Manually calculate beam “k” values for older sections?

[StructureMan44]

I’m designed new steel to fit within a steel building composed of shapes from ASD 7. The properties for these shapes are given in the historic shape data spreadsheet on AISC’s website. Unfortunately the spreadsheet does not include K or T values. It does have the d and tf values though. Is there a rule of them for the ratio of T/d or k/d? If not is there a general radius size between the web and flange that I can add to tf to get a value for k?

 

[structSU10]

What exactly do you need to know the k for? is it so coped beams can fit under existing steel? I would think you could assume a k = 2*tf and be conservative in general, as I flip through the steel sections.

 

[JStephen]

If it's existing steel, you could go measure it.

 

[dhengr]

StructureMan44:
The “k” value has been shown in the AISC Manuals all long. The earliest one which I have right at hand is a 1958 printing, and the latest edition which I have also has them tabulated.

 

[StructureMan44]

StructSU10: if k=2*tf is conservative enough I'll use that, thanks.

JStephen: It is existing but it's in another state and there are many difference sizes in use.

dhengr: I don't have any manuals older than the 13th edition, I've only used the AISC spreadsheets:

http://www.aisc.org/content.aspx?id=2868

 

[JoshPlumSE]

Here is what I've done before: It's not exactly accurate, but it is a simple concept that will get you in the ballpark. You might be off by 20 or 30%, but you won't be off by a factor of an order of magnitude.

Calculate the area of the member (based on d, tw, bf and tf) subtract that from the area given in the table. Any extra area is equally split among the k areas. Assume them to be simple triangles and you've got a reasonable approximation of the k areas.

 

[StructureMan44]

It looks like k=2*tf may not be conservative, it may need to be 3*tf or 4*tf. Maybe there is general rule for the radius size?

 

[WillisV]

It is not a set distance. It is not based on any formula. It is determined by the rollers and can vary mill to mill. See:

https://www.aisc.org/bookstore/itemRedirector.aspx?id=15224

 

[StructureMan44]

It appears that every k value for the versions available in AISC historic database (for the 14th edition, 13th edition, LRFD 1-3, ASD 8,9) is less than 3.1*tf.

 

[dhengr]

StructureMan44:
Well, there you are..., you have developed your very own rule of thumb for something. It’s yours, use it at your own discretion and risk. In the mean time, most of us will probably continue to look in the AISC Manual for that info. since it has always been tabulated there with all the other section design dimensions, or detailing dimensions.

 

[StructureMan44]

JoshPlum: That's a very good idea and more accurate than my idea, thank you.

dhengr: I agree, I would use the tabulated data if I had the ASD 7 manual

 

[NOLAENG]

AISC offers some of the older manuals free to download for members.
See: Older Manuals