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load bearing clay brick wall

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发表于 2009-9-10 10:58:33 | 显示全部楼层 |阅读模式
load bearing clay brick wall
hi guys,
i need to provide a concrete stair that is adjacent to a historic building to provide new access. the building itself is classified a "historic landmark" so it cannot be touched.
the architect has the idea of using 110mm (4.5") wide loadbearing clay brick to support this stair so it has the same appearance as the landmark building which was built before 1900.
i do not know much about masonry design in general but i have done some numbers which show the clay brick wall has capacity for 93kn (9.3 tonnes / 20kipf) and the ultimate load from my analysis is 110kn (11 tonnes / 25kipf).
the wall dimensions are 2000 (7') wide and 3010 (10') high.
my questions are as follows:
1. what should i be looking at when designing loadbearing clay brick walls? i think a slenderness ratio has to be satisfied.
2. how can i strengthed this wall so it can support the load required? can i provide reinforcement of any nature.
just by looking at the section my natural instict is that the wall doesn't look right. i would rather provide a concrete masonry unit wall with a non-loadbearing clay brick vaneer.
all comments will be appreciated.
asixth,
go with your instinct.  you can build the wall in brick, but not single skin.  check the robustness requirements of as3700.
could you provide brick piers to reduce the slenderness?
i am in-line with hokie. cmu with vaneer is better/simpler solution.
just an add-on question, my calcs show that the brickwall can support 93kn (20kipf or 9.3 tonnes). this seems like alot of load for that wall to support, is there any typically detailing available for brickwalls supporting concrete slabs?
asixth,
you really can't connect the 110 single skin of brick to the slab, as there is no place to put reinforcing.  my advice would be either to use a double brick wall, 230 thick; or otherwise use a 350 x 350 square pier at each end.  in the piers, you can build in a vertical bar.
tell the architect that it is not structurally honest to use a single skin bearing wall in a historic building, as they would never have used just a single skin in those days.
i think you'll get lateral forces at the top of the wall due to the geometry of the stair. to deal with this often the top of the wall is taken to be a roller allowing the staircase in tension to restrain the load (providing you can transfer the load at the other end). in practice, i'm not convined you can get it to behave as a roller though. i've seen engineers specify slip membranes to creat a roller effect but not sure how successful these are.
i don't think that lateral force or movement of the landing is an issue.  the thickened section at the bottom will be restrained by the slab, and the stair itself is quite stiff.
i think it will come down to the stiffness of the joint between the landing and stair. i would do a quick model and take the wall support as a roller and see what lateral movoment you get. then if it's less than the allowable deflection at the top of a wall (about h/300) then you're ok
oxbridge,
if you want to match the existing brickwork it is unlikely that stretcher bond will be accurate.
it will possibly be english or colonial bond (see
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