Shear in Circular Concrete Columns
Shear in Circular Concrete Columns
(OP)
I have two questions regarding circular concrete columns that I could use some help with:
1) How do you calculate the effective shear area in a circular concrete column? What is analagous to b x d in a rectangular column? Are others just using a percentage of the gross area (85%) or is there specific code guidance provided?
2)When Vc is insufficient to resist shear, can spiral stirrups be used to resist shear? If so, how is Vs calculated? In my office, we generally just slip rectangular hoops into the column cage when shear reinforcing is needed. Is this what others typically do?
1) How do you calculate the effective shear area in a circular concrete column? What is analagous to b x d in a rectangular column? Are others just using a percentage of the gross area (85%) or is there specific code guidance provided?
2)When Vc is insufficient to resist shear, can spiral stirrups be used to resist shear? If so, how is Vs calculated? In my office, we generally just slip rectangular hoops into the column cage when shear reinforcing is needed. Is this what others typically do?






RE: Shear in Circular Concrete Columns
2.) See ACI 318-05 11.5.1.1c and 11.5.7.3
RE: Shear in Circular Concrete Columns
RE: Shear in Circular Concrete Columns
Regardless, thanks for your help.
This spawns two more questions though:
1) According to ACI, you can use 0.8 x d^2 for the effective shear area. However, that's 1.0186 more than the gross area. How the heck can the effective area be more than the gross area? Short of ordering the ACI references, can anybody offer an explanation?
2) When using spiral reinforcement for shear with reversible loads, do you treat the spirals like regular inclined reinforcement working at an UNFAVORABLE pitch? By unfavorable, I mean a pitch oriented in the same sense as the expected shear crack?
RE: Shear in Circular Concrete Columns
RE: Shear in Circular Concrete Columns
RE: Shear in Circular Concrete Columns
BTW: what does ACI 11.5.7.3 say? My 2002 ACI only goes up to 11.5.6.9.
RE: Shear in Circular Concrete Columns
RE: Shear in Circular Concrete Columns
Vs = (Av x fy x(sin(alpha) + cos(alpha))*d)/s ? That's what I've got as 11.5.6.4
RE: Shear in Circular Concrete Columns
RE: Shear in Circular Concrete Columns
When I have checked this for bending it has come in less than 5% different from the exact method.
There is an exact method for these in the IStructE (UK) magazine which actually allows for the slope and shape of the helical reinforcement.
RE: Shear in Circular Concrete Columns
RE: Shear in Circular Concrete Columns