huangyhg

unbraced(cantilever) masonry wall question
i have a client who is planning an addition to a building which will result in an exterior, load bearing wall which will be 50' long and about 20' high. he would like to use cmu's up to about 10' high and then wood framing the rest of the way up. the roof trusses will set on the wood framing. there are no interior walls, second floor or other bracing which means the 10' high cmu wall will have no bracing at the top. is this something i should even consider? i thought about using pilasters but they too would be unbraced at the top. i also thought about using a bond beam at the top of the cmu's but 50' seems like an awful long span for a bond beam to provide effective bracing. any thoughts or suggestions are appreciated.
hemifun,
you are right to be concerned about this one.
cantilevering the cmu wall is an option, but you need to all for any second order effects from the vertical load as well as the wind reaction.
other option that would be much cheaper/better:
1. full height steel studs with the lower half given a rendered finish.
2. embed full height steel posts to act as wind mullions.
it is good to give thema few alternate options so that they can see you have thought about it.
good luck
csd
it seems as if there will also be fire protection issues that might negate any advantage to this system.
without checking any numbers, i think the cantilever cmu wall is a possibility, but...
i like the idea of using full height studs (steel or wood, whichever works best). the architect can easily specify a cmu veneer, which will give the same appearance on the exterior.
or maybe this building is a good candidate for being a pre-engineered metal building!
daveatkins
i would check the wall as a cantilever or provide masonry full height. is the client aware that making the wall a cantilever will also increase the footing cost?
i would look at continuing cmu columns up from the cmu wall to the top, say at 8' or 10' spacing. frame between the columns and clad over the lot for the top 10'.

__________________
借用达朗贝尔的名言：前进吧，你会得到信心!
[url="http://www.dimcax.com"]几何尺寸与公差标准[/url]