Seismic Design Manual EX. 3.14

[ChrisNYCEng]

I am having an issue understanding example 3.17 of the Seismic Design Manual. On page 3-137, when calculating the required column strength in accordance with section 15.8 (at bottom in page), we need to calculate the strength of the column to be greater than the sum of shear reactions from all links above the column due to the strain hardened expected yield strength of said link beams plus the factored gravity loads. When calculating this value, the manual uses 1.1x1.1x(318 + 205) = 633 kips for the summation on link beam shears. I don't understand where the 318kips comes from. Based on the givens, I would assume this value would be 1.1x1.1x205x4 = 992k since there are 4 levels above column C-1 and the only given beam size is the w16x77 from example 3.14.

Any guidance or clarification would be appreciated.

 

[joengineering]

Chrys,

Any chance you can scan the example?

JO

 

[JAE]

I think the text of that paragraph states: "By calculations not shown here, it was determined that the sum of the nominal shear strengths of teh links at teh fourth level and roof is 318 kips".

So they are simply saying that the second level is 205 kips (see Example 3.14 earlier in the text where they calculate this value) and they are saying that the two levels above (4th and roof) total 318 kips. They don't show the calculation but just ask you to assume that it is true.

So above column C-1 you have the "second" level at 205 and you have the two levels above that (4th and roof) that total 318. So the total is 205 + 318.

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[ChrisNYCEng]

JAE, I see what you mean on page 3-136. Another question then, if we are checking the column between base and level 2, why are we not considering the load from the link ON level 2, and only considering the links on 3,4 and roof?

I have attached Example 3.14, 3.15, 3.16 and 3.17 if that helps.

 

[ChrisNYCEng]

Attached.

 

[JAE]

Not sure Chris. The text of 15.8 specifically says "...of all links above the levels under consideration".

It seems to me that a leaning EBF frame would have the link at the level at the top of the column drive its shear into the column as well.
You might have to dig into the background of EBF's to figure it out.



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