Shear strength of concrete
Shear strength of concrete
(OP)
The shear strength of concrete (Canada) is given by the formula:
Vc = 0.2 x λ x ᶲc x √f'c x bw x d
Where λ = 1 for normal weight concrete
ᶲc = 0.6
f'c = compressive strength of concrete
bw = width
d = depth
Suppose we have a dowel (say rebar) in the center of a concrete panel with thickness 150mm.
If the dowel (15 mm) is placed at the centreline of the panel, then bw = 15 + 2 x 75 and d = 75
The question is, doesn't the length of the dowel have an effect on the shear strength? However there is nothing in the equation to account for the length? That is, doesn't the third dimension have an impact on the shear strength?
Vc = 0.2 x λ x ᶲc x √f'c x bw x d
Where λ = 1 for normal weight concrete
ᶲc = 0.6
f'c = compressive strength of concrete
bw = width
d = depth
Suppose we have a dowel (say rebar) in the center of a concrete panel with thickness 150mm.
If the dowel (15 mm) is placed at the centreline of the panel, then bw = 15 + 2 x 75 and d = 75
The question is, doesn't the length of the dowel have an effect on the shear strength? However there is nothing in the equation to account for the length? That is, doesn't the third dimension have an impact on the shear strength?






RE: Shear strength of concrete
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.
RE: Shear strength of concrete
RE: Shear strength of concrete
The length of the dowel will matter but only to a point. Beyond a certain distance, the flexibility of the dowel prevents it from engaging more concrete breakout surface. Back in the days before we had rigorous anchorage provisions, I was taught that six times the bar diameter was a good dowel length to consider effective.
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.
RE: Shear strength of concrete
This References that shear reinforcement should be anchored at both ends as spec'd in 12.13 in order to develop yield strength of the reinforcement.
From your sketch it looks like you will have to epoxy the dowel into the (tilt up?) panel.
RE: Shear strength of concrete
Signious, if the concrete shear strength is sufficient then there is no need to ensure that the yield strength is reached as the shear will govern.
Also shear reinforcement is only required if the factored shear force is more than 50% of the shear capacity. I'll check out A23.3 Thanks.
RE: Shear strength of concrete
Which Canadian code formula have you quoted? The flexure formula has a Beta term in it which is conditional on reinforcement strain and moments etc. In this formula the flexural reinforcement is supposed to be fully developed past the shear plane.
RE: Shear strength of concrete