Column Splice

[Adeeel]

I am comparing between the design of Column splice for SCBF and SMF.

1- Nominal Flexural Strength

For SCBF, AISC 341 page 3-163

Nominal Flexural Strength was determine using Table 6-1 and from Mn = 8/9bx phi

For SMF, AISC 341 page 4-75

Mpc was determined as Mpc = Fy * Zx

Any Explanation?

2- Shear Strength

For SCBF, AISC 341 page 3-164

Vu= Muc/H was Not compared with Vu from load combinations

For SMF, AISC 341 page 4-75

Vu - Muc/H was Compared with Vu from load combination and larger value was taken

Any Explanation?

 

[Adeeel]

any thoughts?

 

[McEngr]

What printing do you have of AISC 341-05? I had the 1st printing going into the SE III (oblivious to the errors in the first printing the first time I took the test). You can exchange your AISC 341 for a newer printing for free b/c AISC realized how poorly the early editions were. You might have to pay for shipping, however.

 

[Adeeel]

What printing do you have of AISC 341-05? I had the 1st printing going into the SE III (oblivious to the errors in the first printing the first time I took the test). You can exchange your AISC 341 for a newer printing for free b/c AISC realized how poorly the early editions were. You might have to pay for shipping, however.

This is not the first printing, it is the second one. I think there are no errors in the second one. There should be an explanation for my comments.

 

[kevo_55]

I am comparing between the design of Column splice for SCBF and SMF.
1- Nominal Flexural Strength

For SCBF, AISC 341 page 3-163

Nominal Flexural Strength was determine using Table 6-1 and from Mn = 8/9bx phi

For SMF, AISC 341 page 4-75

Mpc was determined as Mpc = Fy * Zx

Any Explanation?

2- Shear Strength

For SCBF, AISC 341 page 3-164

Vu= Muc/H was Not compared with Vu from load combinations

For SMF, AISC 341 page 4-75

Vu - Muc/H was Compared with Vu from load combination and larger value was taken

Any Explanation?

#1: For the SCBF see section 13.5 of AISC 341. For the SMF see section 9.9. I believe this is self explanatory.

#2: See #1.

I hope this helps!

 

[Adeeel]

I am comparing between the design of Column splice for SCBF and SMF.
1- Nominal Flexural Strength

For SCBF, AISC 341 page 3-163

Nominal Flexural Strength was determine using Table 6-1 and from Mn = 8/9bx phi

For SMF, AISC 341 page 4-75

Mpc was determined as Mpc = Fy * Zx

Any Explanation?

2- Shear Strength

For SCBF, AISC 341 page 3-164

Vu= Muc/H was Not compared with Vu from load combinations

For SMF, AISC 341 page 4-75

Vu - Muc/H was Compared with Vu from load combination and larger value was taken

Any Explanation?

#1: For the SCBF see section 13.5 of AISC 341. For the SMF see section 9.9. I believe this is self explanatory.

#2: See #1.

I hope this helps!

Thanks Kevo for your reply. However, I read these parts many times before and I really do not see anything that explains these differences.

 

[kevo_55]

Adeeel,

For SCBF section 13.5 of the seismic provisions state that column splices must be able to develop 50% of the flexural strength of the smaller of the two column members. Furthermore, it should be able to develop the shear strength equivalent of the column hinging out at the floor lines.

For SMF section 9.9 of the seismic provisions state that the splice must equal to the plastic flexural strength multiplied by Ry. The shear strength is similar to the SCBF.

Am I not seeing something from your question? I agree when checking the shear, you should use the larger of the shear acting or the plastic hinging action at this location.

Thanks.

 

[Adeeel]

Kevo,

Let me express my question in different way

Why Mn for SCBF was not determined as Fy * Zx as the case in SMF. for SCBF, Mn was determind as 8/9 bx phi.

I hope my question is clear enough

 

[kevo_55]

Kevo,Let me express my question in different way

Why Mn for SCBF was not determined as Fy * Zx as the case in SMF. for SCBF, Mn was determind as 8/9 bx phi.

I hope my question is clear enough

Andeel,

Ok, now I think that I understand your problem.

Like all things seismic, the devil is in the details.

For SMF, the flexural strength is defined as Ry*Fy*Z (LRFD). For SCBF, the flexural strength is not defined as anything special.

Looking at seismic systems in general, you should know what is really doing the work. For MF systems, it is really both the beams & the columns. For BF systems it is really the brace itself that is doing the work.

With that said, MF systems (in general) will have something above and beyond what the actual forces involved with respect to their beams & columns. BF systems (in general) will have something above and beyond the actual forces for their braces.

Now getting to the problem at hand, for the SCBF system you are only looking at general "demand" with respect to the EQ H1-1 (A or B ) simply because it was not stated that you must do anything else. For the SMF system, it actually defined what demand moment must be dealt with.

Hopefully, this is a bit clearer for you.

 

[Adeeel]

Thank you Kevo, this explains a lot.

Any thoughts for question # 2?

Why is SCBF the Vu from Muc/H was not compared with Vu from load combinations while in SCF it was compared with load combinations and the larger value was taken?

Thanks again.

 

[kevo_55]

Adeeel,

I think that there is an error in the Seismic Design Manual with respect to item #2. Yes, you must check the plastic hinge shear force for both the SMF & the SCBF but you always must choose the higher of this and the actual shear force from loads.