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baseplate/column in uplift

baseplate/column in uplift

baseplate/column in uplift

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

thanks.  

RE: baseplate/column in uplift

See the updated AISC Design Guide #1.

RE: baseplate/column in uplift

(OP)
sorry Uk based. Unless that is freely available

RE: baseplate/column in uplift

What element is given you the most trouble

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







 

RE: baseplate/column in uplift

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

RE: baseplate/column in uplift

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

RE: baseplate/column in uplift

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

RE: baseplate/column in uplift

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

RE: baseplate/column in uplift

(OP)
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).  

RE: baseplate/column in uplift

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

RE: baseplate/column in uplift

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

RE: baseplate/column in uplift

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.

RE: baseplate/column in uplift

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

RE: baseplate/column in uplift

of course they're right

RE: baseplate/column in uplift

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

RE: baseplate/column in uplift

(OP)
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?

RE: baseplate/column in uplift

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

RE: baseplate/column in uplift

(OP)
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.  

RE: baseplate/column in uplift

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

RE: baseplate/column in uplift

I don't see how that configuration can work for a 610UB. The standard design for the 610UB is M30 anchors (1-1/4") a 25mm baseplate and this gives a capacity of 720kN??

I wouldn't be able to prove that a 25mm baseplate and transfer this force thru bending?

I'll dig out my AISC baseplate guidelines and green book and see where my calculations are going wrong.

I also wouldn't call up M30's, I would use M20's.

RE: baseplate/column in uplift

Asixth,
Call me captain dangerous, please note that 700kN is for pure tension, if you were to combine in shear as required you bolt capacity will reduce the overall component strength.  

Don't ask me if you can develop the M30 bolts in the footing this I don't know. Nevertheless the M20-24 rule only applies to 8.8 bolts, it would impose high construction tolerances to use 8.8/s for foundation bolts, in my experience M30 4.6/s are not uncommon.
 

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

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