Reinforced Masonry CMU wall with SBEDS

[cooksumrice]

I have to designed an enclosed control room (15') to withstand a 3psi load with a duration of 40ms. After entering my inputs for a masonry wall with #5 bar in every cell filled with grout the program tells me it works (incident angle < 2 degrees). My gut tells me this is inadequate. Anyone else have these results?

 

[MrHershey]

Not really enough information provided to tell one way or the other. Have no clue if you're using 6" block, 8" block, 12" block. Don't know boundary conditions. Don't know what, if any, axial loads there are to contend with. May very well be fine, that's a lot of reinforcing and a relatively small 15' span.

Not sure I understand your loading criteria though. Are you saying a constant 3 psi for 40 ms and then drops to zero? I'm not familiar with any standard blast loadings that take this form, should be a peak pressure that dies out quickly and then goes into a negative rebound phase. If that 3 psi is your peak pressure and then dies off over 40 ms then what you have would very likely be overkill. 3 psi is pretty small peak pressure as far as blast is concerned.

 

[JedClampett]

Are you sure you have the units right? Most CMU programs are written for psf, not psi. Big difference.

 

[XR250]

I have used SBEDS for metal stud walls. So you have 432 PSF for 40 ms. Maybe there is enough mass in the wall to absorb that. I recall that was the case with metal studs as the heavier the wall got (adding veneer etc.), the lower the peak loads.

 

[MrHershey]

Jed- OP is talking explosion/blast loads, SBEDS is a blast program/spreadsheet developed by the US Army Corps of Engineers. Psi is actually correct, 3 psi is reasonable for an average if you're just dividing your impulse by time, pretty low if that's your peak pressure. We routinely see peak pressures much larger than that, but it drops off quickly.

 

[haynewp]

Why do you feel that <2 degrees is inadequate?