Out-of-plane at openings 2

[Schneidly]

I am evaluating an existing 8IN CMU structure that is partially grouted with #5 at 24”. I wanted to know how to determine how much wall I can use on either side of an opening for the out-of-plane check. There are 8ft-8Iin, 5ft-4in and 3ft-4in openings. The walls are 13ft-4in tall. The openings are 7ft-4in tall. The load I am checking against is 21psf.

 

[JAE]

We've used 24 to 36 inches - another concept is that from the MSJC code to use 8 x wall thickness for concentrated loads. Out of plane loads at openings are not axially applied concentrated loads but we've looked at it that way since they are laterally concentrated loads at the headers.

 

[a2mfk]

I'm with JAE, its hard for me to believe lateral pressures that produce concentrated loading at jambs can be "spread out" into the CMU beyond 2-3 feet unless you have a solid grouted walls and multiple horizontal bond beams. Also remember the additional trib area of the jamb itself, and half the distance to the next filled cell spacing. And the moment from floor framing if you have it from an eccentricity (applied concurrently with negative lateral pressure)..

 

[sandman21]

We use 6t, this was discussed here as well

http://eng-tips.com/viewthread.cfm?qid=297042

 

[pmblair]

At my firm we have went through the exercise of examining the msjc and arguing the meaning multiple times. Without the code in front of me.... We have concluded 24" for 8" CMU.

 

[gte447f]

There is an article on page 27 of the May issue of Structure magazine where the author suggests "half the typical bar spacing for the wall, but not to exceed 3t (3t being half the allowable bar spacing of 6t for a partially grouted, fully reinforced wall)".

Personally, I think 3t, regardless of the typical bar spacing, makes since.

 

[csd72]

hopefully this helps:

http://www.structuremag.org/article.aspx?articleID=1253