Basement wall analysis
Basement wall analysis
(OP)
Sorry this is so long, I just want to make sure I don't leave out important details.
I am analysing a 10" x 9' basement wall with #4 18" horizontal and 36" vertical and a 8' imbalance. The wall is already in place. According to standards, 18" is the max rebar spacing you should use, but the IRC charts state basement walls can use greater spacings. When I anylize the wall as cantilevered, and no lateral support (the joists run parallel) it is a marginal failure with 36" verticals. There are 2 walls below the upper level garage that can be considered counterforts 12' in from the corners and 22' apart with a slab inbetween at the top of the basemetn wall. I am told they ate 9' tall and 4' long before stepping up, but they are not visible.
So what I'm wondering is, should I refrain from treating it like a standard cantilevered wall, and also, what impact the counterforts may have on the wall itself. Any input or even mere opinion would be appreciated.
I am analysing a 10" x 9' basement wall with #4 18" horizontal and 36" vertical and a 8' imbalance. The wall is already in place. According to standards, 18" is the max rebar spacing you should use, but the IRC charts state basement walls can use greater spacings. When I anylize the wall as cantilevered, and no lateral support (the joists run parallel) it is a marginal failure with 36" verticals. There are 2 walls below the upper level garage that can be considered counterforts 12' in from the corners and 22' apart with a slab inbetween at the top of the basemetn wall. I am told they ate 9' tall and 4' long before stepping up, but they are not visible.
So what I'm wondering is, should I refrain from treating it like a standard cantilevered wall, and also, what impact the counterforts may have on the wall itself. Any input or even mere opinion would be appreciated.






RE: Basement wall analysis
Usually this is done by providing spaced struts, or blocking, perpendicular to the wall, which are extended into the floor system (between joists) and attached to the diaphragm floor.
Trying to use a cantilevered wall system can work, but you have to design the wall AND the foundation under the wall as a traditional cantilevered system - which probably isn't what has been done on your particular project.
The counterfort (perpendicular) walls do help - you end up with a wall that is connected at its base and vertical sides with a free edge along the top. This is more difficult to analyze - using finite elements or Roarks Formulae might be the way to go....but this is not usually done in most buildings.
RE: Basement wall analysis
RE: Basement wall analysis
Never, but never question engineer's judgement
RE: Basement wall analysis
RE: Basement wall analysis
When I have a wall this long then typically I have a wider and thicker footing, more vertical rebar, fewer horizontal rebar. Unless you have a counterfort or buttress on the middle of the span.
Never, but never question engineer's judgement