IBC Shear Adjustment

[akastud]

Hi all,

The municipalities in our area are just starting to adopt the International codes, and as I am working on one project, I see something that baffles me. I was hoping one of you could help me understand. In table 2305.3.7.2 of the 2000 IBC there are adjustment factors for "shear walls with openings not designed for force transfer". The values I question are the values along the 0% Full height sheathing line. If I have a 3'-4" tall window in a 10'-0" wall that extends the entire length of the wall, I get 100% of the tabulated shear value for the full length of the wall, and I don't have to design any force transer? This does not make sense to me, but it will make my architects very happy if it is right.

akastud

 

[DaveAtkins]

I think that row is there for interpolation purposes. You must still take the shear at the top of the shear wall and divide by the summation of lengths of full height segments, which meet the aspect ratio per Code. So in your case, you would get an infinitely high shear per foot in at the base of the shear wall, which is unacceptable.

DaveAtkins

 

[akastud]

I read it different Dave, from 2305.3.7.2 it says "The total shear capacity, pounds, shall be equal to the adjusted shear capacity (table 2306.4.1 value times adjustmant table 2305.3.7.2 value), plf, times the sum of the widths of shear wall segments meeting the aspect ratio requirements" not sum of full height segments. Therefore the situation I described would get the full shear capacity as if the wall had no window. Am I misunderstanding it?

akastud

 

[JAE]

I would say that in the situation you described, you would have NO shear wall segments - a shear wall segment must extend from story to story AND meet the aspect ratios of Table 2305.3.3.

 

[akastud]

That's what I would think to, however, the code says that 0% of the wall is full height sheathing. I am with you guys, I am just trying to reason what possibly the code writers meant. The aspect ratio is easy to meet in this case.

alastud

 

[antimatter]

In the 2003 IBC %full height sheathing starts at 10% and not 0%. A revision bar is beside this area indicating change. Hope this helped.