# AISC sdm page 5-20



## McEngr (Apr 19, 2012)

Page 5-20 very generally discusses a 5/8tplate to develop the full force of the plate. However, I cannot get the same number:

3.09 D/Fu = 3.09x16/65=.76, not .625

Please help!


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## ipswitch (Apr 19, 2012)

Phi = 0.8? Perhaps?


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## McEngr (Apr 19, 2012)

OK. I think I've got it. Since to develop the full plate strength of say, A572 Grade 50 plate, you would have to use 1.1RyFy as follows:

t = 6.19D/Fu , but substitute Fu with 1.1*1.1*Fy= 60.5 ksi. Then solve for D, but remember D is in 16ths: D=1.1RyFy/(6.19*16)=0.610. 0.610 is very close to 5/8.

If anyone could clarify or converse with me on this at some point, I'd appreciate it.


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## McEngr (Apr 20, 2012)

Also, because 6.19 is based on shear rupture (theta=zero), I believe that it could increase by 1.5 for a transverse weld, which would reduce the 0.61 to 0.407 (or roughly 7/16 of the plate if in pure tension).

The collector on page 5-20 has shear and tension going on, so in this example a shear rupture weld is conservative.


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## ipswitch (Apr 20, 2012)

McEngr:

Is this the latest edition of SEAOC Vol 1? http://www.iccsafe.org/Store/Pages/Product.aspx?id=9011S091


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## kevo_55 (Apr 20, 2012)

^^ I don't think you can buy those yet.

I'm personally thinking about buying a set but I am waiting for all of the errors to be corrected from the 1st printing.


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## ipswitch (Apr 20, 2012)

kevo_55 said:


> ^^ I don't think you can buy those yet. I'm personally thinking about buying a set but I am waiting for all of the errors to be corrected from the 1st printing.


Which edition should be acquired for the exam?


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## kevo_55 (Apr 20, 2012)

I would get the ones based on the 2009 IBC whenever they become available, just realize that there will be mistakes in them.


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## dakota_79 (Apr 20, 2012)

McEngr:

From AISC Manual pg 9-5 for a 2-sided fillet, tmin = 6.19*D/Fu.

Therfore to develop the plate, Dmin = tp*Fu/6.19 = tp*(58/6.19) = tp*9.4

Therfore weld leg size, w = tp*(9.4/16) ~ tp*(5/8)

This derivation is a common unstated simplification of the manual equation used in connection design (read: underived - just state in your calcs "use 5/8*tp to develop plate").


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## McEngr (Apr 20, 2012)

Dakota, I guess you disagree with the author? The calc you provide is different.


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## dakota_79 (Apr 20, 2012)

The calc I state is the same: 5/8*tp to develop the plate, no?


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## dakota_79 (Apr 20, 2012)

Note they're using a 36 ksi plate (Fu = 58ksi, not 65), but the approximation ends up nearly the same for 50 ksi plate (Fu = 65):

Dmin = tp*(65/6.19) = tp*10.5

wmin = tp*(10.5/16) ~ tp*(5/8)


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## McEngr (Apr 20, 2012)

Dakota, I follow you now. I thought the tildy was a minus sign. I agree with you. Because .5875 isn't very close, I thought I was n't correct.


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## dakota_79 (Apr 20, 2012)

Sorry - couldn't find the ole' double tildy! Hope that helps.

ip: What Kevo said - get the versions for IBC2009 if available but watch for errors. That said, though, I studied using the versions written for IBC2006, and they were more than adequate, since a) IBC2009 still references ASCE7-05 (same as IBC2006), and B) changes made to IBC2009 for seismic were few and minor.

The most major changes would be in volumne 3 for concrete, since reference changed from ACI318-05 to 318-08, but even there it's mostly section number changes, not substantive changes - so more of a PITA than anything else.


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## McEngr (Apr 21, 2012)

Sorry I never responded ip. I think if you already have the 2006 edition, there's np need.If you are buying for the first time, them its a good choice.


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## dakota_79 (May 1, 2012)

Hey McEngr, I happened to be reading through this publication written by Larry Muir, and came across a much more pure, truly theoretical derivation of the (5/8)*tp. Pages 70-71.

http://larrymuir.com/Documents/Design%20of%20Unstiffened%20Extended%20Single%20Plate%20Shear%20Connections.pdf


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## McEngr (May 1, 2012)

dakota: very nice find! One thing I noticed is that the SDM is incorrect as the Muir article makes the correlation between 50 ksi yield and 70 ksi electrodes. Of course using 5/8 with 36ksi is conservative forthat example.


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## dakota_79 (May 1, 2012)

Blind squirrels and nuts and all that.


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## McEngr (May 1, 2012)

not a great speller with my phone... I frequent this site on my droid. Stupid swype texting doesn't always work the way I want...


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