Shear walls too long?

[EngineerofSteel]

I was surprised recently to receive this comment in a review letter. It was not listed with the 9 items for correction, but in a summary paragraph at the end. Here it is, verbatim:

"There are a couple of walls 20'+/- that do not meet aspect ratio along with several of the 10' walls."

I am well familiar with 2:1 max ratio, but what is he talking about here? The longest wall is 10' high and 26 feet long. (It separates two unique family dwellings.)

Code: CBC 2001 (modified UBC 97).

Any idea what is referenced here?

 

[EngineerofSteel]

Any help? I read through Chapter 23 last night... no help. Could he be concerned about differences in distribution of load due to deflection?

 

[msquared48]

Are there any doors or windows in these walls that could alter the aspect ratio? And by the way, you can go 3.5:1 on the ratio.

Mike McCann
MMC Engineering

 

[EngineerofSteel]

In the long walls questioned, there are no openings. The 26' long wall is a 2-hour fire wall. I don't want to open it.... the wall is already built.

This review came after a revision. I'm not sure why the question was not asked of the previous design team.

I know about the MAX ratio of 3.5:1 (2:1 on this project in EQ Zone 4), but is there a limit at the other end?

It doesn't make sense to me... I've designed long wall sections before... but they did have windows!

I'm calling him... I just wanted to know what section it came from before I called so I could have a solution - and not look uninformed!

 

[frv]

Perhaps the reviewer is a little slow, and assumed that the aspect ratio applies in either direction? (i.e. L/H as well as (H/L)

 

[EngineerofSteel]

NEVERMIND...

I called. He was referring to vertical wall sections, not horizontal sections. Because he had already mentioned the vertical issue in a comment above, I misread his intention.

Anyhow... It was a nice review of chapter 23.