Z-Purlin Specs

[vmirat]

Since I work for the federal government, I have to specify products as generically as possible for competitive bidding purposes. With that said, I specified a z-purlin using the AISI Manual for Cold Formed Steel Design, thinking that it's like the AISC Steel Manual and everyone in the purlin making business had comparible products. Well, you know what they say about "assume."

I called AISI and asked them why they have these lenthy tables which use z-purlin designations that no one else in the industry uses. They said that they did their best to create a representative sample. What the heck is that!

So, how do you all specify z-purlins without referring to any one specific manufacturer?

 

[mudflaps]

When I specify steel deck and studs I have the same problem. For DSA work I specify a particular manufacturer and "or equal". To make sure you get an "equal" you may have to specify gage thickness and "S" & "I". The only other method is to specify loading and deflection criteria and any special considerations you might be looking for.

In California we can specify a minimum of three manufacturers and call it good.

Old CA SE

 

[vmirat]

mudflaps,

Yeah, looks like I'll have to go manufacturer-specific and use the old "or equal" clause. 99% of the time, the contractor gives us what we ask for anyway.

I just don't understand AISI though. I must have contacted four or five manufacturers across the country and they all use the same designation system. I get so frustrated with these standards organizations that make up their own stuff thinking that the industry will follow them, kind of like the federal government requiring projects to be designed using metric.

The other reason I used the AISI manual was because the IBC requires the use of AISI-NAS for cold formed steel. I guess I figured AISI knew what they were doing.

I went back and read the AISI manual and there was a statement which says, "This naming convention is not an industry standard. Individual manufacturers and industry groups have adopted their own systems, and these systems should be used when specifying actual products." I don't understand why AISI devoted so much time and effort to develop these tables if they aren't used by anyone else but them. AISI is suppose to be an industry standardization organization.

 

[valleyboy]

Could you just specify the loads acting on the purlins, their centres, and any specific requirements you have, and ask for Contractors proposals with their tender documentation / submission?

VB