Shear in Concrete Wall
Shear in Concrete Wall
(OP)
I am designing a concrete wall that backs into a hill for a condo. The concrete wall will hopefully be 10" to 12" thick.
Factored Moment --> 107kN*m (79,000 lbs*ft)
Factored Shear --> 255kN (~57,300 lbs)
Based on my calculations, I will require shear reinfocing (i.e. stirrups of some sort). My question is will horizontal reinforcing act as shear reinforcing or do I need stirrups? I've never seen shear reinforcing in a basement wall.
Help would be great!
Thanks,
JrEng
Factored Moment --> 107kN*m (79,000 lbs*ft)
Factored Shear --> 255kN (~57,300 lbs)
Based on my calculations, I will require shear reinfocing (i.e. stirrups of some sort). My question is will horizontal reinforcing act as shear reinforcing or do I need stirrups? I've never seen shear reinforcing in a basement wall.
Help would be great!
Thanks,
JrEng






RE: Shear in Concrete Wall
RE: Shear in Concrete Wall
The moment is a bit curious. Is it as induced by the shear at the base of the wall?
RE: Shear in Concrete Wall
the walls looks like this. I will attempt to draw
/| |<---Floor system
/ | |
Soil Pressure/->| | 3m span
14.1kN/m3 / | |
/ | |<---Floor system
/---->| |
/ | |
/ | | 3m span
/------->| |
/ | |
/ | |<---Floor System (max shear here)
/---------->| |
/ | | 1.5m span (crawlspace)
/-------------| |
Sorry for all the metric units. I modelled the wall with the bottom as a 'cantilever'. I was hoping not rely on much lateral resistance from the concrete pile foundation (there is no concrete slab in the crawl space to take out the lateral load)
Hope that clarifies things, more help would be GREATLY appreciated.
RE: Shear in Concrete Wall
Grade Level
_____
/|<-----support
/ | 3m
/ |
/ |<-----support
/ | 3m
/ |
/ |<-----support
/ | 1.5m
(cant)
RE: Shear in Concrete Wall
Any thoughts?!
RE: Shear in Concrete Wall
A forest of shear ties through a wall is a mess and impedes the deposition of concrete.
RE: Shear in Concrete Wall
Two more questions on that topic:
1) If they pour that wall in 2 or 3 pours, would it be best to place the cold joints at the supports to encourage simple span action? My reasoning is to get away with using only one mat of reinfocing (i.e. on the inside face) As opposed to using 2 mats of reinforcing to carry the negative moment at the supports.
Just a thought. Otherwise I will likely cold joint it at minimum moment location and try to achieve a continuous "beam/wall" using two mats of reinforcing.
2)Do you have any thoughts about me adding that kind of axial load into the floor system. I know this is a general question, but i'm worried about how much axial load the floor system will be required to resist. It's a LOT larger than any of my previous designs.
RE: Shear in Concrete Wall
Mike McCann
McCann Engineering
RE: Shear in Concrete Wall
RE: Shear in Concrete Wall
RE: Shear in Concrete Wall
RE: Shear in Concrete Wall
I would definitely verify the lateral stability of the structure to resist the 7.5m of earth thrust. I understand your reservations about putting too much lateral load into the piles - but this thrust has to be resisted somewhere.... I take it the rest of the building is suspended and on piles?
What is the construction of the building? Is there enough bracing to resist this load and can floor diaphragms distribute the loads to these points? I assume the bracing is rigid and the loads will not cause serviceability concerns?
As this wall will have to be constructed hard up against the building there may be potential to utilize existing bracing walls built into and perpendicular to the backwall. If a connection to the vertical bracing elements can be justified these walls will serve as 'buttresses' and enable two way action in the wall and subsequent reduction in BM and shear.
I might be a bit of track here but i thought id put my 2c in.
By the way, i specify cold joints as scabbled with bonding agents and the reinforcing continuous. As such from a bending perspective the wall acts effectively continuous. I specify cold joints in the middle third of the span as i am more concerned about the shear rather than BM at these locations. I would not specify a cold joint at a support.
Cheers
LJK
RE: Shear in Concrete Wall
RE: Shear in Concrete Wall
to answer your question LJK, its a wood framed 4 storey stepped condominium. I-joist construction with concrete foundation walls supported soley on concrete piles.
RE: Shear in Concrete Wall