How to trasform blast load to static load 3

i don't care if the numbers work out right, metal studs won't stand up to a blast loading.

first off "curtain wall" and "blast loads" don't seem to be a good combination, but what do i know ?

2nd, can you explain your blast load units ??

3rd, what if you built into the wall a flapper vent that would open if a high enough pressure was applied (relieving the wall) ???

You also have to be concerned about the 'reflected' loads... I've done reports where the reflected load has pulled the curtain wall anchorage from the concrete slab as well as 'torn' anchorages from the mullions...

Dik

dcceecy, get ahold of UFC 4-010-01 from which will explain the equivalent static procedure. There's no easy conversion, if you want to use static loads, you'll have to figure them out yourself. Also, a caution, when using static analysis to design supporting structure, the loads are required to be multiplied by 8. Use dynamic analysis if you can.

Vandede, not true. I've seen videos of CFS studs working just fine in a blast scenario. They may need to be a heavy gauge and/or built-up members, but you can get them to work. Curtain walls too.

From UFC 4-010-01 , I found this
ASTM Standard F2248-03, Standard Practice for Specifying an Equivalent 3-Second Duration Design Loading for Blast Resistant Glazing Fabricated with Laminated Glass.

Does any body use this method to calculate the equivalent static load?

dcceecy
My understanding is that the F2248-03 which is titled "Specifying an Equivalent 3-Second duration design loading for blast resistant Glazing Fabricated with Laminated Glass" is just for glazig so I'm not sure you can use it for a curtain walls. I think your best bet is to obtain a copy of a program called SBEDS that you can use to determine the loads on light gage walls among other systems. You can also determine all other parameters such as ductility and rotation of the wall which determine the adequacy of the wall. This software is restircted so you or your company has to register with the Protective Design Center in order to obtain it.

Another resource I would use is the UFC 3-340-02 which as I recall has a method of figuring out the equivalent static pressure.

Good luck.

kmead, following up on that question, I use SBEDS and HazL for blast design, but it seems that SBEDS is inadequate for designing structural supports for windows because there's nowhere to input the window size. HazL will give you the dynamic edge pressures to apply to the structure, but how do you then analyze the window structure dynamically?

Basically, you end up with a 2D frame with a dynamic, quick-acting pressure out of plane. Does anyone know of software capable of designing this? (doesn't have to be blast-specific, necessarily)

You kind of have to fake it in SBEDS. You just have to set the proper tributary area for the surrounding window elements by adjusting the member spacing. The response should be pretty similar to what actually happens from the window reaction.

The UFC3-340-02 document cited earlier has cold formed steel design examples. My experience with blast design is to use ultimate material values including the Dynamic increase factors as stated in the UFC manual. SBEDS is useful to check your ductility and rotations.

You might consider hiring a pro in this field who can look at the dynamic effect rather than just crudely converting the blast to a static equivalent.

I agree with Steellion that SBEDS is not really meant to give you window reactions and I also agree with Gumpmaster that you can fake it in SBEDS by changing the stud spacing. However, I would either use Table 6-6 in the UFC 3-340-02 which gives you the static design strength of windows that you can then use to determine the reactions (Also see section 6-30) . Or I would use the requirements of UFC-4-010-01 section B-3.1.2 which requires the glazing support members to be designed for "8 times the glazing resistance determined using ASTM E 1300 in conjunction with ASTM F 2248".
The latter is more conservative in my opinion and I would tend not to use it.


I hope this helps.

kmead, thanks for the reference. However, I think that using Table 6-6/Section 6-30 still gives you a static load that you would need to multiply by 8 to design the structural support for.

My company does a lot of military design. We started out using the static procedure, but I've determined that it is too conservative with the 8x multiplier you need to use. Running the static calculations lead to using HSS tubes around each window, which in reality are not needed. So I've graduated to using SBEDS and "faking it". I want to take the next step and perform a window frame support analysis using actual dimensions and blast loads. Surely there is some software out there that can accomplish this!

I think maybe the next level up of dynamic analysis from SBEDS is probably something like LS Dyna where you can analyze the system, and not just one component.

That wouldn't be somewhere I'd want to go for just a window.

The hardest parts of getting light gage framing to work around a window are the connections and getting the concentrated load from the header and sill to not fail your jambs. For the connection, a typical light gage connection plate doesn't really cut it. One testing project I saw shows that a bolted connection with actual steel plate (not just sheet metal) was needed to develop the plasticity and forces required required at the ends of the members. Getting the jambs to not cripple requires hefty stiffeners.

We've bitten the bullet and just use HSS surrounds around all windows. It opens up a lot of flexibility and our window sizes aren't as limited as they would be using cold formed window surrounds.

I think It's better to try and do a full dynamic analysis .. there is an aproximation used to convert the multi-degrees of fredom system into a single-degree of freedom system, But by assuming a "static load" i think you'll pretty much miss the real behavior of the wall.
You may find good information in the TM5-1300 code for Blast loads.
or you can use SAP2000 program, I am not sure if it's capable of analysing a 2D opjects subjected to blast loads , But I used it to analys steel beams and frames for dynamic blast loads, and it gave reasonable results.