Lightgage Framing Design 1

[Atomic25]

What references do you use to design lightgage or cold formed steel members? I have the SSMA Product Technical Information guide. Also have the AISI Cold Formed Steel Manual but think it's one of the most poorly organized books ever written. I'm looking for something a little more practical. Any recommendations would be great.

thanks

 

[ash060]

Lightgage has only 2 textbooks that I know off. The AISI Manual which does have some good tables in it. Also, there is Cold-Formed Steel Design by Yu.

I do not think that you will find any material that presents cold-formed in an easy to do manner. The material is just too complicated.

If you keep the stuff sheathed on both sides it will work fine. If the stuff has any unbraced length beyond about 36 in you are going to trouble

 

[jike]

Clark Steel Framing has some great info. and free downloads. Sample drawings and details, AISIWINv7.0, etc. Some of the best that I have seen!

http://www.clarksteel.com/

Good luck!

 

[UcfSE]

I would stick with the NASPEC and the SSMA you referenced. Some manufacturers provide information but it is substantially the same as the SSMA. The Manual, different from the NASPEC, I agree isn't much use. IMO, your best bet is to follow the NASPEC and write your own spreadsheets or mathcad sheets. For fasteners, follow the NASPEC and the manufacturers' information. By comparing tests to calculations, you'll get a better feel for who (manufacturers) padded the values they report.

Of course, there is always software. You'll find several programs available but few that also check web crippling. If you can find one that does it all it may worth having.

 

[structuralnerd]

If you are looking for some software to help you out, the new versions of RISA have cold form sections in there. I've used it a couple times, but I'm not 100% sure how reliable it is.

 

[DaveAtkins]

I do a lot of cold formed design, and as mentioned above, if the members are sheathed on both sides, or braced properly, there is no reason to use the Cold Formed Steel Design Manual. You just need to use manufacturer supplied tables (I use Dietrich).

DaveAtkins

 

[ash060]

Atomic 25

Follow DaveAtkins advice, call Dietrich and order one of their catalogs. They have more information than any other supplier I have seen in their new catalog. They also have a bunch of pre-fab connections with allowable load tables for just about any condition.

Remember to check combined bending and shear, bending and web crippling in the negative moment areas one of these two cases will control 90% of the time.

 

[vmirat]

I spec steel studs using the SSMA designation but our architects still use size/gage (i.e. 3-1/2" 20 gage) on their drawings. Am I being to narrow minded to insist on the SSMA system?

 

[Lion06]

I don't think Dietrich, Marinoware, etc... have their own catalogs anymore. I think they have all switched to SSMA.

 

[Lion06]

I recently reviewed calcs where bracing was used at 6'0" o.c. and the program spit out that there was no reduction in the allowable moment.

 

[ash060]

Dietrich has a big binder that uses the SSMA designations and their catalog. The best thing about their catalog is all the connection hardware.
Be careful SSMA studs are their own thing, they have different properties than there C-Stud counterparts. They also have punched holes along the length of the member.
Their may not be a reduction at 6', 36" is just a rule of thumb

 

[CFSEng]

The purpose of SSMA was to provide consistent properties of studs among the roll formers. So when we design a light gauge project, we can specify 600S162-43 (33) and state the manufacturer of the stud must be SSMA compliant. Maybe I am misunderstanding the above post by ash060, but the SSMA is not its own thing, it is a governing association that any roll former that is a member must produce shapes that meet its minimum requirements.

Also be careful when using published tables. Always make sure you read the general notes and footnotes and agree with all the assumptions used to generate the tables.

Some software we use is CFS by RSG Software

Some good sites to reference for cold formed steel (light gauge)
Cold Formed Steel Engineers Institute
Steel Framing Alliance

And for anyone and everyone designing / specifying cold formed steel, I highly recommend you read and reference the code of standard practice
AISI Code of Standard Practice

 

[ash060]

I was refering to the Tables in the AISI Specification

The properties for SSMA are a little different C-Studs in the AISI Manual

 

[UcfSE]

The studs in the AISI manual do not match what is commnonly produced.

CFSEng, good post.

As for no reduction at 6' unbraced length, that must have been quite a massive stud. Most will have some sort of reduction for LTB around 3-4 feet and smaller studs and tracks maybe less. that's why it is important to do the engineering instead of rely on rules of thumb.

 

[DaveAtkins]

vmirat,

None of the drywall contractors I work with use the SSMA designations. Therefore, on the shop drawings I produce, I use the "traditional" designations--e.g., 6" X 16 GA. I'm not saying I'm right--I'm just being practical.

DaveAtkins

 

[CFSEng]

I would be careful using the old school designations for specifying metal studs. While very true most of our clients still use the older method, there is some possibility for confusion using the older method. The SSMA designation is very clear on web depth, flange width, and mil thickness (there are two different 20 ga studs, 30 mil and 33 mil). Also you should always specify the yield strength in the call out, not just in your general notes. We found most if not all of our clients were unaware that 54 mil (16 gauge) studs need to be 50 ksi steel even though our notes explicitly state so. Unless of course you are designing for only 33 ksi steel, then this is less important

Some things we did to help our clients was contact SSMA and get permission to put a copy of the inside cover of the SSMA Product Technical guide into our submittals. And we put a copy of the 'Thickness - Steel Components' table in our submittals so they can convert from mil thickness to gauge. We also try and get kick-off meetings for projects and bring copies of the SSMA guide with us and explain how to read the designations.

I guess my point is, just be sure they are using what you designed.

 

[vmirat]

I think the problem is that there is nothing that forces contractors or manufacturers to use the SSMA system. The IBC doesn't specifically require it and references the AISI specification which also does not require it. The AISI design manual uses the SSMA system, but it's not regulatory. Our local code has not required it either.

On the one hand, I understand DaveAtkins' practical approach to the situation. On the other hand, I agree with CFSEng in that the SSMA system is much more specific than than the old system and we need to make sure we are getting what we designed. This product so widely used we should have a common system in the industry, just like structural steel. Unfortunately, the stud manufacturers make their money from construction contractors, not engineers (we're not the ones buying their product), so they are going to accomodate their customer base. I have found stud manufacturers that have tables using both systems, but that still doesn't force the construction contractor to learn the SSMA system.

I guess the only way we can deal with this situation is to follow what CFSEng does. Train each contractor individually.

 

[Atomic25]

I think you guys have underlined my frustration with the AISI Manual. It's amazing how unorganized the metal stud industry feels compared to wood stud industry.

I am a proponent of SSMA designations only...then again, I feel no sympathy for those who don't keep with the times.

The book by Yu seems to be what I'm looking for, thanks for the heads up.

 

[UcfSE]

When I did a lot of specialty cfs engineering, I started using the SSMA designations. My clients did not seem to mind (at least not in front of me )and recognized it as the new thing in their industry. When or if they didn't know a designation, they called. I put a table similar to the SSMA in my notes showing how the designations should be read. It never created a problem for me and they got used to it after one job.