baseplate/column in uplift

[oneintheeye]

how do you confirm capacity of simple column baseplate in uplift conditions. Uplift dived by 4 bolts (plus any prying force). Baseplate?

thanks.

 

[Lion06]

See the updated AISC Design Guide #1.

 

[oneintheeye]

sorry Uk based. Unless that is freely available

 

[asixth]

What element is given you the most trouble

1. Baseplate bending
2. H.D. Bolt capacity
3. Footing for ulift

 

[oneintheeye]

checking baseplate bending, can do it for bending but not simple supported with axial tension (uplift).

 

[ToadJones]

What is your baseplate, bolt and column arrangement?
bolts "inside" the column? "outside" the column?

 

[oneintheeye]

bolts inside but looking at it generally really. Can picture the mechanism but how to do a quick hand check?

 

[slickdeals]

This screams for a sketch. In the time we keep posting multiple versions, its easier to see it.

 

[oneintheeye]

I haven't a scanner available. Its a 610 UB column. Uplift applied with shear at braced bay. Bolts inside the column flanges 300 apart and 200 apart in other direction (4 no).

 

[spats]

Attached is a PDF file showing a very old, but very simple analysis technique for distributing bolt loads to calculate plate bending. It's definitely conservative, and you can avoid getting into a lot of yield-line theory.

 

[ToadJones]

Old, but looks good to me.
AISC design guide One uses similiar approaches

 

[csd72]

There are good uk references, I would suggest you google it.

 

[asixth]

Do you practice in Australia?

The steel institute has put out publications regarding the design of baseplates. Immediately when I hear a 610UB bracing column I would think 25mm thick baseplate, possibly a 40mm plate depending on the magnitude of the uplift forces.

Basically, the axial force is assumed uniform across the UB cross section and must be transferred into the anchor bolts by plate bending.

I have posted pp 239 from the Australian Steel Institutes publications 'Design of Structural Connections'. The basic equation that it breaks down into is

ti=sqrt(Nt*bt/(0.225*be*fy*nb))

My calculations show that a 40mm baseplate can take an axial tension of 157kN (35kips) while a 25mm baseplate can take 61kN (14kips).

Didn't look in great depth to the notes that spats posted but I'm sure that they will produce similar results.

All the best.

 

[rowingengineer]

asixth,
those numbers don't sound right.

An expert is a man who has made all the mistakes which can be made in a very narrow field

 

[asixth]

of course they're right

 

[Ron]

asixth...check again, something seems off there as RE noted. Looks like the capacity of the 25mm plate should be higher.

 

[oneintheeye]

cheers asinxth. in the equation what is b1. i.e what is the moment in figure 5.12.8 a? bolt spacing 300 long ways 200 short ways? not asking for you to giv me answer but what figures are where?

 

[rowingengineer]

Asixth the number are not stacking up, I have attached the specs for footipak which I use for checking of other people work as I have found it half reliable (However they do assume only 2 of 4 bolts can take shear, I don't mind this assumption myself). And they get 10x the amount. This is an order of magnitude, sure you didn’t miss a zero, aka the answer should be 610KN????.

Oneintheeye, given you are in the UK I WOULDN’T suggest adopting the attached design values from the attached for your design, As I know the baseplate configurations used in the UK differ from the Aust.


An expert is a man who has made all the mistakes which can be made in a very narrow field

 

[oneintheeye]

i would generally agree but to me a baseplate in US is a base plate in UK i.e. flat piece of steel. If its not failing in US under x load in US/Australia then it won't fail here regardless of how I prove it.

 

[rowingengineer]

I would agree but the bolt locations drive the analysis, that is the blot locations drive the yield lines, if you bolt locations do not allow the yield lines to develop the analysis is up the duff. There is also the construction techniques that they analysis relies upon, this being depth of grout, tensioning requirements, plate grades and bolt grades, welds, grout holes ect.

Last Time I checked I believe the UK standard was to have bolts outside the flanges, grout holes, and a few other local standards. These don’t match the aust way and analysis.


An expert is a man who has made all the mistakes which can be made in a very narrow field