Plastic Section Modulus for Cold Formed Steel Sections 1

[dcredskins]

How can we calculate the plastic section modulus for cold formed steel sections? I am the light gage speciality engineer. The EOR has asked me to design connections based on plastic section modulus for blast resistance design. I would appreciate your response.

 

[Lion06]

271828-
You are probably right. I actually learned ASD in school, just 3 years ago. I never learned how to calc Z, but I figured I should know how so I just figured it out.

 

[271828]

Good job. I'm amazed that anybody taught 89 ASD in 2005!

 

[Lion06]

Tell me about it. I didn't realize until I started working that everyone else learned LRFD (even though everyone in our office and most of the offices in the surrounding area used the Green Book). That only lasted until the 13th edition manual came out and then we switched to LRFD.

 

[nutte]

271828, nicely done! I, however, am a renaissance man. 9th ASD, 2nd LRFD, 3rd LRFD, 13th ASD, 13th LRFD... Doing connections, we have to use whichever code the EOR calls for, so we have to become proficient in all of them.

I also enjoy going through the older specs (8th edition and earlier) to see how the equations have changed over the years. How sad is that, that I "enjoy" such things!

 

[271828]

If he had taught LRFD instead, the transition to the 13th Ed. would be trivial.

LOL, I hope your former professor isn't on your Christmas card list, due to his short-sightedness. About 1-1.5 years before the 13th Ed. Spec. was available, the steel prof. at our school was teaching from a draft copy so that his students wouldn't have to make the trivial transition from 3rd Ed. LRFD to 12th Ed. LRFD/ASD.

You seem to have come out fine, but it seems to be from work ethic and the wilingness to study.

 

[271828]

Oops, you know I meant 13th Ed., not 12th Ed. LOL. I guess that was the "phantom spec."

 

[tedamiao]

Nutte, thanks for the input. The thing is for connection design, screws are always control rather than section itself. Also we will not try to make moment connection. Almost every connection was considered as pin connection.

 

[nutte]

You are correct, but I think the goal here is to size the connection for the plastic capacity of the section, even though it can never get to plastic, to ensure a ductile failure. This is the same process used for seismic connections, where you size the connection for more than the gross member can take to ensure a ductile failure in the member rather than a brittle failure in the connection.