls, designed those to resist the blast with lots of reinforcing, tie downs, etc.